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What Does Quantum Theory Actually Tell Us about Reality?

2018-09-10T11:00:00.000-07:00

Nearly a century after its founding, physicists and philosophers still don’t know—but they’re working on it

By Anil Ananthaswamy on September 3, 2018

Credit: Alexandre Gondran Wikimedia (CC BY-SA 4.0)

For a demonstration that overturned the great Isaac Newton’s ideas about the nature of light, it was staggeringly simple. It “may be repeated with great ease, wherever the sun shines,” the English physicist Thomas Young told the members of the Royal Society in London in November 1803, describing what is now known as a double-slit experiment, and Young wasn’t being overly melodramatic. He had come up with an elegant and decidedly homespun experiment to show light’s wavelike nature, and in doing so refuted Newton’s theory that light is made of corpuscles, or particles.

But the birth of quantum physics in the early 1900s made it clear that light is made of tiny, indivisible units, or quanta, of energy, which we call photons. Young’s experiment, when done with single photons or even single particles of matter, such as electrons and neutrons, is a conundrum to behold, raising fundamental questions about the very nature of reality. Some have even used it to argue that the quantum world is influenced by human consciousness, giving our minds an agency and a place in the ontology of the universe. But does the simple experiment really make such a case?

In the modern quantum form, Young’s experiment involves beaming individual particles of light or matter at two slits or openings cut into an otherwise opaque barrier. On the other side of the barrier is a screen that records the arrival of the particles (say, a photographic plate in the case of photons). Common sense leads us to expect that photons should go through one slit or the other and pile up behind each slit.

They don’t. Rather, they go to certain parts of the screen and avoid others, creating alternating bands of light and dark. These so-called interference fringes, the kind you get when two sets of waves overlap. When the crests of one wave line up with the crests of another, you get constructive interference (bright bands), and when the crests align with troughs you get destructive interference (darkness).

But there’s only one photon going through the apparatus at any one time. It’s as ifeach photon is going through both slits at once and interfering with itself. This doesn’t make classical sense.

Mathematically speaking, however, what goes through both slits is not a physical particle or a physical wave but something called a wave function—an abstract mathematical function that represents the photon’s state (in this case its position). The wave function behaves like a wave. It hits the two slits, and new waves emanate from each slit on the other side, spread and eventually interfere with each other. The combined wave function can be used to work out the probabilities of where one might find the photon.

The photon has a high probability of being found where the two wave functions constructively interfere and is unlikely to be found in regions of destructive interference. The measurement—in this case the interaction of the wave function with the photographic plate—is said to “collapse” the wave function. It goes from being spread out before measurement to peaking at one of those places where the photon materializes upon measurement.

This apparent measurement-induced collapse of the wave function is the source of many conceptual difficulties in quantum mechanics. Before the collapse, there’s no way to tell with certainty where the photon will land; it can appear at any one of the places of non-zero probability. There’s no way to chart the photon’s trajectory from the source to the detector. The photon is not real in the sense that a plane flying from San Francisco to New York is real.

Werner Heisenberg, among others, interpreted the mathematics to mean that reality doesn’t exist until observed. “The idea of an objective real world whose smallest parts exist objectively in the same sense as stones or trees exist, independently of whether or not we observe them ... is impossible,” he wrote. John Wheeler, too, used a variant of the double-slit experiment to argue that “no elementary quantum phenomenon is a phenomenon until it is a registered (‘observed,’ ‘indelibly recorded’) phenomenon.”

But quantum theory is entirely unclear about what constitutes a “measurement.” It simply postulates that the measuring device must be classical, without defining where such a boundary between the classical and quantum lies, thus leaving the door open for those who think that human consciousness needs to be invoked for collapse. Last May, Henry Stapp and colleagues argued, in this forum, that the double-slit experiment and its modern variants provide evidence that “a conscious observer may be indispensable” to make sense of the quantum realm and that a transpersonal mind underlies the material world.

But these experiments don’t constitute empirical evidence for such claims. In the double-slit experiment done with single photons, all one can do is verify the probabilistic predictions of the mathematics. If the probabilities are borne out over the course of sending tens of thousands of identical photons through the double slit, the theory claims that each photon’s wave function collapsed—thanks to an ill-defined process called measurement. That’s all.

Also, there are other ways of interpreting the double-slit experiment. Take the de Broglie-Bohm theory, which says that reality is both wave and particle. A photon heads towards the double slit with a definite position at all times and goes through one slit or the other; so each photon has a trajectory. It’s riding a pilot wave, which goes through both slits, interferes and then guides the photon to a location of constructive interference.

In 1979, Chris Dewdney and colleagues at Birkbeck College, London, simulated the theory’s prediction for the trajectories of particles going through the double slit. In the past decade, experimentalists have verified that such trajectories exist, albeit by using a controversial technique called weak measurements. The controversy notwithstanding, the experiments show that the de Broglie-Bohm theory remains in the running as an explanation for the behavior of the quantum world.

Crucially, the theory does not need observers or measurements or a non-material consciousness.

Neither do so-called collapse theories, which argue that wave functions collapse randomly: the more the number of particles in the quantum system, the more likely the collapse. Observers merely discover the outcome. Markus Arndt’s team at the University of Vienna in Austria has been testing these theories by sending larger and larger molecules through the double slit.

Collapse theories predict that when particles of matter become more massive than some threshold, they cannot remain in a quantum superposition of going through both slits at once, and this will destroy the interference pattern. Arndt’s team has sent a molecule with more than 800 atoms through the double slit, and they still see interference. The search for the threshold continues.

Roger Penrose has his own version of a collapse theory, in which the more massive the mass of the object in superposition, the faster it’ll collapse to one state or the other, because of gravitational instabilities. Again, it’s an observer-independent theory. No consciousness needed. Dirk Bouwmeester at the University of California, Santa Barbara, is testing Penrose’s idea with a version of the double-slit experiment.

Conceptually, the idea is to not just put a photon into a superposition of going through two slits at once, but to also put one of the slits in a superposition of being in two locations at once. According to Penrose, the displaced slit will either stay in superposition or collapse while the photon is in flight, leading to different types of interference patterns. The collapse will depend on the mass of the slits. Bouwmeester has been at work on this experiment for a decade and may soon be able to verify or refute Penrose’s claims.

If nothing else, these experiments are showing that we cannot yet make any claims about the nature of reality, even if the claims are well-motivated mathematically or philosophically. And given that neuroscientists and philosophers of mind don’t agree on the nature of consciousness, claims that it collapses wave functions are premature at best and misleading and wrong at worst.

ABOUT THE AUTHOR(S)

Anil Ananthaswamy

Anil Ananthaswamy is the author of The Edge of Physics, The Man Who Wasn't There and, most recently, Through Two Doors at Once: The Elegant Experiment That Captures the Enigma of Our Quantum Reality.

SOURCE:

Scientific American Space & Physics

7 SEPT. 2018

A Neuroscientist Explores the "Sanskrit Effect"

2018-01-11T06:28:00.000-08:00

MRI scans show that memorizing ancient mantras increases the size of brain regions associated with cognitive function

By James Hartzell on January 2, 2018

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Manjuvajramandala with 43 deities, from Tibet. Credit: Google Cultural Institute Wikimedia

A hundred dhoti-clad young men sat cross-legged on the floor in facing rows, chatting amongst themselves. At a sign from their teacher the hall went quiet. Then they began the recitation. Without pause or error, entirely from memory, one side of the room intoned one line of the text, then the other side of the room answered with the next line. Bass and baritone voices filled the hall with sonorous prosody, every word distinctly heard, their right arms moving together to mark pitch and accent. The effect was hypnotic, ancient sound reverberating through the room, saturating brain and body. After 20 minutes they halted, in unison. It was just a demonstration. The full recitation of one of India´s most ancient Sanskrit texts, the Shukla Yajurveda, takes six hours.

I spent many years studying and translating Sanskrit, and became fascinated by its apparent impact on mind and memory. In India's ancient learning methods textual memorization is standard: traditional scholars, or pandits, master many different types of Sanskrit poetry and prose texts; and the tradition holds that exactly memorizing and reciting the ancient words and phrases, known as mantras, enhances both memory and thinking.

I had also noticed that the more Sanskrit I studied and translated, the better my verbal memory seemed to become. Fellow students and teachers often remarked on my ability to exactly repeat lecturers’ own sentences when asking them questions in class. Other translators of Sanskrit told me of similar cognitive shifts. So I was curious: was there actually a language-specific “Sanskrit effect” as claimed by the tradition?

When I entered the cognitive neuroscience doctoral program at the University of Trento (Italy) in 2011, I had the opportunity to start investigating this question. India's Vedic Sanskrit pandits train for years to orally memorize and exactly recite 3,000-year old oral texts ranging from 40,000 to over 100,000 words. We wanted to find out how such intense verbal memory training affects the physical structure of their brains.

Through the India-Trento Partnership for Advanced Research (ITPAR), we recruited professional Vedic pandits from several government-sponsored schools in the Delhi region; then we used structural magnetic resonance imaging (MRI) at India’s National Brain Research Center to scan the brains of pandits and controls matched for age, gender, handedness, eye-dominance and multilingualism.

What we discovered from the structural MRI scanning was remarkable. Numerous regions in the brains of the pandits were dramatically larger than those of controls, with over 10 percent more grey matter across both cerebral hemispheres, and substantial increases in cortical thickness. Although the exact cellular underpinnings of gray matter and cortical thickness measures are still under investigation, increases in these metrics consistently correlate with enhanced cognitive function.

Most interestingly for verbal memory was that the pandits' right hippocampus—a region of the brain that plays a vital role in both short and long-term memory—had more gray matter than controls across nearly 75 percent of this subcortical structure. Our brains have two hippocampi, one on the left and one on the right, and without them we cannot record any new information. Many memory functions are shared by the two hippocampi. The right is, however, more specialized for patterns, whether sound, spatial or visual, so the large gray matter increases we found in the pandits’ right hippocampus made sense: accurate recitation requires highly precise sound pattern encoding and reproduction. The pandits also showed substantially thickening of right temporal cortex regions that are associated with speech prosody and voice identity.

Our study was a first foray into imaging the brains of professionally trained Sanskrit pandits in India. Although this initial research, focused on intergroup comparison of brain structure, could not directly address the Sanskrit effect question (that requires detailed functional studies with cross-language memorization comparisons, for which we are currently seeking funding), we found something specific about intensive verbal memory training.

Does the pandits’ substantial increase in the gray matter of critical verbal memory organs mean they are less prone to devastating memory pathologies such as Alzheimer's? We don't know yet, though anecdotal reports from India's Ayurvedic doctors suggest this may be the case. If so, this raises the possibility that verbal memory “exercising ‘or training might help elderly people at risk of mild cognitive impairment retard or, even more radically, prevent its onset.

If so, the training might need to be exact. One day I was filming four senior pandit teachers demonstrating the different recitation speeds. Partway into one session all four suddenly stopped. “What’s wrong? ‘ I asked. “One of us made a slight error," came the response. "I don’t mind," I said. "Yes, but we do," and they restarted the entire recitation from the beginning.

Author's note: Senior personnel responsible for this project were not involved in the conception or writing of the blog text; it was not presented to them for approval; any opinions or conclusions expressed in the blog are Dr. Hartzell's alone.

This post was written by a graduate of the online course Share Your Science: Blogging for Magazines, Newspapers and More, offered by Scientific American and the Alan Alda Center for Communicating Science at Stony Brook University, with sponsorship from the Kavli Foundation.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

ABOUT THE AUTHOR(S)

James Hartzell

James Hartzell is a postdoctoral researcher at the Basque Center on Cognition, Brain and Language, in Spain; a Guest Researcher at the Center for Mind/Brain Sciences at University of Trento, in Italy, and a Consultant for the Center for Buddhist Studies at Columbia University, in New York.

SOURCE:

MIND & BRAIN

January 10, 2018

2017-12-22T12:46:00.000-08:00

A Physicist’s Physicist Ponders the Nature of Reality

Edward Witten reflects on the meaning of dualities in physics and math, emergent space-time, and the pursuit of a complete description of nature.

Natalie Wolchover

Senior Writer

November 28 2017

Among the brilliant theorists cloistered in the quiet woodside campus of the Institute for Advanced Study in Princeton, New Jersey, Edward Witten stands out as a kind of high priest. The sole physicist ever to win the Fields Medal, mathematics’ premier prize, Witten is also known for discovering M-theory, the leading candidate for a unified physical “theory of everything.” A genius’s genius, Witten is tall and rectangular, with hazy eyes and an air of being only one-quarter tuned in to reality until someone draws him back from more abstract thoughts.

During a visit this fall, I spotted Witten on the Institute’s central lawn and requested an interview; in his quick, alto voice, he said he couldn’t promise to be able to answer my questions but would try. Later, when I passed him on the stone paths, he often didn’t seem to see me.

Physics luminaries since Albert Einstein, who lived out his days in the same intellectual haven, have sought to unify gravity with the other forces of nature by finding a more fundamental quantum theory to replace Einstein’s approximate picture of gravity as curves in the geometry of space-time. M-theory, which Witten proposed in 1995, could conceivably offer this deeper description, but only some aspects of the theory are known. M-theory incorporates within a single mathematical structure all five versions of string theory, which renders the elements of nature as minuscule vibrating strings. These five string theories connect to each other through “dualities,” or mathematical equivalences. Over the past 30 years, Witten and others have learned that the string theories are also mathematically dual to quantum field theories — descriptions of particles moving through electromagnetic and other fields that serve as the language of the reigning “Standard Model” of particle physics. While he’s best known as a string theorist, Witten has discovered many new quantum field theories and explored how all these different descriptions are connected. His physical insights have led time and again to deep mathematical discoveries.

That’s extremely strange, that the world is based so much on a mathematical structure that’s so difficult.

Researchers pore over his work and hope he’ll take an interest in theirs. But for all his scholarly influence, Witten, who is 66, does not often broadcast his views on the implications of modern theoretical discoveries. Even his close colleagues eagerly suggested questions they wanted me to ask him.

When I arrived at his office at the appointed hour on a summery Thursday last month, Witten wasn’t there. His door was ajar. Papers covered his coffee table and desk — not stacks, but floods: text oriented every which way, some pages close to spilling onto the floor. (Research papers get lost in the maelstrom as he finishes with them, he later explained, and every so often he throws the heaps away.) Two girls smiled out from a framed photo on a shelf; children’s artwork decorated the walls, one celebrating Grandparents’ Day. When Witten arrived minutes later, we spoke for an hour and a half about the meaning of dualities in physics and math, the current prospects of M-theory, what he’s reading, what he’s looking for, and the nature of reality. The interview has been condensed and edited for clarity.

Physicists are talking more than ever lately about dualities, but you’ve been studying them for decades. Why does the subject interest you?

People keep finding new facets of dualities. Dualities are interesting because they frequently answer questions that are otherwise out of reach. For example, you might have spent years pondering a quantum theory and you understand what happens when the quantum effects are small, but textbooks don’t tell you what you do if the quantum effects are big; you’re generally in trouble if you want to know that. Frequently dualities answer such questions. They give you another description, and the questions you can answer in one description are different than the questions you can answer in a different description.

What are some of these newfound facets of dualities?

It’s open-ended because there are so many different kinds of dualities. There are dualities between a gauge theory [a theory, such as a quantum field theory, that respects certain symmetries] and another gauge theory, or between a string theory for weak coupling [describing strings that move almost independently from one another] and a string theory for strong coupling. Then there’s AdS/CFT duality, between a gauge theory and a gravitational description. That duality was discovered 20 years ago, and it’s amazing to what extent it’s still fruitful. And that’s largely because around 10 years ago, new ideas were introduced that rejuvenated it. People had new insights about entropy in quantum field theory — the whole story about “it from qubit.”

The AdS/CFT duality connects a theory of gravity in a space-time region called anti-de Sitter space (which curves differently than our universe) to an equivalent quantum field theory describing that region’s gravity-free boundary. Everything there is to know about AdS space — often called the “bulk” since it’s the higher-dimensional region — is encoded, like in a hologram, in quantum interactions between particles on the lower-dimensional boundary. Thus, AdS/CFT gives physicists a “holographic” understanding of the quantum nature of gravity.

That’s the idea that space-time and everything in it emerges like a hologram out of information stored in the entangled quantum states of particles.

Yes. Then there are dualities in math, which can sometimes be interpreted physically as consequences of dualities between two quantum field theories. There are so many ways these things are interconnected that any simple statement I try to make on the fly, as soon as I’ve said it I realize it didn’t capture the whole reality. You have to imagine a web of different relationships, where the same physics has different descriptions, revealing different properties. In the simplest case, there are only two important descriptions, and that might be enough. If you ask me about a more complicated example, there might be many, many different ones.

Given this web of relationships and the issue of how hard it is to characterize all duality, do you feel that this reflects a lack of understanding of the structure, or is it that we’re seeing the structure, only it’s very complicated?

I’m not certain what we should hope for. Traditionally, quantum field theory was constructed by starting with the classical picture [of a smooth field] and then quantizing it. Now we’ve learned that there are a lot of things that happen that that description doesn’t do justice to. And the same quantum theory can come from different classical theories. Now, Nati Seiberg [a theoretical physicist who works down the hall] would possibly tell you that he has faith that there’s a better formulation of quantum field theory that we don’t know about that would make everything clearer. I’m not sure how much you should expect that to exist. That would be a dream, but it might be too much to hope for; I really don’t know.

There’s another curious fact that you might want to consider, which is that quantum field theory is very central to physics, and it’s actually also clearly very important for math. But it’s extremely difficult for mathematicians to study; the way physicists define it is very hard for mathematicians to follow with a rigorous theory. That’s extremely strange, that the world is based so much on a mathematical structure that’s so difficult.

What do you see as the relationship between math and physics?

I prefer not to give you a cosmic answer but to comment on where we are now. Physics in quantum field theory and string theory somehow has a lot of mathematical secrets in it, which we don’t know how to extract in a systematic way. Physicists are able to come up with things that surprise the mathematicians. Because it’s hard to describe mathematically in the known formulation, the things you learn about quantum field theory you have to learn from physics.

I find it hard to believe there’s a new formulation that’s universal. I think it’s too much to hope for. I could point to theories where the standard approach really seems inadequate, so at least for those classes of quantum field theories, you could hope for a new formulation. But I really can’t imagine what it would be.

You can’t imagine it at all?

No, I can’t. Traditionally it was thought that interacting quantum field theory couldn’t exist above four dimensions, and there was the interesting fact that that’s the dimension we live in. But one of the offshoots of the string dualities of the 1990s was that it was discovered that quantum field theories actually exist in five and six dimensions. And it’s amazing how much is known about their properties.

If there’s a radically different dual description of the real world, maybe some things physicists worry about would be clearer, but the dual description might be one in which everyday life would be hard to describe.

I’ve heard about the mysterious (2,0) theory, a quantum field theory describing particles in six dimensions, which is dual to M-theory describing strings and gravity in seven-dimensional AdS space. Does this (2,0) theory play an important role in the web of dualities?

Yes, that’s the pinnacle. In terms of conventional quantum field theory without gravity, there is nothing quite like it above six dimensions. From the (2,0) theory’s existence and main properties, you can deduce an incredible amount about what happens in lower dimensions. An awful lot of important dualities in four and fewer dimensions follow from this six-dimensional theory and its properties. However, whereas what we know about quantum field theory is normally from quantizing a classical field theory, there’s no reasonable classical starting point of the (2,0) theory. The (2,0) theory has properties [such as combinations of symmetries] that sound impossible when you first hear about them. So you can ask why dualities exist, but you can also ask why is there a 6-D theory with such and such properties? This seems to me a more fundamental restatement.

Dualities sometimes make it hard to maintain a sense of what’s real in the world, given that there are radically different ways you can describe a single system. How would you describe what’s real or fundamental?

What aspect of what’s real are you interested in? What does it mean that we exist? Or how do we fit into our mathematical descriptions?

The latter.

Well, one thing I’ll tell you is that in general, when you have dualities, things that are easy to see in one description can be hard to see in the other description. So you and I, for example, are fairly simple to describe in the usual approach to physics as developed by Newton and his successors. But if there’s a radically different dual description of the real world, maybe some things physicists worry about would be clearer, but the dual description might be one in which everyday life would be hard to describe.

What would you say about the prospect of an even more optimistic idea that there could be one single quantum gravity description that really does help you in every case in the real world?

Well, unfortunately, even if it’s correct I can’t guarantee it would help. Part of what makes it difficult to help is that the description we have now, even though it’s not complete, does explain an awful lot. And so it’s a little hard to say, even if you had a truly better description or a more complete description, whether it would help in practice.

Are you speaking of M-theory?

M-theory is the candidate for the better description.

You proposed M-theory 22 years ago. What are its prospects today?

Personally, I thought it was extremely clear it existed 22 years ago, but the level of confidence has got to be much higher today because AdS/CFT has given us precise definitions, at least in AdS space-time geometries. I think our understanding of what it is, though, is still very hazy. AdS/CFT and whatever’s come from it is the main new perspective compared to 22 years ago, but I think it’s perfectly possible that AdS/CFT is only one side of a multifaceted story. There might be other equally important facets.

What’s an example of something else we might need?

Maybe a bulk description of the quantum properties of space-time itself, rather than a holographic boundary description. There hasn’t been much progress in a long time in getting a better bulk description. And I think that might be because the answer is of a different kind than anything we’re used to. That would be my guess.

Are you willing to speculate about how it would be different?

I really doubt I can say anything useful. I guess I suspect that there’s an extra layer of abstractness compared to what we’re used to. I tend to think that there isn’t a precise quantum description of space-time — except in the types of situations where we know that there is, such as in AdS space. I tend to think, otherwise, things are a little bit murkier than an exact quantum description. But I can’t say anything useful.

The other night I was reading an old essay by the 20th-century Princeton physicist John Wheeler. He was a visionary, certainly. If you take what he says literally, it’s hopelessly vague. And therefore, if I had read this essay when it came out 30 years ago, which I may have done, I would have rejected it as being so vague that you couldn’t work on it, even if he was on the right track.

You’re referring to Information, Physics, Quantum, Wheeler’s 1989 essay propounding the idea that the physical universe arises from information, which he dubbed “it from bit.” Why were you reading it?

I’m trying to learn about what people are trying to say with the phrase “it from qubit.” Wheeler talked about “it from bit,” but you have to remember that this essay was written probably before the term “qubit” was coined and certainly before it was in wide currency. Reading it, I really think he was talking about qubits, not bits, so “it from qubit” is actually just a modern translation.

I tend to assume that space-time and everything in it are in some sense emergent.

Don’t expect me to be able to tell you anything useful about it — about whether he was right. When I was a beginning grad student, they had a series of lectures by faculty members to the new students about theoretical research, and one of the people who gave such a lecture was Wheeler. He drew a picture on the blackboard of the universe visualized as an eye looking at itself. I had no idea what he was talking about. It’s obvious to me in hindsight that he was explaining what it meant to talk about quantum mechanics when the observer is part of the quantum system. I imagine there is something we don’t understand about that.

Observing a quantum system irreversibly changes it, creating a distinction between past and future. So the observer issue seems possibly related to the question of time, which we also don’t understand. With the AdS/CFT duality, we’ve learned that new spatial dimensions can pop up like a hologram from quantum information on the boundary. Do you think time is also emergent — that it arises from a timeless complete description?

I tend to assume that space-time and everything in it are in some sense emergent. By the way, you’ll certainly find that that’s what Wheeler expected in his essay. As you’ll read, he thought the continuum was wrong in both physics and math. He did not think one’s microscopic description of space-time should use a continuum of any kind — neither a continuum of space nor a continuum of time, nor even a continuum of real numbers. On the space and time, I’m sympathetic to that. On the real numbers, I’ve got to plead ignorance or agnosticism. It is something I wonder about, but I’ve tried to imagine what it could mean to not use the continuum of real numbers, and the one logician I tried discussing it with didn’t help me.

Do you consider Wheeler a hero?

I wouldn’t call him a hero, necessarily, no. Really I just became curious what he meant by “it from bit,” and what he was saying. He definitely had visionary ideas, but they were too far ahead of their time. I think I was more patient in reading a vague but inspirational essay than I might have been 20 years ago. He’s also got roughly 100 interesting-sounding references in that essay. If you decided to read them all, you’d have to spend weeks doing it. I might decide to look at a few of them.

Why do you have more patience for such things now?

I think when I was younger I always thought the next thing I did might be the best thing in my life. But at this point in life I’m less persuaded of that. If I waste a little time reading somebody’s essay, it doesn’t seem that bad.

Do you ever take your mind off physics and math?

My favorite pastime is tennis. I am a very average but enthusiastic tennis player.

In contrast to Wheeler, it seems like your working style is to come to the insights through the calculations, rather than chasing a vague vision.

In my career I’ve only been able to take small jumps. Relatively small jumps. What Wheeler was talking about was an enormous jump. And he does say at the beginning of the essay that he has no idea if this will take 10, 100 or 1,000 years.

And he was talking about explaining how physics arises from information.

Yes. The way he phrases it is broader: He wants to explain the meaning of existence. That was actually why I thought you were asking if I wanted to explain the meaning of existence.

I see. Does he have any hypotheses?

No. He only talks about things you shouldn’t do and things you should do in trying to arrive at a more fundamental description of physics.

Do you have any ideas about the meaning of existence?

No. [Laughs.]

Correction: This article was updated on Nov. 29, 2017, to clarify that M-theory is the leading candidate for a unified theory of everything. Other ideas have been proposed that also claim to unify the fundamental forces.

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SOURCE: Quanta Magazine

Jean Sweep for Quanta Magazine

2017-10-11T13:02:00.000-07:00

Climate meetings pose serious test in the Trump era

Annual jamborees fail to ignite public passion but are crucial to progress on global-warming.

NATURE | EDITORIAL

10 October 2017

Rights & Permissions

Adrien Morlent/AFP Photo/Getty

In the aftermath of the successful 2015 Paris climate conference, the public remained unengaged.

Climate change is a popular topic in Germany right now. Leading researchers are converging in Potsdam this week to take stock of the economic and societal impacts of global warming across sectors from health to agriculture. In Berlin, experts are meeting to discuss the potential and risks of various geoengineering technologies intended to counteract the effects of climate change. And next month, at the climax of the climate-meeting season, thousands of delegates will flock to the United Nation’s annual climate summit, this year in Bonn.

The Paris accord, although based on merely voluntary national contributions, was undoubtedly a rare triumph for international climate diplomacy. It was the most that was possible and the least that was needed. Alas, the excitement did not last long. The subsequent U-turn of the United States — President Donald Trump has resolved to leave the deal, deeming it half-baked, essentially unnecessary and intolerably unfair to the US economy — has dampened spirits. Even so, the rest of the world has pledged to stand firm. The first conference of the parties to the agreement in the Trump era must now work out how to proceed without the world’s largest economy.

In theory, the annual climate roller coaster is idling through one of the low-key phases in which success is measured by nothing going wrong. In practice, the Bonn meeting will serve as a litmus test of how the rest of the world plans to stand united and to keep the spirit of Paris alive.At the UN meeting, governments will discuss the next steps in implementing the global climate agreement that they reached in Paris almost two years ago. The landmark deal, which came into force last November, aims to limit global warming to 1.5 °C above pre-industrial temperatures. To achieve this ambitious (many say unrealistic) goal, the world’s major economies might need to phase out emissions of heat-trapping greenhouse gases entirely within a few decades.

Keynote speakers in Bonn (and presenters in Berlin and Potsdam) will no doubt reiterate the severity of the global-warming threat and the urgent need to act. Major meetings often galvanize debate among researchers, pundits and policy watchers. But beyond this predictable fuss in the expert world, do high-level climate meetings and policy events, and the media coverage they bring, help push the wider public to engage with the climate problem?

“Climate change remains marginal to most people’s personal and political choices.”

Not quite, it seems. Results of a survey of the German public, published this week in Nature Climate Change, suggest that extensive media coverage of the Paris climate summit had a soothing rather than a mobilizing effect (M. Brüggemann et al. Nature Clim. Change http://dx.doi.org/10.1038/nclimate3409; 2017).

Respondents who had taken notice of media reports (and many said they had not) had slightly more trust in the efficacy of global climate policy after the unusually successful meeting. However, fewer were in favour of their own country taking a leading role, and most said that they did not intend to change their behaviour. In essence, respondents were relieved that a political deal had finally materialized, but were disinclined to engage further with the issue.

The researchers who conducted the survey say that this is a missed opportunity. The annual UN meetings bring guaranteed media attention to a topic that many news editors are bored with, and so they are an opportunity to mobilize action. As such, the study authors go so far as to suggest that the lack of public engagement is a failure of journalism.

It might indeed seem worrying that despite the avalanche of information, climate change remains marginal to most people’s personal and political choices — Germany’s strong green movement notwithstanding. It might even seem like a bad case of civil indifference. Does it matter? There is an argument that climate action does not have to depend on media-stirred engagement from agitated citizens. People often choose to leave responsible decision-makers to deal with complex global problems that only concerted international effort can hope to solve, and this has brought progress on issues such as nuclear non-proliferation and the phase-out of ozone-depleting chemicals.

But climate change is a more complex issue, and one that cuts across many overlapping and sometimes contradictory concerns, from cultural and political issues to ethical and psychological ones. As such, organizations, businesses, scientists, policymakers and others who advocate action on global warming must continue to strive to take the public with them. As many experts have pointed out, that will take creativity and more than repeated references to the serious nature of the problem — in Bonn and elsewhere.

SOURCE: Nature 550, 158 (12 October 2017) , doi:10.1038/550158a

INFINITY

2017-09-15T14:22:00.000-07:00

Mathematicians Measure Infinities and Find They’re Equal

Two mathematicians have proved that two different infinities are equal in size, settling a long-standing question. Their proof rests on a surprising link between the sizes of infinities and the complexity of mathematical theories.

Continuum HypothesisInfinityMathematical LogicMathematicsModel TheorySet Theory

In a breakthrough that disproves decades of conventional wisdom, two mathematicians have shown that two different variants of infinity are actually the same size. The advance touches on one of the most famous and intractable problems in mathematics: whether there exist infinities between the infinite size of the natural numbers and the larger infinite size of the real numbers.

The problem was first identified over a century ago. At the time, mathematicians knew that “the real numbers are bigger than the natural numbers, but not how much bigger. Is it the next biggest size, or is there a size in between?” said Maryanthe Malliaris of the University of Chicago, co-author of the new work along with Saharon Shelah of the Hebrew University of Jerusalem and Rutgers University.

In their new work, Malliaris and Shelah resolve a related 70-year-old question about whether one infinity (call it p) is smaller than another infinity (call it t). They proved the two are in fact equal, much to the surprise of mathematicians.

“It was certainly my opinion, and the general opinion, that p should be less than t,” Shelah said.

Malliaris and Shelah published their proof last year in the Journal of the American Mathematical Society and were honored this past Julywith one of the top prizes in the field of set theory. But their work has ramifications far beyond the specific question of how those two infinities are related. It opens an unexpected link between the sizes of infinite sets and a parallel effort to map the complexity of mathematical theories.

Many Infinities

The notion of infinity is mind-bending. But the idea that there can be different sizes of infinity? That’s perhaps the most counterintuitive mathematical discovery ever made. It emerges, however, from a matching game even kids could understand.

Suppose you have two groups of objects, or two “sets,” as mathematicians would call them: a set of cars and a set of drivers. If there is exactly one driver for each car, with no empty cars and no drivers left behind, then you know that the number of cars equals the number of drivers (even if you don’t know what that number is).

In the late 19th century, the German mathematician Georg Cantor captured the spirit of this matching strategy in the formal language of mathematics. He proved that two sets have the same size, or “cardinality,” when they can be put into one-to-one correspondence with each other — when there is exactly one driver for every car. Perhaps more surprisingly, he showed that this approach works for infinitely large sets as well.

Consider the natural numbers: 1, 2, 3 and so on. The set of natural numbers is infinite. But what about the set of just the even numbers, or just the prime numbers? Each of these sets would at first seem to be a smaller subset of the natural numbers. And indeed, over any finite stretch of the number line, there are about half as many even numbers as natural numbers, and still fewer primes.

Yet infinite sets behave differently. Cantor showed that there’s a one-to-one correspondence between the elements of each of these infinite sets.

1	2	3	4	5	…	(natural numbers)
2	4	6	8	10	…	(evens)
2	3	5	7	11	…	(primes)

Because of this, Cantor concluded that all three sets are the same size. Mathematicians call sets of this size “countable,” because you can assign one counting number to each element in each set.

After he established that the sizes of infinite sets can be compared by putting them into one-to-one correspondence with each other, Cantor made an even bigger leap: He proved that some infinite sets are even larger than the set of natural numbers.

Consider the real numbers, which are all the points on the number line. The real numbers are sometimes referred to as the “continuum,” reflecting their continuous nature: There’s no space between one real number and the next. Cantor was able to show that the real numbers can’t be put into a one-to-one correspondence with the natural numbers: Even after you create an infinite list pairing natural numbers with real numbers, it’s always possible to come up with another real number that’s not on your list. Because of this, he concluded that the set of real numbers is larger than the set of natural numbers. Thus, a second kind of infinity was born: the uncountably infinite.

What Cantor couldn’t figure out was whether there exists an intermediate size of infinity — something between the size of the countable natural numbers and the uncountable real numbers. He guessed not, a conjecture now known as the continuum hypothesis.

In 1900, the German mathematician David Hilbert made a list of 23 of the most important problems in mathematics. He put the continuum hypothesis at the top. “It seemed like an obviously urgent question to answer,” Malliaris said.

In the century since, the question has proved itself to be almost uniquely resistant to mathematicians’ best efforts. Do in-between infinities exist? We may never know.

Forced Out

Throughout the first half of the 20th century, mathematicians tried to resolve the continuum hypothesis by studying various infinite sets that appeared in many areas of mathematics. They hoped that by comparing these infinities, they might start to understand the possibly non-empty space between the size of the natural numbers and the size of the real numbers.

Many of the comparisons proved to be hard to draw. In the 1960s, the mathematician Paul Cohen explained why. Cohen developed a method called “forcing” that demonstrated that the continuum hypothesis is independent of the axioms of mathematics — that is, it couldn’t be proved within the framework of set theory. (Cohen’s work complemented work by Kurt Gödel in 1940 that showed that the continuum hypothesis couldn’t be disproved within the usual axioms of mathematics.)

Cohen’s work won him the Fields Medal (one of math’s highest honors) in 1966. Mathematicians subsequently used forcing to resolve many of the comparisons between infinities that had been posed over the previous half-century, showing that these too could not be answered within the framework of set theory. (Specifically, Zermelo-Fraenkel set theory plus the axiom of choice.)

Some problems remained, though, including a question from the 1940s about whether p is equal to t. Both p and t are orders of infinity that quantify the minimum size of collections of subsets of the natural numbers in precise (and seemingly unique) ways.

Briefly, p is the minimum size of a collection of infinite sets of the natural numbers that have a “strong finite intersection property” and no “pseudointersection,” which means the subsets overlap each other in a particular way; t is called the “tower number” and is the minimum size of a collection of subsets of the natural numbers that is ordered in a way called “reverse almost inclusion” and has no pseudointersection.

The details of the two sizes don’t much matter. What’s more important is that mathematicians quickly figured out two things about the sizes of p and t. First, both sets are larger than the natural numbers. Second, p is always less than or equal to t. Therefore, if p is less than t, then p would be an intermediate infinity — something between the size of the natural numbers and the size of the real numbers. The continuum hypothesis would be false.

Mathematicians tended to assume that the relationship between p and t couldn’t be proved within the framework of set theory, but they couldn’t establish the independence of the problem either. The relationship between p and t remained in this undetermined state for decades. When Malliaris and Shelah found a way to solve it, it was only because they were looking for something else.

An Order of Complexity

Around the same time that Paul Cohen was forcing the continuum hypothesis beyond the reach of mathematics, a very different line of work was getting under way in the field of model theory.

H. Jerome Keisler invented “Keisler’s order.”

Courtesy of H. Jerome Keisler

For a model theorist, a “theory” is the set of axioms, or rules, that define an area of mathematics. You can think of model theory as a way to classify mathematical theories — an exploration of the source code of mathematics. “I think the reason people are interested in classifying theories is they want to understand what is really causing certain things to happen in very different areas of mathematics,” said H. Jerome Keisler, emeritus professor of mathematics at the University of Wisconsin, Madison.

In 1967, Keisler introduced what’s now called Keisler’s order, which seeks to classify mathematical theories on the basis of their complexity. He proposed a technique for measuring complexity and managed to prove that mathematical theories can be sorted into at least two classes: those that are minimally complex and those that are maximally complex. “It was a small starting point, but my feeling at that point was there would be infinitely many classes,” Keisler said.

It isn’t always obvious what it means for a theory to be complex. Much work in the field is motivated in part by a desire to understand that question. Keisler describes complexity as the range of things that can happen in a theory — and theories where more things can happen are more complex than theories where fewer things can happen.

A little more than a decade after Keisler introduced his order, Shelah published an influential book, which included an important chapter showing that there are naturally occurring jumps in complexity — dividing lines that distinguish more complex theories from less complex ones. After that, little progress was made on Keisler’s order for 30 years.

Saharon Shelah is a co-author of the new proof.

Yael Shelah

Then, in her 2009 doctoral thesis and other early papers, Malliaris reopened the work on Keisler’s order and provided new evidence for its power as a classification program. In 2011, she and Shelah started working together to better understand the structure of the order. One of their goals was to identify more of the properties that make a theory maximally complex according to Keisler’s criterion.

Malliaris and Shelah eyed two properties in particular. They already knew that the first one causes maximal complexity. They wanted to know whether the second one did as well. As their work progressed, they realized that this question was parallel to the question of whether p and t are equal. In 2016, Malliaris and Shelah published a 60-page paper that solved both problems: They proved that the two properties are equally complex (they both cause maximal complexity), and they proved that p equals t.

“Somehow everything lined up,” Malliaris said. “It’s a constellation of things that got solved.”

This past July, Malliaris and Shelah were awarded the Hausdorff medal, one of the top prizes in set theory. The honor reflects the surprising, and surprisingly powerful, nature of their proof. Most mathematicians had expected that p was less than t, and that a proof of that inequality would be impossible within the framework of set theory. Malliaris and Shelah proved that the two infinities are equal. Their work also revealed that the relationship between p and t has much more depth to it than mathematicians had realized.

“I think people thought that if by chance the two cardinals were provably equal, the proof would maybe be surprising, but it would be some short, clever argument that doesn’t involve building any real machinery,” said Justin Moore, a mathematician at Cornell University who has published a brief overview of Malliaris and Shelah’s proof.

1. Instead, Malliaris and Shelah proved that p and t are equal by cutting a path between model theory and set theory that is already opening new frontiers of research in both fields. Their work also finally puts to rest a problem that mathematicians had hoped would help settle the continuum hypothesis. Still, the overwhelming feeling among experts is that this apparently unresolvable proposition is false: While infinity is strange in many ways, it would be almost too strange if there weren’t many more sizes of it than the ones we’ve already found.

------------------------------------------------------------------------------------

1 To Settle Infinity Dispute, a New Law of Logic

2. Is Infinity Real?

3. Mathematicians Bridge Finite-Infinite Divide

Clarification: On September 12, this article was revised to clarify that mathematicians in the first half of the 20th century wondered if the continuum hypothesis was true. As the article states, the question was largely put to rest with the work of Paul Cohen.

SOURCE: https://www.quantamagazine.org/mathematicians-measure-infinities-find-theyre-equal-20170912/?utm_source=Quanta+Magazine&utm_campaign=aeff1d0f67-EMAIL_CAMPAIGN_2017_09_14&utm_medium=email&utm_term=0_f0cb61321c-aeff1d0f67-389390733

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2017-09-09T13:41:00.000-07:00

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By NATALIE WOLCHOVER

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How Neanderthals Gave Us Secret Power

2017-08-28T13:50:00.000-07:00

Interbreeding with our fellow hominins appears to have helped humans survive harsh climates.

· MAY 31, 2016

Native Tibetans make use of a gene derived from Denisovans to stay healthy at high altitudes.

By EMILY SINGER

TEXT SIZE

Early human history was a promiscuous affair. As modern humans began to spread out of Africa roughly 50,000 years ago, they encountered other species that looked remarkably like them—the Neanderthals and Denisovans, two groups of archaic humans that shared an ancestor with us roughly 600,000 years earlier. This motley mix of humans coexisted in Europe for at least 2,500 years, and we now know that they interbred, leaving a lasting legacy in our DNA.

The DNA of non-Africans is made up of roughly 1 to 2 percent Neanderthal DNA, and some Asian and Oceanic island populations have as much as 6 percent Denisovan DNA.

Over the last few years, scientists have dug deeper into the Neanderthal and Denisovan sections of our genomes and come to a surprising conclusion. Certain Neanderthal and Denisovan genes seem to have swept through the modern human population—one variant, for example, is present in 70 percent of Europeans—suggesting that these genes brought great advantage to their bearers and spread rapidly.

“In some spots of our genome, we are more Neanderthal than human,” said Joshua Akey, a geneticist at the University of Washington. “It seems pretty clear that at least some of the sequences we inherited from archaic hominins were adaptive, that they helped us survive and reproduce.”

But what, exactly, do these fragments of Neanderthal and Denisovan DNA do? What survival advantage did they confer on our ancestors? Scientists are starting to pick up hints. Some of these genes are tied to our immune system, to our skin and hair, and perhaps to our metabolism and tolerance for cold weather, all of which might have helped emigrating humans survive in new lands.

“What allowed us to survive came from other species,” said Rasmus Nielsen, an evolutionary biologist at the University of California, Berkeley. “It’s not just noise, it’s a very important substantial part of who we are.

Illustration by Lucy Reading-Ikkanda for Quanta Magazine, based on a map by Sriram Sankararaman.

* * *

The Tibetan plateau is a vast stretch of high-altitude real estate isolated by massive mountain ranges. The scant oxygen at 14,000 feet—roughly 40 percent lower than the concentrations at sea level—makes it a harsh environment. People who move there suffer higher rates of miscarriage, blood clots, and stroke on account of the extra red blood cells their bodies produce to feed oxygen-starved tissue.

Native Tibetans, however, manage just fine. Despite the meager air, they don’t make as many red blood cells as the rest of us would at those altitudes, which helps to protect their health.

In 2010, scientists discovered that Tibetans owe their tolerance of low oxygen levels in part to an unusual variant in a gene known as EPAS1. About 90 percent of the Tibetan population and a smattering of Han Chinese (who share a recent ancestor with Tibetans) carry the high-altitude variant. But it’s completely absent from a database of 1,000 human genomes from other populations.

The unique gene then flourished in those who lived at high altitudes and faded away in descendants who colonized less harsh environments.

In 2014, Nielsen and colleagues found that Tibetans or their ancestors likely acquired the unusual DNA sequence from Denisovans, a group of early humans first described in 2010 that are more closely related to Neanderthals than to us.

The unique gene then flourished in those who lived at high altitudes and faded away in descendants who colonized less harsh environments. “That’s one of the most clear-cut examples of how [interbreeding] can lead to adaptation,” said Sriram Sankararaman, a geneticist and computer scientist at the University of California, Los Angeles.

The idea that closely related species can benefit from interbreeding, known in evolutionary terms as adaptive introgression, is not a new one. As a species expands into a new territory, it grapples with a whole new set of challenges—different climate, food, predators, and pathogens.

Species can adapt through traditional natural selection, in which spontaneous mutations that happen to be helpful gradually spread through the population. But such mutations strike rarely, making it a very slow process. A more expedient option is to mate with species that have already adapted to the region and co-opt some of their helpful DNA. (Species are traditionally defined by their inability to mate with one another, but closely related species often interbreed.)

This phenomenon has been well documented in a number of species, including mice that adopted other species’ tolerance to pesticides and butterflies that appropriated other species’ wing patterning. But it was difficult to study adaptive introgression in humans until the first Neanderthal genome was sequenced in 2010, providing scientists with hominin DNA to compare to our own.

Neanderthals and Denisovans would have been a good source of helpful DNA for our ancestors. They had lived in Europe and Asia for hundreds of thousands of years—enough time to adjust to the cold climate, weak sun and local microbes. “What better way to quickly adapt than to pick up a gene variant from a population that had probably already been there for 300,000 years?” Akey said.

Indeed, the Neanderthal and Denisovan genes with the greatest signs of selection in the modern human genome “largely have to do with how humans interact with the environment,” he said.

Illustration by Lucy Reading-Ikkanda for Quanta Magazine, based on a map by Sriram Sankararaman.

To find these adaptive segments, scientists search the genomes of contemporary humans for regions of archaic DNA that are either more common or longer than expected. Over time, useless pieces of Neanderthal DNA—those that don’t help the carrier—are likely to be lost. And long sections of archaic DNA are likely to be split into smaller segments unless there is selective pressure to keep them intact.

In 2014, two groups, one led by Akey and the other by David Reich, a geneticist at Harvard Medical School, independently published genetic maps that charted where in our genomes Neanderthal DNA is most likely to be found. To Akey’s surprise, both maps found that the most common adaptive Neanderthal-derived genes are those linked to skin and hair growth. One of the most striking examples is a gene called BNC2, which is linked to skin pigmentation and freckling in Europeans.

Nearly 70 percent of Europeans carry the Neanderthal version.

Scientists surmise that BNC2 and other skin genes helped modern humans adapt to northern climates, but it’s not clear exactly how. Skin can have many functions, any one of which might have been helpful. “Maybe skin pigmentation, or wound healing, or pathogen defense, or how much water loss you have in an environment, making you more or less susceptible to dehydration,” Akey said. “So many potential things could be driving this—we don’t know what differences were most important.”

* * *

One of the deadliest foes that modern humans had to fight as they ventured into new territories was also the smallest—novel infectious diseases for which they had no immunity. “Pathogens are one of the strongest selective forces out there,” said Janet Kelso, a bioinformatician at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

Earlier this year, Kelso and collaborators identified a large stretch of Neanderthal DNA—143,000 DNA base-pairs long—that may have played a key role in helping modern humans fight off disease. The region spans three different genes that are part of the innate immune system, a molecular surveillance system that forms the first line of defense against pathogens. These genes produce proteins called toll-like receptors, which help immune cells detect foreign invaders and trigger the immune system to attack.

Modern humans can have several different versions of this stretch of DNA. But at least three of the variants appear to have come from archaic humans—two from Neanderthals and one from Denisovans.

To figure out what those variants do, Kelso’s team scoured public databases housing reams of genomic and health data. They found that people carrying one of the Neanderthal variants are less likely to be infected with H. pylori, a microbe that causes ulcers, but more likely to suffer from common allergies such as hay fever.

Kelso speculates that this variant might have boosted early humans’ resistance to different kinds of bacteria. That would have helped modern humans as they colonized new territories. Yet this added resistance came at a price. “The trade-off for that was a more sensitive immune system that was more sensitive to nonpathogenic allergens,” said Kelso.

But she was careful to point out that this is just a theory. “At this point, we can hypothesize a lot, but we don’t know exactly how this is working.”

Most of the Neanderthal and Denisovan genes found in the modern genome are more mysterious. Scientists have only a vague idea of what these genes do, let alone how the Neanderthal or Denisovan version might have helped our ancestors. “It’s important to understand the biology of these genes better, to understand what selective pressures were driving the changes we see in present-day populations,” Akey said.

A number of studies like Kelso’s are now under way, trying to link Neanderthal and Denisovan variants frequently found in contemporary humans with specific traits, such as body-fat distribution, metabolism or other factors.

One study of roughly 28,000 people of European descent, published in Science in February, matched archaic gene variants with data from electronic health records. Overall, Neanderthal variants are linked to higher risk of neurological and psychiatric disorders and lower risk of digestive problems. (That study didn’t focus on adaptive DNA, so it’s unclear how the segments of archaic DNA that show signs of selection affect us today.)

At present, much of the data available for such studies is weighted toward medical problems—most of these databases were designed to find genes linked to diseases such as diabetes or schizophrenia. But a few, such as the U.K. Biobank, are much broader, storing information on participants’ vision, cognitive test scores, mental health assessments, lung capacity and fitness.

Direct-to-consumer genetics companies also have large, diverse data sets. For example, 23andMe analyzes users’ genetics for clues about ancestry, health risk and other sometimes bizarre traits, such as whether they have a sweet tooth or a unibrow.

Of course, not all the DNA we got from Neanderthals and Denisovans was good. The majority was probably detrimental. Indeed, we tend to have less Neanderthal DNA near genes, suggesting that it was weeded out by natural selection over time. Researchers are very interested in these parts of our genomes where archaic DNA is conspicuously absent.

“There are some really big places in the genome with no Neanderthal or Denisovan ancestry as far as we can see—some process is purging the archaic material from these regions,” Sankararaman said. “Perhaps they are functionally important for modern humans.”

SOURCE: https://www.quantamagazine.org/how-neanderthal-dna-helps-humanity-20160526/?utm_source=Quanta+Magazine&utm_campaign=510f4dd932-EMAIL_CAMPAIGN_2017_08_24&utm_medium=email&utm_term=0_f0cb61321c-510f4dd932-389390733

SCIENTIFIC AMERICAN REVIEW STATES.......

2017-08-19T09:53:00.000-07:00

White Nationalists Are Flocking to Genetic Ancestry Tests--with Surprising Results

Sometimes they find they are not as “white” as they’d hoped

By Eric Boodman, STAT on August 16, 2017

Credit: Andrew Brookes Getty Images

It was a strange moment of triumph against racism: The gun-slinging white supremacist Craig Cobb, dressed up for daytime TV in a dark suit and red tie, hearing that his DNA testing revealed his ancestry to be only “86 percent European, and … 14 percent Sub-Saharan African.” The studio audience whooped and laughed and cheered. And Cobb—who was, in 2013, charged with terrorizing people while trying to create an all-white enclave in North Dakota—reacted like a sore loser in the schoolyard.

“Wait a minute, wait a minute, hold on, just wait a minute,” he said, trying to put on an all-knowing smile. “This is called statistical noise.”

Then, according to the Southern Poverty Law Center, he took to the white nationalist website Stormfront to dispute those results. That’s not uncommon: With the rise of spit-in-a-cup genetic testing, there’s a trend of white nationalists using these services to prove their racial identity, and then using online forums to discuss the results.

But like Cobb, many are disappointed to find out that their ancestry is not as “white” as they’d hoped. In a new study, sociologists Aaron Panofsky and Joan Donovan examined years’ worth of posts on Stormfront to see how members dealt with the news.

It’s striking, they say, that white nationalists would post these results online at all. After all, as Panofsky put it, “they will basically say if you want to be a member of Stormfront you have to be 100 percent white European, not Jewish.”

But instead of rejecting members who get contrary results, Donovan said, the conversations are “overwhelmingly” focused on helping the person to rethink the validity of the genetic test. And some of those critiques—while emerging from deep-seated racism—are close to scientists’ own qualms about commercial genetic ancestry testing.

Panofsky and Donovan presented their findings at a sociology conference in Montreal on Monday. The timing of the talk—some 48 hours after the violent white nationalist rally in Charlottesville, Va.—was coincidental. But the analysis provides a useful, if frightening, window into how these extremist groups think about their genes.

RECKONING WITH RESULTS

Stormfront was launched in the mid-1990s by Don Black, a former grand wizard of the Ku Klux Klan. His skills in computer programming were directly related to his criminal activities: He learned them while in prison for trying to invade the Caribbean island nation of Dominica in 1981, and then worked as a web developer after he got out. That means this website dates back to the early years of the internet, forming a kind of deep archive of online hate.

To find relevant comments in the 12 million posts written by over 300,000 members, the authors enlisted a team at the University of California, Los Angeles, to search for terms like “DNA test,” “haplotype,” “23andMe,” and “National Geographic.” Then the researchers combed through the posts they found, not to mention many others as background. Donovan, who has moved from UCLA to the Data & Society Research Institute, estimated that she spent some four hours a day reading Stormfront in 2016. The team winnowed their results down to 70 discussion threads in which 153 users posted their genetic ancestry test results, with over 3,000 individual posts.

About a third of the people posting their results were pleased with what they found. “Pretty damn pure blood,” said a user with the username Sloth. But the majority didn’t find themselves in that situation. Instead, the community often helped them reject the test, or argue with its results.

Some rejected the tests entirely, saying that an individual’s knowledge about his or her own genealogy is better than whatever a genetic test can reveal. “They will talk about the mirror test,” said Panofsky, who is a sociologist of science at UCLA’s Institute for Society and Genetics. “They will say things like, ‘If you see a Jew in the mirror looking back at you, that’s a problem; if you don’t, you’re fine.'” Others, he said, responded to unwanted genetic results by saying that those kinds of tests don’t matter if you are truly committed to being a white nationalist. Yet others tried to discredit the genetic tests as a Jewish conspiracy “that is trying to confuse true white Americans about their ancestry,” Panofsky said.

But some took a more scientific angle in their critiques, calling into doubt the method by which these companies determine ancestry—specifically how companies pick those people whose genetic material will be considered the reference for a particular geographical group.

And that criticism, though motivated by very different ideas, is one that some researchers have made as well, even as other scientists have used similar data to better understand how populations move and change.

“There is a mainstream critical literature on genetic ancestry tests—geneticists and anthropologists and sociologists who have said precisely those things: that these tests give an illusion of certainty, but once you know how the sausage is made, you should be much more cautious about these results,” said Panofsky.

A COMMUNITY’S GENETIC RULES

Companies like Ancestry.com and 23andMe are meticulous in how they analyze your genetic material. As points of comparison, they use both preexisting datasets as well as some reference populations that they have recruited themselves. The protocol includes genetic material from thousands of individuals, and looks at thousands of genetic variations.

“When a 23andMe research participant tells us that they have four grandparents all born in the same country—and the country isn’t a colonial nation like the U.S., Canada, or Australia—that person becomes a candidate for inclusion in the reference data,” explained Jhulianna Cintron, a product specialist at 23andMe. Then, she went on, the company excludes close relatives, as that could distort the data, and removes outliers whose genetic data don’t seem to match with what they wrote on their survey.

But specialists both inside and outside these companies recognize that the geopolitical boundaries we use now are pretty new, and so consumers may be using imprecise categories when thinking about their own genetic ancestry within the sweeping history of human migration. And users’ ancestry results can change depending on the dataset to which their genetic material is being compared—a fact which some Stormfront users said they took advantage of, uploading their data to various sites to get a more “white” result.

J. Scott Roberts, an associate professor at the University of Michigan, who has studied consumer use of genetic tests and was not involved with the study, said the companies tend to be reliable at identifying genetic variants. Interpreting them in terms of health risk or ancestry, though, is another story. “The science is often murky in those areas and gives ambiguous information,” he said. “They try to give specific percentages from this region, or x percent disease risk, and my sense is that that is an artificially precise estimate.”

For the study authors, what was most interesting was to watch this online community negotiating its own boundaries, rethinking who counts as “white.” That involved plenty of contradictions. They saw people excluded for their genetic test results, often in very nasty (and unquotable) ways, but that tended to happen for newer members of the anonymous online community, Panofsky said, and not so much for longtime, trusted members. Others were told that they could remain part of white nationalist groups, in spite of the ancestry they revealed, as long as they didn’t “mate,” or only had children with certain ethnic groups. Still others used these test results to put forth a twisted notion of diversity, one “that allows them to say, ‘No, we’re really diverse and we don’t need non-white people to have a diverse society,'” said Panofsky.

That’s a far cry from the message of reconciliation that genetic ancestry testing companies hope to promote.

“Sweetheart, you have a little black in you,” the talk show host Trisha Goddard told Craig Cobb on that day in 2013. But that didn’t stop him from redoing the test with a different company, trying to alter or parse the data until it matched his racist worldview.

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2017-08-13T09:55:00.001-07:00

How Humans Evolved Supersize Brains

Scientists have begun to identify the symphony of biological triggers that powered the extraordinary expansion of the human brain.

Ferris Jabr , Contributing Writer , November 10, 2015

There it was, sitting on the mantelpiece, staring at her with hollow eyes and a naked grin. She could not stop staring back. It looked distinctly like the fossilized skull of an extinct baboon. That was the sort of thing Josephine Salmons was likely to know. At the time — 1924 — she was one of the only female students of anatomy attending the University of the Witwatersrand in South Africa. On this particular day she was visiting her friend Pat Izod, whose father managed a quarry company that had been excavating limestone near the town of Taung. Workers had unearthed numerous fossils during the excavation, and the Izods had kept this one as a memento. Salmons brought news of the skull to her professor, Raymond Dart, an anthropologist with a particular interest in the brain. He was incredulous. Very few primate fossils had been uncovered this far south in Africa. If the Taung site really housed such fossils, it would be an invaluable treasure trove. The next morning Salmons brought Dart the skull, and he could see that she was right: The skull was undeniably simian/

Dart promptly arranged to have other primate fossils from the Taung quarry sent to him. Later that year, as he was preparing to attend a close friend’s wedding, he received a large crate. One of the specimens it contained was so mesmerizing that he nearly missed the ceremony. It came in two pieces: a natural endocast — the fossilized mold of the inner cranium, preserving the brain’s topography — and its matching skeletal face, with eye sockets, nose, jaw and teeth all intact. Dart noticed right away that this was the fossil of an extinct ape, not a monkey. The teeth suggested that the individual had died at age 6 or so. The point where the spinal cord had joined the skull was too far forward for a knuckle walker, indicating bipedalism. And the endocast, which was a little too large for a nonhuman ape of that age, had surface features characteristic of a human brain. After further study, Dart reached a bold conclusion: this was the fossil of a previously unknown ancestor of modern humans — Australopithecus africanus, the “Man-Ape of South Africa.”

Raymond Dart with the Taung child.

New York Public Library / Science Source

At first, the greater scientific community lambasted Dart’s proposal. If the Taung child, as the fossil was nicknamed, truly belonged to a hominin, surely it would have a far larger brain. Its cranium was a bit bigger than that of a chimpanzee, but not by much. Besides, it was generally believed that humans had evolved in Asia, not Africa. The “absurdly tiny” illustration accompanying Dart’s 1925 Nature paper, and his initial possessiveness of the specimen, did not help matters. Eventually, though, as prominent experts got to see the Taung child for themselves, and similar fossil discoveries came to light, attitudes began to change. By the 1950s, anthropologists had accepted that Taung was indeed a hominin and that an exceptionally large brain had not always been a distinguishing characteristic of humans. Dean Falk, a professor of anthropology at Florida State University and an expert on brain evolution, has called the Taung child “one of the most (if not the most) important hominin discoveries of the 20th century.”

In subsequent decades, by uncovering and comparing other fossil skulls and endocasts, paleontologists documented one of the most dramatic transitions in human evolution. We might call it the Brain Boom. Humans, chimps and bonobos split from their last common ancestor between 6 and 8 million years ago. For the next few million years, the brains of early hominins did not grow much larger than those of our ape ancestors and cousins. Starting around 3 million years ago, however, the hominin brain began a massive expansion. By the time our species, Homo sapiens, emerged about 200,000 years ago, the human brain had swelled from about 350 grams to more than 1,300 grams. In that 3-million-year sprint, the human brain almost quadrupled the size its predecessors had attained over the previous 60 million years of primate evolution.

Fossils established the Brain Boom as fact. But they tell us next to nothing about how and why the human brain grew so large so quickly. There are plenty of theories, of course, especially regarding why: increasingly complex social networks, a culture built around tool use and collaboration, the challenge of adapting to a mercurial and often harsh climate — any or all of these evolutionary pressures could have selected for bigger brains.

Although these possibilities are fascinating, they are extremely difficult to test. In the last eight years, however, scientists have started to answer the “how” of human brain expansion — that is, the question of how the supersizing happened on a cellular level and how human physiology reconfigured itself to accommodate a dramatically enlarged and energy-guzzling brain. “It was all speculation up until now, but we finally have the tools to really get some traction,” said Gregory Wray, an evolutionary biologist at Duke University. “What kinds of mutations occurred, and what did they do? We’re starting to get answers and a deeper appreciation for just how complicated this process was.”

What Makes the Human Brain Special

One scientist, in particular, has transformed the way researchers size up brains. Rather than fixating on mass or volume as a proxy for brainpower, she has focused on counting a brain’s constituent parts.

In her laboratory at the Institute of Biomedical Sciences at the Federal University of Rio de Janeiro, Suzana Herculano-Houzelroutinely dissolves brains into a soup of nuclei — cells’ genetic control rooms. Each neuron has one nucleus. By tagging the nuclei with fluorescent molecules and measuring the glow, she can get a precise tally of individual brain cells. Using this method on a wide variety of mammalian brains, she has shown that, contrary to long-standing assumptions, larger mammalian brains do not always have more neurons, and the ones they do have are not always distributed in the same way.

When it comes to brains, size isn’t everything. The human brain is much smaller than that of an elephant or whale. But there are far more neurons in a human’s cerebral cortex than in the cortex of any other animal.

Data taken from the following studies: Cellular scaling rules for primate brains; Cellular scaling rules for rodent brains; Gorilla and Orangutan Brains Conform to the Primate Cellular Scaling Rules: Implications for Human Evolution; The elephant brain in numbers.

Olena Shmahalo/Quanta Magazine; source: BrainMuseum.org and Herculano-Houzel et al.

The human brain has 86 billion neurons in all: 69 billion in the cerebellum, a dense lump at the back of the brain that helps orchestrate basic bodily functions and movement; 16 billion in the cerebral cortex, the brain’s thick corona and the seat of our most sophisticated mental talents, such as self-awareness, language, problem solving and abstract thought; and 1 billion in the brain stem and its extensions into the core of the brain. In contrast, the elephant brain, which is three times the size of our own, has 251 billion neurons in its cerebellum, which helps manage a giant, versatile trunk, and only 5.6 billion in its cortex. Considering brain mass or volume alone masks these important distinctions.

Based on her studies, Herculano-Houzel has concluded that primates evolved a way to pack far more neurons into the cerebral cortex than other mammals did. The great apes are tiny compared to elephants and whales, yet their cortices are far denser: Orangutans and gorillas have 9 billion cortical neurons, and chimps have 6 billion. Of all the great apes, we have the largest brains, so we come out on top with our 16 billion neurons in the cortex. In fact, humans appear to have the most cortical neurons of any species on Earth. “That’s the clearest difference between human and nonhuman brains,” Herculano-Houzel says. It’s all about the architecture, not just size.

The human brain is also unique in its unsurpassed gluttony. Although it makes up only 2 percent of body weight, the human brain consumes a whopping 20 percent of the body’s total energy at rest. In contrast, the chimpanzee brain needs only half that. Researchers have long wondered how the human body adapted to sustain such a uniquely ravenous organ. In 1995, the anthropologist Leslie Aielloand the evolutionary biologist Peter Wheeler proposed the “expensive tissue hypothesis” as a possible answer. The underlying logic is straightforward: Human brain evolution likely required a metabolic trade-off. In order for the brain to grow, other organs, namely the gut, had to shrink, and energy that would typically have gone to the latter was redirected to the former. For evidence, they pointed to data showing that primates with larger brains have smaller intestines.

A few years later, the anthropologist Richard Wrangham built on this idea, arguing that the invention of cooking was crucial to human brain evolution. Soft, cooked foods are much easier to digest than tough raw ones, yielding more calories for less gastrointestinal work. Perhaps, then, learning to cook permitted a bloating of the human brain at the expense of the gut. Other researchers have proposed that similar trade-offs might have occurred between brain and muscle, given how much stronger chimps are than humans.

Collectively, these hypotheses and observations of modern anatomy are compelling. But they are based on the echoes of biological changes that are thought to have occurred millions of years ago. To be certain of what happened, to pinpoint the physiological adaptations that made the brain’s evolutionary growth spurt possible, we will have to dive deeper than flesh, into our very genome.

How does the number of neurons in the cerebral cortex vary with the size of that part of the brain? Different scaling rules apply. In rodents, a 10-fold increase in the number of cortical neurons leads to a 50-fold increase in the size of the cortex. In primates, by contrast, the same neural increase leads to only a 10-fold increase in cortex size — a far more economical relationship.

Olena Shmahalo/Quanta Magazine; source: Herculano-Houzel et. al. (2014)

How Genes Build the Brain

About eight years ago, Wray and his colleagues began to investigate a family of genes that influence the movement of glucose into cells to be used as energy. One member of the gene family is especially active in brain tissue, whereas another is most active in muscle. If the size of the human brain required a metabolic trade-off between brain tissue and muscle, then these genes should behave differently in humans and chimpanzees.

Wray and his team collected brain, muscle and liver samples from deceased humans and chimpanzees and attempted to measure gene activity in each sample. When a cell “expresses” a gene, it translates the DNA first into a signature messenger RNA (mRNA) sequence and subsequently into a chain of amino acids that forms a protein. Varying levels of distinct mRNAs can therefore provide a snapshot of gene activity in a particular type of tissue.

Wray’s team extracted mRNA from the tissues and amplified it many times over in the lab in order to measure the relative abundance of different mRNAs. They found that the brain-centric glucose-transporting gene was 3.2 times more active in human brain tissue than in the chimp brain, whereas the muscle-centric gene was 1.6 times more active in chimp muscle than in human muscle. Yet the two genes behaved similarly in the liver of both species.

Given that the human and chimp gene sequences are nearly identical, something else must explain their variable behavior. Wray and his colleagues found some intriguing differences between the genes’ corresponding regulatory sequences — stretches of DNA that stimulate or stifle gene activity. In humans, but not in chimps, the regulatory sequences for the muscle and brain-focused glucose-transporting genes had accumulated more mutations than would be expected by chance alone, indicating that these regions had undergone accelerated evolution. In other words, there was a strong evolutionary pressure to modify the human regulatory regions in a way that sapped energy from muscle and channeled it to the brain. Genes had corroborated the expensive tissue hypothesis in a way fossils never could.

Last year, the computational biologist Kasia Bozek, who now works at the Okinawa Institute for Science and Technology in Japan, published a similar study that examined metabolism from a different angle. In addition to looking at gene expression, Bozek and her colleagues analyzed levels of metabolites, a diverse group of small molecules that includes sugars, nucleic acids and neurotransmitters. Many metabolites are either necessary for metabolism or produced by it. Different organs have distinct metabolite profiles, depending on what they do and how much energy they require. In general, metabolite levels in the organs of closely related species are more in sync than levels between distantly related species. Bozek found that the metabolite profiles of human and chimp kidneys, for example, were pretty similar. But the variation between chimp and human brain metabolite levels was four times higher than would be expected based on a typical rate of evolution; muscle metabolites differed from the expected levels by a factor of seven. “A single gene can probably regulate a lot of metabolites,” Bozek said. “So even if the difference is not huge at the gene level, you could get a big difference in the metabolite levels.”

“It wasn’t just a couple mutations and — bam! — you get a bigger brain.”

Bozek and her colleagues then pitted 42 humans, including college basketball players and professional rock climbers, against chimpanzees and macaques in a test of strength. All of the primates had to pull a sliding shelf saddled with weights toward themselves. Accounting for body size and weight, the chimps and macaques were twice as strong as the humans. It’s not entirely clear why, but it is possible that our primate cousins get more power out of their muscles than we get out of ours because they feed their muscles more energy. “Compared to other primates, we lost muscle power in favor of sparing energy for our brains,” Bozek said. “It doesn’t mean that our muscles are inherently weaker. We might just have a different metabolism.”

Meanwhile, Wray had turned to his Duke colleague Debra Silver, an expert in embryonic brain development, to embark on a pioneering experiment. Not only were they going to identify relevant genetic mutations from our brain’s evolutionary past, they were also going to weave those mutations into the genomes of lab mice and observe the consequences. “This is something no one had attempted before,” Silver said.

The researchers began by scanning a database of human accelerated regions (HARs); these regulatory DNA sequences are common to all vertebrates but have rapidly mutated in humans. They decided to focus on HARE5, which seemed to control genes that orchestrate brain development. The human version of HARE5 differs from its chimp correlate by 16 DNA letters. Silver and Wray introduced the chimpanzee copy of HARE5 into one group of mice and the human edition into a separate group. They then observed how the embryonic mice brains grew.

After nine days of development, mice embryos begin to form a cortex, the outer wrinkly layer of the brain associated with the most sophisticated mental talents. On day 10, the human version of HARE5 was much more active in the budding mice brains than the chimp copy, ultimately producing a brain that was 12 percent larger. Further tests revealed that HARE5 shortened the time required for certain embryonic brain cells to divide and multiply from 12 hours to nine. Mice with the human HARE5 were creating new neurons more rapidly.

“This sort of study would have been impossible to do 10 years ago when we didn’t have the full genome sequences,” Silver said. “It’s really exciting.” But she also stressed that it will take a great deal more research to fully answer how the human brain blew up. “It’s a mistake to think we can explain brain size with just one or two mutations. I think that is dead wrong. We have probably acquired many little changes that are in some ways coopting the developmental rules.”

Wray concurs: “It wasn’t just a couple mutations and — bam! — you get a bigger brain. As we learn more about the changes between human and chimp brains, we realize there will be lots and lots of genes involved, each contributing a piece to that. The door is now open to get in there and really start understanding. The brain is modified in so many subtle and nonobvious ways.”

Brain and Body

Although the mechanics of the human brain’s expansion have long been mysterious, its importance has rarely been questioned. Again and again, researchers have cited the evolutionary surge in human brain size as the key reason for our exceptionally high degree of intelligence compared to other animals. As recent research on whale and elephant brains makes clear, size is not everything, but it certainly counts for something. The reason we have so many more cortical neurons than our great-ape cousins is not that we have denser brains, but rather that we evolved ways to support brains that are large enough to accommodate all those extra cells.

There’s a danger, though, in becoming too enamored with our own big heads. Yes, a large brain packed with neurons is essential to what we consider high intelligence. But it’s not sufficient. Consider, for a moment, what the world would be like if dolphins had hands. Dolphins are impressively brainy. They have demonstrated self-awareness, cooperation, planning and the rudiments of language and grammar. Compared to apes, though, they are severely limited in their ability to manipulate the world’s raw materials. Dolphins will never enter the Stone Age; flippers cannot finesse.

Similarly, we know that chimps and bonobos can understand human language and even form simple sentences with touch-screen keyboards, but their vocal tracts are inadequate for producing the distinct series of sounds required for speech. Conversely, some birds have the right vocal anatomy to flawlessly mimic human speech, but their brains are not large enough or wired in the right way to master complex language.

No matter how large the human brain grew, or how much energy we lavished upon it, it would have been useless without the right body. Three particularly crucial adaptations worked in tandem with our burgeoning brain to dramatically increase our overall intelligence: bipedalism, which freed up our hands for tool making, fire building and hunting; manual dexterity surpassing that of any other animal; and a vocal tract that allowed us to speak and sing. Human intelligence, then, cannot be traced to a single organ, no matter how large; it emerged from a serendipitous confluence of adaptations throughout the body. Despite our ongoing obsession with the size of our noggins, the fact is that our intelligence has always been so much bigger than our brain.
...................................................................................................................................................

IN THIS SERIES

Life’s Big Leaps: Critical Moments in Evolution

1. Mongrel Microbe Tests Story of Complex Life

2. Life’s Secrets Sought in a Snowflake

3. The Woman Who Stared at Wasps

4. How Humans Evolved Supersize Brains

SOURCE: https://www.quantamagazine.org/how-humans-evolved-supersize-brains-20151110/?utm_source=Quanta+Magazine&utm_campaign=6e1fed74c2-EMAIL_CAMPAIGN_2017_08_10&utm_medium=email&utm_term=0_f0cb61321c-6e1fed74c2-389390733

DOWNLOAD AS PDF This article was reprinted on BusinessInsider.com and Wired.com.

2017-07-19T13:30:00.000-07:00

How scientists reacted to the US leaving the Paris climate agreement

What the United States' departure from the historic pact means for efforts to fight global warming.

Jeff Tollefson
& Quirin Schiermeier 02 June 2017

Luke Sharrett/Bloomberg/Getty

US President Donald Trump wants to boost the US coal industry.

Nature rounds up reaction from researchers around the world to US President Donald Trump's decision to pull the United States out of the Paris climate agreement.

Jane Lubchenco, marine ecologist at Oregon State University in Corvallis and former administrator of the US National Oceanic and Atmospheric Administration:

Where to start? President Trump’s decision to withdraw from the Paris Agreement shows a blatant disregard for the wishes of most Americans and business leaders, an irresponsible and callous dismissal of the health, safety and economic well-being of Americans, a moral emptiness in ignoring impacts to the poorest people in the US and around the world, and gross ignorance about overwhelming scientific evidence. Far from “protecting America” as the president stated, withdrawing from Paris will make America more vulnerable and diminish its world leadership. It is terrifying that the individual who should be leading the rest of the world is so arrogant and irresponsible.

Our collective future and that of much of the rest of life on Earth depends in part on confronting climate change and ocean acidification. Doing so requires global collective action. It’s hard to imagine anyone consciously choosing to leave a legacy of impoverishment, economic disruption, increasingly bizarre weather, health impacts ranging from heat strokes to spread of diseases, rising sea levels and flooding — but that is just what the president has done. Moreover, the new path and the president’s proposed budget would forego significant economic opportunities.

Fortunately, mayors, governors, faith leaders, scientists and business executives understand what is at risk, respect the scientific evidence, and see the powerful economic potential and moral imperative in shifting to renewable energy, preparing to adapt to changes already under way, and investing in science and monitoring to guide future decisions. There is strong economic momentum to continue these actions, but they would have been accelerated and more effective with strong action and forceful leadership from the president. Alas, he has chosen instead to stick his head in the sand.

Jean-Pascal van Ypersele, climate scientist at the Catholic University of Louvain in Louvain-la-Neuve, Belgium, and former vice-chair of the Intergovernmental Panel on Climate Change (IPCC):

President Trump's decision to introduce a request to leave the Paris agreement in 2020 is regrettable. It negates both the results of (1) serious scientific analyses (many made by US scientists) about the urgency to address the climate change problem; and (2) the rigorous assessment made by the IPCC about the technical and socio-economic aspects of response options, including their significant co-benefits in other areas like air quality, energy security, health or job creation.

President Trump's speech attempting to justify his decision was an amazing concentrate of some of the worst climate confusers' and fossil lobbyists' arguments.

The United States has played a very important role over the years to foster and nurture quality scientific research about the causes and processes of climate change, the potential risks and the response options. It is a shame that this leadership by the US is temporarily lost. Others in Europe, Asia and emerging economies will most likely compensate for this loss, transforming a difficulty into an opportunity.

Almost 150 countries, representing close to 85% of greenhouse-gas emissions, have now ratified the Paris agreement. Removing the US contribution from this total still leaves almost two-thirds of the emissions covered by the remaining countries, which have confirmed their plans to honour the agreement. This means that the transition to a low-carbon economy, now seen as an opportunity by many, will continue unabated, with or without the US.

Susanne Dröge, climate-policy researcher at the German Institute for International and Security Affairs in Berlin:

The US pull-out is bad news for the international climate process. The United Nations negotiations need to focus on implementation. This will become more difficult, also because it is unclear how Trump wants to renegotiate the agreement. Political attention is absorbed due to the US move, attention that is needed for much more important issues such as bringing climate action forward.

Thomas Stocker, former co-chair of climate science for the IPCC, and climate and environmental physicist at the University of Bern, Switzerland:

Trump’s decision to ignore scientific facts of climate disruption and the high risks of climate-change impacts is irresponsible not only towards his own people but to all people and life on this planet. The US administration prefers old technology over innovation and transformation. It is rejecting the enormous benefits and returns that leadership in the next industrial revolution — decarbonization — has to offer.

The United States is the second-biggest emitter of carbon dioxide worldwide (and has contributed, with Europe, 52% of the share of cumulative carbon emissions since industrialization). It is withdrawing from its historical responsibility to reduce greenhouse-gas emissions and lead the way forward. Given the continuous commitment of most countries to reduce emissions, and the firm leadership of Europe, China and Russia in shaping the transformation towards a decarbonized economy, the United States runs the risk of being left behind and missing one of the greatest economic opportunities of our time.

Susan Lozier, oceanographer at Duke University in Durham, North Carolina:

Trump’s decision is as short-sighted as it is disheartening. The oceans already hold about 35% of the carbon dioxide that has been released to the atmosphere since the Industrial Revolution. Nothing good for the ocean and the life it contains comes from this storage. Whether you simply admire marine life or count on it for your livelihood, this decision shouldn’t sit well. An already fragile ocean is further imperilled.

Kevin Anderson, deputy director of the Tyndall Centre for Climate Change Research in Manchester, UK:

Beneath the veil of the low-carbon rhetoric of the Paris agreement, there is no evidence of a mitigation agenda even approaching the scale of our international obligations. Trump’s ostensibly reckless decision can be used either as a further excuse for continued apathy or as a catalyst for transforming our comfortable rhetoric into meaningful and timely action. In that regard, Trump’s ignorant blunderings can inadvertently be a force for good. Channelled positively, it could yet oblige the rest of us to forego our increasing reliance on speculative technologies and incremental carbon prices and begin to shape a mitigation agenda that is fit for purpose.

We need to take Trump at face value. If he is successful in returning the US to a coal-based economy (and that looks unlikely), then the European Union needs to borrow his ‘protectionist’ cloak and put in place carbon standards for imported goods.

Finally, let’s keep Trump in context. US states and cities have considerable devolved powers — and many of their leaders continue to favour climate science.

Joeri Rogelj, energy researcher at the International Institute for Applied Systems Analysis in Laxenburg, Austria:

The US withdrawing from the Paris agreement is damaging for international collaborative efforts to limit climate change, but will likely be most damaging to the US economy itself. The US has decided to sideline itself, internationally, diplomatically and morally — not to prepare itself for the future, but to gaze into the past for a few more years. Many other major economies, including China and the European Union, have indicated their strong commitment to implementing the climate agreement. This signal will spur innovation and business development in these regions. However, the US government refuses to give US businesses such a clear sense of direction and is disregarding the most robust scientific evidence by doing so. By setting research, innovation and business priorities based on misleading short-term political goals, the US will miss the boat and might become a laggard in the global technology and innovation landscape.

The climate issue is a global and a cumulative problem that was not solved in one go with the Paris agreement, but requires incremental updates and adjustments of climate action. To halt climate change, global carbon dioxide emissions need to be capped and annual emissions need to be brought to zero. One country failing on its commitments thus implies that deeper emissions cuts are required in other regions or later in the future. This makes the problem harder and less equitable to solve.

Oliver Geden, visiting research fellow at the Institute for Science, Innovation and Society, University of Oxford, UK:

The United States gave up climate leadership on the day of Trump's inauguration. In March, Trump announced his rollback of Obama-era climate regulations. So it’s been clear for some time that the US federal government is not going to act on climate change in the foreseeable future. Withdrawing from the Paris agreement is just another step, although a highly symbolic one.

For now, it seems that this step reunites the rest of the world, but only on the symbolic level. It is quite easy for a government to declare that it will stick to the Paris agreement. But in a regime of bottom-up climate policy that still aims to achieve top-down temperature targets, other governments would need to step up and declare that they increase their mitigation pledges — and act accordingly. That's obviously the harder thing to do.

Katharine Hayhoe, director of the Climate Science Center at Texas Tech University in Lubbock:

The biggest loser from the decision could be the United States itself. Why? Because although the Paris agreement is a climate treaty, a triumph for evidence-based decision-making, it’s also much more: a trade agreement, an investment blueprint and a strong incentive for innovation in the energy and the economy of the future.

Earlier this week, India broke its own record for the lowest bids for electricity from solar power. Last month, Ernst & Young listed its most attractive markets for renewables: the United States came third, behind China and India. And earlier this year, China announced a US$360-billion investment in clean energy to create 13 million new jobs. The US announcement shows that it will be doing its best to turn back the clock, while the rest of the world accelerates into the future.

It’s true that federal policy is only one piece of the pie, and not even the biggest one. Cities, states and private industry have arguably played an even more important role in shaping US technological innovation, energy mix and carbon emissions over the past ten years, even under proactive federal climate policy. But Trump’s announcement sends a strong message that the US would rather be one of only two nations in the world that is not interested in preventing “dangerous anthropogenic interference with the climate system”. That other nation? War-torn Syria. (Note that Nicaragua is also opting out of the agreement — but in that case it’s because it wants to do more, not less.)

Atte Korhola, climate-policy and environmental-change researcher at the University of Helsinki, Finland:

The US withdrawal from the Paris climate agreement is very disappointing and unfavourable for the United States and the rest of the world. Many climate scientists consider the Paris agreement insufficient for limiting warming to 2 °C, so the task will be all the harder now. However, international climate agreements have not been very effective so far in reducing emissions, so there is still hope that the United States will proceed on other fronts, such as through bilateral agreements, clean-tech development and investing in new ‘negative emissions’ technologies.

But the plans by the Trump administration to cut more than 30% from the Environmental Protection Agency’s budget and about 70% of the funding for renewable-energy research and development unfortunately don’t point in this direction. The situation in all respects is quite depressing. The only hope is that the US states, cities and companies will continue their effective work to cut emissions.

Benjamin Santer, climate scientist at Lawrence Livermore National Laboratory in California:

In Shakespeare's Julius Caesar, Brutus said these famous lines: "There is a tide in the affairs of men. Which, taken at the flood, leads on to fortune; Omitted, all the voyage of their life is bound in shallows and in miseries."

Today, the United States pulled out of the Paris climate agreement and missed the rising tide. Far from "Making America Great Again", this decision condemns the United States to becoming one of the 'has-beens' of history. We will become increasingly irrelevant to the rest of the world. They are going forward; we are going backward.

Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research in Potsdam, Germany:

It will not substantially hamper global climate progress if the US really quits the Paris agreement, but it will hurt the American economy and society alike. China and Europe have become world leaders on the path towards green development already and will strengthen their position if the US slips back at the national level. Innovative states such as California, the world's sixth-largest economy, will keep going for climate action, however. The Washington people around Trump hide in the trenches of the past instead of building the future. They fail to recognize that the climate wars are over, while the race for sustainable prosperity is on.

David Victor, climate-policy expert at the University of California, San Diego:

The odds of other countries renegotiating Paris are low to zero. The whole structure of the Paris agreement is to allow countries to set their own commitments. So there is nobody to negotiate with if a country needs to adjust. This claim that the problem with Paris is that the deal wasn’t struck properly is a disingenuous argument that is not informed by how Paris actually works, nor by any reality about how the world actually crafts big complex deals.

Glen Peters, climate-policy expert at the Center for International Climate and Environmental Research in Oslo:

It seems that Trump and his advisers have completely misconceived what the Paris agreement is. All his reasons for pulling out were basically the concessions that forged the path to the creation of the Paris agreement. Paris is the agreement that Trump desires!

The genius of Paris is to allow countries to put forward emission pledges that they feel they can meet (Nationally Determined Contributions). The US pledge was put forward by the US, alone. Countries are already enacting their emissions pledges, and — as could be expected by the design of the Paris agreement — most countries show signs of exceeding their conservative emissions pledges. China looks like it may peak its emissions a decade earlier than pledged. India has slowed down on coal consumption and sped up on solar deployment. Even the US has made great strides in the past decade, and was poised to make more.

The irony is that Paris is working, because it is designed to be flexible to the national circumstances that Trump himself champions!

Myles Allen, climate scientist at the University of Oxford, UK:

The Paris agreement is far from perfect, and one of its problems, as we are seeing now, is the lack of any real penalty for pulling out. Talk of trade sanctions is pure hyperbole and the last thing the world needs right now. But perhaps it is time to think about a simple product label: “Made in and sourced from regions that support the Paris climate agreement.” With California and Oregon insisting they will abide by the terms of the Paris agreement anyway, we could then have an interesting discussion about whether and how this could be stuck on Californian orange juice — or computers containing Intel chips.

Painful though it may be for the agreement’s supporters, acknowledging that it isn’t perfect must also be part of the response to this proposal to renegotiate the US terms of participation. Some, no doubt, will see this as just a distraction tactic. Others would argue that even to begin to negotiate would be to deliver Trump an ill-deserved political “win”. But thinking beyond 2020, we will eventually need to work out how to make the agreement both more effective and more acceptable to nations, companies and individuals that own substantial fossil-fuel reserves — or the US won’t be the last to leave.

Benjamin Sanderson, climate modeller at the National Center for Atmospheric Research in Boulder, Colorado:

Today's announcement that the US will depart from the Paris agreement is unfortunate, but it is no time for fatalism. From this point forward, there are now large uncertainties in global mitigation efforts over the coming years. The long-term evolution of the climate hinges on what other countries, and agents both within and outside of the US, do in response to the US departure from the agreement.

A complete failure of the agreement at this point, with business-as-usual growth for another decade, would almost certainly commit the planet to significantly more warming than the Paris goals, and the human consequences of this would be catastrophic. However, some major remaining signatories have expressed a commitment to increasing mitigation goals, and within the US, many states, cities and some of the country's largest companies are committed to mitigation irrespective of the US participation in the agreement.

Decisions made today are made in the context of confident projections of future warming with continued emissions, but clearly there is more to do to better characterize the human and economic consequences of delaying action on climate change and how to frame these issues in the context of other concerns. The role of the scientific community is more important than ever, both to continue to provide the best possible research to inform decisions, and to communicate any risks associated with further emissions in a publicly accessible fashion.

Nature

doi:10.1038/nature.2017.22098

Xi-cc++

2017-07-15T07:55:00.000-07:00

LHC Physicists Unveil a Charming New Particle

The discovery could offer fresh insight into how fundamental forces bind together subatomic particles

By Lee Billings on July 7, 2017

A view of CERN's Large Hadron Collider in Geneva, Switzerland. Credit: View Pictures Getty Images

Physicists using the Large Hadron Collider beauty (LHCb) experiment at CERN in Geneva, Switzerland, have discovered a new kind of heavy particle, they announced this week at a conference in Venice.

The particle, known as Xi-cc++ (pronounced “Ksī-CC plus-plus”), is composed of three smaller elementary particles called quarks—specifically, one lighter-weight “up” quark like those found in protons and neutrons as well as two “charm” quarks, which are a heavier and more exotic variety.

(The designations “up” and “charm” are two of the six “flavors” physicists assigned to quarks based on the particles’ varying masses and charges.) The Standard Model of particle physics predicts Xi-cc++ and many other possible particles with various configurations of the six known flavors of quarks. But until now such “doubly charmed” particles had eluded conclusive detection.

Further studies of the new particle—and other members of the doubly charmed particle family—could reinforce the Standard Model or lead to new vistas in particle physics. Either way, the new particle could be a tool to unlock a deeper understanding of the fundamental “strong” force that binds quarks together to form protons and neutrons, which in turn form atoms—as well as planets, stars, galaxies and people.

Any particle made of quarks is called a hadron. The world’s largest and most powerful particle accelerator, CERN’s Large Hadron Collider (LHC), slams these particles together in search of new particles and interactions. Hadrons fall into two broad families: mesons, exotic particles with one quark and one antiquark; and baryons, particles composed of three quarks. The new Xi-cc++ particle is a baryon. But due to its doubly charmed nature it is almost four times heavier than more familiar baryons such as protons and neutrons, which are made up entirely of light quarks rather than heavy ones.

“Finding a doubly heavy quark baryon is of great interest, as it will provide a unique tool to further probe quantum chromodynamics [QCD]—the theory that describes the strong [force], one of the four fundamental forces,” LHCb spokesperson Giovanni Passaleva said in a statement. “Such particles will thus help us improve the predictive power of our theories.”

The featherweight quark triplets within protons and neutrons all uniformly zip around one another at nearly the speed of light, making them very challenging to study. In a Xi-cc++ particle, the sole light quark whips at high speed around the heavier, slower-moving heavy quark pair, creating a situation easier for physicists to investigate.

The situation, says former LHCb spokesperson and University of Oxford physicist Guy Wilkinson, is roughly analogous to a planetary system in which the light quark is akin to a planet orbiting a binary pair of massive stars.

Credit: Amanda Montañez

Led by University of Glasgow physicist Patrick Spradlin, the LHCb team found evidence of more than 300 of the new particles in data collected last year by the experiment, teasing out their signals from a dense forest of more common particles produced by high-energy proton collisions at the LHC.

Specifically, they looked for a telltale distribution of “daughter” particles, including other baryons as well as kaons and pions—exotic particles produced by the decay of short-lived Xi-cc++ particles. The distributions they observed show not only that the LHC’s collisions are producing Xi-cc++ particles but also hint that other researchers’ previous claims of double-charm particle production may be spurious.

In 2002 researchers using the SELEX experiment at the Fermilab accelerator in Illinois announced they had found a similar particle. That detection, however, was just below the threshold of unassailable statistical significance, and the putative particle’s estimated mass was wildly out of sync with predictions.

After other facilities failed to confirm the results, many theorists began questioning the claim. By contrast, the signal of the LHCb’s newfound particle “is statistically overwhelming and matches very nicely with the theoretical expectations,” Wilkinson says. “It looks, smells and tastes like a doubly charmed baryon should.” The LHCb team’s findings have been submitted to Physical Review Letters.

With the detection of the new, heavy particle firmly in hand, physicists at the LHC are now producing more of these particles to precisely measure their lifetimes and learn exactly how often they are created in collisions.

Next, Wilkinson says, the LHCb experiment will seek out other postulated members of the doubly charmed family, such as the Xi-cc+ and Omega-cc particles. “All these results can be compared against predictions to test QCD,” he says. “There are exciting times ahead!”

ABOUT THE AUTHOR(S)

Lee Billings

Lee Billings is an editor at Scientific American covering space and physics.

Credit: Nick Higgins

See Hypervelocity stars arosinhg from the Milky Way

2017-06-27T12:53:00.001-07:00

ARTIFICIAL BRAIN HELPS GAIA CATCH SPEEDING STARS

26 June 2017

With the help of software that mimics a human brain, ESA's Gaia satellite spotted six stars zipping at high speed from the centre of our Galaxy to its outskirts.

This could provide key information about some of the most obscure regions of the Milky Way.

Stars speeding through the Galaxy. Credit: ESA, CC BY-SA 3.0 IGO

Our galactic home, the Milky Way, houses more than a hundred billion stars, all kept together by gravity. Most are located in a flattened structure – the Galactic disc – with a bulge at its centre, while the remaining stars are distributed in a wider spherical halo extending out to about 650 000 light-years from the centre.

Stars are not motionless in the Galaxy but move around its centre with a variety of velocities depending on their location – for example, the Sun orbits at about 220 km/s, while the average in the halo is of about 150 km/s.

Occasionally, a few stars exceed these already quite impressive velocities.

Some are accelerated by a close stellar encounter or the supernova explosion of a stellar companion, resulting in runaway stars with speeds up to a few hundred km/s above the average.

A new class of high-speed stars was discovered just over a decade ago. Swooping through the Galaxy at several hundred of km/s, they are the result of past interactions with the supermassive black hole that sits at the centre of the Milky Way and, with a mass of four million Suns, governs the orbits of stars in its vicinity.

"These hypervelocity stars are extremely important to study the overall structure of our Milky Way," says Elena Maria Rossi from Leiden University in the Netherlands, who presented Gaia's discovery of six new such stars today at the European Week of Astronomy and Space Science in Prague, Czech Republic.

Catching speeding stars. Click here for details and large versions of the video.
Credit: ESA/Gaia/DPAC

"These are stars that have travelled great distances through the Galaxy but can be traced back to its core – an area so dense and obscured by interstellar gas and dust that it is normally very difficult to observe – so they yield crucial information about the gravitational field of the Milky Way from the centre to its outskirts."

Unfortunately, fast-moving stars are extremely difficult to find in the stellar haystack of the Milky Way, as current surveys list the speed of at most a few hundred thousand stars.

Artist's impression of Gaia. Credit: ESA/ATG medialab; background image: ESO/S. Brunier

To find them, scientists have been looking for young, massive stars that would stand out as interlopers in the old stellar population of the Galactic halo. Given away by their out-of-place age, these stars are likely to have received an extra kick to reach the halo. Further measurements of their speeds and estimates of their past paths can confirm if they are indeed hypervelocity stars that were shoved away from the centre of the Milky Way.

So far, only 20 such stars have been spotted. Owing to the specific selection of this method, these are all young stars with a mass 2.5 to 4 times that of the Sun. However, scientists believe that many more stars of other ages or masses are speeding through the Galaxy but remain unrevealed by this type of search.

The billion-star census being performed by Gaia offers a unique opportunity, so Elena and her collaborators started wondering how to use such a vast dataset to optimise the search for fast-moving stars.

After testing various methods, they turned to software through which the computer learns from previous experience.

"In the end, we chose to use an artificial neural network, which is software designed to mimic how our brain works," explains Tommaso Marchetti, PhD student at Leiden University and lead author of the paper describing the results published in Monthly Notices of the Royal Astronomical Society.

"After proper 'training', it can learn how to recognise certain objects or patterns in a huge dataset. In our case, we taught it to spot hypervelocity stars in a stellar catalogue like the one compiled with Gaia."

As part of Elena's research project to study these stars, the team started developing and training this program in the first half of 2016, in order to be ready for the first release of Gaia data a few months later, on 14 September.

Gaia's first sky map. Credit: ESA/Gaia/DPAC. Acknowledgement: A. Moitinho & M. Barros (CENTRA – University of Lisbon), on behalf of DPAC.

Besides a map of over a billion stellar positions, this first release included a smaller catalogue with distances and motions for two million stars, combining observations from Gaia's first year with those from ESA's Hipparcos mission, which charted the sky more than two decades ago. Referred to as the Tycho–Gaia Astrometric Solution, or TGAS, this resource is a taster for future catalogues that will be based solely on Gaia data.

"On the day of the data release, we ran our brand new algorithm on the two million stars of TGAS," says Elena.

"In just one hour, the artificial brain had already reduced the dataset to some 20 000 potential high-speed stars, reducing its size to about 1%.

"A further selection including only measurements above a certain precision in distance and motion brought this down to 80 candidate stars."

The team looked at these 80 stars in further detail. Since only information on the star's motion across the sky are included in the TGAS data, they had to find additional clues to infer their velocity, looking at previous stellar catalogues or performing new observations.

"Combining all these data, we found that six stars can be traced back to the Galactic Centre, all with velocities above 360 km/s," says Tommaso.

Most importantly, the scientists succeeded at probing a different population from the 20 stars that were already known: the newly identified stars all have lower masses, similar to the mass of our Sun.

One of the six stars seems to be speeding so fast, at over 500 km/s, that it is no longer bound by the gravity of the Galaxy and will eventually leave. But the other, slightly slower stars, are perhaps even more fascinating, as scientists are eager to learn what slowed them down – the invisible dark matter that is thought to pervade the Milky Way might also have played a role.

While the new program was optimised to search for stars that were accelerated at the centre of the Galaxy, it also identified five of the more traditional runaway stars, which owe their high speeds to stellar encounters elsewhere in the Milky Way.

"This result showcases the great potential of Gaia opening up new avenues to investigate the structure and dynamics of our Galaxy," says Anthony Brown from Leiden University, a co-author on the study and chair of the Gaia Data Processing and Analysis Consortium.

The scientists are looking forward to using data from the next Gaia release, which is planned for April 2018 and will include distances and motions on the sky for over a billion stars, as well as velocities for a subset.

Dealing with a billion stars, rather than the two million explored so far, is an enormous challenge, so the team is busy upgrading their program to handle such a huge catalogue and to uncover the many speeding stars that will be lurking in the data.

"The sheer number of stars probed by Gaia is an exciting but also challenging opportunity for astronomers, and we are glad to see that they are happily embracing the challenge," says Timo Prusti, Gaia project scientist at ESA.

NOTES FOR EDITORS

"An artificial neural network to discover Hypervelocity stars: Candidates in Gaia DR1/TGAS," by T. Marchetti et al., is published in Monthly Notices of the Royal Astronomical Society.

These results were presented today at the European Week of Astronomy and Space Science in Prague, Czech Republic.

FOR FURTHER INFORMATION, PLEASE CONTACT:

Elena Maria Rossi
Leiden Observatory
The Netherlands
Tel: +31 6 8112 1440
Email: emrstrw.leidenuniv.nl

Tommaso Marchetti
Leiden Observatory
The Netherlands
Tel: +31 6 4776 9205
Email: marchettistrw.leidenuniv.nl

Anthony Brown
Leiden Observatory, Leiden University
Leiden, The Netherlands
Email: brownstrw.leidenuniv.nl

Timo Prusti
Gaia Project Scientist
European Space Agency
Email: timo.prustiesa.int

Markus Bauer
ESA Science and Robotic Exploration Communication Officer
Tel: +31 71 565 6799
Mob: +31 61 594 3 954
Email: markus.baueresa.int

Last Update: 26 June 2017

SOURCE:
http://sci.esa.int/gaia/59263-artificial-brain-helps-gaia-catch-speeding-stars/

A Theory of Reality as More Than the Sum of Its Parts

2017-06-23T15:34:00.000-07:00

CONSCIOUSNESS

New math shows how, contrary to conventional scientific wisdom, conscious beings and other macroscopic entities might have greater influence over the future than does the sum of their microscopic components. Olena Shmahalo/Quanta Magazine

Natalie Wolchover

Senior Writer

June 1, 2017

In his 1890 opus, The Principles of Psychology, William James invoked Romeo and Juliet to illustrate what makes conscious beings so different from the particles that make them up.

“Romeo wants Juliet as the filings want the magnet; and if no obstacles intervene he moves towards her by as straight a line as they,” James wrote. “But Romeo and Juliet, if a wall be built between them, do not remain idiotically pressing their faces against its opposite sides like the magnet and the filings. … Romeo soon finds a circuitous way, by scaling the wall or otherwise, of touching Juliet’s lips directly.”

Erik Hoel, a 29-year-old theoretical neuroscientist and writer, quoted the passage in a recent essay in which he laid out his new mathematical explanation of how consciousness and agency arise. The existence of agents — beings with intentions and goal-oriented behavior — has long seemed profoundly at odds with the reductionist assumption that all behavior arises from mechanistic interactions between particles. Agency doesn’t exist among the atoms, and so reductionism suggests agents don’t exist at all: that Romeo’s desires and psychological states are not the real causes of his actions, but merely approximate the unknowably complicated causes and effects between the atoms in his brain and surroundings.

Hoel’s theory, called “causal emergence,” roundly rejects this reductionist assumption.

“Causal emergence is a way of claiming that your agent description is really real,” said Hoel, a postdoctoral researcher at Columbia University who first proposed the idea with Larissa Albantakis and Giulio Tononi of the University of Wisconsin, Madison. “If you just say something like, ‘Oh, my atoms made me do it’ — well, that might not be true. And it might be provably not true.”

Erik Hoel, a theoretical neuroscientist at Columbia University.

Julia Buntaine

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Using the mathematical language of information theory, Hoel and his collaborators claim to show that new causes — things that produce effects — can emerge at macroscopic scales. They say coarse-grained macroscopic states of a physical system (such as the psychological state of a brain) can have more causal power over the system’s future than a more detailed, fine-grained description of the system possibly could. Macroscopic states, such as desires or beliefs, “are not just shorthand for the real causes,” explained Simon DeDeo, an information theorist and cognitive scientist at Carnegie Mellon University and the Santa Fe Institute who is not involved in the work, “but it’s actually a description of the real causes, and a more fine-grained description would actually miss those causes.”

“To me, that seems like the right way to talk about it,” DeDeo said, “because we do want to attribute causal properties to higher-order events [and] things like mental states.”

Hoel and collaborators have been developing the mathematics behind their idea since 2013. In a May paper in the journal Entropy, Hoel placed causal emergence on a firmer theoretical footing by showing that macro scales gain causal power in exactly the same way, mathematically, that error-correcting codes increase the amount of information that can be sent over information channels. Just as codes reduce noise (and thus uncertainty) in transmitted data — Claude Shannon’s 1948 insight that formed the bedrock of information theory — Hoel claims that macro states also reduce noise and uncertainty in a system’s causal structure, strengthening causal relationships and making the system’s behavior more deterministic.

“I think it’s very significant,” George Ellis, a South African cosmologist who has also written about top-down causation in nature, said of Hoel’s new paper. Ellis thinks causal emergence could account for many emergent phenomena such as superconductivityand topological phases of matter. Collective systems like bird flocks and superorganisms — and even simple structures like crystals and waves — might also exhibit causal emergence, researchers said.

The work on causal emergence is not yet widely known among physicists, who for centuries have taken a reductionist view of nature and largely avoided further philosophical thinking on the matter. But at the interfaces between physics, biology, information theory and philosophy, where puzzles crop up, the new ideas have generated excitement. Their ultimate usefulness in explaining the world and its mysteries — including consciousness, other kinds of emergence, and the relationships between the micro and macro levels of reality — will come down to whether Hoel has nailed the notoriously tricky notion of causation: Namely, what’s a cause? “If you brought 20 practicing scientists into a room and asked what causation was, they would all disagree,” DeDeo said. “We get mixed up about it.”

A Theory of Cause

In a fatal drunk driving accident, what’s the cause of death? Doctors name a ruptured organ, while a psychologist blames impaired decision-making abilities and a sociologist points to permissive attitudes toward alcohol. Biologists, chemists and physicists, in turn, see ever more elemental causes. “Famously, Aristotle had a half-dozen notions of causes,” DeDeo said. “We as scientists have rejected all of them except things being in literal contact, touching and pushing.”

The true causes, to a physicist, are the fundamental forces acting between particles; all effects ripple out from there. Indeed, these forces, when they can be isolated, appear perfectly deterministic and reliable — physicists can predict with high precision the outcomes of particle collisions at the Large Hadron Collider, for instance. In this view, causes and effects become hard to predict from first principles only when there are too many variables to track.

It’s a bit of a bold thing to do to talk about the mathematics of causation.

Simon DeDeo

Furthermore, philosophers have argued that causal power existing at two scales at once would be twice what the world needs; to avoid double-counting, the “exclusion argument” says all causal power must originate at the micro level. But it’s almost always easier to discuss causes and effects in terms of macroscopic entities. When we look for the cause of a fatal car crash, or Romeo’s decision to start climbing, “it doesn’t seem right to go all the way down to microscopic scales of neurons firing,” DeDeo said. “That’s where Erik [Hoel] is jumping in. It’s a bit of a bold thing to do to talk about the mathematics of causation.”

Friendly and large-limbed, Hoel grew up reading books at Jabberwocky, his family’s bookstore in Newburyport, Massachusetts. He studied creative writing as an undergraduate and planned to become a writer. (He still writes fiction and has started a novel.) But he was also drawn to the question of consciousness — what it is, and why and how we have it — because he saw it as an immature scientific subject that allowed for creativity. For graduate school, he went to Madison, Wisconsin, to work with Tononi — the only person at the time, in Hoel’s view, who had a truly scientific theory of consciousness.

Tononi conceives of consciousness as information: bits that are encoded not in the states of individual neurons, but in the complex networking of neurons, which link together in the brain into larger and larger ensembles. Tononi argues that this special “integrated information” corresponds to the unified, integrated state that we experience as subjective awareness. Integrated information theory has gained prominence in the last few years, even as debates have ensued about whether it is an accurate and sufficient proxy for consciousness. But when Hoel first got to Madison in 2010, only the two of them were working on it there.

Giulio Tononi, a neuroscientist and psychiatrist at the University of Wisconsin, Madison, best known for his research on sleep and consciousness. John Maniaci/UW Health

Tononi tasked Hoel with exploring the general mathematical relationship between scales and information. The scientists later focused on how the amount of integrated information in a neural network changes as you move up the hierarchy of spatiotemporal scales, looking at links between larger and larger groups of neurons. They hoped to figure out which ensemble size might be associated with maximum integrated information — and thus, possibly, with conscious thoughts and decisions. Hoel taught himself information theory and plunged into the philosophical debates around consciousness, reductionism and causation.

Hoel soon saw that understanding how consciousness emerges at macro scales would require a way of quantifying the causal power of brain states. He realized, he said, that “the best measure of causation is in bits.” He also read the works of the computer scientist and philosopher Judea Pearl, who developed a logical language for studying causal relationships in the 1990s called causal calculus. With Albantakis and Tononi, Hoel formalized a measure of causal power called “effective information,” which indicates how effectively a particular state influences the future state of a system. (Effective information can be used to help calculate integrated information, but it is simpler and more general and, as a measure of causal power, does not rely on Tononi’s other ideas about consciousness.)

The researchers showed that in simple models of neural networks, the amount of effective information increases as you coarse-grain over the neurons in the network — that is, treat groups of them as single units. The possible states of these interlinked units form a causal structure, where transitions between states can be mathematically modeled using so-called Markov chains. At a certain macroscopic scale, effective information peaks: This is the scale at which states of the system have the most causal power, predicting future states in the most reliable, effective manner. Coarse-grain further, and you start to lose important details about the system’s causal structure. Tononi and colleagues hypothesize that the scale of peak causation should correspond, in the brain, to the scale of conscious decisions; based on brain imaging studies, Albantakis guesses that this might happen at the scale of neuronal microcolumns, which consist of around 100 neurons.

Causation is what you need to give structure to the universe.

...Larissa Albantakis, a theoretical neuroscientist at the University of Wisconsin, Madison. Sophia Loschky

Causal emergence is possible, Hoel explained, because of the randomness and redundancy that plagues the base scale of neurons. As a simple example, he said to imagine a network consisting of two groups of 10 neurons each. Each neuron in group A is linked to several neurons in group B, and when a neuron in group A fires, it usually causes one of the B neurons to fire as well. Exactly which linked neuron fires is unpredictable. If, say, the state of group A is {1,0,0,1,1,1,0,1,1,0}, where 1s and 0s represent neurons that do and don’t fire, respectively, the resulting state of group B can have myriad possible combinations of 1s and 0s. On average, six neurons in group B will fire, but which six is nearly random; the micro state is hopelessly indeterministic. Now, imagine that we coarse-grain over the system, so that this time, we group all the A neurons together and simply count the total number that fire. The state of group A is {6}. This state is highly likely to lead to the state of group B also being {6}. The macro state is more reliable and effective; calculations show it has more effective information.

A real-world example cements the point. “Our life is very noisy,” Hoel said. “If you just give me your atomic state, it may be totally impossible to guess where your future [atomic] state will be in 12 hours. Try running that forward; there’s going to be so much noise, you’d have no idea. Now give a psychological description, or a physiological one: Where are you going to be in 12 hours?” he said (it was mid-day). “You’re going to be asleep — easy. So these higher-level relationships are the things that seem reliable. That would be a super simple example of causal emergence.”

For any given system, effective information peaks at the scale with the largest and most reliable causal structure. In addition to conscious agents, Hoel says this might pick out the natural scales of rocks, tsunamis, planets and all other objects that we normally notice in the world. “And the reason why we’re tuned into them evolutionarily [might be] because they are reliable and effective, but that also means they are causally emergent,” Hoel said.

Brain-imaging experiments are being planned in Madison and New York, where Hoel has joined the lab of the Columbia neuroscientist Rafael Yuste. Both groups will examine the brains of model organisms to try to home in on the spatiotemporal scales that have the most causal control over the future. Brain activity at these scales should most reliably predict future activity. As Hoel put it, “Where does the causal structure of the brain pop out?” If the data support their hypothesis, they’ll see the results as evidence of a more general fact of nature. “Agency or consciousness is where this idea becomes most obvious,” said William Marshall, a postdoctoral researcher in the Wisconsin group. “But if we do find that causal emergence is happening, the reductionist assumption would have to be re-evaluated, and that would have to be applied broadly.”

New Philosophical Thinking

Sara Walker, a physicist and astrobiologist at Arizona State University who studies the origins of life, hopes measures like effective information and integrated information will help define what she sees as the gray scale leading between nonlife and life (with viruses and cell cycles somewhere in the gray area). Walker has been collaborating with Tononi’s team on studies of real and artificial cell cycles, with preliminary indications that integrated information might correlate with being alive.

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4. How Life (and Death) Spring From Disorder

In other recent work, the Madison group has developed a way of measuring causal emergence called “black-boxing” that they say works well for something like a single neuron. A neuron isn’t simply the average of its component atoms and so isn’t amenable to coarse-graining. Black-boxing is like putting a box around a neuron and measuring the box’s overall inputs and outputs, instead of assuming anything about its inner workings. “Black-boxing is the truly general form of causal emergence and is especially important for biological and engineering systems,” Tononi said in an email.

Walker is also a fan of Hoel’s new work tracing effective information and causal emergence to the foundations of information theory and Shannon’s noisy-channel theorem. “We’re in such deep conceptual territory it’s not really clear which direction to go,” she said, “so I think any bifurcations in this general area are good and constructive.”

Robert Bishop, a philosopher and physicist at Wheaton College, said, “My take on EI” —effective information — “is that it can be a useful measure of emergence but likely isn’t the only one.” Hoel’s measure has the charm of being simple, reflecting only reliability and the number of causal relationships, but according to Bishop, it could be one of several proxies for causation that apply in different situations.

Hoel’s ideas do not impress Scott Aaronson, a theoretical computer scientist at the University of Texas, Austin. He says causal emergence isn’t radical in its basic premise. After reading Hoel’s recent essay for the Foundational Questions Institute, “Agent Above, Atom Below” (the one that featured Romeo and Juliet), Aaronson said, “It was hard for me to find anything in the essay that the world’s most orthodox reductionist would disagree with. Yes, of course you want to pass to higher abstraction layers in order to make predictions, and to tell causal stories that are predictively useful — and the essay explains some of the reasons why.”

It didn’t seem so obvious to others, given how the exclusion argument has stymied efforts to get a handle on higher-level causation. Hoel says his arguments go further than Aaronson acknowledges in showing that “higher scales have provably more information and causal influence than their underlying ones. It’s the ‘provably’ part that’s hard and is directly opposite to most reductionist thinking.”

Moreover, causal emergence isn’t merely a claim about our descriptions or “causal stories” about the world, as Aaronson suggests. Hoel and his collaborators aim to show that higher-level causes — as well as agents and other macroscopic things — ontologically exist. The distinction relates to one that the philosopher David Chalmers makes about consciousness: There’s the “easy problem” of how neural circuitry gives rise to complex behaviors, and the “hard problem,” which asks, essentially, what distinguishes conscious beings from lifeless automatons. “Is EI measuring causal power of the kind that we feel that we have in action, the kind that we want our conscious experiences or selves to have?” said Hedda Hassel Mørch, a philosopher at New York University and a protégé of Chalmers’. She says it’s possible that effective information could “track real ontological emergence, but this requires some new philosophical thinking about the nature of laws, powers and how they relate.”

The criticism that hits Hoel and Albantakis the hardest is one physicists sometimes make upon hearing the idea: They assert that noise, the driving force behind causal emergence, doesn’t really exist; noise is just what physicists call all the stuff that their models leave out. “It’s a typical physics point of view,” Albantakis said, that if you knew the exact microscopic state of the entire universe, “then I can predict what happens until the end of time, and there is no reason to talk about something like cause-effect power.”

One rejoinder is that perfect knowledge of the universe isn’t possible, even in principle. But even if the universe could be thought of as a single unit evolving autonomously, this picture wouldn’t be informative. “What is left out there is to identify entities — things that exist,” Albantakis said. Causation “is really the measure or quantity that is necessary to identify where in this whole state of the universe do I have groups of elements that make up entities? … Causation is what you need to give structure to the universe.” Treating causes as real is a necessary tool for making sense of the world.

Maybe we sort of knew all along, as Aaronson contends, that higher scales wrest the controls from lower scales. But if these scientists are right, then causal emergence might be how that works, mathematically. “It’s like we cracked the door open,” Hoel said. “And actually proving that that door is a little bit open is very important. Because anyone can hand-wave and say, yeah, probably, maybe, and so on. But now you can say, ‘Here’s a system [that has these higher-level causal events]; prove me wrong on it.’”

Correction: This article was revised on June 1, 2017, to clarify that Erik Hoel was not Giulio Tononi’s first collaborator on integrated information theory and that Tononi, Hoel and Larissa Albantakis formalized, but did not devise, the measure used to assess causal emergence.

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This article was reprinted on Wired.com.

SOURCE: https://www.quantamagazine.org/a-theory-of-reality-as-more-than-the-sum-of-its-parts-20170601/

2017-06-08T10:10:00.000-07:00

Descubren en Marruecos los fósiles de 'Homo sapiens' más antiguos, con 315.000 años.....

RTVE.es / EUROPA PRESS

Los restos más antiguos conocidos de Homo Sapiens han sido hallados en un lugar de Marruecos llamado Yebel Irhoud, unos 150 kilómetros al oeste de Marrakech, según un estudio publicado en la revista especializada Nature. Este descubrimiento cambiaría el origen de nuestra especie, situado hasta ahora en África Oriental, en diferentes puntos de Etiopía, aunque según el trabajo científico los restos confirman que el Homo Sapiens estuvo presente en todo el continente africano.

Los hallazgos datan de hace unos 315.000 años y representan la evidencia fósil más antigua de la especie humana, según los autores.

Tanto los datos genéticos de los seres humanos actuales como los restos fósiles apuntan a un origen africano del Homo sapiens.

Anteriormente, los fósiles de esta especie más antiguos y con datación segura eran del sitio de Omo Kibish, en Etiopía, fechado hace 195.000 años. En Herto, también en Etiopía, un fósil de Homo sapiens está fechado hace 160.000 años.

"Solíamos pensar que había una cuna de la humanidad hace 200.000 años en el este de África, pero nuestros nuevos datos revelan que el Homo sapiens se extendió por todo el continente africano hace unos 300.000 años. Mucho antes de la dispersión fuera de África del Homo sapiens, hubo dispersión dentro de África", ha explicado el paleoantropólogo Jean-Jacques Hublin.

Jebel Irhoud es el sitio más antiguo y más rico de homínidos en África

El sitio marroquí de Jebel Irhoud ha sido bien conocido desde la década de 1960 por sus fósiles humanos y por sus artefactos de la Edad de Piedra. Sin embargo, la interpretación de los homínidos de Irhoud ha sido complicada por las persistentes incertidumbres que rodean su edad geológica. El nuevo proyecto de excavación, que comenzó en 2004, dio lugar al descubrimiento in situ de nuevos fósiles de Homo sapiens, aumentando su número de seis a 22.

Estos hallazgos confirman la importancia de Jebel Irhoud como el sitio más antiguo y más rico de homínidos de la Edad Media de la Edad de Piedra en África, una etapa temprana de nuestra especie. Los restos fósiles de Jebel Irhoud comprenden cráneos, dientes y huesos largos de al menos cinco individuos.

Para proporcionar una cronología precisa de estos hallazgos, los investigadores utilizaron el método de datación por termoluminiscencia sobre pedernales calentados encontrados en los mismos depósitos. Estos pedernales eran de hace aproximadamente 300.000 años y, por lo tanto, empujan hacia atrás los orígenes de nuestra especie en 100.000 años.

El cráneo de los seres humanos modernos que viven hoy se caracteriza por una combinación de rasgos que nos distinguen de nuestros parientes fósiles y antepasados: una cara pequeña y una caja del cráneo globular.

Los fósiles de Jebel Irhoud exhiben un rostro y dientes de apariencia moderna y una coraza grande, pero de apariencia más arcaica. Hublin y su equipo utilizaron exploraciones micro tomográficas computarizadas de última generación y análisis de forma estadística basados en cientos de medidas 3D para mostrar que la forma facial de los fósiles de Jebel Irhoud es casi indistinguible de la de los seres humanos modernos que viven hoy.

Sin embargo, en contraste con su morfología facial moderna, la cría de Jebel Irhoud conserva una forma arcaica algo alargada de la cintura. "La forma interna de la caja del cráneo refleja la forma del cerebro", ha señalado el paleontólogo Philipp Gunz, del Instituto Max Planck de Antropología Evolutiva de Leipzig. "Nuestros hallazgos sugieren que la moderna morfología facial humana se estableció desde el principio en la historia de nuestra especie y que la forma cerebral y posiblemente el cerebro, que se desarrolló dentro del linaje del Homo sapiens".

Las comparaciones de ADN antiguo extraído de Neanderthales y denisovanos al ADN de los seres humanos actuales han revelado diferencias en los genes que afectan al cerebro y el sistema nervioso. La morfología y la edad de los fósiles de Jebel Irhoud también corroboran la interpretación de un enigmático cráneo parcial de Florisbad, al sur de África, como uno de los primeros representantes del Homo sapiens.

Conexiones estrechas del Magreb con el resto del continente

Los primeros fósiles Homo sapiens se encuentran en todo el continente africano: Jebel Irhoud, Marruecos (315.000 años), Florisbad, Sudáfrica (260.000 años) y Omo Kibish, Etiopía (195.000 años), lo que indica una compleja historia evolutiva de nuestra especie, posiblemente involucrando a todo el continente africano.

· Este descubrimiento amplía los orígenes de nuestra especie en 100.000 años

· Cambiaría la cuna de la humanidad, situada hasta ahora en Etiopía

· Los restos son cráneos, dientes y huesos largos de al menos cinco individuos

"Se ha descuidado el norte de África en los debates sobre el origen de nuestra especie. Los espectaculares descubrimientos de Jebel Irhoud demuestran las conexiones estrechas del Magreb con el resto del continente africano en el momento de la emergencia del Homo sapiens", dice Abdelouahed Ben-Ncer. Los fósiles se encontraron en depósitos que contenían huesos de animales que mostraban evidencia de haber sido cazados, siendo las gacelas la especie más frecuente.

Las herramientas de piedra asociadas con estos fósiles pertenecen a la Edad Media de Piedra y los artefactos de Jebel Irhoud muestran el uso de técnicas de Levallois y las formas puntiagudas son las más comunes. La mayoría de las herramientas de piedra se hicieron de sílex de alta calidad importados en el sitio. Las hachas de mano, una herramienta comúnmente encontrada en sitios antiguos, no están presentes en Jebel Irhoud.

"Los artefactos de piedra de Jebel Irhoud parecen muy similares a los de depósitos de edad similar en el este y sur de África. Es probable que las innovaciones tecnológicas de la Edad Media de Piedra en África estén relacionadas con la aparición del Homo sapiens", ha dicho el arqueólogo del Instituto Max Planck, Shannon McPherron.

FUENTE: http://www.rtve.es/noticias/20170607/descubren-marruecos-fosiles-homo-sapiens-mas-antiguos-hace-300000-anos/1561647.shtml

2017-06-02T12:22:00.000-07:00

FRANCIA REHUSA ACEPTAR LA DECISION DE TRUMP

Y LLAMA A FILAS...

A LOS NORTEAMERICANOS QUE REHUSEN LA ABSURDA DECISION DEL PRESIDENTE NORTEAMERICANO

DE NEGAR LA EXISTENCIA DEL CAMBIO CLIMNTICO

Y POR TANTO SABEN DE LA NECESIDAD DE LUCHAR EN SU CONTRA......

2016-10-05T08:19:00.000-07:00

A genomic history of Aboriginal Australia

Nature

(2016)

doi:10.1038/nature18299

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Received: 02 October 2015
Accepted: 04 May 2016
Published online: 21 September 2016

Abstract

The population history of Aboriginal Australians remains largely uncharacterized. Here we generate high-coverage genomes for 83 Aboriginal Australians (speakers of Pama–Nyungan languages) and 25 Papuans from the New Guinea Highlands. We find that Papuan and Aboriginal

Australian ancestors diversified 25–40 thousand years ago (kya), suggesting pre-Holocene population structure in the ancient continent of Sahul (Australia, New Guinea and Tasmania). However, all of the studied Aboriginal Australians descend from a single founding population that differentiated ~10–32 kya. We infer a population expansion in northeast Australia during the Holocene epoch (past 10,000 years) associated with limited gene flow from this region to the rest of Australia, consistent with the spread of the Pama–Nyungan languages. We estimate that Aboriginal Australians and Papuans diverged from Eurasians 51–72 kya, following a single out-of-Africa dispersal, and subsequently admixed with archaic populations. Finally, we report evidence of selection in Aboriginal Australians potentially associated with living in the desert.

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Author information

Author footnotes

These authors contributed equally to this work.
- Anna-Sapfo Malaspinas,
- Michael C. Westaway,
- Craig Muller,
- Vitor C. Sousa,
- Oscar Lao,
- Isabel Alves &
- Anders Bergström

Affiliations

Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen, Denmark
- Anna-Sapfo Malaspinas,
- Craig Muller,
- Ashot Margaryan,
- Thorfinn S. Korneliussen,
- J. Víctor Moreno-Mayar,
- Martin Sikora,
- Paula F. Campos,
- Robert A. Foley,
- Marta Mirazón Lahr,
- Rasmus Nielsen &
- Eske Willerslev
Institute of Ecology and Evolution, University of Bern, Baltzerstrasse 6, 3012 Bern, Switzerland
- Anna-Sapfo Malaspinas,
- Vitor C. Sousa,
- Isabel Alves,
- Isabelle Dupanloup &
- Laurent Excoffier
Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland
- Anna-Sapfo Malaspinas,
- Vitor C. Sousa,
- Isabel Alves,
- Stephan Peischl,
- Isabelle Dupanloup &
- Laurent Excoffier
Research Centre for Human Evolution, Environmental Futures Research Institute, Griffith University, Nathan, Queensland 4111, Australia
- Michael C. Westaway,
- Tim H. Heupink,
- Sankar Subramanian,
- Joanne L. Wright &
- David M. Lambert
CNAG-CRG, Centre for Genomic Regulation (CRG), Barcelona Institute of Science and Technology (BIST), Baldiri i Reixac 4, 08028 Barcelona, Spain
- Oscar Lao
Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
- Oscar Lao
Population and Conservation Genetics Group, Instituto Gulbenkian de Ciência, 2780-156 Oeiras, Portugal
- Isabel Alves
Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridge CB10 1SA, UK
- Anders Bergström,
- Yali Xue,
- Chris Tyler-Smith,
- Richard Durbin,
- Manjinder S. Sandhu &
- Eske Willerslev
Bioinformatics Research Centre, Aarhus University, 8000 Aarhus, Denmark
- Georgios Athanasiadis,
- Jade Y. Cheng,
- Mikkel H. Schierup &
- Thomas Mailund
Department of Integrative Biology, University of California, Berkeley, California 94720, USA
- Jade Y. Cheng,
- Jacob E. Crawford &
- Fernando Racimo
Verily Life Sciences, 2425 Garcia Ave, Mountain View, California 94043, USA
- Jacob E. Crawford
Department of Evolutionary Genetics, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
- Enrico Macholdt,
- Chiara Barbieri,
- Irina Pugach,
- Shengyu Ni &
- Mark Stoneking
Interfaculty Bioinformatics Unit University of Bern, Baltzerstrasse 6, CH-3012 Bern, Switzerland
- Stephan Peischl
Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark, Kemitorvet, Building 208, 2800 Kongens Lyngby, Denmark
- Simon Rasmussen
Department for Archaeogenetics, Max Planck Institute for the Science of Human History, Kahlaische Straße 10, D-07745 Jena, Germany
- Stephan Schiffels
The Bioinformatics Centre, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen, Denmark
- Anders Albrechtsen &
- Ida Moltke
Department of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Kahlaische Straße 10, D-07745 Jena, Germany
- Chiara Barbieri
Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
- Anders Eriksson,
- Andrea Manica &
- Eske Willerslev
Integrative Systems Biology Laboratory, Division of Biological and Environmental Sciences & Engineering, King Abdullah University of Science and Technology, 23955-6900 Thuwal, Saudi Arabia
- Anders Eriksson
Institute for Theoretical Physics, ETH Zürich, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland
- Ivan P. Levkivskyi
Jeffrey Cheah School of Medicine & Health Sciences, Monash University Malaysia, Jalan Lagoon Selatan, Sunway City, 46150 Selangor, Malaysia
- Farhang A. Aghakhanian &
- Maude E. Phipps
Evolutionary Medicine Group, Laboratoire d’Anthropologie Moléculaire et Imagerie de Synthèse, UMR 5288, Centre National de la Recherche Scientifique, Université de Toulouse 3, 31073 Toulouse, France
- Nicolas Brucato &
- Francois-Xavier Ricaut
Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
- Søren Brunak
CIMAR/CIIMAR, Centro Interdisciplinar de Investigação Marinha e Ambiental, Universidade do Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal
- Paula F. Campos
National Parks and Wildlife, Sturt Highway, Buronga, New South Wales 2739, Australia
- Warren Clark
Explico Foundation, Vågavegen 16, 6900 Florø, Norway
- Sturla Ellingvåg
Giriwandi, Gimuy Yidinji Country, Queensland 4868, Australia
- Gudjugudju Fourmile
Research Department of Genetics, Evolution and Environment, University College London, Gower Street, London WC1E 6BT, UK
- Pascale Gerbault &
- Mark G. Thomas
UCL Department of Anthropology, 14 Taviton Street, London WC1H 0BW, UK
- Pascale Gerbault &
- Andrea B. Migliano
Yinhawangka elder, Perth, Western Australia 6062, Australia
- Darren Injie
Papua New Guinea Institute of Medical Research, PO Box 60, Goroka, Papua New Guinea
- George Koki,
- William Pomat &
- Peter Siba
Archaeology, School of Humanities & Social Sciences, University PO Box 320, University of Papua New Guinea & College of Arts, Society & Education, James Cook University, Cairns, Queensland 4811, Australia
- Matthew Leavesley
Ngadju elder, Coolgardie, Western Australia 6429, Australia
- Betty Logan
Wongatha elder, Kurrawang, Western Australia 6430, Australia
- Aubrey Lynch
Department of Anatomy, University of Otago, Dunedin 9054, New Zealand
- Elizabeth A. Matisoo-Smith
2209 Springbrook Road, Springbrook, Queensland 4213, Australia
- Peter J. McAllister
Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
- Alexander J. Mentzer
Estonian Biocentre, Riia 23b, Tartu 51010, Estonia
- Mait Metspalu
86 Workshop Road, Yarrabah, Queensland 4871, Australia
- Les Murgha
Esperance Nyungar elder, Esperance, Western Australia 6450, Australia
- Doc Reynolds
Atakani Street, Napranum, Queensland 4874, Australia
- Thomas Wales
2 Wynnum North Road, Wynnum, Queensland 4178, Australia
- Colleen Ma’run Wall
School of Anthropology and Museum Ethnography, Oxford University, Oxford OX2 6PE, UK
- Stephen J. Oppenheimer
Centre for Rock Art Research and Management, M257, University of Western Australia, Perth, Western Australia 6009, Australia
- Joe Dortch
Leverhulme Centre for Human Evolutionary Studies, Department of Archaeology and Anthropology, University of Cambridge, Fitzwilliam Street, Cambridge CB2 1QH, UK
- Robert A. Foley &
- Marta Mirazón Lahr
Department of Linguistics, Yale University, 370 Temple Street, New Haven, Connecticut 06520, USA
- Claire Bowern
Institute for Human Genetics, University of California, San Francisco, California 94143, USA
- Jeffrey D. Wall
Departments of Integrative Biology and Statistics, University of California, Berkeley, California 94720, USA
- Rasmus Nielsen

Contributions

G.A., J.Y.C., J.E.C., T.H.H., E.M., S.P., S.R., S.Sc., S.Su. and J.L.W. contributed equally and are listed alphabetically in the author list; A.A., C.Ba., I.D., A.E., A.Mar., I.M. and I.P. contributed equally and are listed alphabetically in the author list; T.S.K., I.P.L., J.V.M.-M., S.N., F.R., M.Si. and Y.X. contributed equally and are listed alphabetically in the author list. E.W. and D.M.L. initially conceived and headed the project. L.E. led the genetic load and the SFS-based demographic analyses. M.S.S. headed the research at the Wellcome Trust Sanger Institute. A.-S.M. planned and coordinated the genetic analyses and the sequencing of the Aboriginal Australian genomes. C.M., J.L.W., T.H.H., P.F.C., W.C., G.F., D.I., B.L., A.L., P.J.M., L.M., D.R., T.W., C.W., J.D., M.C.W. and E.W. collaborated with local groups to collect Aboriginal Australian samples. N.B., P.G., G.K., M.L., A.J.M., A.B.M., W.P., F.-X.R., P.S., M.G.T. and S.J.O. collaborated with local groups to collect Papuan samples. S.E. collaborated with local groups to collect the Rapanui sample. A.Mar. extracted DNA for the Aboriginal Australian genomes. M.S.S., A.B. and C.T.-S. coordinated the design and sequencing of the Papuan genomes. O.L., V.C.S., I.A., A.-S.M., A.B., G.A., J.Y.C., J.E.C., T.H.H., E.M., S.P., S.R., S.Sc., S.Su., J.L.W., A.A., C.Ba., I.D., A.E., A.Man., I.M., I.P., T.S.K., I.P.L., J.V.M.-M., S.N., F.R., M.Si., F.A., S.B., L.E., J.D.W. and T.M. analysed genetic data. C.Bo. collected and analysed linguistic data. L.E., E.W., D.M.L., Y.X., M.E.P., C.T.-S., R.D., M.S.S., A.Man., M.H.S., T.M., M.St. and R.N. supervised genetic analyses. M.C.W., C.M., W.C., G.F., D.I., B.L., A.L., P.J.M., L.M., D.R., T.W., C.W., E.A.M.-S., M.M., M.E.P., S.J.O., J.D., A.B.M., R.A.F. and M.M.L. provided archaeological, anthropological and historical context. A.-S.M., V.C.S., O.L., I.A., A.B., M.M.L., R.N., L.E., D.M.L. and E.W. wrote the manuscript with critical input from G.A., T.H.H., E.M., S.Sc., S.Su., J.L.W., C.Ba., A.E., I.P., E.A.M.-S., M.S.S., S.J.O., C.T.-S., R.D., M.G.T., J.D., A.Man., M.H.S., R.A.F., C.Bo., J.D.W., T.M., M.St. and all other coauthors. A.-S.M., V.C.S., O.L., I.A. and A.B. revised and compiled the Supplementary Information.

Competing financial interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to:

The Aboriginal Australian and Papuan whole genome sequence data generated in this study have been deposited at the European Genome-phenome Archive (EGA, http://www.ebi.ac.uk/ega/), which is hosted by the EBI, under the accession numbers EGAS00001001766 andEGAS00001001247, respectively. The Papuan SNP array data generated in this study can be found under http://geogenetics.ku.dk/latest-news/alle_nyheder/2016/data.

Extended data figures and tables

Abstract•
References•
Author information•
Extended data figures and tables•
Supplementary information

Extended Data Figures

Extended Data Figure 1: Per-individual admixture proportions of K = 7 ancestral components including Aboriginal Australians, New Guineans, Europeans, Africans, Melanesians and Polynesians. (581 KB)

The genome of each individual is depicted as a bar and is coloured according to the estimated genome-wide proportions of ancestry components. An unrooted tree showing the relationships between the identified ancestral components is also estimated by our method. Each ancestry has been labelled with the name of the population (see also map) showing the highest fraction of that ancestral component. The cross-validation error is minimized for this value of K for fivefold cross-validation. The rooted tree supports the shared genetic origin of Aboriginal Australians, Papuans and Bougainvilleans. Note that only individuals with more than 50% of Aboriginal Australian ancestry in their genomes (defined in Supplementary Information section S06) were included in the analyses. Refer to ref. 58 and Supplementary Information section S05 for details about the method and the analysis. Map data ©2016 Google, INEGI. Tree constructed with http://jade-cheng.com/trees/.
Extended Data Figure 2: Genetic relationships of Aboriginal Australians and Papuans. (491 KB)

a, Genetic affinities between a western central desert (WCD02) genome and Aboriginal Australians and Papuans. Outgroup f3 statistics between WCD02 and all other Aboriginal Australians and Highland Papuan individuals that were whole-genome sequenced for this study, using the genotypes called from the sequencing data. Because the widespread recent admixture in Aboriginal Australians has large confounding effects on the f3statistics, the values were adjusted using the slope coefficient from a simple linear regression model fitted to the relationship between f3 and the fraction of non-indigenous (that is, neither Aboriginal Australian nor Papuan) ancestry in each individual genome. The adjusted f3 statistics display a genetic gradient that separates western and eastern Aboriginal Australian populations. However, we find no differences between Papuan population samples in their level of Aboriginal Australian affinity (Kruskal–Wallis test, P = 0.083). Horizontal lines correspond to ±1 standard error. b, Genetic affinities between a Papuan highlander genome and Aboriginal Australians and Papuans. The Papuan highlander sample MAR01 from the Marawaka area was arbitrarily chosen as a reference point for this analysis. f3 values were adjusted for recent admixture as in a. All Aboriginal Australian groups display a similar level of Highland Papuan affinity (with the exception of three outlier individuals from the north-eastern WPA and CAI populations: WPA06, WPA05 and CAI10, the latter two of which are known to have at least one parent with origins in Papua New Guinea or the Torres Strait Islands). While some differences between groups are actually statistically significant (Kruskal–Wallis test, P = 0.0002, after removing the three outliers), which could be consistent with, for example, low levels of Papuan gene flow into some Aboriginal Australian groups (see Supplementary Information sections S06 and S07), we caution that some of these differences are probably due to imperfect adjustment for Eurasian admixture (the adjusted f3 is highest in the WCD population, which has the least Eurasian admixture). Horizontal lines correspond to ±1 standard error. c, MSMC analyses. Linear interpolation through the midpoints of the time intervals of the relative cross coalescence rate estimates from MSMC²⁵ using pairs of individuals including one HGDP-Papuan and one other individual as indicated. We used CAI01, PIL06, WCD01, WON03 and an ECCAC sample for this analysis (see Supplementary Information section S08 for details). The MSMC results were scaled using a mutation rate of 1.25×10⁻⁸ per generation per site as suggested in ref. 41 and a generation time of 29 years, corresponding to the average hunter–gatherer generation interval for males and females⁴².
Extended Data Figure 3: Introgressed archaic sites and putative Denisovan and Neanderthal haplotypes. (876 KB)

a, Distribution of number of putative introgressed sites per individual from archaic humans. The number of Neanderthal-specific introgressed sites per individual increases from Europe to Australia, and then decreases in Amerindians, which is consistent with recurrent Neanderthal (or Neanderthal-related archaic) gene flow during the expansion into Eurasia. Our results are thus indicative of several pulses of Neanderthal gene flow into modern humans, as inferred previously^48, 49, 50. We note, however, that the apparent high levels of Neanderthal-specific introgressed sites in Australo-Papuans can be explained by the expected number of misclassified Neanderthal introgressed sites resulting from the shared ancestry with Denisovans (see Supplementary Information section S11 for details). b–e, Putative Denisovan (PDH) and Neanderthal haplotypes (PNH). The putative haplotypes correspond to clusters (four or more SNPs spanning at least 4 kb) of heterozygous or homozygous genotypes in complete linkage disequilibrium (‘diplotypes’) that are potentially the result of Neanderthal or Denisovan admixture. Those diplotypes are homozygous ancestral in 10 Africans, homozygous derived in the Denisovan for the PDH (respectively Neanderthal for the PNH), homozygous ancestral in the Neanderthal for the PDH (respectively Denisovan for the PNH), and with the derived allele segregating in all other contemporary non-African humans (see Supplementary Information section S10 for details). We report the average number of PDHs and PNHs (b), the correlation between the estimated amount of Australo-Papuan ancestry (see Fig. 2a, Extended Data Fig. 1, Supplementary Information section S05) and the number of identified PDHs for each Australian sample (c), the sum of the lengths (d) and the average length (e) of the PDHs and PNHs per individual for worldwide populations included in our reference panel (see Supplementary Information section S04).
Extended Data Figure 4: Out of Africa: admixture graphs based on D-statistics and MSMC analyses. (303 KB)

a, Admixture graphs representing some of the topologies considered for the two waves and one wave Out of Africa models assuming Denisovan admixture. All topologies are identical except for the coloured lineages representing Australo-Papuans (green), Neanderthal (Nea, orange) and Denisovan (Den, blue). The graphs differ in (1) the number of OoA events, and (2) the number of Neanderthal admixture pulses. Png, HGDP-Papuan. b, Sum of squared errors between the observed D-statistics and the expectations for each quartet in the graph involving the chimpanzee as an outgroup for each of the admixture graphs shown in a and the corresponding four without Denisovan admixture. Each point is the result of the optimization procedure with a different starting point. See Supplementary Information section S09 for details. c, Relative cross coalescence rate (CCR) estimates from MSMC²⁵ for pairs of individuals including one African sample (Yoruba, Dinka and San) and one other, as indicated in the legend. d, Simulation study to assess the effect of archaic admixture on the CCR rates. Relative CCR estimated for data simulated under a simple two-population divergence model where one of the populations admixed at different rates with an archaic population. SeeSupplementary Information section S08 for details.
Extended Data Figure 5: Inferred deleterious mutations. (121 KB)

a, Box plot of the number of derived homozygous sites per individual for worldwide populations that are predicted to be deleterious. Deleteriousness of SNPs was inferred using genomic evolutionary rate profiling (GERP) rejected substitution scores. Derived alleles with a rejected substitution score larger than 2 were considered to be deleterious, see Supplementary Information section S11. b, c, Average rejected substitution score per individual calculated across heterozygous sites (b), and derived homozygous sites (c). Each coloured symbol corresponds to estimates from a single individual. Homozygosity is calculated as the number of derived homozygous sites divided by the number of sites at which an individual carries at least one copy of the derived allele. Solid lines show the linear regression of homozygosity against average rejected substitution score per individual for non-African modern humans. Dashed lines indicate the 95% confidence interval for the linear regression. See Supplementary Information S11 for details.
Extended Data Figure 6: Effective population size changes over time. (213 KB)

a, Population size estimates from MSMC for pairs of individuals from several populations within and outside of Australia. For each run, we used two individuals from each population, that is, four haplotypes in each run. MSMC results were scaled as in Fig. 3. b, Bayesian skyline plots (BSP) calculated from the mtDNA genome sequences, showing the effective population size estimates over time when considering either groups from northeastern Australia (CAI, WPA) or groups from southwestern Australia (ENY, NGA, WCD, WON). Solid lines are the estimates, dashed lines are the corresponding 95% credible intervals (see Supplementary Information section S12).
Extended Data Figure 7: Genetics mirrors geography and languages. (488 KB)

a, b, Procrustes analyses of the first two dimensions of a classical multidimensional scaling (MDS) analysis of the Aboriginal Australian genome sequences (autosomes). We considered two cases: an analysis including all variants (a), or only the variants remaining after genomic regions of putative recent European and East Asian origin are ‘masked’ (b,Supplementary Information section S06). Both MDS plots have been rotated towards the best overlap with geographic sampling locations as defined by Procrustes analysis⁵¹. In each plot, the connecting lines indicate the error of the MDS coordinates towards the assigned population-sampling geographic coordinates. We find that the genetic relationships within Australia mirrors geography, with a significant correlation for both cases, that is, rGEN,GEO = 0.59, P < 0.0005 for all variants and even higher, rGEN,GEO = 0.77, P <0 .0005="" 65="" a="" aboriginal="" an="" angle="" approach="" at="" australian="" axis="" bearing="" compared="" correlogram="" data-saferedirecturl="https://www.google.com/url?hl=en&q=http://www.nature.com/nature/journal/vaop/ncurrent/full/nature18299.html%23supplementary-information&source=gmail&ust=1475765934850000&usg=AFQjCNEPahU7QRpnRRAgqfCbdabAJgn6Rw" data.="" differentiation="" direction="" equator="" find="" for="" genetic="" genomes="" href="http://www.nature.com/nature/journal/vaop/ncurrent/full/nature18299.html#supplementary-information" in="" is="" main="" masked="" northeast="" of="" southwest="" style="color: #5c7996; text-decoration: none;" target="_blank" that="" the="" to="" using="" we="">Supplementary Information section S13

). c, d, Correspondence between genetics and linguistics. c, Unrooted neighbour-joining FST-based genetic tree (cladogram). Weir and Cockerham FST distance was computed between the Aboriginal Australian populations after masking the Eurasian tracts. Statistical robustness of each branch was estimated by means of a bootstrap analysis (1,000 replicates, Supplementary Information section S05). d, Bayesian phylogenetic tree for the 28 different Pama–Nyungan languages represented in this sample (from ref. 13, see Supplementary Information section S15). Posterior probabilities are also indicated. Note that one language group can be shared by different Aboriginal Australian groups. The linguistic tree was built with BEAST⁵². e–g, Gene flow across the continent. e, Mantel non-parametric r (estimating the goodness of fit between genetic differentiation and connectivity) versus ratios of resistance of inland to coastal nodes, showing a peak at 1.7.f, Best fit of pairwise population genetic differentiation, FST (computed between the nine Aboriginal Australian groups after masking Eurasian tracts (Supplementary Information section S06)), versus pairwise connectivity based on the environment (estimated as resistance) when moving inland is 1.7 times harder than moving along coastal nodes. g, Gene flow across the Australian landscape, quantified as the cumulative current for pairwise connections among Aboriginal Australian groups (black circles), with larger current (warmer colours) representing greater gene flow.

Extended Data Figure 8: European, East Asian and Papuan genomic tracts in Aboriginal Australians. (137 KB): a, Distribution of the tracts assigned to Aboriginal Australian (WCD), Papuan, East Asian or European ancestry for 58 unrelated non-WCD Aboriginal Australian samples. Most of the shorter tracts were of Papuan origin, suggesting that a large fraction of the Papuan gene flow is much older than that from Europe and East Asia, consistent with a Papuan influence spreading slowly from northeastern to southwestern Australia by ancient migration. b, Corresponding scatter plot with fitted line of per-individual variance in Papuan tract length versus geographic distance from WCD, the latter calculated using the great-circle distance formula for pairs of individual GPS coordinates. Papuan tract distribution showed a strong and significant correlation with distance from WCD (r = 0.64;P < 1 × 10⁻⁵), with ‘younger tracts’ (that is, with a larger variance) closer to New Guinea and ‘older tracts’ (that is, with a smaller variance) closer to WCD. This is also consistent with continuous Papuan gene flow spreading from the northeast.

Extended Data Tables

Supplementary information

PDF files

Supplementary Information (18 MB)

This file contains Supplementary Text and Data, Supplementary Figures, Supplementary Tables and additional references (see Contents for more details).

FIGURES: Show only the first Figure. The rest must be consulted at the original site.

SOURCE: NATURE

Nature

(2016)

doi:10.1038/nature18299

Received

02 October 2015

Accepted

04 May 2016

Published online

21 September 2016

2016-09-23T11:02:00.000-07:00

FROM HIPPARCHUS TO HIPPARCOS: A SONIFICATION OF STELLAR CATALOGUES

22 September 2016

ESA's Gaia mission recently released its first batch of data, based on observations obtained with the satellite during its first 14 months of science operations. This ambitious mission is the culmination of over two thousand years of astrometry – the science of charting the sky.

A new sonification demonstrates in a novel way the remarkable progress that has been made in the lead up to the first data release from Gaia.

Astrometry through the ages. Credit: ESA

Astronomy is one of the first natural sciences developed by early civilisations across the globe, and astrometry is one of the oldest branches of astronomy. Over the centuries, as technical advances were made and new instruments became available, the history of mapping the heavens gradually unfolded. Astronomers could see fainter and more distant celestial objects, measuring the position, brightness and colour of each star ever more accurately to determine their distance, their velocity through the Galaxy and their physical composition.

To convey the progress made in the field of astrometry, a new representation has been created using sonification – the practice of turning data into sound – by Jamie Ferguson in collaboration with ESA.

Jamie first became interested in sonification during his Masters Degree studies in computer science, and he has recently applied this technique to the challenge of communicating astronomy to visually impaired students. He is soon to begin his PhD studies on using sonification in the context of astronomy research, education and outreach.

"The human ear is incredibly efficient at recognising patterns in sounds, making sonification an ideal tool for locating patterns and anomalies in extensive datasets that are common in astronomy – such as the enormous quantity of data contained in stellar catalogues," said Jamie.

"Sonification is not only an incredibly useful research tool in astronomy, but it is beginning to allow the field to be more open and engaging to people who are visually impaired and cannot interact with the common visual supports that accompany astronomy in the media."

After analysing a number of ancient and modern catalogues of stars, Jamie created a software to map the various astronomical parameters provided in each catalogue into different dimensions in a soundscape. The result is a short audio clip, From Hipparchus to Hipparcos: A sonification of stellar catalogues, which can be listened to and downloaded from ESA's SoundCloud channel.

This project was developed in the weeks leading to the first Gaia data release, so it portrays the status of astrometric catalogues prior to the advent of Gaia. An extension of the sonification, including data from the first Gaia release, will follow.

From Hipparchus to Hipparcos starts with a sonification of the ancient star catalogue compiled by Greek astronomer Hipparchus of Nicaea in the second century BCE and proceeds through several other historical catalogues, before ending with the Hipparcos Catalogue, published in 1997 and based on data from ESA's Hipparcos satellite, Gaia's predecessor and the first space mission dedicated to astrometry.

The improvement in the quantity and precision of data, as well as the increased information content and dimensions contained in each catalogue, are palpable as the sound clip evolves from the ancient Hipparchus to the modern Hipparcos.

For the most ancient five catalogues (see list below), which only list stellar positions and brightnesses, Jamie mapped each star in a virtual sound space based on its 2D position on the sky, and used the brightness of each star to modulate the pitch of each sound. He also added a background of white noise to convey the accuracy of the measurements – this becomes less audible for the more modern and accurate catalogues.

In the case of the first three catalogues (Hipparchus, Ulugh Beg and Tycho Brahe), the sound corresponding to each star is played individually; for the later, larger catalogues (Flamsteed, Lalande, the Yale Trigonometric Parallax Catalogue and the Hipparcos Catalogue), the sounds corresponding to more than one star are played simultaneously to compress the great number of stars contained in these catalogues in the same time length.

Since the distances to the stars were not known until the nineteenth century, the sounds all have the same volume in the first five catalogues. Volume is then used as an additional parameter in the final two catalogues (the Yale Trigonometric Parallax Catalogue and the Hipparcos Catalogue) to convey the stellar distances measured via parallax – the annual shift of a star's position in the sky, caused by Earth's motion around the Sun and inversely proportional to the star's distance.

The modern catalogues contain a wealth of information beyond stellar positions and distances, so Jamie had to create additional sounds to convey the extra dimensions probed by these catalogues. He added a 'hiss' sound, which is played once for every 5 iterations of the main sound, to represent the stellar colours (which are, in turn, indicative of stellar temperatures). The frequency of the hiss is lower for bluer/hotter stars and higher for redder/cooler ones.

For the Hipparcos Catalogue, at the end of the clip, Jamie encoded information about the proper motion of the stars – the projection on the sky of the star's true motion through space – in the duration of the hiss, which is short for fast-moving stars and longer for slower-moving stars.

More information about the sampled catalogues can be found below.

FROM HIPPARCHUS TO HIPPARCOS: A SONIFICATION OF STELLAR CATALOGUES - DETAILS OF THE AUDIO FILE

The sonification of each catalogue lasts about 15 seconds in the sound clip.

Instruments: Naked eye observations, astrolabes, sextants and quadrants

1) Hipparchus of Nicaea compiled the oldest known comprehensive catalogue of stellar positions in the second century BCE. His work, based on even more ancient observations from Assyro-Babylonian astronomers, was handed down three hundred years later by Ptolemy, in his second-century treatise known as the Almagest, 'The Greatest'.

Hipparchus's catalogue was compiled with naked-eye observations and the few instruments available at the time (gnomons, astrolabes, and armillary spheres). It lists the positions of 850 stars with a precision of less than one degree [1].

Parameters used to create the sound: Pitch (star brightness) and location in the sound space (star position: right ascension and declination); background noise to convey accuracy of measurements. Each star is played individually.

2) In the fifteenth century, Ulugh Beg of the Timurid dynasty created a catalogue of 994 stars. Ruling over Central Asia, he was also an astronomer and mathematician, and constructed an enormous sextant with a radius of 36 metres in Samarkand, located in present-day Uzbekistan. Ulugh Beg's catalogue has a precision slightly better than that of Hipparchus.

3) In the late sixteenth century, Danish astronomer Tycho Brahe measured the positions of about 1000 stars with a precision of about one arcminute [2], using large quadrants and sextants at the Uraniborg observatory on the island of Hven (in present-day Sweden). His catalogue was completed in 1598 and published in 1627.

Parameters used to create the sound: Pitch (star brightness) and location in the sound space (2D position: right ascension and declination); background noise to convey accuracy of measurements. Each star is played individually.

Instruments: Telescope, quadrants, sextants

4) In 1725, English astronomer John Flamsteed published the first stellar catalogue compiled with the aid of a telescope, listing the positions of almost 3000 stars with a precision of 10-20 arcseconds.

5) In 1801, French astronomer Jérôme Lalande published an even greater catalogue with the position of 50 000 stars and a precision of around three arcseconds.

Instruments: Telescope, photography

6) The Yale Trigonometric Parallax Catalogue was published in 1995 by American astronomer William van Altena, who completed the work started by Frank Schlesinger in 1924 (who had made a huge step forward in the field thanks to progresses in the use of photographic plates) and continued by Louise Freeland Jenkins in 1952. It is the largest catalogue of stellar parallaxes compiled with ground-based telescopes, listing positions and parallaxes for over 8000 stars, with a precision of about 0.01 arcseconds.

Parameters used to create the sound: Pitch (star brightness) and location in the sound space (2D position: right ascension and declination); volume (distance); hiss (colour); background noise to convey accuracy of measurements. Groups of five stars are played simultaneously.

Instrument: Space telescope

7) ESA's Hipparcos mission, operating from 1989 to 1993, was the first space telescope devoted to measuring stellar positions. The Hipparcos catalogue, released in 1997, contains the position, parallax and proper motion of 117 955 stars with a precision of 0.001 arcseconds, allowing astronomers to probe stellar distances out to over 300 light-years.

Parameters used to create the sound: Pitch (star brightness) and location in the sound space (2D position: right ascension and declination); volume (distance); hiss (colour); length of hiss (proper motion). The very high accuracy of this catalogue is conveyed by there being no background noise. Groups of ten stars are played simultaneously.

[1] One degree is twice the angular size of the full Moon, or the width of one's little finger seen at arm's length.

[2] Minutes, or seconds, of arc are used to describe very small angles. An arcminute is 1/60 of a degree and an arcsecond is 1/60 of an arcminute. One arcminute is roughly the width of the edge of a bank card seen from a distance of 2.5m; one arcsecond is the width of a human hair seen from a distance of 10 m.

Read more in the History of Astrometry series: http://sci.esa.int/gaia/history-of-astrometry

FOR FURTHER INFORMATION, PLEASE CONTACT:

Jamie Ferguson
Email: j.ferguson.4research.gla.ac.uk
Website: http://jfergusoncompsci.co.uk

Last Update: 22 September 2016- EUROPEAN SPACE AGENCY

SOURCE OF THIS DOCUMENT: http://sci.esa.int/gaia/58311- from-hipparchus-to-hipparcos-a-sonification-of-stellar-catalogues/

2016-09-20T08:54:00.000-07:00

Ciencia

¿Había algo antes del Big-Bang?

Según la teoría de la Cosmología Cíclica Conforme, de Sir Roger Penrose,
el Universo vive un ciclo continuo e infinito de «creaciones»

Para observar correctamente el gráfico expositivo de Penrose hay que desplazarse al video original ,que se encuentra en esta direccion:

http://www.abc.es/ciencia/abci-habia-algo-antes-big-bang-201609170155_noticia.html

La Nebulosa del Cangrejo, formada tras una explosión de supernova. El término «explosión» se queda muy corto para describir lo que ocurrió en el Big Bang - NASA, ESA, J. Hester, A. Loll (ASU)

Sir Roger Penrose es una leyenda viva de la Física. Durante el festival Starmus tuve el placer de escucharle explicando su controvertida teoría cosmológica. Su exposición fue tan elocuente, convincente e incluso divertida, que me causó una profunda impresión. A ver si en este artículo consigo explicarla de forma mínimamente coherente.

Estamos bastante seguros de que el Universo entero comenzó con lo que se llama el Big Bang (la «gran explosión») hace la friolera de 13,700 millones de años. En realidad, lo de la explosión no es una muy buena metáfora. Este nombre lo acuñó despectivamente el astrofísico Fred Hoyle durante la retransmisión de un programa de radio de la BBC en 1949. Hoyle se burlaba con él de la absurda teoría que había propuesto el sacerdote (además de físico y matemático) Georges Lemaître. El propio Einstein al principio tampoco creía en las ideas de Lemaître. El prejuicio de la época era que el Universo debía ser algo estático e inmutable. Pero las matemáticas de Lemaître eran impepinables.

Su solución de las ecuaciones de Einstein implicaba que el Universo debía estar o bienexpandiéndose o bien colapsando, cayendo sobre sí mismo como un edificio en demolición. Visto con perspectiva histórica, debe dar mucha rabia eso de que alguien coja las ecuaciones que son el trabajo de tu vida y las resuelva magistralmente para llegar a una conclusión que aborreces. Las discusiones entre Einstein y Lemaître, que llevaron al primero a proponer la existencia de una «constante cosmológica», merecerían un artículo aparte. Por lo pronto, baste decir que, como buen científico, Einstein acabó aceptando la evidencia, tanto teórica como empírica, que comenzaba a acumularse. Pese a sus prejuicios iniciales, terminó abrazando la idea de que, efectivamente, el Universo se estaba expandiendo.

La singularidad original

La historia sería más o menos así: Al principio de los tiempos, todo el Universo estaba concentrado en una singularidad, un punto de densidad infinita que repentinamente estalló en ese instante inicial, saltando toda la materia, energía y espacio despedidos en todas direcciones. A medida que pasa el tiempo, la Física nos dice que las galaxias van a sentir el tirón gravitatorio unas de otras, y esto debería hacer que poco a poco se vayan frenando. Cuánto se van a frenar dependerá de cuánta masa haya en el Universo. Si hay mucha, la gravedad terminará por dominar, la expansión se detendrá y el Universo volverá a caer sobre sí mismo.

NASA / WMAP Science Team

Si hay poca, la atracción será incapaz de frenar la expansión y el Universo continuará expandiéndose por toda la eternidad, aunque a menor velocidad. La distinción es trascendental, con implicaciones hasta en el plano espiritual. Porque un Universo que vuelve a colapsar se presta a la perspectiva del ciclo infinito de big bang-big crunch, el ciclo continuo y eterno de creación y destrucción. Mientras que la otra posibilidad nos lleva a una insulsa muerte final de toda la existencia, más que nada por aburrimiento.

La sorpresa de la densidad crítica

La cantidad de masa (o, hablando con más precisión, de energía) que se necesita para pasar de un comportamiento a otro se llama «densidad crítica». No hace mucho, cuando yo estudiaba, sin ir más lejos (y créanme que tampoco hace tanto de eso), nos preguntábamos si en el Universo había más o menos densidad que la crítica. Parecía que no, que era muy pequeña, que no sería suficiente toda la masa para volver a cerrar el ciclo. Pero claro, en aquella época no se conocían la materia y la energía oscura. Si tenemos en cuenta estos factores, nos encontramos con uno de los grandes misterios de la cosmología moderna: ¡Resulta que tiene exactamente la densidad crítica!

Radiación de fondo de microondas, una de las mayores evidencias de que ocurrió un Big Bang- WIKIPEDIA

La revelación de que la densidad del Universo es exactamente la crítica (con tanta precisión como somos capaces de medir), sacudió el mundo de la Física. Y es que, aunque sea en el plano subconsciente, se hace difícil no evocar la imagen de un creador para explicar tal coincidencia cósmica. La situación de crisis existencial se resolvió poco después, para alivio de muchos, con la llegada de la teoría de la inflación.

Por ponerlo en términos muy simples, esta teoría nos dice que durante la primera fracción de segundo (técnicamente, desde los 10-36 hasta los 10-32 segundos), el Universo sufrió una expansión tan brutalmente violenta, que el término «explosión» se queda muy corto para describir lo que ocurrió. La expansión en esa época fue acelerada exponencialmente, que es una forma que hay en Física de decir enormemente rápida.

Los cosmólogos suelen decir que todo lo que existe pasó de tener el tamaño de un átomo al de un melón. Por alguna razón se suele usar el melón como medida de referencia. Podrían decir que medía 30 centímetros, que era como un balón de baloncesto o como un florero grande. Pero no, parece que lo del melón lleva camino de convertirse en la unidad estándar de volumen cósmico, algo así como el campo de fútbol lo es hoy en día para medir áreas de monte quemado.

La cuestión es que a este disparatado crecimiento del espacio, infinitamente más rápido que la luz, se le llama inflación. Es un poco contraintuitivo porque, en lenguaje cotidiano, el verbo inflar nos suena mucho más suave y benigno que explotar. Es bien conocido que los físicos no son muy buenos para poner nombres a las cosas. No entendemos bien cómo y por qué ocurrió la inflación salvo que parece estar relacionado con lo que se llama «gran unificación», la época en la que las tres fuerzas fundamentales de la naturaleza eran una, grande y única.

El Universo no se frena

El otro gran descubrimiento que ha tenido lugar desde los tiempos de Einstein es otro hallazgo reciente que también ha causado cierta zozobra existencial. Discutíamos antes las dos posibilidades sobre hasta qué punto sería la gravedad capaz de frenar la expansión del Universo, creando un ciclo continuo de explosión-colapso (Big Bang-Big Crunch) o bien una expansión que se iría ralentizando eternamente pero sin llegar nunca a detenerse del todo. Pues bien, hoy en día sabemos que no va a ser ni lo uno ni lo otro. Resulta que el Universo no se está frenando. No tiene visos de querer volver a colapsar pero tampoco está ralentizando su marcha.

Antes al contrario, las observaciones nos muestran que desde hace 5,000 millones de años (un tercio de su vida), el Universo ha dejado de frenarse y¡ha comenzado a acelerar! Este resultado fue obtenido por dos grupos independientemente y ambos recibieron el Premio Nobel en 2011. Fue tan sorprendente que ninguno de los dos grupos se atrevió a publicarlo hasta que se enteraron de los resultados del otro. Para explicar el fenómeno, los teóricos han tenido que postular la existencia de una «energía oscura», que sería omnipresente en todo el espacio vacío.

El ciclo continuo de Penrose

Hasta aquí hemos explicado la cosmología moderna canónica, la visión aceptada mayoritariamente por los expertos en el tema. ¿Qué es, entonces, lo que añade Penrose? Pues, según su teoría, estas dos revelaciones, la inflación y la expansión acelerada del Universo, están íntimamente relacionadas. De hecho, serían la misma cosa. Para Penrose, el Universo vive un ciclo continuo e infinito de «creaciones», pero no en el modelo tradicional de explosión-colapso.

En su lugar, Penrose postula que cada uno de los ciclos (que él llama eones) acaba con una fase de expansión acelerada que se convierte en la inflación del eón siguiente. Lo de Penrose no es una ocurrencia, es una teoría. Esto significa que ha resuelto las ecuaciones de la relatividad general y los números cuadran salvo por un factor de escala. Quiere decirse que las escalas del nuevo universo son mucho mayores, tanto en el espacio como en el tiempo.

De Universo a melón

Así, todo nuestro Universo en expansión acelerada, está camino de convertirse en lo que sería un melón del Universo siguiente. Y los miles de millones de años que dura esta expansión serían la breve fracción de segundo en aquel nuevo Universo. Quizás en un futuro increíblemente distante, habrá criaturas inconcebiblemente grandes y lentas en el siguiente eón, investigando esta época en la que vivimos hoy en día, a la que quizás den el absurdo nombre de inflación y quizás la consideren el origen de su universo. Una implicación particularmente profunda de todo esto es que, de ser cierto, estaríamos ahora mismo viviendo un nuevo big bang que comenzó hace 5,000 millones de años y lo estaríamos viendo transcurrir a cámara superlenta.

Quiero resaltar que esta teoría, llamada Cosmología Cíclica Conforme, no es la aceptada por la mayoría de los cosmólogos. Sin embargo, no hay nada incorrecto o erróneo en ella, que sepamos. Penrose es uno de los mayores expertos mundiales en la física de la relatividad general y la cosmología. Su teoría cumple con la física conocida y esto sí que es un mérito que le concede la comunidad. Al igual que hizo Lemaître hace un siglo, ha encontrado una solución matemática correcta a las ecuaciones de la Física que conocemos, pero es una solución que aborrecen sus colegas por razones más filosóficas que científicas.

Un aspecto particularmente fascinante es que, como toda buena teoría, la naturaleza cuantitativa de la cosmología de Penrose le permite hacer predicciones. Las ecuaciones indican que los eones no son completamente independientes y algo de información se puede transmitir de uno a otro. En particular, las ondas gravitacionales (ésas que recientemente detectó el experimento LIGO) creadas por catástrofes cósmicas en el eón anterior podrían atravesar la época de la inflación y llegar hasta nuestros días. Estas ondas producirían patrones de anillos concéntricos en el fondo cósmico de microondas. Ni que decir tiene que muchos investigadores están ya manos a la obra buscando esos anillos. Si se encontraran, sería la primera observación de algo que ocurrió antes del Big Bang.

Autor :

Héctor Socas Navarro , investigador del Instituto de Astrofísica de Canarias (IAC) y divulgador en «Coffe Break». El autor agradece al Dr Jose Alberto Rubiño por su lectura crítica y comentarios para mejorar este artículo.

FUENTE:

Ciencia

Para una correcta lectura del gráfico expuesto por Penrose debe ir a esta direccion:

http://www.abc.es/ciencia/abci-habia-algo-antes-big-bang-201609170155_noticia.html

NEWS IN SCIENCE...SCIENCE NEWS...

2016-09-14T13:10:00.000-07:00

Announcements from the Simons Foundation

September 2016

Physics of Feather Color Holds Clues to Diversity of Life

Hidden in the color of birds and their mating choices, says Junior Fellow Rafael Maia, is information that can help elucidate the evolution of complex behaviors.

Prime Numbers Reveal the Practicality of Impracticality

Understanding primes can lead to many applications, but overemphasizing the practicalities of primes has its perils.

Announcing the Simons Collaboration on Special Holonomy in Geometry, Analysis and Physics

The collaboration will advance the theory and applications of spaces with special holonomy and the geometric structures, calibrated submanifolds and instantons associated with them.

Announcing the Simons Collaboration on the Non-Perturbative Bootstrap

The critical challenge for this new collaboration is to map and understand the whole space of quantum field theories, including strongly coupled models.

Events

Metagenomic DNA Sequencing to Detect and Diagnose Infections

In this lecture, Dr. Steven Salzberg will describe how scientists are using the latest sequencing technology in combination with new, very fast algorithms to sequence a complex mixture of DNA from a sick patient and, in some cases, identify the causative agent of an infection.

Wednesday, September 21, 2016
5:00pm - 6:15pm
Gerald D. Fischbach Auditorium

The Monster at the Heart of our Galaxy

Dr. Andrea Ghez will discuss the latest developments in the study of black holes, specifically how the environment around the black hole at the center of the Milky Way is quite different than astronomers expected. She will also describe how studying the orbits of stars at the galactic center could improve our understanding of gravity.

Wednesday, September 28, 2016
5:00pm - 6:15pm
Gerald D. Fischbach Auditorium

Tuberous Sclerosis: Shedding Light on the Neural Circuitry of Autism

Dr. Mustafa Sahin, who studies the basis of Tuberous Sclerosis Complex (TSC) in cell culture, animal models and the clinic, will present an update on translational research in TSC.

Wednesday, October 5, 2016
5:00pm - 6:15pm
Gerald D. Fischbach Auditorium

Funding Opportunities

Simons Fellows Program in Mathematics and Physical Sciences

The Fellows Programs provide funds to faculty for up to a semester-long research leave from classroom teaching and administrative obligations.

DEADLINE: September 29, 2016.

Simons Collaboration on the Global Brain Postdoctoral Fellowships

The Simons Collaboration on the Global Brain (SCGB) seeks applicants for postdoctoral fellowships. Intended work is at the interface of theory and experiment on the nature, role and mechanisms of the neural activity that produces cognition.

DEADLINE: October 3, 2016.

Simons Collaborations in Mathematics and the Physical Sciences

The aim of the Simons Collaborations in MPS program is to stimulate progress on fundamental scientific questions of major importance in the broad area of mathematics, theoretical physics and theoretical computer science.

DEADLINE: October 3, 2016.

Targeted Grants to Institutes in Mathematics and Physical Sciences

The Targeted Grants to Institutes program is intended to support institutions in the mathematics and physical sciences through funding to centers of excellence, to help establish scientific culture and strengthen contacts within the international scientific community.

DEADLINE: October 13, 2016

Simons Early Career Investigator in Marine Microbial Ecology and Evolution Awards

The purpose of these awards is to help launch the careers of outstanding investigators who use quantitative approaches to advance understanding of marine microbial ecology and evolution.

DEADLINE: November 7, 2016

Simons Symposia Program

The program brings mathematicians, theoretical physicists and theoretical computer scientists together to interact and collaborate on one topic, or tightly connected groups of topics, over a series of meetings.

DEADLINE: November 9, 2016

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2016-09-10T17:14:00.000-07:00

Colliding Black Holes Tell New Story of Stars

By Natalie Wolchover

September 6, 2016

Just months after their discovery, gravitational waves coming from the mergers of black holes are shaking up astrophysics.

Ana Kova for Quanta Magazine

At a talk last month in Santa Barbara, California, addressing some of the world’s leading astrophysicists, Selma de Mink cut to the chase. “How did they form?” she began.

“They,” as everybody knew, were the two massive black holes that, more than 1 billion years ago and in a remote corner of the cosmos, spiraled together and merged, making waves in the fabric of space and time. These “gravitational waves” rippled outward and, on Sept. 14, 2015, swept past Earth, strumming the ultrasensitive detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO). LIGO’s discovery, announced in February, triumphantly vindicated Albert Einstein’s 1916 prediction that gravitational waves exist. By tuning in to these tiny tremors in space-time and revealing for the first time the invisible activity of black holes — objects so dense that not even light can escape their gravitational pull — LIGO promised to open a new window on the universe, akin, some said, to when Galileo first pointed a telescope at the sky.

Already, the new gravitational-wave data has shaken up the field of astrophysics. In response, three dozen experts spent two weeks in August sorting through the implications at the Kavli Institute for Theoretical Physics (KITP) in Santa Barbara.

Jump-starting the discussions, de Mink, an assistant professor of astrophysics at the University of Amsterdam, explained that of the two — and possibly more — black-hole mergers that LIGO has detected so far, the first and mightiest event, labeled GW150914, presented the biggest puzzle. LIGO was expected to spot pairs of black holes weighing in the neighborhood of 10 times the mass of the sun, but these packed roughly 30 solar masses apiece. “They are there — massive black holes, much more massive than we thought they were,” de Mink said to the room. “So, how did they form?”

The mystery, she explained, is twofold: How did the black holes get so massive, considering that stars, some of which collapse to form black holes, typically blow off most of their mass before they die, and how did they get so close to each other — close enough to merge within the lifetime of the universe? “These are two things that are sort of mutually exclusive,” de Mink said. A pair of stars that are born huge and close together will normally mingle and then merge before ever collapsing into black holes, failing to kick up detectable gravitational waves.

Selma de Mink of the University of Amsterdam has devised a new theory stating that pairs of black hole close enough to merge come from massive stars whose contents have been mixed until they are homogeneous throughout.

Nailing down the story behind GW150914 “is challenging all our understanding,” said Matteo Cantiello, an astrophysicist at KITP. Experts must retrace the uncertain steps from the moment of the merger back through the death, life and birth of a pair of stars — a sequence that involves much unresolved astrophysics. “This will really reinvigorate certain old questions in our understanding of stars,” said Eliot Quataert, a professor of astronomy at the University of California, Berkeley, and one of the organizers of the KITP program.

Understanding LIGO’s data will demand a reckoning of when and why stars go supernova; which ones turn into which kinds of stellar remnants; how stars’ composition, mass and rotation affect their evolution; how their magnetic fields operate; and more.

The work has just begun, but already LIGO’s first few detections have pushed two theories of binary black-hole formation to the front of the pack. Over the two weeks in Santa Barbara, a rivalry heated up between the new “chemically homogeneous” model for the formation of black-hole binaries, proposed by de Mink and colleagues earlier this year, and the classic “common envelope” model espoused by many other experts. Both theories (and a cluster of competitors) might be true somewhere in the cosmos, but probably only one of them accounts for the vast majority of black-hole mergers. “In science,” said Daniel Holz of the University of Chicago, a common-envelope proponent, “there’s usually only one dominant process — for anything.”

NASA, ESA, F. Paresce, R. O’Connell and the Wide Field Camera 3 Science Oversight Committee

The R136 star cluster at the heart of the Tarantula Nebula gives rise to many massive stars, which are thought to be the progenitors of black-hole binaries.

The story of GW150914 almost certainly starts with massive stars — those that are at least eight times as heavy as the sun and which, though rare, play a starring role in galaxies. Massive stars are the ones that explode as supernovas, spewing matter into space to be recycled as new stars; only their cores then collapse into black holes and neutron stars, which drive exotic and influential phenomena such as gamma-ray bursts, pulsars and X-ray binaries.

De Mink and collaborators showed in 2012 that most known massive stars live in binary systems. Binary massive stars, in her telling, “dance” and “kiss” and suck each other’s hydrogen fuel “like vampires,” depending on the circumstances. But which circumstances lead them to shrink down to points that recede behind veils of darkness, and then collide?

The conventional common-envelope story, developed over decades starting with the 1970s work of the Soviet scientists Aleksandr Tutukov and Lev Yungelson, tells of a pair of massive stars that are born in a wide orbit. As the first star runs out of fuel in its core, its outer layers of hydrogen puff up, forming a “red supergiant.” Much of this hydrogen gas gets sucked away by the second star, vampire-style, and the core of the first star eventually collapses into a black hole.

The interaction draws the pair closer, so that when the second star puffs up into a supergiant, it engulfs the two of them in a common envelope. The companions sink ever closer as they wade through the hydrogen gas. Eventually, the envelope is lost to space, and the core of the second star, like the first, collapses into a black hole. The two black holes are close enough to someday merge.

Because the stars shed so much mass, this model is expected to yield pairs of black holes on the lighter side, weighing in the ballpark of 10 solar masses.LIGO’s second signal, from the merger of eight- and 14-solar-mass black holes, is a home run for the model. But some experts say that the first event, GW150914, is a stretch.

In a June paper in Nature, Holz and collaborators Krzysztof Belczynski, Tomasz Bulik and Richard O’Shaughnessy argued that common envelopes can theoretically produce mergers of 30-solar-mass black holes if the progenitor stars weigh something like 90 solar masses and contain almost no metal (which accelerates mass loss).

Such heavy binary systems are likely to be relatively rare in the universe, raising doubts in some minds about whether LIGO would have observed such an outlier so soon. In Santa Barbara, scientists agreed that if LIGO detects many very heavy mergers relative to lighter ones, this will weaken the case for the common-envelope scenario.

Lucy Reading-Ikkanda for Quanta Magazine

This weakness of the conventional theory has created an opening for new ideas. One such idea began brewing in 2014, when de Mink and Ilya Mandel, an astrophysicist at the University of Birmingham and a member of the LIGO collaboration, realized that a type of binary-star system that de Mink has studied for years might be just the ticket to forming massive binary black holes.

The chemically homogeneous model begins with a pair of massive stars that are rotating around each other extremely rapidly and so close together that they become “tidally locked,” like tango dancers. In tango, “you are extremely close, so your bodies face each other all the time,” said de Mink, a dancer herself. “And that means you are spinning around each other, but it also forces you to spin around your own axis as well.” This spinning stirs the stars, making them hot and homogeneous throughout. And this process might allow the stars to undergo fusion throughout their whole interiors, rather than just their cores, until both stars use up all their fuel. Because the stars never expand, they do not intermingle or shed mass. Instead, each collapses wholesale under its own weight into a massive black hole. The black holes dance for a few billion years, gradually spiraling closer and closer until, in a space-time-buckling split second, they coalesce.

De Mink and Mandel made their case for the chemically homogeneous model in a paper posted online in January.

Another paper proposing the same idea, by researchers at the University of Bonn led by the graduate student Pablo Marchant, appeared days later. When LIGO announced the detection of GW150914 the following month, the chemically homogeneous theory shot to prominence. “What I’m discussing was a pretty crazy story up to the moment that it made, very nicely, black holes of the right mass,” de Mink said.

However, aside from some provisional evidence, the existence of stirred stars is speculative. And some experts question the model’s efficacy. Simulations suggest that the chemically homogeneous model struggles to explain smaller black-hole binaries like those in LIGO’s second signal. Worse, doubt has arisen as to how well the theory really accounts for GW150914, which is supposed to be its main success story. “It’s a very elegant model,” Holz said. “It’s very compelling. The problem is that it doesn’t seem to fully work.”

All Spun Up

Along with the masses of the colliding black holes, LIGO’s gravitational-wave signals also reveal whether the black holes were spinning. At first, researchers paid less attention to the spin measurement, in part because gravitational waves only register spin if black holes are spinning around the same axis that they orbit each other around, saying nothing about spin in other directions.

However, in a May paper, researchers at the Institute for Advanced Study in Princeton, N.J., and the Hebrew University of Jerusalem argued that the kind of spin that LIGO measures is exactly the kind black holes would be expected to have if they formed via the chemically homogeneous channel. (Tango dancers spin and orbit each other in the same direction.) And yet, the 30-solar-mass black holes in GW150914 were measured to have very low spin, if any, seemingly striking a blow against the tango scenario.

Courtesy of Daniel Holz

Daniel Holz of the University of Chicago works on the classic common-envelope explanation for the formation of black-hole binaries.

“Is spin a problem for the chemically homogeneous channel?”Sterl Phinney, a professor of astrophysics at the California Institute of Technology, prompted the Santa Barbara group one afternoon. After some debate, the scientists agreed that the answer was yes.

However, mere days later, de Mink, Marchant, and Cantiello found a possible way out for the theory. Cantiello, who has recently made strides in studying stellar magnetic fields, realized that the tangoing stars in the chemically homogeneous channel are essentially spinning balls of charge that would have powerful magnetic fields, and these magnetic fields are likely to cause the star’s outer layers to stream into strong poles. In the same way that a spinning figure skater slows down when she extends her arms, these poles would act like brakes, gradually reducing the stars’ spin. The trio has since been working to see if their simulations bear out this picture. Quataert called the idea “plausible but perhaps a little weaselly.”

Lucy Reading-Ikkanda for Quanta Magazine; Source: LIGO

On the last day of the program, setting the stage for an eventful autumn as LIGO comes back online with higher sensitivity and more gravitational-wave signals roll in, the scientists signed “Phinney’s Declaration,” a list of concrete statements about what their various theories predict. “Though all models for black hole binaries may be created equal (except those inferior ones proposed by our competitors),” begins the declaration, drafted by Phinney, “we hope that observational data will soon make them decidedly unequal.”

As the data pile up, an underdog theory of black-hole binary formation could conceivably gain traction — for instance, the notion that binaries form through dynamical interactions inside dense star-forming regions called “globular clusters.” LIGO’s first run suggested that black-hole mergers are more common than the globular-cluster model predicts. But perhaps the experiment just got lucky last time and the estimated merger rate will drop.

Adding to the mix, a group of cosmologists recently theorized that GW150914 might have come from the merger of primordial black holes, which were never stars to begin with but rather formed shortly after the Big Bang from the collapse of energetic patches of space-time. Intriguingly, the researchers argued in a recent paper in Physical Review Letters that such 30-solar-mass primordial black holes could comprise some or all of the missing “dark matter” that pervades the cosmos. There’s a way of testing the idea against astrophysical signals called fast radio bursts.

It’s perhaps too soon to dwell on such an enticing possibility; astrophysicists point out that it would require suspiciously good luck for black holes from the Big Bang to happen to merge at just the right time for us to detect them, 13.8 billion years later. This is another example of the new logic that researchers must confront at the dawn of gravitational-wave astronomy. “We’re at a really fun stage,” de Mink said. “This is the first time we’re thinking in these pictures.”

SOURCE < QUANTA MAGAZINE

EXTRATERRIAL LIFE IN THE UNIVERSE.._DOUBTFUL

2016-09-06T14:04:00.000-07:00

Have We Detected an Alien Signal? It's Highly Doubtful

A blip of energy picked up by a Russian radio telescope might have

been nothing more than a satellite passing overhead—or even a

software glitch

· STAFF By Lee Billings on August 30, 2016

The VLA radio telescopes in New Mexico Credit: By Hajor via Wikimedia Commons under Creative Commons license

Based on breathless news reports from many prominent media outlets that should know better, this week’s biggest non-story in science is the discovery of a possible radio signal from talkative aliens elsewhere in the Milky Way. I’m here to tell you, alas, that anyone hoping for this to be the moment of First Contact with another galactic civilization is very likely to be disappointed.

It all started innocently enough, with a carefully worded blog post this past Saturday from the respected science journalist Paul Gilster. Gilster wrote about a message he had received from some SETI (Search for Extraterrestrial Intelligence) researchers who reported a curiously powerful 3-second burst of radio waves from a star less than 100 light-years away. The researchers, led by Nikolai Bursov of the Russian Academy of Sciences, couldn't rule out the possibility that the signal was artificial, and were intrigued enough that they called for “permanent monitoring” of the star.

Gilster’s post ignited a firestorm of sensationalistic and credulous news coverage that is still blazing as I write this, burning through newspapers and websites to astound most everyone who encounters it. Soon, I predict, it will burn out—as these sorts of stories (almost) always do.

Here's what happened: in May of 2015, the RATAN-600 radio telescope in Zelenchukskaya, Russia detected the signal from the direction of HD 164595, a star about 94 light-years away in the constellation Hercules. This is a star very much like our Sun albeit slightly older, with an estimated age of 6.3 billion years. It also harbors at least one known planet, an uninhabitable Neptune-sized world, though of course others more habitable could exist in the system.

If the signal really is artificial, and really does come from HD 164595, its energy source must be gargantuan. According to Seth Shostak, an astronomer at the SETI Institute in California who was not involved with the research, a radio blast sent out in all directions by a hypothetical alien civilization would take hundreds of times more power than that of all the sunlight bathing the Earth, based on how bright the signal appeared in the Russian telescope (that's because we'd only be seeing a tiny part of of the total radio energy).

If it were instead a beam focused solely on the Earth, the signal would still require twice the electricity used by the United States in an entire year. Clearly, if this is another galactic civilization, they are far, far more advanced than our own.

The trouble is, there is no good reason to think that this signal is due to aliens at all—and there never was, according to Eric Korpela, an astronomer at the University of California in Berkeley. Korpela heads SETI@Home, a citizen-science initiative that processes SETI data using home computers; on the SETI@Home blog, Korpela said that after evaluating the available evidence he was “unimpressed” and that the data was “relatively uninteresting.”

“SETI@home has seen millions of potential signals with similar characteristics, but it takes more than that to make a good candidate,” Korpela continued. “Multiple detections are a minimum criterion.”

That's not what the Russian telescope found. The putative signal only occurred once out of 39 times the RATAN-600 telescope scanned the star, and the scans themselves were performed in such a way that many potential false positives could not be ruled out.

Rather than being a beacon from ET, Korpela said, the signal could just as easily have been due to flares from the target star, the burp of a supermassive black hole in a background galaxy, or even the chance magnification of ordinary, all-natural stellar radio emissions by a passing foreground star or a transient ripple of interstellar plasma.

What this boils down to is that extraordinary claims require extraordinary evidence—evidence that can be very hard to come by for modern SETI programs.

Contrary to Hollywood depictions, SETI efforts tend to have meager budgets that only support infrequent observations of small fractions of the sky in narrow bandwidth ranges. Could the new signal from HD 164595 be a genuine transmission from a cosmic civilization? Well, yes, conceivably it could. But so could the millions of other curious optical blips and radio spikes sitting in SETI archives, each a singular phenomenon that whispered just once into a telescope, never to repeat or return. This has happened before—see, for instance, the tantalizing “Wow! signal” from 1977, and the resulting decades of fruitless efforts see it a second time.

Even assuming there was enough telescope time available (there isn’t), every SETI program on Earth would likely go bankrupt trying to follow-up each of the millions of potential candidates if each received the care and attention bestowed upon the Wow! signal. In such a resource-constrained environment, only the very best and most compelling signals should merit much closer attention—and Korpela isn’t sure the signal from HD 164595 has crossed that threshold.

The real problem, Korpela goes on, is that the media frenzy over HD 164595 means that no reputable SETI program can now afford to not use precious telescope time to look for other signals from HD 164595. These projects need money, and they need public attention—ignoring the signal even if it is overwhelmingly likely to prove spurious is not an option. “We’ll be along for the ride,” he wrote. “And we’ll all find nothing.”

Indeed, according to Shostak, the SETI Institute’s Allen Telescope Array is already looking at the star, though so far they have yet to see anything peculiar.

Other results are now coming in. Just this morning the Breakthrough Listen project, a private SETI endeavor funded by the billionaire Yuri Milner, released results of a follow-up on HD 164595 using archival data as well as new observations from the Green Bank Telescope in West Virginia. Breakthrough found—you guessed it—nothing.

More curiously, Breakthrough’s statistical analysis of the available data suggests that, if produced by natural astrophysical causes, one would expect that previous surveys would have seen such strong signals elsewhere in the sky.

Which means that the RATAN-600 team was “either extremely lucky to detect this source in their observations, or that the transient is due to local interference or other calibration issues.” That is, absent the possibility of aliens, even an astrophysical source for the signal looks suspect—a far more likely explanation for the signal would be the passage of a satellite overhead, or an errant signal from electric currents coursing through wires within the observatory itself, or even a software glitch.

Nevertheless, the Breakthrough Listen team intends to periodically revisit HD 164595 in the future to keep looking for a repetition of the signal. Other SETI programs will undoubtedly do the same. And perhaps they should. But let’s not fool ourselves: Even in the lofty, noble quest to break our cosmic solitude, sometimes the tail can wag the dog.

Now if you’re interested in a truly epochal discovery relevant to the search for extraterrestrial life,

I would refer you to last week’s announcement of a rocky planet found in a habitable orbit around the Sun’s nearest neighboring star, Proxima Centauri—which frustratingly seems to have made less of an impression than this week’s far more questionable news.

Lee Billings

Lee Billings is an editor at Scientific American covering space and physics.

Nick Higgins

SOURCE….Sky and Telescope

NEW ESSAYS,NEW IDEAS ON THE UNIVERSE BY EDGE...

2016-09-06T13:43:00.000-07:00

To arrive at the edge of the world's knowledge, seek out the most complex and sophisticated minds, put them in a room together, and have them ask each other the questions they are asking themselves.

September 1, 2016

THE THIRD CULTURE

Summer Reading: Highlights from the Edge Archive

"Deliciously creative, the variety astonishes. Intellectual skyrockets of stunning brilliance. Nobody in the world is doing what Edge is doing...the greatest virtual research university in the world."
— Denis Dutton, Founding Editor, Arts & Letters Daily

[ED NOTE: It’s summer and a good time to reflect on twenty years of Edge. Each week through the rest of the season, we will revisit five highlights from the Edge archives worthy of your time and attention. — JB]

THE NEUROLOGY OF SELF-AWARENESS
Vilayanur Ramachandran
[January 8, 2007]

What is the self? How does the activity of neurons give rise to the sense of being a conscious human being? Even this most ancient of philosophical problems, I believe, will yield to the methods of empirical science. It now seems increasingly likely that the self is not a holistic property of the entire brain; it arises from the activity of specific sets of interlinked brain circuits. But we need to know which circuits are critically involved and what their functions might be. It is the "turning inward" aspect of the self—its recursiveness—that gives it its peculiar paradoxical quality.

[Continue...]

THE ENERGY OF EMPTY SPACE THAT ISN'T ZERO
Lawrence Krauss
[July 5, 2006]

I invited a group of cosmologists, experimentalists, theorists, and particle physicists. Stephen Hawking came. We had three Nobel laureates: Gerard 't Hooft, David Gross, Frank Wilczek; well-known cosmologists and physicists such as Jim Peebles at Princeton, Alan Guth at MIT, Kip Thorne at Caltech, Lisa Randall at Harvard; experimentalists, such as Barry Barish of LIGO, the gravitational wave observatory; we had observational cosmologists, people looking at the cosmic microwave background; we had Maria Spiropulu from CERN, who's working on the Large Hadron Collider—which, a decade ago, people wouldn't have thought it was a probe of gravity, but now due to recent work in the possibility of extra dimensions it might be.

[Continue...]

LAYERS OF REALITY
Sean Carroll
[May 28, 2015]

We know there's a law of nature—he second law of thermodynamics—that says that disorderliness grows with time. Is there another law of nature that governs the complexity of what happens? That talks about multiple layers of the structures and how they interact with each other? Embarrassingly enough, we don't even know how to define this problem yet. We don't know the right quantitative description for complexity. This is very early days. This is Copernicus, not even Kepler, much less Galileo or Newton. This is guessing at the ways to think about these problems

[Continue...]

EINSTEIN AND POINCARE
Peter Galison
[June 22, 2003]

I'm interested in bending the edges of the spectrum to make the abstract and the concrete hit one another more directly

[Continue...]

MOUSE MODELS
Azra Raza
[January 1, 2014]

It's time to let go of the mouse models—at least, as surrogates for bringing drugs to the bedside. Remember what Mark Twain said: "What gets us into trouble is not what we don't know; it's what we know for sure that just ain't so."

[Continue...]

INNOVATION ON THE EDGES
Joichi Ito
[June 21, 2012]

Today, what you want is to have resilience and agility, and you want to be able to participate in, and interact with the disruptive things. Everybody loves the word "disruptive innovation." Well, how and where does disruptive innovation happen? It doesn't happen in the big planned R&D labs; it happens on the edges of the network. Most important ideas, especially in the consumer Internet space, but more and more now in other things like hardware and biotech, you're finding it happening around the edges

[Continue...]

DIGITAL REALITY
Neil Gershenfeld
[January 23, 2015]

Today, you can send a design to a fab lab and you need ten different machines to turn the data into something. Twenty years from now, all of that will be in one machine that fits in your pocket. This is the sense in which it doesn't matter. You can do it today. How it works today isn't how it's going to work in the future but you don't need to wait twenty years for it. Anybody can make almost anything almost anywhere.

[Continue...]

REINVENTING SOCIETY IN THE WAKE OF BIG DATA
Alex Pentland
[August 30, 2012]

With Big Data we can now begin to actually look at the details of social interaction and how those play out, and are no longer limited to averages like market indices or election results. This is an astounding change. The ability to see the details of the market, of political revolutions, and to be able to predict and control them is definitely a case of Promethean fire—it could be used for good or for ill, and so Big Data brings us to interesting times. We're going to end up reinventing what it means to have a human society

[Continue...]

TO BRING BACK THE EXTINCT
Ryan Phelan
[August 28, 2012]

One of the fundamental questions here is, is extinction a good thing? Is it "nature's way?" And if it's nature's way, who in the world says anyone should go about changing nature's way? If something was meant to go extinct, then who are we to screw around with it and bring it back? I don't think it's really nature's way. I think that the extinction that we've seen since man is 99.9 percent caused by man

[Continue...]

WE NEED A MODERN ORIGIN STORY: A BIG HISTORY
David Christian
[May 21, 2015]

I'm increasingly thinking that this idea that modernity puts us in a world without meaning—philosophers have banged on about this for a century-and-a-half—may be completely wrong. We may be living in an intellectual building site, where a new story is being constructed. It's vastly more powerful than the previous stories because it's the first one that is global. It's not anchored in a particular culture or a particular society. This is an origin story that works for humans in Beijing as well as in Buenos Aires.

It's a global origin story, and it sums over vastly more information than any early origin story. This is very, very powerful stuff. It's full of meaning. We're now at the point where, across so many domains, the amount of information, of good, rigorous ideas, is so rich that we can tease out that story.

[Continue...]

SHAMING AT SCALE
Jennifer Jacquet
[November 18, 2014]

Shaming, in this case, was a fairly low-cost form of punishment that had high reputational impact on the U.S. government, and led to a change in behavior. It worked at scale—one group of people using it against another group of people at the group level. This is the kind of scale that interests me. And the other thing that it points to, which is interesting, is the question of when shaming works. In part, it's when there's an absence of any other option. Shaming is a little bit like antibiotics. We can overuse it and actually dilute its effectiveness, because it's linked to attention, and attention is finite. With punishment, in general, using it sparingly is best. But in the international arena, and in cases in which there is no other option, there is no formalized institution, or no formal legislation, shaming might be the only tool that we have, and that's why it interests me.

[Continue...]

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2016-08-31T13:56:00.001-07:00

FIRST STARS FORMED EVEN LATER THAN PREVIOUSLY THOUGHT

31 August 2016

ESA's Planck satellite has revealed that the first stars in the Universe started forming later than previous observations of the Cosmic Microwave Background indicated. This new analysis also shows that these stars were the only sources needed to account for reionising atoms in the cosmos, having completed half of this process when the Universe had reached an age of 700 million years.

Cosmic reionisation. Credit: ESA – C. Carreau

With the multitude of stars and galaxies that populate the present Universe, it's hard to imagine how different our 13.8 billion year cosmos was when it was only a few seconds old. At that early phase, it was a hot, dense primordial soup of particles, mostly electrons, protons, neutrinos, and photons – the particles of light.

In such a dense environment the Universe appeared like an 'opaque' fog, as light particles could not travel any significant distance before colliding with electrons.

As the cosmos expanded, the Universe grew cooler and more rarefied and, after about 380 000 years, finally became 'transparent'.

By then, particle collisions were extremely sporadic and photons could travel freely across the cosmos.

History of the Universe. Credit: ESA

Today, telescopes like Planck can observe this fossil light across the entire sky as the Cosmic Microwave Background, or CMB. Its distribution on the sky reveals tiny fluctuations that contain a wealth of information about the history, composition and geometry of the Universe.

The release of the CMB happened at the time when electrons and protons joined to form hydrogen atoms. This is the first moment in the history of the cosmos when matter was in an electrically neutral state.

After that, a few hundred million years passed before these atoms could assemble and eventually give rise to the Universe's first generation of stars.

As these first stars came to life, they filled their surroundings with light, which subsequently split neutral atoms apart, turning them back into their constituent particles: electrons and protons. Scientists refer to this as the 'epoch of reionisation'. It did not take long for most material in the Universe to become completely ionised, and – except in a very few, isolated places – it has been like that ever since.

Observations of very distant galaxies hosting supermassive black holes indicate that the Universe had been completely reionised by the time it was about 900 million years old. The starting point of this process, however, is much harder to determine and has been a hotly debated topic in recent years.

"The CMB can tell us when the epoch of reionisation started and, in turn, when the first stars formed in the Universe," explains Jan Tauber, Planck project scientist at ESA.

To make this measurement, scientists exploit the fact that a fraction of the CMB is polarised: part of the light vibrates in a preferred direction. This results from CMB photons bouncing off electrons – something that happened very frequently in the primordial soup, before the CMB was released, and then again later, after reionisation, when light from the first stars brought free electrons back onto the cosmic stage.

"It is in the tiny fluctuations of the CMB polarisation that we can see the influence of the reionisation process and deduce when it began," adds Tauber.

Polarisation of the Cosmic Microwave Background. Credit: ESA and the Planck Collaboration

A first estimate of the epoch of reionisation came in 2003 from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), suggesting that this process might have started early in cosmic history, when the Universe was only a couple of hundred million years old.

This result was problematic, because there is no evidence that any stars had formed by then, which would mean postulating the existence of other, exotic sources that could have caused the reionisation at that time.

This first estimate was soon to be corrected, as subsequent data from WMAP pushed the starting time to later epochs, indicating that the Universe had not been significantly reionised until at least some 450 million years into its history.

This eased, but did not completely solve the puzzle: although the earliest of the first stars have been observed to be present already when the Universe was 300 to 400 million years old, it remained unclear whether these stars were the main culprits for reionising fully the cosmos or whether additional, more exotic sources must have played a role too.

In 2015, the Planck Collaboration provided new data to tackle the problem, moving the reionisation epoch even later in cosmic history and revealing that this process was about half-way through when the Universe was around 550 million years old.

The result was based on Planck's first all-sky maps of the CMB polarisation, obtained with its Low-Frequency Instrument (LFI).

Now, a new analysis of data from Planck's other detector, the High-Frequency Instrument (HFI), which is more sensitive to this phenomenon than any other so far, shows that reionisation started even later – much later than any previous data have suggested.

"The highly sensitive measurements from HFI have clearly demonstrated that reionisation was a very quick process, starting fairly late in cosmic history and having half-reionised the Universe by the time it was about 700 million years old," says Jean-Loup Puget from Institut d'Astrophysique Spatiale in Orsay, France, principal investigator of Planck's HFI.

"These results are now helping us to model the beginning of the reionisation phase.""We have also confirmed that no other agents are needed, besides the first stars, to reionise the Universe," adds Matthieu Tristram, a Planck Collaboration scientist at Laboratoire de l'Accélérateur Linéaire in Orsay, France.

The new study locates the formation of the first stars much later than previously thought on the cosmic timeline, suggesting that the first generation of galaxies are well within the observational reach of future astronomical facilities, and possibly even some current ones.

In fact, it is likely that some of the very first galaxies have already been detected with long exposures, such as the Hubble Ultra

Deep Field observed with the NASA/ESA Hubble Space Telescope, and it will be easier than expected to catch many more with future observatories such as the NASA/ESA/CSA James Webb Space Telescope.

NOTES FOR EDITORS

'Planck intermediate results. XLVII. Planck constraints on reionization history' and 'Planck intermediate results. XLVI.

Reduction of large-scale systematic effects in HFI polarization maps and estimation of the reionization optical depth'

by the Planck Collaboration are published in Astronomy and Astrophysics.

MORE ABOUT PLANCK

Launched in 2009, Planck was designed to map the sky in nine frequencies using two state-of-the-art instruments:

the Low Frequency Instrument (LFI), which includes three frequency bands in the range 30-70 GHz, and the High Frequency Instrument (HFI), which includes six frequency bands in the range 100-857 GHz.

HFI completed its survey in January 2012, while LFI continued to make science observations until 3 October 2013, before being switched off on 19 October 2013. Seven of Planck's nine frequency channels were equipped with polarisation-sensitive detectors.

The Planck Scientific Collaboration consists of all the scientists who have contributed to the development of the mission, and who participate in the scientific exploitation of the data during the proprietary period.

These scientists are members of one or more of four consortia: the LFI Consortium, the HFI Consortium, the DK-Planck Consortium, and ESA's Planck Science Office. The two European-led Planck Data Processing Centres are located in Paris, France and Trieste, Italy.

The LFI consortium is led by N. Mandolesi, Università degli Studi di Ferrara, Italy (deputy PI: M. Bersanelli, Università degli Studi di Milano, Italy), and was responsible for the development and operation of LFI. The HFI consortium is led by J.L. Puget, Institut d'Astrophysique Spatiale in Orsay (CNRS/Université Paris-Sud), France (deputy PI: F. Bouchet, Institut d'Astrophysique de Paris (CNRS/UPMC), France), and was responsible for the development and operation of HFI.

FOR FURTHER INFORMATION, PLEASE CONTACT:

Jan Tauber

ESA Planck Project Scientist

Scientific Support Office

Directorate of Science

European Space Agency

Email: jan.tauberesa.int

Phone: +31-71-565-5342

Jean-Loup Puget

Principal Investigator, High Frequency Instrument

Institut d'Astrophysique Spatiale

Orsay, France

Email: jean-loup.pugetias.u-psud.fr

Phone: +33-169858665

Matthieu Tristram

CNRS - IN2P3

Laboratoire de l'Accélérateur Linéaire

Université Paris-Sud 11

Orsay, France

Email: tristramlal.in2p3.fr

Phone: +33-164468388

SOURCE:

SciTech.editorial@esa.int by e -mail notification

ESPANA CON FUERTE ASCENDENCIA JUDIA ,ORIENTE MEDIO Y MAGREB

2016-08-31T11:48:00.000-07:00

Estudio genético revela : uno de cada cinco españoles tiene ascendencia judía y uno de cada 10 tiene genes heredados de los habitantes del Norte de África.
( Uno de cada tres españoles tiene marcadores genéticos de Oriente Medio o el Magreb)

La revista científica ‘American Journal of Human Genetics’, publicó en su mas reciente edición los resultados de un estudio realizado en la península Ibérica por un equipo internacional de investigadores compuesto por científicos británicos, españoles, portugueses, franceses e israelíes llegan a la conclusión de que uno de cada 5 españoles tiene ascendencia judía y uno de cada 10 tiene genes heredados de los habitantes del Norte de África.

El grupo de investigadores que estuvo dirigido por el británico Mark Jobling de la Universidad de Leicester realizó un estudio genético entre 1.140 hombres de 18 poblaciones de la península y las Islas Baleares para determinar los orígenes genéticos de la población española.

Los resultados de la investigación son sorprendentes pues sirven para desmitificar ciertas percepciones históricas que establecieron unas visiones de claros tintes racistas, islamofobas o antisemitas en algunos momentos de la historia de España. Estas percepciones históricas ligadas a eventos de la historia de España como la Reconquista, la expulsión de los judíos y de los moriscos en 1492 han prevalecido durante siglos en amplios sectores de la población española y dejaron su particular legado no solo en aspectos como la limpieza de sangre o la conversión de judíos y moros, también en la huella genética de la actual población española.

Pero ahora a raíz de este esclarecedor estudio se puede producir un interesante debate entre las pruebas científicas aportadas por genética y la historia, pues según las conclusiones del estudio “un 10% de la población actual tiene características genéticas propias de los habitantes del norte de África y un 20% de los judíos sefarditas”.

¿Como se realizó el estudio?
Para llegar a esta conclusión, los científicos comenzaron a trabajar en el 2000 en un estudio en donde recogieron muestras de 1.140 hombres de 18 poblaciones de la península y las Islas Baleares. El grupo de científicos llevaron a “cabo un análisis del cromosoma Y, únicamente presente en los hombres y que se transmite de padres a hijos”.

Según el doctor Calafell de la Uiversidad Pompeu Fabra, “la investigación se centró en el análisis del cromosoma Y porque no se recombina en la reproducción, lo que hace que sólo las mutaciones lo modifiquen, por lo que los científicos pueden determinar su orden de aparición”.

Posteriormente, las muestras obtenidas se analizaron y se “compararon con las poblaciones de judíos sefarditas y de individuos del norte de África, que tienen la ventaja de ser muy diferentes a las poblaciones receptoras originarias de la Península Ibérica, por lo que su diferenciación es sencilla”. De este modo, llegaron a la conclusión de “que uno de cada tres españoles tiene ascendentes moriscos o judíos”.

¿Son confiables estos resultados?
De acuerdo con el doctor Calafell, “mientras que los datos obtenidos para el origen norteafricano apenas arrojan dudas metodológicas y parece plausible que un 10% de la población proceda de musulmanes norteafricanos llegados a la Península a partir del 711, los marcadores genéticos usados para distinguir a la población con ancestros sefardíes pueden producir distorsiones”.

Las razones esgrimidas por el experto se basan en el hecho de que los elementos genéticos que tiene la población de origen sefardí, también son “compartidos por otros pueblos de Oriente Medio desde Turquía hasta Líbano, con lo que en realidad, ese 20% de españoles que el estudio señala como descendientes de sefardíes podrían haber heredado ese rasgo de movimiento más antiguos, como el de los fenicios o, incluso, primeros pobladores neolíticos que llegaron al península hace miles de años”.

Por tal motivo, les aconsejo que si tienen la oportunidad consulten mi post del pasado 2 de noviembre,titulado: “Los fenicios desaparecieron hace mas de 2.000 años pero dejaron una profunda huella genética en los pueblos del Mediterráneo” en el cual comento los resultados de un interesante estudio hecho para determinar la huella genética de los fenicios sobre los actuales pueblos del mediterráneo. Dicho estudio también fue publicado en la edición del mes de octubre de la revista American Journal of Human Genetics
La genética y la historia

¿Cuál es en realidad el vestigio genético dejado por ocho siglos de presencia musulmana en España y muchos más de convivencia judía? En opinión de los autores del estudio la genética aporta algunas de las respuestas. Aquí puede que se encuentre una de las más sorprendentes revelaciones de la investigación, la correlación que existe entre la genética y la historia para contrastar datos históricos.

Por ejemplo, los investigadores encontraron que la presencia de genes norteafricanos es mayor en la mitad occidental de España en las provincias de León, Salamanca, y Zamora, que en la mitad oriental de la península como en las provincias de Granada. De acuerdo con los datos obtenidos por el estudio “no hay evidencia de un gradiente sur-norte en los cromosomas norteafricanos. Más bien hay una divisoria entre el oeste (alta frecuencia) y el este (baja): la ascendencia norteafricana va de 0% en los Pirineos al 20% en Galicia y el 22% en Castilla noroccidental. Andalucía tiene uno de los índices más bajos.”

El aspecto mas interesante a efectos históricos según el artículo “es que ese dato concuerda perfectamente con los registros históricos. Tras la revuelta de los moriscos en el siglo XVI, la mayoría de ellos fueron deportados de sus lugares de origen en Granada y Valencia llevados al exilio al noroeste de España” por las ordenes de expulsión de moriscos ordenadas por Felipe III en 1609, que “diezmaron los guetos de Valencia y Andalucía, pero que poco pudieron hacer contra las dispersas e integradas poblaciones de Extremadura y Galicia”. Así que “quinientos años después, el genoma de los españoles lo demuestra: hay más descendientes de moriscos en la plaza de Salamanca que en el Albaicín granadino.”

En cuanto a los cromosomas de origen sefardí, a pesar de ser de una época más remota, aparecen distribuidos por el territorio español de forma más homogénea. Excepto en el noreste de Castilla, Cataluña y los Pirineos, en donde su frecuencia es muy baja. Estos datos revelan, según los autores, “un alto nivel de conversión, voluntaria o forzosa, impulsada por episodios históricos de intolerancia social y religiosa, y que condujo a la integración de los descendientes”. Hoy día, se supone que la población actual de sefardíes en todo el mundo es de unos dos millones de personas. Pero ahora sabemos gracias a los resultados de estudio que sólo los descendientes españoles de sefardíes suman más de ocho millones.

Estudios genéticos como esté que he comentado resultan muy esclarecedores para conocer sobre los grandes flujos migratorios, pero como vemos aún queda mucho margen para ampliar nuestro conocimiento.

En un futuro próximo, se podrán realizar estudios similares para estudiar los efectos de las invasiones, migraciones y otros movimientos de población registrados en la historia del Humanidad como: la conquista y colonización de América por parte de los españoles y portugueses, la influencia demográfica de los incas sobre los pueblos andinos, la conquista española de las Islas Canarias; la repoblación de la ribera del Guadalquivir con personas del centro de Europa según fue ordenada Carlos V en el siglo XVI, la conquista inglesa de Norteamérica, la influencia de los pueblos gitanos en Europa, la llegada de millones de esclavos africanos a América o la masiva migración de millones de europeos a los Estados Unidos, Argentina, Chile, Venezuela, Canadá y Australia.

Estoy convencido que muchos de esos trabajos resultaran decisivos no solo para desmitificar y esclarecer eventos históricos también para generar una nueva conciencia, una mayor solidaridad entre las personas y los pueblos del mundo mas alejada de estrechas percepciones racistas, nacionalistas y etnocéntricas.

Fuente: Wordpress, https://unbohemioburguesenmadrid.wordpress.com/2008/12/15/uno-de-cada-tres-espanoles-tiene-marcadores-geneticos-de-oriente-medio-o-el-magreb/

WEST MEET EAST - EAST MEET WEST

2016-08-30T07:26:00.000-07:00

Western and Eastern Thought Traditions : A Necessary Conjunction for Exploring the Nature of Mind and Life

THE Necessary Conjunction

of Western and Eastern

Thought Traditions for

Exploring the Nature

of Mind and Life

A Necessary Conjunction of the Western and Eastern Thought Traditions for Exploring

the Nature of Mind and Life

Special issue on Integral Biomathics:

Editors: Tom Blundell and Denis Noble
Guest Editors (GE): Plamen L. Simeonov, Arran Gare, Koichiro Matsuno, Abir U. Igamberdiev, Alex Hankey

Timeline:

Deadline for abstracts: 1st October 2016
Deadline for submitting papers: 1st May, 2017
Deadline for submitting revised papers: 1st August, 2017
Final deadline for GE’s to accept all papers: 1st October, 2017
Publication deadline: November/December 2017

Scope

This special journal issue continues the tradition of the previous three volumes of the series on Integral Biomathics in 2015, 2013 and 2012 ([1, 2, 3]), which originated from the 2011 EC FP7 collaboration initiative INBIOSA [4] (www.inbiosa.eu) and a 2010 programme vision paper [5] and its 2013 and 2015 updates [6, 7].

The project is now carried forward as a periodic JPBMB focused report made possible by the generous support of Prof. Denis Noble, FRS and the members of our worldwide multidisciplinary research community.

This time we take on an essential aspect of our discourse that was touched upon in some of the previous contributions, but still has not been considered sufficiently in contemporary biomathematical and biocomputational models.

We experience a global crisis in many aspects of science and philosophy today [5, 8-15]. Therefore, the intention of this volume is to put the emphasis on the connection between the Eastern and Western thought traditions because we consider this relation and exchange as central and leading elements of scientific development.

Well-known examples in this respect are the Einstein-Tagore and Bohm-Krishnamurthi discussions, as well as Capra’s book “The Tao of Physics”. But now we wish to explore how life sciences can be advanced by Eastern thought.

Eastern and Western approaches to knowledge are opposite:

1.- The West demands primary emphasis on objective (reproducible) experiments to test research hypotheses specified in crisp and logically sound (causal) language.

2.- The East holds that our language employed for addressing possible implications latent in the reported experiments may allow for an infusion of something [vague]¹.

The Eastern tradition implies methods to acquiring knowledge such as the practices of Taoism (Wu Wei) and Buddhism (Sahaja) that have not been systematically studied in the West.

This special issue on Integral Biomathics intends to elucidate the complementation between the Eastern and Western paths to exploration, and show how the foundations of a unified approach to knowledge and science can be rigorously formulated to accommodate both approaches.

………………………………………………………………………………………………………………………………….

Are welcome original contributions exploring the borderlines between Eastern philosophy and cognitive science, neuroscience, biology, ecological/ environmental science, biosemiotics, autopoiesis, second-order cybernetics, artificial intelligence, pure mathematics and computation, chaos and complexity science. They can be developed along the lines of thought of both Eastern and Western philosophical traditions in exploring the nature of mind and life.

Note to Authors
Manuscripts and their abstracts should be written in clear, straightforward language suitable for an interdisciplinary readership. The Guest Editors are happy to discuss the substance of papers with authors, but, since we do not have copy editors for our Special Issue, we ask authors to assume responsibility for their own copy editing (spelling, grammatical construction, consistency, etc.).

Abstracts should be submitted by October 1st, and should not exceed 400 words.

//////////////////////////////////////////////////////////////////////////////////////

References

[1] Simeonov, P. L., Gare, A., Rosen, S.M. (Eds.) 2015. Life Sciences, Mathematics, and Phenomenological Philosophy. Special Theme Issue on Integral Biomathics J. Progress in Biophysics and Molecular Biology. 119(2). Elsevier, ISSN: 0079-6107.http://www.sciencedirect.com/science/journal/00796107/119/3.

[2] Simeonov, P. L., Matsuno, K., Root-Bernstein, R. S. (Eds.) 2013. Can Biology Create a Profoundly New Mathematics and Computation? Special Theme Issue on Integral Biomathics. Journal Progress of Biophysics and Molecular Biology. 113(1). Elsevier, ISSN: 0079-6107.
http://www.sciencedirect.com/science/journal/00796107/113/1.

[3] Simeonov, P. L., Smith, L., S., Ehresmann, A. C. (Eds.), 2012. Integral Biomathics: Tracing the Road to Reality, Proceedings of iBioMath 2011, Paris and ACIB ’11, Stirling UK. Springer-Verlag, Heidelberg. ISBN-10: 3642281109; ISBN-13: 978-3642281105. OCLC WorldCat Number: 800365119.

[4] Simeonov, P. L., Brezina, E., Cottam, Ehresmann, A. C., Gare, A., Goranson, T., Gomez-Ramirez, J., Josephson, B. D., Marchal, B., Matsuno, K., Root-Bernstein, R. S., Rössler, O. E., Salthe, Schroeder, M., S. N., Seaman, Siregar, P., B., Smith, L. S. 2012. Stepping Beyond the Newtonian Paradigm in Biology. Towards an Integrable Computational Model of Life: Accelerating Discovery in the Biological Foundations of Science. INBIOSA White Paper. In: Integral Biomathics: Tracing the Road to Reality, Proc. of iBioMath 2011, Paris and ACIB ’11, Stirling UK, P. L. Simeonov, L. S. Smith, A. C. Ehresmann (Eds.), 319-419. Springer-Verlag, Heidelberg, ISBN-10: 3642281109; ISBN-13: 978-3642281105.

[5] Simeonov, P. L. 2010. Integral Biomathics: A Post-Newtonian View into the Logos of Bio. J. Progress in Biophysics and Molecular Biology, 102 (2/3): 85-121. Elsevier, ISSN: 0079-6107, DOI: 10.1016/j.pbiomolbio.2010.01.005.http://dx.doi.org/10.1016j.pbio molbio.2010.01.005. also: http://arxiv.org/abs/cs.NE/0703002.

[6] Simeonov, P. L. 2013. On Some Recent Insights in Integral Biomathics. J. Progress in Biophysics and Molecular Biology. Special Theme Issue on Integral Biomathics: Can Biology Create a Profoundly New Mathematics and Computation? 113(1): 216-228. Elsevier. ISSN: 0079-6107. DOI:10.1016/j.pbiomolbio.2013.06.001. http://arxiv.org/abs/1306.2843.

[7] Simeonov, P. L., Cottam, R. 2015. Integral Biomathics Reloaded: 2015. J. Progress in Biophysics and Molecular Biology. Special Theme Issue on Integral Biomathics: Life Sciences, Mathematics, and Phenomenological Philosophy.119(2): 728-733. Elsevier. ISSN: 0079-6107.http://philpapers.org/archive/SIMIBR.pdf.http://www.sciencedirect.com/science/article/pii/S0079610715001509.

[8] Smolin, L. 2006. The Trouble With Physics: The Rise of String Theory, The Fall of a Science, and What Comes Next. Houghton Mifflin Company; Mariner Books; Reprint edition (September 4, 2007). ISBN-10: 061891868X; ISBN-13: 978-0618918683.

[9] Gare, A. 2013. Overcoming the Newtonian Paradigm: the unfinished project of theoretical biology from a Schelingian perspective. J. Progress in Biophysics and Molecular Biology. Special Theme Issue on Integral Biomathics: Can Biology Create a Profoundly New Mathematics and Computation? 113(1): 5-24. Elsevier. ISSN: 0079-6107.

[10] Schroeder, M. J. 2013. Crisis in Science: In Search for new theoretical foundations. J. Progress in Biophysics and Molecular Biology. Special Theme Issue on Integral Biomathics: Can Biology Create a Profoundly New Mathematics and Computation?113(1):25-32. Elsevier, ISSN: 0079-6107.

[11] Bal, L. 2015. Is science broken? The reproducibility crisis. BioMed Central. 20. March 2015. https://blogs.biomedcentral.com/on-biology/2015/03/20/is-science-broken-a-reproducibility-crisis/.

[12] Nature Video. 2015. Is There a Reproducibility Crisis in Science? Scientific American. May 28, 2016.http://www.scientificamerican.com/video/is-there-a-reproducibility-crisis-in-science/.

[13] Kauffman, S. A., Gare, A. 2015. Beyond Descartes and Newton. Recovering life and humanity. J. Progress in Biophysics and Molecular Biology. Special Theme Issue on Integral Biomathics: Life Sciences, Mathematics, and Phenomenological Philosophy. 119(2): 219-244. Elsevier, ISSN: 0079-6107.

[14] Kousta S, Ferguson C, Ganley E. 2016. Meta-Research: Broadening the Scope of PLOS Biology. PLoS Biol 14(1): e1002334. doi:10.1371/journal.pbio.1002334. http://dx.doi.org/10.1371/journal.pbio.1002334.

[15] Valverde, S., Porcar, M. Pereto, J. Sole, R.V. 2016. The Software Crisis of Synthetic Biology. biorRXiv. 29. Feb. 2016. doi:http://dx.doi.org/10.1101/041640. http://biorxiv.org/content/early/2016/02/29/041640.

Organization

http://www.inbiosa.eu/, http://ibiomath.org/

For more information about the project please contact: Plamen L.

Simeonov, email: plamen@simeio.org

//////////////////////////////////////////////////////////////////////////////////////////

Source:

ELSEVIER - Plamen L. Simeonov, email: plamen@simeio.org

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Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland

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Evolutionary Medicine Group, Laboratoire d’Anthropologie Moléculaire et Imagerie de Synthèse, UMR 5288, Centre National de la Recherche Scientifique, Université de Toulouse 3, 31073 Toulouse, France

Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark

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