Physics Buzz

How Complicated is Scrabble?

2012-01-27T16:30:00.000-05:00

According to new research, pretty complex. Word lovers have long touted the cleverness required to win scrabble matches. Now they have proof.

Theoretical computer scientists have crunched the numbers to determine the computational complexity of a player's decisions in the classic board game. Researchers have investigated numerous other board games for awhile. And now scrabble has been proven to be PSPACE-complete, the most difficult status within the realm of PSPACE problems.

So what makes Scrabble difficult? The researchers suggest that it comes down to two things the player has to consider:

1. Players have to choose where to use their tile on the board and account for the other pieces on the board.

2. Players have to decide which of their own tiles to use and form a word to play.

In the paper published on the arXiv preprint server, the authors write, "Scrabble players need to perform not one, but two computationally hard tasks, which is probably the reason why Scrabble is so much fun to play." You can certainly debate the entertainment value of scrabble, but the complexity proof is solid.

What the researchers ultimately proved can be quite technical, but it's a useful tool for theorists trying to measure complexity. But the researchers did have to make a few assumptions for the proof. For instance, it was assumed that each player knew which tiles would come out of the bag next. Consequently, they would know each other's letters—an unacceptable condition for die-hard scrabble aficionados. But for the sake of the mathematical proof, it doesn't really matter.

So now when Alec Baldwin's Words with Friends habit gets him into trouble, he can cite this research as proof that he was working on important, complex work.

For more information on PSPACE-completeness in board games, check out this site.

"Touch" TV Series Uses Numbers to Connect People

2012-01-26T16:45:00.000-05:00

Mathematician explains how series can make use of actual patterns that exist in nature.

Credit: Brian Bowen Smith/FOX. L-R: Cast members David Mazouz, Kiefer Sutherland and Gugu Mbatha-Raw.

Think about all of the different people that you come in contact with on any given day: family, friends, coworkers and strangers going about their lives. The fateful hijacking of Flight 93 on 9/11 showed how a plane full of people could be connected in a way that none of the passengers could have imagined as they boarded their flights.

Is everything connected? Is the world a predictable set of patterns? Can one person really make a difference? Fox’s new sci-fi television series, "Touch," will tell stories of how unrelated people and events can be linked together, with the overall theme that one person does have the power to "touch" the world.

"People are hungry to believe that they are all connected and that what they do matters," said Carol Barbee, executive producer of "Touch." "I am inspired by people living their lives, doing what they love and care about. This show has a rare opportunity to tell stories about ordinary people. The best stories come from real life and anyone could be a character on the show."

The show centers on Martin Bohm (played by Kiefer Sutherland), who is trying desperately to find a way to connect with his autistic son, Jake (played by David Mazouz). Jake is unable to speak and doesn't like to be touched, but he does see where patterns intersect. Martin's discovery that his son is using numbers instead of words to communicate compels him to try to put together a puzzle full of seemingly unrelated pieces.

"Numbers are part of mathematical patterns," said Keith Devlin, a mathematician at Stanford University, The Math Guy on NPR’s 'Weekend Edition,' and a consultant for the 2005-2010 CBS show "Numb3rs." "There is a scene in (the movie) "A Beautiful Mind" that illustrates this idea beautifully.”

When John Nash (played by Russell Crowe) shows his future wife, Alicia Nash (played by Jennifer Connelly) the night sky, at first all she sees is a sky full of stars until he takes her hand and traces a pattern connecting the stars. When she recognizes the pattern, Nash remarks, "Now, you are a mathematician!"

So, if numbers are like stars and mathematics is like a constellation, then it would seem that anyone can see mathematics and the patterns in everyday things.

"Mathematics sees patterns that are already there, but normally are invisible," said Devlin. "If the show uses that idea, they would capture the very essence of mathematics."

For example, the Fibonacci sequence follows a pattern where the first two numbers are added together to get the next number (0, 1, 1, 2, 3, 5, 8, 13, 21, 34). Fibonacci numbers are found throughout nature, such as the number of petals in a rose. Most people wouldn't notice the mathematical patterns in these objects or identify the sequence of numbers; they would just enjoy the beauty of nature.

So, while storytellers may take poetic license with the mathematics presented, the show's themes can bring awareness to how mathematics touches everything and connects the world, including people, in universal ways.

"I hope that viewers will come away with an awareness of the effects that they have on people and a drive to do good work in the real world," said Barbee. "I hope people understand the power of an individual, you have no idea the power of your reach on a daily basis or how many lives you touch."

By Emilie Lorditch, ISNS Contributor

Inside Science News Service

State of the Union on Science

2012-01-25T12:11:00.003-05:00

As many of you know, President Obama gave the State of the Union address last night. I, of course, was listening for the word "science." He made some interesting statements and I would like to sum them up here.

First off, I'm very glad he mentioned it and not in the context of cutting the budget. The first thing that made me and hopefully the scientific community applaude was his commitment to funding basic scientific research. Basic research is almost always on the chopping block. It is often ridiculed like the "shrimp on a treadmill" incident. However, in the State of the Union Mr. Obama highlighted the great things that come from this type of research including better cancer treatments and bullet proof vests that keep cops safe. As a scientist, this makes me breath a bit of a sigh of relief, at least the big guy is behind us.

"Innovation also demands basic research. Today, the discoveries taking place in our federally financed labs and universities could lead to new treatments that kill cancer cells but leave healthy ones untouched. New lightweight vests for cops and soldiers that can stop any bullet. Don’t gut these investments in our budget. Don’t let other countries win the race for the future. Support the same kind of research and innovation that led to the computer chip and the Internet; to new American jobs and new American industries."

He then brought science back around to the issue of job creation. He pointed out a very important fact, that there are two times as many tech jobs as there are qualified people to fill them. This is a problem but there is a solution, train people to do those jobs. Luckily there are people out their doing just that. Mr. Obama mentioned several specific groups, but I instantly thought of one of our LaserFest partners, Op-Tech. Groups such as these train people to be laser (or other types of) technicians, filling innumerable empty jobs.

In general he highlighted science and science education and training in the context of job creation. Seeing as he is up for reelction it was no shock that he focused so much on creating jobs, but it was neat to have him show the direct link between science and scientific research and job creation. It is often difficult to see how atom smashing and understanding crystal structure can lead to new technology and a better economy. I am glad that a politician, particularly the one leading the country, very clearly stated this in such a clear way.

But I was sad there was no mention of "human-animal hybrids," "the value of every life" or "our creator." Darn, I guess a speech like that only happens once in a lifetime.

Behind the Scenes: How Physicists Maintain Movie Realism

2012-01-24T16:30:00.000-05:00

Moviegoers crave imaginative storytelling and fantastic settings. But they also want movies to be believable, and that's where scientists play their part. Behind some of Hollywood's biggest movies—such as Watchmen, Tron: Legacy, and Star Trek—there's a team of science consultants that help directors create new worlds that remain (mostly) true to the laws of physics. And some of that movie magic has translated into exciting new technologies.

Since 2008, the Science & Entertainment Exchange has connected filmmakers with scientists in an effort to more accurately depict science in movies and television. The exchange is a program of the National Academy of Sciences, bringing together some of the brightest minds in science research across many disciplines. Nonetheless, before the exchange existed, scientists still regularly contributed their expertise to film studios.

For instance, the 2002 film Minority Report featured Tom Cruise deftly controlling his computer special gloves and various hand gestures recommended by a computer scientist. Although the technology seemed a bit far-fetched at the time, it has evolved into something very real. John Underkoffler served as the science adviser for Minority Report and created the system Cruise used in the movie. After working at MIT for many years, Underkoffler has started his own company focused on the innovative g-speak spatial operating environment originally featured in the movie. It's akin to Xbox Kinect on steroids, and you can see all of the cool motion capture in the video below.

Video Courtesy Oblong Industries.

Other consultants deal with more esoteric, theoretical physics. 2009's Star Trek, for instance, featured wormhole time traveling and warp speed spacecraft. Technologies like these won't be around any time soon, but they are certainly plausible consequences of theoretical physics.

Similarly, the comic book movie Watchmen featured input from University of Minnesota Physicist James Kakalios, particularly for the character Dr. Manhattan. Dr. Manhattan—a former physicist turned demigod after a physics experiment gone awry—has many superpowers: He can clone himself, travel to remote areas almost instantaneously and take apart complex objects with a wave of his hand.

In the video below, Kakalios explains how Dr. Manhattan's "intrinsic field" was removed. Although there's no such intrinsic field, Kakalios details how you can cancel out two waves by adding one with another that is 180 degrees out of phase, effectively removing a field. Kakalios also invokes quantum mechanics to explain how diffraction patterns could explain Dr. Manhattan's cloning ability. The filmmakers certainly stretched the available science pretty far, but Kakalios hopes that his consulting gave them a stronger scientific basis for their development of Dr. Manhattan.

Video Courtesy University of Minnesota.

While scientists are trying to keep accurate science in movies, nitpickers will always find scientific fallacies in movie scripts. But part of the enjoyment derived from movies, at least for this blogger, stems from stretching the imagination just beyond what is possible.

For more information on science consulting in film, check out the Science & Entertainment Exchange's website. If you're a scientist looking to break into the exciting albeit not so lucrative field of science consulting for entertainers, take a look at this blog post by Jennifer Ouellette.

From left to right, the top images are courtesy of Warner Brothers, Paramount Pictures, and Disney, respectively.

High Schoolers Compete to Control NASA Satellites

2012-01-23T16:30:00.000-05:00

Ask any kid what they want to be when they grow up, and there's a good chance they'll say astronaut. Now kids don't have to wait quite as long to work with NASA. High School students from around the country were given the chance to furnish code that controls bowling-ball sized satellites aboard the International Space Station. Earlier today, NASA beamed down footage of the students' code at work, and a winner for the best-designed code was announced.

The Proba-2 micro satellite. Image Credit: ESA/P. Carril.

The Zero Robotics SPHERES Challenge began three years ago through a partnership among NASA, MIT and the Defense Advanced Research Projects Agency. For the competition, high school students program the satellites to conduct a series of complex maneuvers in the ISS' microgravity. Objectives include positioning, docking and assembly. The team with the highest "software performance" wins the competition, and this year's winner is Team Rocket from Maryland, according to a tweet from NASA.

Today marked the culmination of months-long projects for the students with several milestones along the way. Students had to propose their projects, submit simulations and conduct ground testing before the flight testing. NASA hopes that requiring these steps will help strengthen participants' communication and project management skills in addition to their coding. For many of the students, the opportunity to conduct experiments in space was well worth the wait.

Outside of the competition, the mini SPHERES satellites are used to test NASA programs that will be implemented on larger satellites. The controlled ISS environment serves as a galactic space lab, leading to developments in more easily maintained, debris-avoiding spacecrafts.

You can see an example of what students have done before in the video below from the 2010 competition.

For more information on the program, see NASA's webpage and this article from the Santa Cruz Sentinel.

Recreating a Star's Sizzling-Hot Surface

2012-01-20T16:30:00.000-05:00

Scientists have used a burst of X-rays to recreate conditions in aging stars called white dwarfs.

The Z Machine at Sandia National Labs generates bursts of x-rays that scientists have used to replicate the temperature and density conditions in white dwarf stars. Credit: Z Machine Collaboration | Sandia National Lab | Lockheed Martin | NNSA | DOE

Because we can't go to the stars yet, let's bring the stars to us. In a giant X-ray-producing facility, astronomers and plasma physicists have heated a cigar-sized sample of gas to over 17,000 degrees Fahrenheit in order to replicate the surface of stars called white dwarfs.

"As an astronomer, I am used to looking at these stars from light-years away," says Don Winget of the University of Texas at Austin.

One of the primary methods astronomers use to study a distant object is to analyze its spectrum of light as it reaches Earth.

"So it was a remarkable moment the first time we took a spectrum from a distance of just 5 centimeters," said Winget.

That first time was in April 2010. Since then, the team has been refining their experiment inside the Z Machine at Sandia National Laboratories in Albuquerque, N.M. The goal is to make precision measurements of a laboratory-recreated white dwarf surface in order to improve interpretations of data from spaced-based white dwarfs. Winget described the project today at an American Astronomical Society meeting in Austin.

White dwarfs currently occupy part of the limelight in astronomical circles, as researchers recently confirmed that one of them exploded in a nearby galaxy, producing a "Type IA supernova" that astronomers use to measure the size and acceleration of the universe. Winget said that his team's work could eventually increase our understanding of these cosmic yardsticks, by providing details about what's going on in the white dwarfs before they go boom.

Stellar Fossils

White dwarfs are the burnt embers of once bright-shining stars. Our sun is expected to "retire" to a white dwarf when it runs out of nuclear fuel in roughly 7 billion years. Without the energy from nuclear fusion, the sun will shrink down to about the size of Earth due to the inward pull of its gravity.

This has already been the fate of billions of stars in our galaxy. Although no longer burning fuel, white dwarfs contain a lot of heat. Relatively young ones can be more than 180,000 degrees F on their surface. But as the heat radiates away over time, the white dwarfs tend to cool down to less than 18,000 degrees.

Because these are some of the oldest stars around, these "graybeards" can often unravel the evolutionary history of our galaxy. To estimate the age of a white dwarf, astronomers analyze the spectra of light coming from the stars. Specifically, they look at how some of the light is absorbed in the outer surface of the white dwarf. In most white dwarfs, hydrogen, the simplest of elements, absorbs this light.

"Everyone assumes we know hydrogen so well," Winget said. "As it turns out, that's not the case."

The surface of a white dwarf is largely a plasma, or electrically charged gas. In the midst of this dense plasma, hydrogen absorbs light in a slightly different way. Better understanding this behavior would help astronomers improve the accuracy of white dwarf age estimates. It would also help scientists studying exotic phenomena like the "freezing" of white dwarf cores as they cool.

"I would very much appreciate any experimental work that could help verify the models and determine the physical and chemical properties of the atmospheres of white dwarfs," said astrophysicist Piotr Kowalski, who is not a part of the project, of the Helmholtz Centre Potsdam in Germany.

From Z to X-rays

Hot hydrogen plasmas have been made before in the lab, but only in small quantities.

"We need to have a large sample in order to observe how the plasma absorbs light," said Ross Falcon, a graduate student at the University of Texas at Austin doing much of the legwork on the project.

To obtain enough plasma in the proper fashion requires an experimental facility that can generate a large amount of energy over a short time. Not many facilities can provide that, but the Z machine can. The Z was built to study nuclear weapons, but it now allots about 15 percent of its experimental time to academic research.

To replicate the conditions of a white dwarf, the team first prepares hydrogen in a gas cell that is several centimeters across. This sample is then placed a foot away from a coil of tungsten wires, which lies at the heart of the Z machine. When a switch is thrown, 26 million amps of current rush through the wires, causing them to implode. A burst of X-rays streams out, quickly ionizing the gas in the cell. Winget's team collects spectra from this "little star" using fiber-optic cables.

As the team gathers data in the coming year, it hopes to improve the understanding of white dwarf stars, Winget said.

"This has been groundbreaking research," said plasma physicist Allan Wootton, also from UT Austin. "It was an unusual experience for these astronomers, but it has opened a door to new experiments that explore the conditions inside stars and other extreme environments."

Michael Schirber, ISNS Contributor
Inside Science News Service

Michael Shirber is a France-based science writer who has also written for Physical Review Focus, ScienceNOW, and Astrobiology Magazine

Orb-Eating Physics Fun

2012-01-19T16:30:00.000-05:00

Eat or be eaten—that's the simple idea behind Hemisphere Games' Osmos. In the popular Iphone/Ipad game, players must maneuver an orb through outer space and devour smaller circular specks. The game's intuitive design, however, belies the complex orbital dynamics and thermodynamics that form the game's backbone. Since its release, the game has garnered numerous awards, and now Android users can share in the physics of orb-gobbling fun.

To control your orb, you have to shoot out a small amount of mass to generate thrust in a certain direction. Absorb smaller orbs, and you'll grow bigger. Players can practice their cosmic cannibalism while enjoying the game's striking visuals and relaxing soundtrack.

But don't let the game's soothing Zen-like music lull you into a false sense of security. Danger lurks in every corner of the Osmos universe. All of the orbs have a gravitational pull, and the bigger ones will pull you toward them more forcefully. Once you've come into contact with an orb that's larger than your own, you're toast.

Although the controls are quite simple—tap in the direction you want to go—the difficulty lies in using gravity to find smaller orbs and balancing between necessary thrust and sufficient mass. One of the game's most interesting modes involves many motes orbiting around one large star, and the player has to coalesce into one giant orbiting planet.

Ultimately, the game is quite open-ended and rewards several different styles. Are you a more conservative gamer? If so, your patience will be rewarded if you use tactical movements and let gravity do most of the work. If you're more aggressive, your quick fingers may compensate for your rapid loss of mass.

Some players have even explored beyond what the game's developers intended. In the video below, for instance, the player collected other orbs then slowly deposited bits of matter into one area. By the end of the level, he had collapsed the entire system and formed an enormous star that looks ready to burst.

Hemisphere Games released Osmos on Tuesday for the Android market. You can download the game for your PC or Mac at their website, or you can find the game in Apple's App Store. Free demos are available on the website.

Plushie Powers of Ten

2012-01-18T16:30:00.000-05:00

The scale of the universe is almost incomprehensible. Galaxies are so massive it bends the mind, while on the other end of the size spectrum, subatomic particles are so tiny it twists the brain in completely different ways. There's a 1977 short movie, "Powers of Ten," which takes viewers on a journey of scale, showing the size of things in the universe from the building blocks of atoms, to the entire cosmos.

It's a great little film, but I always thought it wasn't really huggable enough. Now you can take the same journey, in stuffed animal form! Starting from the very large....

Hugg-A-Star:You can have the whole night sky in your hands with this stuffed globe by Peace Toys. The 12-inch diameter ball of sky features 88 constellations labeled in English and Latin as well as the Milky Way. It's the perfect accessory for falling asleep under the stars, with your head atop the very same stars! Also available are Earth, Mars, the Moon and the US of A! (Image: Peace Toys)

Celestial Buddy - Earth: Our beloved home; spaceship Earth. The only planet in the known universe teeming with life, and it never looked so adorable. All of the continents and oceans are there, just fuzzier than on most globes. It's got a line of friends too, with the Moon, the Sun and Mars already available, with more planetary buddies in the works. (Image: Celestial Buddies)

Albert Einstein Little Thinker: In 1905 Albert Einstein revolutionized physics with his theory of special relativity, and what better way to celebrate his work than with his little plushie doppelganger. He's brought to you by the Unemployed Philosopher's guild, the same folks who make the Nicola Tesla and Thomas Edison finger puppets we've featured on the blog before, along with a whole other line of other stuffed scientists, philosophers artists and other thinkers. Einstein is an easy one for the medium of plushie, he's naturally got a hairdo that looks like he's been consulting with the Muppets for grooming advice. (Image: The Unemployed Philosophers Guild)

I Heart Guts - Big Brain: The brains of the operation. The human cerebral cortex is one of the most complex and intricate feats of engineering in the world. We've all got one, but it spends most of its time safely protected in our heads. This twee little guy you can take out and show your friends, and not have it be a whole big thing! As its name implies, I Heart Guts has just about every human internal organ available in bright colors. (Image: I Heart Guts)

GIANTmicrobes - Brain Cell (Neuron): It's what matters in "gray matter." Neurons make up the brain and are essentially its microprocessors. They function in much the same way that the processors of computers work, by sending information as electrical signals to other neurons in the network. GIANTmicrobes has made a name for themselves for their huge line of darling microorganisms, ranging from benign li'l amoebas to the cutest flesh eating bacteria I've ever seen. (Image: GIANTmicrobes)

Biochemies - DNA Molecule Plush Dolls: These folks are the newcomers to the science plushie industry. It was started by Jun Axup, a PhD student in in chemical biology, as a Kickstarter.com project that blew away its funding goal. Kickstarter is an online service that lets people raise money for start-up projects through donor contributions. The DNA molecules are now up for pre-order, and you can get all four base pairs that make up DNA. The best part is that each molecule has magnets so they can stick to their corresponding base pair just like the actual molecules bond with one another. (Image: Biochemies)

The Particle Zoo - Big Neutron with Mini Quarks and Gluons: It doesn't get much more fundamental than this. Julie Peasley has been hand making any subatomic particle you could possibly think of since 2008. The Neutron here is especially cool because the big blue particle is actually a pocket that holds the fundamental particles that make it up, two down quarks and an up quark held together by a gluon. Each of her particle plushies are weighted with poly fill, sand or gravel to reflect the relative mass of each. Her line of science plushies really do run the gamut of the vast to the itty-bitty, including the cosmic microwave background radiation of the whole universe, to the the strings of string theory. (Image: The Particle Zoo)

National Science Fair Reveals Students' Compelling Backgrounds

2012-01-17T16:30:00.000-05:00

Every year, the Society for Science and the Public hosts a nationwide science fair for high school seniors. Sponsored by Intel, the fair grants over $1.2 million in awards to bright young scientists for projects covering everything from cancer research to secure satellite communication. Not only is the research compelling, but also some of the students' personal difficulties have revealed true determination. One such case is Samantha Garvey—a homeless teenager.

Garvey is one of 300 applicants who were accepted as semifinalists. Each semifinalist, along with their school, will receive $1,000 for making it this far. But over half of the prize money has yet to be awarded. The winner of the fair will receive $100,000.

Garvey's story has inspired numerous news articles and donation pledges from neighbors and strangers. Since her family began living in a homeless shelter on New Year's Day, her local county has arranged for her family to live in a subsidized house and corporations have donated furnishings. And today, Representative Steve Israel of Long Island invited her to see President Obama's State of the Union address on January 24.

Although Garvey's project focuses on the predators and environment of bivalve mussels, projects this year span all science disciplines. Many of the projects involve physics research often reserved for undergraduate or even graduate students. For instance, semifinalist research projects include studies on quark gluon plasma, 3D visualization of the human genome, and theoretical graphene research. All of these projects, remember, are being done by high school students.

On January 25, the 40 finalists will be announced. And if a student makes it that far, they'll certainly be in good company. Former finalists of the science fair include physics all-stars Brian Greene, Lisa Randall and four Nobel laureates in physics.

Be sure to look for the list of finalists next week. Eventually, the finalists will have their names published in Science News, the flagship publication of the Society for Science and the Public. For now, you can see all of the semifinalists and their respective projects here.

Top Image Courtesy Regina M. Sullivan/University of Oklahoma

Fear of Diagnostic Radiation Is Overblown

2012-01-13T16:30:00.000-05:00

Patients should not decline X-ray imaging for medically advised procedures, physics group says.

Credit: Aidan Jones via flickr

An association of physicists in the medical field has warned patients not to decline diagnostic radiation procedures because of perceptions that the tests may be harmful.

The American Association of Physicists in Medicine said the benefits of diagnostic -- mostly imaging -- technology far outweighed the risks. Machines that deliver much higher levels of radiation for treating cancer have been the subject of media stories uncovering improper use and accidents, and journal articles have cautioned physicians to minimize diagnostic CT scans in children, especially repeated ones. They have raised unfounded fears about radiation procedures in general, the association said.

The statement touched on a long-debated topic: whether all radiation is bad or if some of it can be tolerated without danger.

"Discussion of risks related to radiation dose from medical imaging procedures should be accompanied by acknowledgment of the benefits of the procedures. Risks of medical imaging at effective doses below 50 mSv (milliSieverts) for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent," said the statement released by the AAPM. "Predictions of hypothetical cancer incidence and deaths in patient populations exposed to such low doses are highly speculative and should be discouraged."

The statement was issued because of concern that papers in scientific journals, warning against dangers from CT scans, were finding their way into the popular media, and "people became fearful and said they were not going to have the exams," said William Hendee of the Medical College of Wisconsin, lead author of the AAPM statement. That was particularly true of parents of children slated for exams.

Hendee said that most of the data on ionizing radiation comes from victims of the atomic bomb attacks on Hiroshima and Nagasaki, and that they do not apply to diagnostic radiation.

The statement was immediately criticized by scientists who think almost any radiation can produce harmful effects, particularly cancer.

"It's a very blasé, a surprising statement from people whose job it is to ensure the safety of what we do," said Rebecca Smith-Bindman, a professor of radiology and several other medical departments at the University of California at San Francisco. "Ionizing radiation is the most studied carcinogen in the world."

Smith-Bindman added that the literature shows a risk for solid tumors and leukemia -- even at low exposure -- although the lower the exposure, the less certain the risk, and that the fear that patients would decline needed CT scans was "unjustified."

"Seventy-five million people -- one in four -- have CT scans every year," Smith-Bindman said. "Few refused necessary exams."

The debate over radiation safety goes back to the discovery of radiation in 1895, and is one of the frustrating instances in which medical experts do not agree.

Radiation is measured in sieverts, which is the amount of energy deposited in living tissue. A full-body CT scan results in 12 mSv; a mammogram 0.13 mSv -- a hundred times less. The risks from these procedures, according to AAPM, are too low to have been determined reliably, and may be "nonexistent."

The risk factor is a matter of extrapolation.

According to a study quoted by the National Academy of Sciences, a 45-year-old adult undergoing 30 annual full-body CT scans would have one chance in 50 of dying of cancer because of the radiation. Almost no one would have that many procedures. The odds of a person born in 1999 dying from a car crash is one in 77.

The academy said that there would be one cancer caused by a single exposure per hundred people of 100 mSv, more than a single CT scan would put out. Of those 100 people, 42 would have solid tumors and leukemia from other causes in their lifetime.

The devices discussed are machines used for diagnosis of disease, not treatment, which uses much higher doses.

Scientists disagree as to whether there is a threshold below which there is no risk. Most experts, including the national academy, accept a "linear no-threshold model" which states that the less the radiation, the less the risk but there is no completely safe threshold.

The problem, said Daniel Low, science council chair of AAPM, is that extrapolation for very low dose assessments of cancers or death, is "inaccurate, unscientific and leads to concern by patients." Such predictions of cancer and deaths from low doses are "speculative," AAPM says in its statement.

People don't understand the uncertainties, Low said.

The situation is made worse by journalists who confuse relative risk with absolute risk in their stories. If the mortality of a disease increases from two persons per 100,000 to four per 100,000, it is true that the relative risk has doubled, but the absolute risk remains very low.

"I wish that all journalists, including science journalists, did a better job of reporting on risk, of making sure that our stories always were set within a realistic perspective," said Deborah Blum, a Pulitzer-Prize winning science writer who now teaches at the University of Wisconsin at Madison.
"Far too often we end up scaring people unnecessarily or focusing attention on unlikely risk scenarios and distracting from the major ones ... Journalists as a pack tend to pick up the different, the dramatic, the one in a million chance of mortality."

Other organizations seem to agree with the AAPM statement.

"We believe that risk of radiation exposure from diagnostic imaging is much less than the risk of not having the examination if the examination is diagnostically warranted," said Penny Butler, senior director at the American College of Radiology.

Mary Mahoney, chair of public information at the Radiological Society of North America and a radiologist at the University of Cincinnati Medical Center, said her organization agrees completely with AAPM and is revising its position on its website to link to the AAPM.

"I don't want anyone not to get critically important information because of fear of the radiation," said Mahoney.

Smith-Bindman said part of the problem is that sometimes the devices are used when they are not necessary, a situation peculiar to the American medical system. In the United Kingdom and Europe the devices are not used unless the need is warranted by the patient's medical condition.
On that, everyone seems to agree.

"[AAPM] acknowledges that medical imaging procedures should be appropriate and conducted at the lowest radiation dose consistent with acquisition of the desired information," the organization said in a press release.

Joel N. Shurkin, ISNS Contributor
Inside Science News Service

Puzzle Piece Found in Search for Extraterrestrial Life

2012-01-12T16:30:00.000-05:00

There are likely over 100 billion planets in our galaxy, according to a review of studies spanning over the past six years. This amounts to about 1.6 planets per star according to a research article published in Nature this week. With this new data, physicists are one step closer to solving a formula used to calculate the amount of extraterrestrial life: the Drake equation.

An artist's rendition of the Milky Way. Magnified orbits illustrate how common planets are in our galaxy. Image Credit: ESO/M. Kornmesser

Named for its creator, physicist Frank Drake, the equation attempts to predict the number of alien civilizations in our galaxy. Drake proposed the equation in 1961 as a way to show how difficult it would be to find alien life. The equation, however, is fairly straightforward—it consists of multiplying a number of variables such as the rate of star formation and the fraction of stars that have planets.

While the equation is easy to calculate, it's extremely difficult to find definitive values for the eight variables in the equation. The variables progressively narrow down the conditions for detectable life. For instance, one has to estimate the number of planets per star; then the number of those planets that support life; then the number of this smaller group of life-supporting planets that develop intelligent life. Values for these variables are highly speculative, but the new research has at least given scientists a better starting point by knocking out the first part of the equation.

The research team reviewed a sample of papers that detected planets with gravitational microlensing. When a massive body, such as a planet, passes in front of a star, the planet's gravity bends the light sent toward observers on Earth. Scientists can detect this gravitational effect on the light and estimate the size of the distant planet.

After reviewing the past research, the astronomers found that most of the planets in the sample were small, like Earth. This agrees with data from other planet-detecting methods, such as those that measure the dip in light when a planet passes in front of a distant star.

This new review of data should take out at least some of the guesswork that goes into calculating the Drake equation, but plenty of work remains. Even with a solid prediction for one of the variables, values for the other parts of the equation, such as the amount of life-supporting planets that go on to produce intelligent life, are still highly speculative. Depending on a scientist's level of pessimism or optimism, Drake equation answers can range from around one alien civilization to hundreds of thousands.

With the recent surge of detected exoplanets over the past decade, however, it seems like only a matter of time before astronomers find a life-supporting planet—and maybe intelligent life—outside of our solar system.

Mathy Arts and Crafts

2012-01-11T13:59:00.005-05:00

One of my favorite hobbies, apart from riding my bike and lighting things on fire, is knitting. I like knitting because there is a lot of math involved. Math is used to figure out how to make stitches create the shapes you want, be they sweater sleeves or cozy wool socks. This holiday season I decided to use the math of knitting to create something, well, mathy; a Klein Bottle.

Most people have heard of a Mobius Strip. I remember hearing about it long ago on Mr. Wizard. For those of you unfamiliar with this neat surface, it is a loop that looks like it should have two sides, but only really has one. It's twist means that if you were an ant on the strip and you started at say, a little sugar cube, you could walk straight ahead, never turning around and come right back to your tasty treat. It is pretty easy to knit a Mobius scarf. It is a pretty standard scarf design and there are a lot of patterns available. When the scarf is first started, a neat little technique, and some ability to visualize how to make strange surfaces makes the half twist needed for this scarf to be a Mobius strip. Though, it is also possible to knit a regular scarf, put a half twist in and sew (or for the knitters, graft) one end to the other.

Klein bottles are just a Mobius strip only a little more involved. They still only have one surface and are made by gluing two Mobius strips together along their edge. Think about that. How would you do that? I hope that at least some of you reached for the paper and tape, made two Mobius strips and tried to figure out exactly where the edges were and how to glue them together. Its about as easy as kissing your elbow (I now hope at least some of you have let go of your mouse and are trying to kiss your elbow). Klein bottles can't really exist in three dimensions without going through themselves. They will happily sit in 4 dimensions with no self intersections. It is interesting and challenging to think of something sitting in 4 dimensions and being different. Try thinking about taking your coffee cup and putting a book on top of it and flattening it to two dimensions. How is it different than it was in 3? For one thing, it can't exactly hold coffee, for another, its now a circle. Very different from its former self. A Klein bottle is much the same. It is a surface that would look one way in 4 dimensions and quite different squashed into three. Though it is a bottle, it, like the smashed coffee cup can't really hold coffee. The inside is the outside and the outside is the inside.

I wanted to make a Klein Bottle hat but I also wanted one that was a continuous surface that that could be sliped through itself to demonstrate that it really is only one sided. Knitting such a Klein Bottle poses a bit of a challenge. There is a company that makes knitted Klein Bottle hats if you don't want to take on the challenge yourself. Though they do not list their pattern. They also make fun blown glass bottles, one of which I have sitting on my mantle right now. There is a pattern for a hat, but the top tube is so narrow that it is impossible to use your new hat to show that the bottle only has really one side. That, and I didn't realize this pattern existed till after I made this hat. So using what I know about both surfaces and knitted things, I created my own pattern. The video above shows me pulling the hat through itself. As you can see, it is only one sided! For those of you interested in the pattern I used, it can be found here in a separate blog post.

Even though this hat has one side fewer than most, it is quite toasty!

Klein Bottle Hat Pattern

2012-01-11T13:52:00.007-05:00

Real Klein Bottle Hat

Read fun stuff about both Klein bottles and the origin of this pattern here:

Size
Fits most heads, unless they are unusually large or small.

Materials

Yarn:
Worsted weight wool in your choice of colors. I used scrap wool that was given to me long ago. Lambs Pride worsted or Cascade 220 would work well. I used roughly 100 yards of each color. Maybe 150 for the main color (buff).

Needles
Set of US #8 DPN

Notions:
Scrap yarn for provisional cast on
Yarn needle

Notes:
I used a stripe pattern that I liked. I’m going to write the pattern as if the hat were all one color, but please put your own special pattern on it. This is a basic hat pattern with the addition of the weird tube at the top.

Directions:

The “outside” of the hat will be knit first, then the “inside.” The “outside” part needs a hole to allow the tube from the “inside” to go through.

“Outside”:

Cast on 80 stitches using provisional cast on.

Place marker and join in round

Work in [K1, P1] ribbing until the piece measures 5” from cast on edge.

Starting in the next round continue in ribbing pattern for 20 stitches, Bind off 4 stitches, continue in ribbing till marker. (76 stitches left on needles).

Work back and forth for 4 rows.

Work 20 stitches from marker, which should bring you to the bound off stitches.
Cast on 4 stitches using backwards loop cast on and work to marker. Continue in the round until the whole piece measures 6”

Begin decrease:

Work 10 stitches and place marker. Continue to end of round.

Work to first marker, knit two together, repeat to end of round.

Repeat this step till you have 16 stitches left on needles.

Knit in the round till the top tube measures 6”

Thread stitches through scrap yarn to hold them.

“Inside”:

Pick up the 80 stitches from the provisional cast on.

Repeat as for inside till decrease except do not bind off stitches to create the hole.

The decrease will be done the same way, only instead of K2T you will P2T (yes, unorthodox, I know).

When you have 16 stitches left on the needles PURL till you have a 6” tube.

Hold stitches on scrap yarn.

Finishing:

Fold “inside” into “outside” pulling the tube of the inside through the hole in the outside. The knit side of the “inside” should now be seen.

Using kitchner stitch, graft the two tubes together. Lining them up will be difficult. The markers, which mark the start of the rounds should line up. This is tricky, but the only way to make it look like one continuous surface.

Wear to your favorite geek conference or present to your favorite math nerd.

Life, Design and the Multiverse

2012-01-10T16:30:00.000-05:00

Fine-tuning evidence has raised compelling questions about the universe's beginning, evolution and eventual end.

Image Courtesy NASA/WMAP Science Team.

Every science student can recall having to memorize certain important numbers during their school years: the gravitational constant, the speed of light and Avogadro’s number, to name a few. In recent years, scientists have found extremely precise values for these fundamental constants. But what if the value of these constants were ever so slightly different? In some cases, life would not even exist.

In recent years, physicists have increasingly accepted the idea that our existence implies that certain properties of the universe could not have been different. In other words, some of these properties — particularly the fundamental constants — might be “finely-tuned” to support life. This “anthropic” reasoning has been around since the early 1970s but gained wider support in the 1980s when Steven Weinberg, a Nobel laureate in physics, used the idea successfully in the realm of cosmology.

“This idea has always been controversial,” said Dr. Alejandro Jenkins, a postdoctoral researcher in high-energy physics at Florida State University. “However, people have taken it more seriously since Weinberg.”

To understand the importance of Weinberg’s prediction, one must start with a history of what Albert Einstein considered to be his own biggest blunder: the cosmological constant.

Blunder or Brilliant?

Albert Einstein originally determined a cosmological constant to maintain a static universe. Edwin Hubble later showed that the universe is increasing in size, however, leading Einstein to consider the cosmological constant obsolete. Observations in the 1990s have shown that not only is the universe expanding, but it is also getting bigger at a faster rate. Although it appears that Einstein was wrong about the universe’s growth, his cosmological constant has become useful in explaining this acceleration.

Under the Big Bang theory, the universe started off extremely small and underwent rapid expansion for about a trillionth of a trillionth of a second. This tiny window of time is known as the inflationary period. “Inflation was a period of humongous, violent, exponential growth,” said Jenkins.

This short-lived period of growth was caused by vacuum energy. Also known as "dark energy," this energy pervades space even in the absence of matter. The amount of this energy in an area of space can be represented by the cosmological constant.

In 1987, Steven Weinberg used anthropic reasoning to predict a value for the cosmological constant that was verified experimentally almost 10 years later. Weinberg considered which values of the constant would support life and concluded that the life-supporting values must be correct. As it turns out, only a small range of values allow for life to exist in the universe.

“A large and positive cosmological constant would lead to everything being ripped apart: the universe would be cold and filled with radiation,” explained Jenkins. “If the constant was large and negative, the universe would immediately re-collapse on itself.”

Therefore, Weinberg concluded correctly that the cosmological constant must be small, or we wouldn’t be here. In a sense, the cosmological constant is finely tuned to a positive non-zero value, and large deviations from this value would lead to the demise of life in the universe.

Since the success of anthropic reasoning in cosmology, researchers have tried to apply the idea in diverse areas of physics, from thermodynamics to the microscopic world of high-energy physics. Research in these other areas, however, has had less success with fine-tuning arguments than in cosmology. For instance, many of the fundamental constants surrounding high-energy physics could vary significantly and still sustain life. Even one of the four fundamental forces, the weak nuclear force, may not be necessary to support life: galaxies and stars can theoretically still form without this force. Despite its shortfalls, fine-tuning evidence remains compelling within the realm of cosmology and raises deep questions about our universe’s beginning, evolution and eventual end.

God and the Multiverse

While anthropic reasoning gave rise to increased physics research, it also ignited a philosophical debate over the role of a supernatural creator in physics. If certain fundamental constants are finely tuned for life and they easily could have been different, then why do we happen to live in the universe that sustains life?

Philosophers and physicists are generally divided between two answers to this question. One group argues that God created the universe and intended for life to exist, hence the finely tuned values of certain constants. On the other hand, most physicists argue that our universe is only one of an infinite amount of others that exists. Within this “multiverse,” we are lucky enough to live in one of the universes that supports life.

“The fine-tuning evidence provides equal support for the multiple universe hypothesis and the God hypothesis,” said Brad Monton, a University of Colorado at Boulder philosopher who specializes in the philosophy of physics. “The probability that goes down when you consider this evidence is the hypothesis that there’s no God and one universe.”

Both Monton and Jenkins argue that physicists generally agree with this sentiment. Consequently, those who favor the God hypothesis have to rely on more than just fine-tuning evidence. Instead of simply using anthropic reasoning, these proponents of the God hypothesis draw from other areas of physics to argue for the existence of God. Perhaps the most well known proponent of the God hypothesis within the physics community is Frank Tipler, a mathematical physicist at Tulane University and co-author of The Anthropic Cosmological Principle.

In his book, Tipler distinguishes between the weak anthropic principle and the final anthropic principle. The weak version typically states that given that life is here, the universe must have properties that support life. The final anthropic principle is much stronger and states that intelligent beings must come into existence in the universe; once they come into existence, they cannot go out of existence.

“Most physicists are concerned with the weak anthropic principle,” said Tipler. “However, the final anthropic principle implies that humans are essential; it’s more controversial.”

Tipler uses fine-tuning evidence for his argument, but he also draws from thermodynamics, quantum mechanics and special relativity. Although the principle relies on a variety of physical theories for support, anthropic reasoning forms the crux of the argument. From this principle, Tipler argues that the universe was designed to have life-sustaining properties by a creator, namely God.

Most physicists, however, remain unconvinced by Tipler's argument. Instead, a large majority of physicists try to keep God out of their explanations because they think religion lies outside the realm of science. The multiverse reasoning doesn’t explicitly deny God’s existence but simply sidesteps the issue.

“A lot of physicists don’t endorse the fine-tuning argument because it’s so controversial,” said Monton.

Despite the small amount of support for these design arguments in physics and philosophy academic circles, political organizations supporting intelligent design, such as the Discovery Institute, have yet to use them.

“These groups really only focus on biology-based arguments, but the fine-tuning argument is really interesting,” said Monton. “People take it seriously, and I don’t know why [these groups] aren’t latching themselves onto it.”

Fine-tuning arguments suggest that science and religion may be more intertwined than previously thought. Although these arguments have yet to truly enter the public arena, scientists and philosophers alike continue to fervently debate the topic. Meanwhile, researchers continue to search for evidence of finely-tuned properties of our universe, reminding us that the smallest of particles can raise some of the universe’s biggest questions.

By Brian Jacobsmeyer

Tesla Coil Science: From Wireless Power to Lightning Secrets

2012-01-09T16:30:00.000-05:00

Tesla coils are the brain child of the early 20th century scientist Nikola Tesla—a man with roughly 300 patents to his name ranging from arc lamps to a helicopter prototype. Although not all of Tesla's ambitious plans came to fruition, his legacy lives on as electricity enthusiasts are still hard at work building enormous Tesla coils. One group is actively seeking funding to build the world's largest pair of Tesla coils capable of producing arcs around 100 yards long.

The proposed 10-story Tesla Coils would be the largest ever built. Image Courtesy Lightning on Demand.

The project, called the Lightning Foundry, is headed by electrical engineer Greg Leyh. A recent push for funding on the website Kickstarter fell through, but the group promises to continue building the coils as time and money permit.

Previously, the group has made impressive tesla coils on a slightly smaller scale. As shown in the video below, one such coil can send out 50-foot electrical discharges.

Video Courtesy Greg Leyh/New Scientist.

So what's going on with these machines? Tesla coils are a form of high-voltage transformer; in fact, voltages for the coils can reach over 1 million volts. The coils take the output from a transformer, bump up the voltage, and then produce dazzling discharge arcs that crackle in the air. Smaller, less powerful versions of Tesla coils are placed in plasma balls, which are common at science museums and demonstrations. Consequently, the electricity only discharges in the ball's gas—usually neon or helium—and doesn't discharge in the surrounding air.

Electrical discharge in air is more difficult, and Tesla coil enthusiasts hope that large-scale projects will help unravel some of the mystery behind lightning bolts. These projects can have interesting applications as well, such as the wireless powered vehicle in the video below. Tesla would be proud.

Video Courtesy Lightning on Demand.

Debunking Psychokinesis, Old School

2012-01-06T16:30:00.000-05:00

I love James Randi. He's better known as The Amazing Randi for his magic act, but I've never seen him doing tricks on stage. It's his commitment to debunking psychic frauds that I truly enjoy.

As I was checking out a few crackpots and fraudsters connected to stuff like cold fusion, perpetual motion machines, and zero point energy generators, I happened to stumble on this clip of Randi making a fool of psychic shyster James Hydrick.

There are several things that make this interesting viewing. The first that occurred to me while watching this clip is just how boring television could be in the old days. It's not so surprising that the panel of scientists are awfully dull, but I would have thought experienced performers like Randi, Hydrick and Bob Barker could have punched it up just a bit for the audience.

What's more surprising is that a primitive reality show like That's My Line would take time to debunk a psychic fraud. This episode was edited down from an hour and a half to fit the half hour TV format, and then cut even further for Youtube. Although it's still about as action packed as paint drying, watching Hydrick sweat and stall kept me on the edge of my seat.

I can't imagine any modern reality shows blowing air time doing something like this, but I would love to see a show based on exposing a different scam artist each week.

James Randi is still debunking frauds at a well-seasoned age of 89 83. Bob finally retired from game hosting TV in 2007. Hydrick eventually admitted his fraud and is now serving time in prison for molesting children.

Teaching Physics with Google Earth

2012-01-05T16:35:00.000-05:00

Google Earth has a number educational uses ranging from flight simulators to undersea exploration. Now a researcher has suggested extending the virtual globe's applications to physics.

From top right: inlets in Egypt, France and Italy mimic wave diffraction through an opening. Image Credit: Fabrizio Logiurato/Google Earth

Fabrizio Logiurato, a postdoctoal physics researcher at the University of Trento in Italy, proposed using Google Earth for teaching wave phenomena in a paper published on the arXiv preprint server. Logiurato argues that real-life examples engender more enthusiasm from students compared to traditional drawings of waves.

Wave refraction off the coast of Venezuela. Image Credit: Fabrizio Logiurato/Google Earth

Wave interference from boat wakes in Thailand. Image Credit: Fabrizio Logiurato/Google Earth

So take a look for yourself on Google Earth. Scouring the satellite images will reveal many different kinds of waves due to the ocean's interactions with boats, islands and coastlines.

Iowa Caucuses Security: Can Quantum Physics Help?

2012-01-03T16:45:00.000-05:00

Image credit: AP via CBS News.

Today, Republican presidential candidates are vying to win the Iowa caucuses. Although winning in Iowa doesn't guarantee the nomination by any means, past results suggest it's a decent predictor of victory. Recent winners who went on to win the nomination for their party include Barack Obama (D), John Kerry (D), Al Gore (D) and George W. Bush (R) in 2000.

The Iowa caucuses can have a significant impact on Presidential campaigns, and the security and integrity of the vote have become a growing concern. This year, a video purportedly posted by a member of the hacker group Anonymous has threatened to shut down the election event's website and disrupt the results. But new advances in quantum cryptography already implemented in foreign elections could help make these votes more secure.

Quantum cryptography—a growing field within the security industry—relies on fundamental quantum mechanics to make sure that transferred data isn't intercepted or altered. The simple act of observing or measuring a quantum mechanical system causes a disturbance. Consequently, if anyone tries to intercept or alter data that is quantum mechanically encrypted, the data itself is changed. This means that users of the system will be alerted to the presence of an eavesdropper. In other words, an eavesdropper will always leave a mark.

So far, several companies have created systems that rely on this technique, and the technique has even been used in Swiss elections. ID Quantique, the company behind the quantum encryption network for a 2007 Swiss election, have been using photons to send data discreetly. Users can use different properties of photons to transmit data, such as polarization or the amount of time traveled by the photon. Recently, the company has started using this system to transmit private banking data.

With quantum cryptography, it would certainly be more difficult to hack into a system and alter election results. Other parts of the security chain could still be open to attack, however. Stay tuned tonight and tomorrow morning for the results. And if Julian Assange—the Wikileaks founder who was supported by the Anonymous hacking group in 2011—is announced as the winner, GOP organizers may want to consider some new quantum security measures.

From Pen to Paper

2011-12-30T16:30:00.001-05:00

Researchers deconstruct the physics of a revered centuries-old process: writing with a fountain pen.

Image Credit: János Fehér

Wetting a fountain pen to compose a thank-you note is a grand way to express gratitude for a holiday gift, yet we often don’t give a thought to what happens when ink moves from pen to paper. But for a team of South Korean and American scientists, the medium is more important than the message -- and can even provide new insights into ancient biological systems.

The researchers first developed a theory of ink flow that involves the basic properties of paper and fountain pen. Then they confirmed the theory using rudimentary pens made of tiny glass tubes, glycerin ink, and faux paper etched on the silicon wafers used to produce electronic devices.

The team reports its findings in the journal Physical Review Letters.

"Writing is one of the most important inventions of human beings," said team leader Ho-Young Kim, professor of mechanical engineering at South Korea’s Seoul National University. "But surprisingly there had been little study of the scientific aspects of the process. This motivated our attempt to understand the phenomenon."

"The topic is interesting and the authors are experts," said Howard Stone, a professor of mechanical and aerospace engineering at Princeton University who was not involved in the project. "Their results are impressive."

The team identified multiple related physical properties responsible for the transmission of ink from pen to paper.

Capillary action allows fluids to flow in thin tubes against the pull of other forces such as gravity. For instance, it causes paint to move up the bristles of a paintbrush, and paper towels to absorb liquid spills through their microscopic, wood-based, cylinder-shaped fibers.

Capillary action results from two processes working together. The first is adhesion, or the attachment of a liquid to a solid object, such as water to a glass tube, due to the attraction between the molecules of the liquid and the solid object it contacts. The second is surface tension, the cohesion of liquid molecules on its surface. Surface tension allows liquids to form round drops and insects called water striders to walk across the taut surfaces of ponds.

Another important phenomenon is viscosity, a fluid's resistance to flowing. For example, tomato ketchup is more viscous than water.

One other factor comes into play: the speed at which the writer moves the pen.

Team member Lakshminarayanan Mahadevan, a professor of mathematics, physics, and biology at Harvard University, explained that the new theory views the process of writing as a competition for the ink between pen and paper.

"The pores [in the paper] draw in the fluid via capillary – surface tension – forces, while the viscosity resists this motion," he said. "The moving pen drags along the fluid, and again viscous forces resist this. Together they shape the blot, if one hesitates, and the line when one's thoughts flow from the mind to the machine that records them – the pen."

To test their theory, the researchers devised "minimal pens," imitation inks, and jury-rigged “paper."

The pens consisted of glass tubes with diameters between half a millimeter and one millimeter. Solutions of glycerin in various concentrations provided the "ink" that filled them. And to mimic paper, the researchers etched tiny pillars, of various heights and separated by distances much less than the pen's diameter, on the surfaces of silicon wafers.

Careful observation showed the glycerin ink from the minimal pen flowing into the valleys between the pillars in the faux paper in just the way the team had predicted. "The agreement was excellent," Kim said.

The shape of the ink front ahead of the moving pen also confirmed the theory.

"Physiologist Douglas Wilkie said that facts and theories are natural enemies," said Mahadevan. "But here they were friends, helping each other along."

The researchers emphasized that their theory does not apply to ballpoint pens. "They use fundamentally different ink from what is used in fountain pens," Kim explained. "It doesn’t spread like usual ink."

However, Mahadevan said, "We are currently thinking of a different theory for this process."

Kim pointed out that, because paper consists of a network of cellulose fibers, the research has implications beyond writing.

"Cellulose is the major constituent of plants' cell walls," he said. "Therefore, understanding liquid flow into a cellulose fiber network has a profound implication for water transport in plants. Our work can be used to enhance our understanding of how water can climb up tall trees without mechanical pumps. And there are functional porous materials [based on cellulose] which are particularly useful in biomedical fields."

###

Peter Gwynne, Inside Science News Service

Evolution of Icicles

2011-12-29T16:30:00.000-05:00

As the holiday season winds down, the weather in many parts of the world remains frightful. In particular, large, sharp icicles often form on gutters, trees and vehicles. Icicles are usually harmless reminders of winter, but they can present huge problems, especially for utility workers faced with power lines that fail under the weight of ice.

In a recently published article on NewScientist, author Michael Brooks explores the applications of physics research on icicle formations. With a better understanding of how icicles grow, scientists hope to provide applicable information for architects, utility workers and even Hollywood CGI specialists.

Over the past year, scientists have learned quite a bit about the evolution of icicles—a field still in its infancy. For instance, physicists from the University of Toronto found that the purity of water can dramatically change the growth of icicles. Pure water tends to lead to icicles that taper nicely into a sharp point. When the scientists used tap water, however, the icicles had more ripples and had large protrusions near the top. These results surprised researchers who generally thought that minor impurities in tap water wouldn't affect the growth of an icicle.

To create these icicles, the scientists created a special icicle growing apparatus. Inside the device, air was constantly circulated and kept at the same temperature while near-freezing water was provided from an external reservoir. In addition to the unforeseen affect of impure water, scientists were able to create several branching icicles with multiple tips. These multi-pronged icicles were more likely to form when the air was still.

Icicles formed in still air are more likely to branch. Image Courtesy Antony Chen/Stephen Morris/University of Toronto. Image Copyright: American Physical Society.

These results contradicted a long-held belief that icicles tend to form self-similar shapes, meaning that the circumference and length are always proportional.

So who can benefit from icicle research? Architects, for instance, have been interested in icicle growth to better design buildings that make it difficult for dangerous stalactites to form easily. Also, CGI experts have increasingly been interested in modeling icicles over time. As reported in the NewScientist article, CGI experts consulted icicle experts for a deleted scene of Superman Returns.

Top image credit: Hans. A Rosbach via Wikipedia.

Sticky Physics

2011-12-27T16:50:00.000-05:00

As anyone can tell you, certain liquids, like water, will usually fall in droplets while others, such as honey, will slowly slide to the ground in a long filament. The key differences between these two liquids are viscosity and surface tension, and scientists have conducted a new experiment to better understand these differences. Volcanoes, ink-jet printers, and archer fish—who use their mouth as a sharpshooting water pistol to hunt prey—all take advantage of the properties of liquid filaments and droplets.

In their study, scientists from Cambridge University created liquid streams ranging from pure water to pure glycerol, a naturally-occurring compound used to sweeten food and manufacture glue. The researchers then used a high-speed camera to record the various substances as they fell to the ground. From this data, the scientists could determine specifically what variations in viscosity and surface tension led to streams forming droplets or pinching off. The experiment provided a verification of previous models, but the data also navigated uncharted territory with the wide selection of previously untested liquids.

With this new data, scientists hope to improve upon several applications that depend heavily on differences in viscosity and surface tension. In ink-jet printing, for example, the printer shoots a stream of ink at high speeds onto the paper, requiring just the right type of liquid to avoid blotting.

Also, patients receiving certain respiratory medicines rely on liquid droplets as opposed to streams. Only small enough droplets can be absorbed in the lungs, so this type of research can help doctors better administer these types of drugs.

This research on fluid dynamics will be published in a forthcoming article in the journal Physical Review Letters.

How the Engineers Stole Christmas

2011-12-24T16:00:00.003-05:00

How the Engineers Stole Christmas

WARNING! THIS POST IS NOT FOR THOSE LITTLE READERS THAT HAVE SENT HONEST, HEART-FELT LETTERS TO THE NORTH POLE AND LEFT OUT MILK AND COOKIES FOR A MAN IN A RED SUIT.

This is an internet meme from a Christmas long, long ago. Our younger contributors, [yes, I'm talking to you Hyperspace] probably haven't seen it before. I hope that those of you who have, hearken back to your internet youth, and those of you to whom this is new, get a good Fermi problem chuckle.

So while you you stay up this evening listening for the sound of reindeer hooves clicking on your roof, here is some physics to ponder.

"I. There are approximately two billion children (persons under 18) in the world. However, since Santa does not visit children of Muslim, Hindu, Jewish or Buddhist religions, this reduces the workload for Christmas night to 15% of the total, or 378 million (according to the Population Reference Bureau).
At an average (census) rate of 3.5 children per house hold, that comes to 108 million homes, presuming that there is at least one good child in each.
II. Santa has about 31 hours of Christmas to work with, thanks to the different time zones and the rotation of the earth, assuming he travels east to west (which seems logical). This works out to 967.7 visits per second. This is to say that for each Christian household with a good child, Santa has around 1/1000th of a second to park the sleigh, hop out, jump down the chimney, fill the stockings, distribute the remaining presents under the tree, eat whatever snacks have been left for him, get back up the chimney, jump into the sleigh and get on to the next house.
Assuming that each of these 108 million stops is evenly distributed around the earth (which, of course, we know to be false, but will accept for the purposes of our calculations), we are now talking about 0.78 miles per household; a total trip of 75.5 million miles, not counting bathroom stops or breaks. This means Santa's sleigh is moving at 650 miles per second --- 3,000 times the speed of sound. For purposes of comparison, the fastest man-made vehicle, the Ulysses space probe, moves at a poky 27.4 miles per second, and a conventional reindeer can run (at best) 15 miles per hour.
III. The payload of the sleigh adds another interesting element. Assuming that each child gets nothing more than a medium sized Lego set (two pounds), the sleigh is carrying over 500 thousand tons, not counting Santa himself. On land, a conventional reindeer can pull no more than 300 pounds. Even granting that the "flying" reindeer could pull ten times the normal amount, the job can't be done with eight or even nine of them--- Santa would need 360,000 of them. This increases the payload, not counting the weight of the sleigh, another 54,000 tons, or roughly seven times the weight of the Queen Elizabeth (the ship, not the monarch).
IV. 600,000 tons traveling at 650 miles per second creates enormous air resistance --- this would heat up the reindeer in the same fashion as a spacecraft re-entering the earth's atmosphere. The lead pair of reindeer would absorb 14.3 quintillion joules of energy per second each. In short, they would burst into flames almost instantaneously, exposing the reindeer behind them and creating deafening sonic booms in their wake.
The entire reindeer team would be vaporized within 4.26 thousandths of a second, or right about the time Santa reached the fifth house on his trip.
Not that it matters, however, since Santa, as a result of accelerating from a dead stop to 650 m.p.s. in .001 seconds, would be subjected to centrifugal forces of 17,500 g's. A 250 pound Santa (which seems ludicrously slim) would be pinned to the back of the sleigh by 4,315,015 pounds of force, instantly crushing his bones and organs and reducing him to a quivering blob of pink goo.
Therefore, if Santa did exist, he's dead now."

Happy Holidays From Science!

2011-12-23T00:00:00.000-05:00

Understanding Deadly Ice Avalanches

2011-12-22T16:30:00.000-05:00

An ice skating phenomenon might explain the snowball effect behind icy avalanches.

Tumbling ice particles collide and melt, accelerating this mini-avalanche. Credit: Barbara Turnbull | University of Nottingham

(ISNS) -- The same physics behind ice skating may explain why massive ice avalanches can develop so quickly according to new research.

In 2002, a small disturbance on a mountain slope in the Russian Republic of North Ossetia set off a deadly ice avalanche, engulfing two glaciers en route to unsuspecting villagers. The destruction started with the collapse of 100 million cubic meters of ice and rock, which eventually stormed through a river valley toward villages at 175 miles per hour. Over 100 villagers were killed, and similar avalanches in the Alps and in North America have threatened local populations over the past few years.

"Ice avalanches can be particularly devastating," said Barbara Turnbull, an avalanche researcher at the University of Nottingham in the U.K. "They often trigger secondary flows [of rock and snow]."

In an effort to better understand these events, Turnbull simulated avalanche conditions in her lab. Her research has just been published in the journal Physical Review Letters.

Turnbull first dipped water droplets into frigid liquid nitrogen to create ice particles for her experiment. Next, she placed the ice particles in a temperature-controlled rotating drum and filmed the interactions of the particles with a high-speed camera. With data from the camera, Turnbull measured the particle velocities and watched the mini-avalanche evolve over time. Turnbull found that even though the particles were held at temperatures below freezing, they still melted due to friction -- a phenomenon best known in the realms of ice skating and skiing.

When a skater glides across an ice rink, the friction between the skate and the ice causes the top layer to melt. This melting creates a slippery liquid surface, allowing the skater to move gracefully. Similarly, during an avalanche, ice particles collide and start melting one another even at sub-zero air temperatures. In turn, frictional melting creates a slippery surface that speeds up the other particles, causing more collisions.

"I'm more surprised and excited about the fact that [frictional heating] was observed in such a small-scale flow," wrote Demian Schneider, an avalanche researcher at the University of Zurich, in an email to Inside Science.

The positive feedback between frictional heating and particle collisions explains why avalanches develop quickly and unexpectedly. "It's about linking these two aspects together," said Turnbull.

This snowballing cycle can even melt solid rock several meters thick once the avalanche has grown large enough. In 2005, an ice and rock avalanche in Alaska became so massive that seismologists picked up readings on the other side of the globe. Researchers have been detecting more of these large avalanches recently, and evidence suggests that climate change coupled with better detection methods is behind the observed increase.

"We have relatively robust evidence of an increase of high-mountain rockfall and avalanches in the European Alps," Christian Huggel, an avalanche researcher from the University of Zurich told Inside Science in an email. "General theoretical considerations but also field measurements are supporting the view that warming in high-mountain [areas] is likely destabilizing slopes."

The limited field measurements of high-mountain ice temperatures indicate that the problems of climate change are amplified within glaciers. Small rises in air temperature can lead to even greater temperature increases within the ice, suggesting that climate change may have contributed to the recent uptick in observed avalanches in glacial areas.

Although laboratory experiments can never fully recreate avalanche conditions, experts argue that they're an indispensable tool for avalanche preparation. Being able to watch a miniature avalanche evolve over a long period of time can be more useful than studying the aftermath of real avalanches. In particular, climate change may render historical avalanche field data less helpful as avalanches start to affect larger areas, according to Schneider.

Scientists hope to apply their better understanding of avalanche physics toward risk-reduction efforts. Hazard maps of high-mountain environments, for instance, could be improved with a better understanding of how avalanches evolve. But ice avalanches remain stubbornly unpredictable.

"Such large and long reaching avalanches are low-frequency, high-impact events which are difficult to handle in terms of risk, similar to nuclear plants," said Schneider.

Nonetheless, Schneider believes that these most recent results represent an important step toward understanding avalanches: "All in all, it's a great basis for future work."

By Brian Jacobsmeyer, Inside Science News Service

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