eufisica

Links for 2012-02-25 [del.icio.us]

Sun, 26 Feb 2012 00:00:00 PST

7 equations that rules your world
Gravity Wells
Pulsars: Fantastic Physics
A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can only be observed when the beam of emission is pointing towards the Earth, much the way a lighthouse can only be seen when the light is pointed in the direction of an observer, and is responsible for the pulsed appearance of emission.
Measure the speed of light with chocolate
Watch the video and follow the calculus.
Neutrino's saga - part 8
Einstein was right, neutrinos can't travel faster than the speed of light. Read what happened in this post.
SciMad
SciMad
Science news, experiments, and everyday science.

ScienceCasts: Alien Matter in the Solar System

noreply@blogger.com (José Gonçalves) — Sat, 25 Feb 2012 15:44:00 PST

Week review

noreply@blogger.com (José Gonçalves) — Sat, 25 Feb 2012 07:01:00 PST

This is a week review from eufisica:

Pulsars: Fantastic Physics - http://eufisica.blogspot.com/2012/02/pulsars-fantastic-physics.html

Evidence of rare hypernucleos - http://eufisica.blogspot.com/2012/02/evidence-of-rare-hypernucleus.html

Measure the speed of light with chocolate - http://eufisica.blogspot.com/2012/02/measure-speed-of-light-with-chocolate.html [hot topic]

The neutrino's Saga part 8 - http://eufisica.blogspot.com/2012/02/neutrinos-saga-part-8.html [hot topic]

Measurement of W boson mass tests Standard Model, Higgs boson limits - http://eufisica.blogspot.com/2012/02/measurement-of-w-boson-mass-tests.html

Posted via email from eufisica's posterous

Measurement of W boson mass tests Standard Model, Higgs boson limits

noreply@blogger.com (José Gonçalves) — Thu, 23 Feb 2012 14:37:00 PST

The new CDF result for the W boson mass, combined with the world's best value for the top quark mass, restricts the Higgs mass to the green area, requiring it to be less than 145 GeV/c2. Direct searches have narrowed the allowed Higgs mass range to 115-127 GeV/c2.

(PhysOrg.com) -- Just as firemen use different methods to narrow the location of a person trapped in a building, scientists employ two techniques to find the hiding place of the theorized Higgs particle: direct searches for Higgs interactions and precision measurements of other particles and forces.

The Neutrino's Saga - Part 8

noreply@blogger.com (José Gonçalves) — Thu, 23 Feb 2012 08:33:00 PST

The saga of superluminal neutrinos seems to be coming to an end. Everything indicates that the results obtained by the OPERA Collaboration in Italy were due to an error in measuring instruments. According to a source connected to the experiment, the observed time discrepancy, 60 nanosecond that was measured, appears to be related to a poor connection between an optical fiber cable which connects the GPS receiver, which is used to correct the time of flight of neutrinos,and a circuit board of a computer.
Remember that the problem began in September 2011 when scientists were experimenting a flux of neutrinos from CERN (Geneva) to the Gran Sasso's laboratory in Italy (about 455 miles away), and reported results that seemed to indicate that the neutrinos traveled faster than the speed of light, reaching about 60 nanoseconds sooner than expected.
After the best tight connection, the researchers found that the time measured for the data running through the distance corresponding to length of optical fiber was less than 60 nanoseconds which had previously obtained, which would nullify the time difference obtained on the flight of the neutrinos. It seems therefore to be found a very simple explanation for the discrepancy of time that had been found in initial experiments. However, it is also necessary to obtain new data to confirm this situation.
It therefore indicates that the Einstein's Theory of Relativity once again winning out over a test of its validity. Since this theory has been confirmed many times in several experiments, most people suspected that there must be some error in the experiment had been conducted, which would escape to the researchers. This error appears to have been now found. It now remains to be confirmed.
You can read about this news here and here.

Measure the Speed of Light with Chocolate

noreply@blogger.com (José Gonçalves) — Wed, 22 Feb 2012 10:55:00 PST

"'C' is for chocolate! 'c' is also the symbol used for the speed of light. Defined as being 299,792,458 meters per second in vacuum, you can take a crack at measuring the ultimate speed using your microwave, a ruler and a bar of chocolate! Yum!" (Jefferson Lab - YouTube)

Well, lets see how they do it:

And now the calculations:

To calculate the speed of light, we can use the math's expression of speed:

v = Dx/Dt

In this case, Dx = l and Dt = T and T = 1/f (T is the period and f the frequency of the wave, and l the wavelength).
The holes that appear in the chocolate corresponds to the maximum and minimum in a steady wave. So the wavelength is two times this distance:
l = 2 x 7.1 cm = 2 x 7.1 x 10^-2 m
The frequency can be read in the back of your microwave. In this case, the value corresponds to f = 2 450 MHz = 2 450 x 10⁶ s^-1.

So, velocity is:
v = l x f <=> v= 2x(7.1 x 10^-2 m) x (2 450 x 10⁶ s^-1) = 3.48 x 10⁸ m s^-1 .

That brings a percent error:

e = |c - v|/|c| x 100 = | 2.99 x 10⁸ - 3.48 x 10⁸|/|2.99 x 10⁸| x 100 = 16 %

Evidence of rare hypernucleus

noreply@blogger.com (José Gonçalves) — Mon, 20 Feb 2012 08:09:00 PST

A view of one of the three events found by FINUDA: a schematic frontal view of the apparatus is shown, and the two blue lines represent the two 'pi' mesons moving along opposite bent trajectories in the magnetic field of the apparatus. Image credit: FINUDA collaboration

(PhysOrg.com) -- Physicists in Italy have discovered the first evidence of a rare nucleus that doesn’t exist in nature and lives for just 10^-10 seconds before decaying. It’s a type of hypernucleus that, like all nuclei, contains an assortment of neutrons and protons. But unlike ordinary nuclei, hypernuclei also contain at least one hyperon, a particle that consists of three quarks, including at least one strange quark. Hypernuclei are thought to form the core of strange matter that may exist in distant parts of the universe, and could also allow physicists to probe the inside of the nucleus.

The particular hypernucleus investigated here, called "hydrogen six Lambda" (⁶_ΛH).

A hypernucleus is a nucleus which contains at least one hyperon in addition to nucleons. The first was discovered by Marian Danysz and Jerzy Pniewski in 1952.

Since the strangeness quantum number is conserved by the strong and electromagnetic interactions, at least hypernuclei containing the lightest hyperon, the Lambda, live long enough to have sharp nuclear energy levels. Therefore they offer opportunities for nuclear spectroscopy, as well as reaction mechanism study and other types of nuclear physics (hypernuclear physics). Their physics is different from that of normal nuclei because a hyperon, having a different value of the strangeness quantum number, can share space and momentum coordinates with the usual four nucleons that can differ from each other in spin and isospin. The ground state of helium-5-Lambda, for example, must resemble helium-4 more than it does helium-5 or lithium-5 and must be stable, except for the weak decay of the Lambda. Sigma hypernuclei have been sought with apparent success.^[1]

Hypernuclei can be made by a nucleus capturing a Lambda or K meson and boiling off neutrons in a compound nuclear reaction, or, perhaps most easily, by the direct strangeness exchange reaction.

K + nucleus → π + hypernucleus

A generalized mass formula developed for both the non-strange normal nuclei and strange hypernuclei can estimate masses of hypernuclei containing Lambda, Lambda-Lambda, Sigma,Cascade and Theta+ hyperon(s).^[2]^[3] The neutron and proton driplines for hypernuclei are predicted and existence of some exotic hypernuclei beyond the normal neutron and proton driplines are suggested.^[4] This generalized mass formula was named as "Samanta Formula" by Botvina and Pochodzalla and used to predict relative yields of hypernuclei in multifragmentation of nuclear spectator matter.^[5]

Hypernuclei were first observed by their energetic but delayed decay, but have also been studied by measuring the momenta of the K and pi mesons in the direct strangeness exchange reactions.

In particle physics, a hyperon is any baryon containing one or more strange quarks, but no charm quarks or bottom quarks.

font wikipedia

Pulsars: Fantastic Physics

noreply@blogger.com (José Gonçalves) — Mon, 20 Feb 2012 08:05:00 PST

A pulsar is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can only be observed when the beam of emission is pointing towards the Earth, much the way a lighthouse can only be seen when the light is pointed in the direction of an observer, and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval, between pulses that range from roughly milliseconds to seconds for an individual pulsar.

The precise periods of pulsars makes them useful tools. Observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12. Certain types of pulsars rival atomic clocks in their accuracy in keeping time. (Wikipedia)

Pulsars, superdense neutron stars, are perhaps the most extraordinary physics laboratories in the Universe. Research on these extreme and exotic objects already has produced two Nobel Prizes. Pulsar researchers now are poised to learn otherwise-unavailable details of nuclear physics, to test General Relativity in conditions of extremely strong gravity, and to directly detect gravitational waves with a "telescope" nearly the size of our Galaxy. (PhysOrg)

Hear the sound and watch the video:

pulsar-psr0950+08-nrao.wav (credit: astrosurf.com)

Gravity wells

noreply@blogger.com (José Gonçalves) — Sat, 18 Feb 2012 07:31:00 PST

Click the image to view in full size.
Watch this video comparing Earth and Moon gravity wells:

7 equations that rules the world

noreply@blogger.com (José Gonçalves) — Sat, 18 Feb 2012 07:25:00 PST

Do you know the seven equations that rules your world?
Well, News Scientist has the answer:

Feynman Diagrams - Sixty Symbols

noreply@blogger.com (José Gonçalves) — Fri, 17 Feb 2012 11:52:00 PST

In this Feynman diagram, an electron and a positronannihilate, producing a virtual photon (represented by the blue wavy line) that becomes a quark-antiquark pair. Then one radiates a gluon (represented by the green spiral).

Feynman diagrams are pictorial representations of the mathematical expressions governing the behavior of subatomic particles. The scheme is named for its inventor, Nobel Prize-winning American physicist Richard Feynman, and was first introduced in 1948. The interaction of sub-atomic particles can be complex and difficult to understand intuitively, and the Feynman diagrams allow for a simple visualization of what would otherwise be a rather arcane and abstract formula.

The calculation of probability amplitudes in theoretical particle physics requires the use of rather large and complicated integrals over a large number of variables. These integrals do, however, have a regular structure, and may be represented graphically as Feynman diagrams. More precisely, and technically, a Feynman diagram is a graphical representation of a perturbative contribution to the transition amplitude or correlation function of a quantum mechanical or statistical field theory.

from Wikipedia

Links for 2012-02-15 [del.icio.us]

Thu, 16 Feb 2012 00:00:00 PST

Beginner’s Guide to Seeing the International Space Station (ISS)
The ISS is major accomplishment for NASA (US), ESA (Europe), JAXA (Japan) CSA (Canada) and all the countries involved (16 in all). The space station is just over 72 m long by 108 m wide and 20 m high

Carbon Monoxide in our Galaxy

noreply@blogger.com (José Gonçalves) — Wed, 15 Feb 2012 12:16:00 PST

This all-sky image shows the distribution of carbon monoxide (CO), a molecule used by astronomers to trace molecular clouds across the sky, as seen by Planck. Image released February 13, 2012.
CREDIT: ESA/Planck Collaboration

The new images come from the European Space Agency's Planck spacecraft, which showed the odd microwave haze during a survey that also turned up previously unseen patches of cold gas where new stars are forming.

in Space.com

Discovery that hints at origin of phenomena like solar flares

noreply@blogger.com (José Gonçalves) — Wed, 15 Feb 2012 11:53:00 PST

An argon plasma jet forms a rapidly growing corkscrew, known as a kink instability. This instability causes an even faster-developing behavior called a Rayleigh-Taylor instability, in which ripples grow and tear the jet apart. This phenomenon, the Caltech researchers say, has never been seen before and could be important in understanding solar flares and in developing nuclear fusion as a future energy source. Credit: A. L. Moser and P. M. Bellan, Caltech

In the experiments, Moser fired jets of hydrogen, nitrogen, and argon plasmas at speeds of about 10 to 50 kilometers per second across a distance of more than 20 centimeters in a vacuum. [...]

The experiment requires 200 million watts of power to produce jets that are a scorching 20,000 degrees Kelvin and carry a current of 100,000 amps. To study the jets, Moser used cameras that can take a snapshot in less than a microsecond, or one millionth of a second.

As in all electrical currents, the flowing electrons in the plasma jet generate a magnetic field, which then exerts a force on the plasma. These electromagnetic interactions between the magnetic field and the plasma can cause the jet to writhe and form a rapidly expanding corkscrew. [...]

She found that—more often than not—the corkscrew shape that developed in her jets grew exponentially and extremely fast. The jets in the experiment formed 20-centimeter-long coils in just 20 to 25 microseconds. She also noticed tiny ripples that began appearing on the inner edge of the coil just before the jet broke—the moment when there was a magnetic reconnection.

font: PhysOrg (click to read entire article)

Mathematical Model Computes Snow Flake Shapes

noreply@blogger.com (José Gonçalves) — Wed, 15 Feb 2012 11:46:00 PST

John Barrett at Imperial College London and a couple of pals reveal their approach to snowflake modelling. The result is that they have been able to compute various snow flake shapes that appear in nature for the first time. These include solid plates, solid prisms, hollow columns, needles, dendrites, capped columns and scrolls on plates.

Entire article here.

Preprint paper here.

Triangular snowflakes here.

Links for 2012-02-12 [del.icio.us]

Mon, 13 Feb 2012 00:00:00 PST

The Big Bang for Beginners
via scienceblogs.com ...

Circuit misconceptions

noreply@blogger.com (José Gonçalves) — Sun, 12 Feb 2012 07:10:00 PST

Jacobs Physics blog bring us a post about Circuit Misconceptions

Circuit misconceptions, and an advance copy of a quiz:

On a problem set last week, I gave students the simple circuit shown to the right. I asked what would happen to various parts of the circuit when I decreased R₂. One of the questions in particular said, "What will happen to the current flowing from the battery when the value of R₂ is decreased?"

The most common answer:

"The current will not change, because it's the same battery, so it will always provide the same current."

Silly students, a battery provides a constant VOLTAGE, not a constant current -- but that's a common misconception in the first week of circuits.

The second most common answer:

"The current will not change, because R₂ is the farthest resistor from the battery, and so the current hasn't reached R₂ yet.

(click here to read entire article and see how Mr. Jacobs solve the students' misconception)

More:
Parallel resistors misconceptions.
Circuits.

The Big Bang for Beginners

noreply@blogger.com (José Gonçalves) — Sun, 12 Feb 2012 06:59:00 PST

via scienceblogs.com

Posted via email from eufisica's posterous

Better understanding of why meson particles disappear

noreply@blogger.com (José Gonçalves) — Sat, 11 Feb 2012 07:40:00 PST

The PHENIX detector at the Relativistic Heavy Ion Collider.
Credit: 2012 Brookhaven National Laboratory

(PhysOrg) - For several years, physicists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), USA, have studied an unusual state of matter called the quark–gluon plasma, which they believe mimics the hot, dense particle soup that existed immediately after the big bang. Now, the PHENIX collaboration at RHIC reports findings about a particle called the J/ψ meson that will help physicists distinguish the properties of the quark–gluon plasma (QGP) from those of normal matter.

in PhysOrg

Watch the table of mesons here,
and video from CERN (Measurement of B_s mixing parameters from B_s → J/&psi φ decays at CDF and D∅).

Links for 2012-02-10 [del.icio.us]

Sat, 11 Feb 2012 00:00:00 PST

"Salários a 300 euros....dá ni
"Salários a 300 euros....dá nisto!" comentário no FB a esta imagem: https://t.co/veOGdIGy

Sigma explained

noreply@blogger.com (José Gonçalves) — Fri, 10 Feb 2012 03:14:00 PST

Credit: CERN

Do you know what it means the "sigma" that appears in data analysis?
The unit of measurement usually given when talking about statistical significance is the standard deviation, sigma (σ). The term refers to the amount of variability in a given set of data: whether the data points are all clustered together, or very spread out.
from PhysOrg (click to read entire article)

Rocket Science

noreply@blogger.com (José Gonçalves) — Tue, 07 Feb 2012 08:54:00 PST

Physics behind rockets: real-world-physics-problems
Playlist with videos about Rocket Science:

Benefits of NASA technologies

noreply@blogger.com (José Gonçalves) — Tue, 07 Feb 2012 08:27:00 PST

Here is the Spinoff 2011 by NASA: Presentation and Report.

NASA spinoffs - Interview with Dan Lockney:

Mars Express updates

noreply@blogger.com (José Gonçalves) — Mon, 06 Feb 2012 09:42:00 PST

Ancient northern ocean on Mars. Credit: ESA

ESA's Mars Express radar gives strong evidence for former Mars ocean

ESA's Mars Express has returned strong evidence for an ocean once covering part of Mars. Using radar, it has detected sediments reminiscent of an ocean floor within the boundaries of previously identified, ancient shorelines on Mars.

in ESA.

Mars Express reveals wind-blown deposits on Mars

New images from ESA’s Mars Express show the Syrtis Major region on Mars. Once thought to be a sea of water, the region is now known to be a volcanic province dating back billions of years.

in ESA

High-precision map of Milky Way's magnetic fields

noreply@blogger.com (José Gonçalves) — Fri, 03 Feb 2012 15:32:00 PST

The sky map of the Faraday effect caused by the magnetic fields of the Milky Way. Red and blue colors indicate regions of the sky where the magnetic field points toward and away from the observer, respectively. The band of the Milky Way (the plane of the Galactic disk) extends horizontally in this panoramic view. The center of the Milky Way lies in the middle of the image. The North celestial pole is at the top left and the South Pole is at the bottom right. Credit: Max Planck Institute for Astrophysics

(PhysOrg.com) -- Scientists at the Naval Research Laboratory (NRL) are part of an international team that has pooled their radio observations into a database, producing the highest precision map to date of the magnetic field within our own Milky Way galaxy.

Dark side of the Moon

noreply@blogger.com (José Gonçalves) — Thu, 02 Feb 2012 05:56:00 PST

A camera aboard one of NASA's twin Gravity Recovery And Interior Laboratory (GRAIL) lunar spacecraft has returned its first unique view of the far side of the moon.

Repulsive gravity as an alternative to dark energy

noreply@blogger.com (José Gonçalves) — Wed, 01 Feb 2012 11:49:00 PST

(PhysOrg.com) -- When scientists discovered in 1998 that the Universe is expanding at an accelerating rate, the possibility that dark energy could explain the observation was intriguing. But because there has been little progress in figuring out exactly what dark energy is, the idea has since become more of a problem than a solution for some scientists. One physicist, Massimo Villata of the National Institute for Astrophysics (INAF) in Pino Torinese, Italy, describes dark energy as “embarrassing,” saying that the concept is an ad hoc element to standard cosmology and is devoid of any physical meaning. Villata is one of many scientists who are looking for new explanations of the Universe’s accelerating expansion that involve some form of repulsive gravity. In this case, the repulsive gravity could stem from antimatter hiding in voids.

(PhysOrg.com) -- During the past few years, CERN physicist Dragan Hajdukovic has been investigating what he thinks may be a widely overlooked part of the cosmos: the quantum vacuum. He suggests that the quantum vacuum has a gravitational charge stemming from the gravitational repulsion of virtual particles and antiparticles. Previously, he has theoretically shown that this repulsive gravity can explain several observations, including effects usually attributed to dark matter. Additionally, this additional gravity suggests that we live in a cyclic Universe (with no Big Bang) and may provide insight into the nature of black holes and an estimate of the neutrino mass. In his most recent paper, published in Astrophysics and Space Science, he shows that the quantum vacuum could explain one more observation: the Universe’s accelerating expansion, without the need for dark energy.

Wireless power could revolutionize highway transportation

noreply@blogger.com (José Gonçalves) — Wed, 01 Feb 2012 11:24:00 PST

Stanford University researchers are developing a technology that uses magnetic fields (shown in red) to wirelessly charge electric vehicles cruising at highway speeds. Credit: Sven Beiker, CARS/Stanford University

A Stanford University research team has designed a high-efficiency charging system that uses magnetic fields to wirelessly transmit large electric currents between metal coils placed several feet apart. The long-term goal of the research is to develop an all-electric highway that wirelessly charges cars and trucks as they cruise down the road.

in PhysOrg

Read the paper at Standford University

Watch the following videos with other concepts:

Piezoelectric materials

Mechanical System

Wind traps

Links for 2012-01-31 [del.icio.us]

Wed, 01 Feb 2012 00:00:00 PST

Construct your own wind meter
An anemometer looks like a weather vane, but instead of measuring which direction the wind is blowing with pointers, it has four cups so that it can more accurately measure wind speed. Each cup is attached to the end of a horizontal arm, each of which is mounted on a central axis, like spokes on a wheel. When wind pushes into the cups, they rotate the axis. The faster the wind, the faster the cups spin the axis.
Nanotube-based terahertz polarizer nears perfection
(PhysOrg.com) -- Researchers at Rice University are using carbon nanotubes as the critical component of a robust terahertz polarizer that could accelerate the development of new security and communication devices, sensors and non-invasive medical imaging systems as well as fundamental studies of low-dimensional condensed matter systems.
Human activity, Solar activity and Global Warming
Human activity affect much more to global warming. Study NASA's says.

Human activity, solar activity and global warming

noreply@blogger.com (José Gonçalves) — Tue, 31 Jan 2012 04:42:00 PST

A graph of the sun's total solar irradiance shows that in recent years irradiance dipped to the lowest levels recorded during the satellite era. The resulting reduction in the amount of solar energy available to affect Earth's climate was about .25 watts per square meter, less than half of Earth's total energy imbalance. Credit: NASA/James Hansen

A new NASA study underscores the fact that greenhouse gases generated by human activity -- not changes in solar activity -- are the primary force driving global warming.

in PhysOrg

A new NASA study underscores the fact that greenhouse gases generated by human activity -- not changes in solar activity -- are the primary force driving global warming.

"The fact that we still see a positive imbalance despite the prolonged solar minimum isn't a surprise given what we've learned about the climate system, but it's worth noting because this provides unequivocal evidence that the sun is not the dominant driver of global warming," Hansen said.

Hansen's team concluded that Earth has absorbed more than half a watt more solar energy per square meter than it let off throughout the six year study period. The calculated value of the imbalance (0.58 watts of excess energy per square meter) is more than twice as much as the reduction in the amount of solar energy supplied to the planet between maximum and minimum solar activity (0.25 watts per square meter).

According to calculations conducted by Hansen and his colleagues, the 0.58 watts per square meter imbalance implies that carbon dioxide levels need to be reduced to about 350 parts per million to restore the energy budget to equilibrium. The most recent measurements show that carbon dioxide levels are currently 392 parts per million and scientists expect that concentration to continue to rise in the future.

in NASA