Interesting+Physics

Just put some interesting blogs and related articles in here Posted: 24 Sep 2011 NZST  If it’s true, it will mark the biggest discovery in physics in the past half-century: Elusive, nearly massless subatomic particles called neutrinos appear to travel just faster than light, a team of physicists in Europe reports. If so, the observation would wreck Einstein’s theory of special relativity, which demands that nothing can travel faster than light. In fact, the result would be so revolutionary that it’s sure to be met with skepticism all over the world. “I suspect that the bulk of the scientific community will not take this as a definitive result unless it can be reproduced by at least one and preferably several experiments,” says V. Alan Kostelecky, a theorist at Indiana University, Bloomington. He adds, however, “I’d be delighted if it were true.” The data come from a 1,300-metric-ton particle detector named Oscillation Project with Emulsion-tRacking Apparatus (OPERA). Lurking in Italy’s subterranean Gran Sasso National Laboratory, OPERA detects neutrinos that are fired through the Earth from the European particle physics laboratory, CERN, near Geneva, Switzerland. As the particles hardly interact at all with other matter, they stream right through the ground, with only a very few striking the material in the detector and making a noticeable shower of particles.
 * = Can Neutrinos Move Faster Than Light? =
 * By Adrian Cho, //Science//NOW **

Over three years, OPERA researchers timed the roughly 16,000 neutrinos that started at CERN and registered a hit in the detector. They found that, on average, the neutrinos made the 730-kilometer, 2.43-millisecond trip roughly 60 nanoseconds faster than expected if they were traveling at light speed. “It’s a straightforward time-of-flight measurement,” says Antonio Ereditato, a physicist at the University of Bern and spokesperson for the 160-member OPERA collaboration. “We measure the distance and we measure the time, and we take the ratio to get the velocity, just as you learned to do in high school.” Ereditato says the uncertainty in the measurement is 10 nanoseconds.

However, even Ereditato says it’s way too early to declare relativity wrong. “I would never say that,” he says. Rather, OPERA researchers are simply presenting a curious result that they cannot explain and asking the community to scrutinize it. “We are forced to say something,” he says. “We could not sweep it under the carpet because that would be dishonest.” The results will be presented at a seminar tomorrow at CERN. The big question is whether OPERA researchers have discovered particles going faster than light, or whether they have been misled by an unidentified “systematic error” in their experiment that’s making the time look artificially short. Chang Kee Jung, a neutrino physicist at Stony Brook University in New York, says he’d wager that the result is the product of a systematic error. “I wouldn’t bet my wife and kids because they’d get mad,” he says. “But I’d bet my house.” Jung, who is spokesperson for a similar experiment in Japan called T2K, says the tricky part is accurately measuring the time between when the neutrinos are born by slamming a burst of protons into a solid target and when they actually reach the detector. That timing relies on the global positioning system, and the GPS measurements can have uncertainties of tens of nanoseconds. “I would be very interested in how they got a 10-nanosecond uncertainty, because from the systematics of GPS and the electronics, I think that’s a very hard number to get.” No previous measurements obviously rule out the result, says Kostelecky, who has spent 25 years developing a theory, called the standard model extension, that accounts for all possible types of violations of special relativity in the context of particle physics. “If you had told me that there was a claim of faster-than-light electrons, I would be a lot more skeptical,” he says. The possibilities for neutrinos are less constrained by previous measurements, he says. Still, Kostelecky repeats the old adage: Extraordinary claims require extraordinary evidence. Even Ereditato says that one measurement does not extraordinary evidence make. This story provided by //Science//NOW, the daily online news service of the journal //Science//. See Also:* Neutrino Transformation Could Help Explain Mystery of Matter ||
 * South Pole Neutrino Detector Comes Up Empty
 * Elusive Neutrino Change-Up Finally Detected
 * Long Baseline Neutrino Experiment

= [|A-levels: physics returns to the top ten] = __ [|Education] __ — By __ [|Lena] __ on August 18, 2011 at 10:50 am

A-level results published this morning by the Joint Council for Qualifications show an increase for the fifth consecutive year in the number of students sitting examinations in physics and, for the first time since 2002, physics is back in the top ten most popular subjects. The total number of students entered for physics A-level has increased by 6.1%, from 30,976 in 2010 to 32,860 in 2011. Professor Sir Peter Knight, incoming-President of the Institute of Physics (IOP), said, “Year on year we are seeing increases in the number of students choosing to sit physics A-level. As physics has enjoyed popular rejuvenation – thanks, in no small part, to the ‘Brian Cox effect’ and the excitement surrounding the Large Hadron Collider – we’re sure that many students are also responding to calls from university leaders, businesses and the Government for students to choose subjects which will provide the skills our country needs. “The incremental increases each year have led to a significant long-term trend. Over the last five years, the number of A-level exams taken across all subjects has risen 7.7% but the growth in the number entering for physics is far stronger – a 19.6% increase over the last five years. Students across the country are hearing the cry for more scientists and rising to the challenge!” The encouraging result at A-level is supported by a continued increase in AS-level numbers, with the number of entrants increasing from 45,534 last year to 58,190 this year. The 27.8% increase is partly explained by a change to funding rules for maintained schools in England, but far outstrips the average increase across all subjects of 17.9%. The striking gender divide in the subject still persists. Despite total number increases in the number of both girls and boys sitting the exam, the gender divide remains at approximately 1 girl for every 4 boys achieving A level physics. This is an issue that schools receiving support through the IOP’s Stimulating Physics Network are working on.

Clare Thomson, Curriculum and Diversity Manager, pre-19 at IOP, added, “When the target of 35,000 students entering physics A-level by 2014 was first announced, many doubted it could be achieved. The work undertaken by governments, universities, businesses and learned societies to turn the tide is paying off. “There is, however, still much work to do – girls and boys alike need to continue seeing the excitement of physics and be helped to understand how physics is relevant to their lives and is the subject providing the toolkit for rising to the most significant challenges of the Twenty First Century.” = Five Awesome Things You (Probably) Didn’t Know Asteroseismology Could Do = by JON VOISEY on AUGUST 22, 2011

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The variations in brightness can be interpreted as vibrations, or oscillations within the stars, using a technique called asteroseismology. The oscillations reveal information about the internal structure of the stars, in much the same way that seismologists use earthquakes to probe the Earth's interior. Credit: Kepler Astroseismology team.

Asteroseismology is a relatively new field in astronomy. This branch uses sound waves in stars to explore their nature in the same way seismologists on Earth have used waves induced by tectonic activity to probe the interior of our planet. These waves aren’t heard directly, but as they strike the surface they can cause it to undulate, shifting the spectral lines this way and that, or compress the outer layers causing them to brighten and fade which can be detected with photometry. By studying these variations, astronomers have begun peering into stars. This much is generally known, but some of the specific tricks aren’t often brought up when discussing the topic. So here’s five things you can do with asteroseismology you may not have known about!

1. Determine the Age of a Star
From high school science you should know sound will travel through a medium at a characteristic speed for a given temperature and pressure. This information tells you something about the chemical composition of the star. This is a fantastic thing since astronomers can then check that against predictions made by stellar models. But astronomers can also take that one step further. Since the core of a star slowly converts hydrogen to helium over its lifetime, that composition will change. How much it has changed from its original composition towards the point where there’s no longer enough hydrogen to support fusion, tells you how far through the main sequence lifetime a star is. Since we know the age of the solar system very well from meteorites, astronomers have calibrated this technique and begun using it on other stars like α Centauri. Spectroscopically, this star is expected to be nearly identical to the Sun; it has very similar spectral type and chemical composition. Yet a 2005 study using this technique pinned α Cen as 6.7 ± 0.5 billion years which is about one and a half billion years older than the Sun. Obviously, this still has a rather large uncertainty to it (nearly 10%), but the technique is still new and will certainly be refined in the future. And if that wasn’t cool enough by itself, astronomers are now beginning to use this technique on stars with known planets to get a better understanding of the planets! This can be important in many cases since planets will initially glow more brightly in younger systems since they still retain heat from their formation and this amount of extra light could confuse astronomers on just how might light is being reflected leading to inaccurate estimates of other properties like size or reflectivity.

2. Determine Internal Rotation
Cover of a Book on the Solar Tachocline showing abrupt transition discovered by helioseismology

We already know that stars rotation is a bit funny. They rotate faster at their equator than at their poles, a phenomenon known as differential rotation. But stars are also expected to have differences in rotation as you get deeper. For stars like the Sun, this effect is related to a difference in energy transport mechanisms: radiative, where energy is conducted by a flow of photons in the deep interior, to convective, where energy is carried by bulk flow of matter, creating the boiling motion we see on the surface. At this boundary, the physical parameters of the system change and the material will flow differentially. This boundary is known as the tachocline. Within the Sun, we’ve known it’s there, but using asteroseismology (which, when used on the Sun is known as helioseismology), astronomers actually pinned it down. It’s 72% the way out from the core.

3. Find Planets
Until very recently, the most reliable way to find planets has been to look for the spectroscopic wiggle as the planets tug the star around. This technique sounds very straightforward, and it can be, unless the star has a lot of wiggle of its own due to the effects that make asteroseismology possible. Those effects can easily be much larger than those created by planets. So if you want to find planets lost in the forest of noise, you’d best understand the effects caused by the pulsating stellar surface. After astronomers cancelled out those effects on V391 Pegasi, they discovered a planet. And what a weird one it was. This planet is orbiting a sub-dwarf star, which is the helium core of a post-main sequence star which has ejected its hydrogen envelope. Of course, this occurs during the red giant phase when the star should have swollen up to engulf the gas giant planet in orbit. But apparently the planet survived, or somehow came along later.

4. Find Buried Sunspots
Turning to recent news, helioseismology recently found some sunspots. This wouldn’t be a big deal. Anyone with a properly filtered telescope can find them. Except these ones were buried some 60,000 km beneath the Sun’s surface. By using the seismic data, astronomers found an overdense region beneath the surface. This region was caused, just as sunspots are, by a tangle in the magnetic field keeping the material in place. As it rose to the surface, it became a sunspot. Here’s the vid:

5. Make “Music”
Because many of the events that create the soundwaves in stars are periodic, they are rhythmic in nature. This has prompted many explorations into using these naturally created beats to make music. A direct example is __ [|this one] __ which simply assigns tones to the modes of pulsation. The site also notes that the beat created by one of the stars, has been used as a base for club music in Belgium. This has also been done for longer “symphonies” by__ [|Zoltan Kollath] __.