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Another day, another wrinkle in the year's biggest physics story

And since that didn’t happen, those neutrinos couldn’t have traveled faster than light. Case closed.

So let’s go a little deeper here. The physicists behind this assessment, Andrew Cohen and Sheldon Glashow of Boston University (Glashow has a Nobel under his belt, so these are no middling minds), ignore the debate over whether or not it’s possible for a fundamental particle to outpace the speed of light, and instead look directly at the OPERA neutrinos themselves.

In looking at the neutrino beams that landed at Italy’s Gran Sasso laboratory, Cohen and Glashow found that it was about the same as the beam emitted from CERN in Switzerland. That is, the neutrinos were of roughly the same high-energy flavor at their origin and at their destination.

But that’s not possible if these neutrinos surpassed the speed of light, they say. A neutrino achieving superluminal speeds would emit other lower energy particles--most likely an electron-positron pair-- along the way, and in doing so lose a good deal of its own energy. So the neutrino beam arriving at Gran Sasso should have been “significantly depleted” of high-energy neutrinos.

But this was not the case. Which means, they say, that in all likelihood these neutrinos never achieved superluminal speeds. The anomaly is an error in the data or measurement of the speed, or some other brand of misunderstanding or miscalculation.

Which makes a certain amount of sense, writes Steve Nerlich over at Universe Today over the weekend. Neutrinos do move very fast, straight through the Earth (neutrinos don’t interact much with normal matter), relying on GPS time-stamping and other methods of man-made measurement that are very precise but certainly not infallible to determine time and distance traveled.

And it’s not like these neutrinos were clocked doubling the speed of light or something like that--the difference is 60 nanoseconds. That’s another way of saying that the neutrinos in question are thought to have traveled at 1.0025 times the speed of light. That’s certainly a small enough margin to be explained away by some kind of measurement error.

Still, the jury remains out on this one, and we certainly don’t want to dismiss a perfectly good game-changing science story just because it seems hard to reconcile with the status quo. After all, if OPERA’s result turns out to be confirmed it is going to completely reorient physics as we know them. More on this as it develops.

[SciAm]

Hadrons are so last-decade anyhow

Here’s where the game stands. America dropped the ball when it dumped millions into the Superconducting Supercollider only to shutter the project back in the ‘90s. It was the next step in particle physics after Tevatron but it never was completed. CERN took up the mantle of high powered particle physics and now has the LHC, which stands as the largest physics lab in the known universe.

The LHC, like Tevatron, smashes hadrons (of which protons are a varietal). These are not fundamental particles, but are made up of smaller subatomic pieces, so when they collide the energy from the collision is split between the constituent quarks. If we could smash fundamental particles--those are particles that aren’t composed of other particles, but are already at the single-component level--more energy would go directly into the collision, and thus into spawning all kinds of exotic matter. Which is exactly what physicists want from a good collider.

And that’s why Fermilab’s physicists are thinking about muons these days. Now, here’s the cool trick--in order to smash muons, they’re going to have to bend time a little bit.

Muons are like electrons but heavier--about 200 times heavier actually--which is a good thing, considering we’re trying to manipulate and smash them together. But they’re also highly unstable, with a life spanning just a few microseconds. After that, they decay into a bunch of other less-useful stuff. A few microseconds isn’t very long, but there is a way to stretch it out long enough to be useful by playing with the rules of relativity.

It would work something like this: You get muons from high-energy particle collisions, which generally impart a good deal of energy to the particles they spawn. Which means the muon, from the moment it falls out of this particle collision, is moving very fast. If you can then grab it and give it a little accelerating up toward the speed of light, relativistic effects start to take over. As the muon approaches light speed, time slows down for the muon relative to the time frame of the surrounding accelerator. So those two microseconds stretch into a lifetime that’s long enough to be relevant to physicists--that is, long enough to smash two of them together.

It’s a complex trick but a feasible one, and such a collider isn’t very big--it would fit in Fermilab’s current footprint. And it would put Fermilab right back at the cutting edge of particle physics--not that it ever really left.

Hadrons. They’re so 2010. More details at Ars.

[Ars Technica]

This is useful because atom interferometers are super sensitive, more so than the inertial sensors used widely on modern aircraft. Those inertial sensors have been known to fail with potentially disastrous results, but more frequently they cause slight errors to creep into navigation systems that must later be corrected. With no moving parts and a high degree of accuracy, atom interferometers could mitigate these problems, recording inertial effects 300 times weaker than the normal fluctuations in the acceleration in a standard aircraft.

But the vibrations in an aircraft have previously made deployment of atom interferometers in planes unfeasible. That’s where Remi Geiger at the Laboratoire Charles Fabry in Paris comes in. He and his colleagues have created a system that compensates for the effects of vibrations via mechanical accelerometers that record the movements of the aircraft itself.

Using that vibration data, their system recalculates the interferometer’s data to compensate for any vibration that might be skewing its final result. By stripping out the vibration noise, they end up with a clean, high-resolution atom interferometer result. The system could go a long way toward delivering better acceleration data to the cockpits of large jets. Geiger and company have already tested their system successfully on an Airbus A300.

But an atom interferometer that can operate free of laboratory constraints isn’t limited to jetliner applications. The researchers hope their method will lead to more precise measurements of geodesy and of gravity itself, enabling some fundamental experiments that have been previously very difficult to conduct and challenging some existing principles of physics with more and better data. More at arXiv.

[Technology]

When subatomic science gets wack, physicists get ILL

Neutrons may seem like the boring cousin to the more active and interesting protons and electrons that make up atoms, but neutrons hold some mysteries that could shed light on the Big Bang and the formation of the cosmos (life, the universe, everything, etc.). They can also mysteriously become other subatomic particles, like protons, electrons, and electron antineutrinos--a pretty neat trick of physics. But it’s precisely because they have no electric charge that they are notoriously difficult to manipulate.

And because they are difficult to trap and manipulate, they are also very difficult to study. Knowing how they pull off this transformation to other subatomic particles would tell physicists quite a bit about neutrons, their role in the Big Bang and the Standard Model, and how the universe came to be.

But experiments thus far have lacked the kind of precision necessary to make accurate assessments, chiefly because when measuring neutrons physicists are trying to hit a moving target. But no more. At the ILL--the single highest-intensity neutron source on the planet--researchers have corralled neutrons at a density of 55 particles per cubic centimeter, a full five times more than they were previously able to bottle up.

They did so by using superfluid helium-4 to chill the neutrons down to -450 degrees--roughly nine degrees above absolute zero. At that temperature everything slows down, bringing even elusive subatomic particles like neutrons under enough control to hit the 55-per-cubic-centimeter mark.

Still, that’s not enough to get the kind of statistical precision researchers need to do the kind of science the researchers want to carry out. To answer the really big questions about the universe, they need even higher densities and higher sample sizes. But with some fine tuning they might be able to reach 1,000 neutrons per cubic centimeter, the lead researcher told BBC.

[BBC]

Now proven by science

Steffen found that simply letting passengers board at random would actually be faster than boarding in the strict blocks we're all used to. That method tends to create bottlenecks, because there's limited room to be storing items in the overhead bin, and everyone is trying to do it at the same time in the same area of the plane. Steffen's method is much more organized, relying more on row number and seat (window, middle, or aisle) than general area of the plane. The plan:

First, passengers sitting in the window seats on one side of the plane all board at once, in alternating rows (row 1, 3, 5, etc.). Then the same is done on the other side of the plane. Then the middle seats, still in alternating rows, boards on the first side of the plane. That continues with the other side's middle seats, then (first one and then the other) aisle seats. Then, do it all again for the even-numbered rows.

It's simple, but very efficient; alternating rows gives everyone enough elbow room, and taking careful notice of seat position reduces bottlenecks from aisle-seaters having to stand up all the time. Steffen's work was published this week in the science collection arXiv, and was demonstrated on the show This vs. That, which you can see below. Steffen did not get the response he was hoping for from the airlines when he first presented his work, but "Now that we have [real data]," he says, "I guess we'll see."

[Consumerist]

Finally, the case is solved, and the villain is dead.

As the two spacecraft retreated into the distance, the data they beamed back showed that they were slowing down a little more than they should have been. Long vaunted as evidence that something was amiss in physics — perhaps that Einstein's theory of gravity was wrong — the anomaly spawned entire academic conferences and thousands of papers.

But, as explained in our coverage of an earlier stage of Turyshev et al.'s work, some scientists believed that the anomaly had a much more mundane explanation. Namely, the scientists suspected that heat was being emitted by the spacecraft's generators anisotropically — more in one direction than the other. If this were the case, the heat would exert an unbalanced recoil force on the spacecraft, causing them to change speed. Indeed, in April, a group of researchers in Portugal came up with just such a model for how the Pioneers' heaters could have created a recoil force.

But many have argued that the data itself ruled out this explanation for the Pioneer Anomaly. As the plutonium-238 that served as the Pioneers' onboard heat source radioactively decayed, it would have emitted less heat over time. Thus, if heat were the source of the Pioneer Anomaly, the anomaly should have lessened with time as well. But the data seemed to suggest that the Pioneer Anomaly was constant — an undying force — and thus much more fundamental.

But for their new analysis [PDF], Turyshev et. al. compiled a lot more data than had ever been analyzed before, spanning a much longer period of the Pioneers' flight times. They studied 23 years of data from Pioneer 10 instead of just 11, and 11 years of data from Pioneer 11 instead of 3. As explained in their new paper, the more complete data sets reveal that the spacecraft's anomalous acceleration did indeed seem to decrease with time. In short, the undying force had been dying after all, just like the decaying plutonium. In that case, it was most likely just a consequence of wonky heaters — mystery solved.

[Arvix]

The NIST and its international partners reconsider the values placed upon the fundamental constants every four years to take into account advances in technology and science that beget better, more accurate values for things like the speed of light, the Newtonian constant of gravitation (G), the Planck constant, and other values preceded by famous names.

The real news here isn’t really that we’ve discovered anything new but that science on the whole has reduced uncertainty, and that in turn impacts all physical science going forward. For instance, uncertainty in the constant alpha (that’s the fine-structure constant or the electromagnetic constant) has been reduced by 0.3 parts per billion, or cut in half based on the last evaluation of the constants in 2006.

Going forward, this adjustment to alpha will make a difference in (and--if the adjustment is correct--reduce the uncertainty of) all kinds of physics. The same is true for various other constants (there’s a nice overview of the heavy hitters here) like the radius of a proton or the Rydberg constant (relating to the atomic spectra in spectroscopy and thus far the most accurately measured fundamental constant--we think), whose values are still not completely “certain” but have been sharpened to introduce less and less uncertainty over the years.

But this year’s realignment of the constants will ripple through the world as we understand it more than most. In October a worldwide vote will redefine the most basic units in the International System of Units (SI) exclusively in light of these fundamental constants. That means that while more nebulous concepts like the G are getting a tiny adjustment now, that change will soon impact more concrete units like the kilogram.

Just think: in October you may gain or lose a tiny yet measurable bit of weight without so much as lifting a finger. Just don’t let it go to your head, which will still likely be busy trying to wrap itself around all of this.