A Possible Victory for Einstein

So it turns out that Einstein may not have been wrong about the universal speed limit. Not only is special relativity safe, it provides an explanation for those faster-than-light neutrinos. They’re not breaking the light-speed barrier; they just appear to be, thanks to the relativistic motion of the clocks checking their speed.

As we all remember, a few weeks ago some scientists at CERN set the physics world on fire when they shared data showing neutrinos were moving faster than light. Specifically, they were showing up at a distant neutrino detector about 60 nanoseconds faster than the time in which light would make the same trip. But the rules of physics said this could not be. 

The Oscillation Project with Emulsion-tRacking Apparatus team (which was not looking for this result, by the way) calibrated their clocks, measured their distances and crunched their numbers in search of an explanation. 

Flummoxed, they dumped their findings on the larger physics community, which proceeded to eviscerate the experiment. In the three weeks since, almost 100 papers have shown up on the preprint server arXiv trying to make sense of it all. Physicists have blamed everything from poor geodesy to ill-timed clocks, and other particle physics observatories are hard at work trying to replicate the results.

Now a Dutch physicist says it’s really very simple — the OPERA team overlooked the relativistic motion of their clocks. Technology Review's arXiv blog highlights the paper here.

OPERA was studying neutrino oscillation, in which these ghostly particles switch from one type to another. They were firing off muon neutrinos from a neutrino beam at CERN and sending them to Gran Sasso, Italy, where researchers counted how many of them had become tau neutrinos. Along with careful Earth-measuring, this experiment required super-precise synchronization of clocks at the two locations. The team did this with GPS satellites, which broadcast a time signal as they orbit about 12,500 miles above the Earth. The OPERA team had to calculate how long it takes for one of these time signals to reach the Earth. But they did not account for the clocks’ relativistic motion, according to physicist Ronald van Elburg at the University of Groningen in the Netherlands.

The radio signals travel from the satellites at light speed, which has nothing to do with the satellites’ speed. This is one of the central tenets of special relativity: “Light is always propagated in empty space with a definite velocity c which is independent of the state of motion of the emitting body,” as Einstein put it himself.

But because the satellites are moving, from their point of view, the positions of the neutrinos and the detector are changing. The neutrinos are moving toward the detector, and the detector appears to be moving toward the neutrino source. So the distance between the origin and destination appears to be shorter than it would if it were being observed on the ground.

“Consequently, in this reference frame the distance traveled by the [particles] is shorter than the distance separating the source and detector,” van Elburg writes. This phenomenon is overlooked because the OPERA team thinks of the clocks as on the ground — which they are, physically — and not in orbit, which is where their synchronizing reference point is located.

Using the altitude, orbital period, inclination to the equator and other metrics, van Elburg calculates the error rate: “The observed time-of-flight should be about 32 ns shorter than the time-of-flight using a baseline bound clock,” he writes. This is done at both clock locations, so double that, and you get an early-arrival time of 64 nanoseconds. That pretty much accounts for the OPERA anomaly. 

“This paper shows that Coordinated Universal Time (UTC) happens to be less universal than the name suggests, and that we have to take in to account how our clocks are moving,” van Elburg writes.

Of course, his paper has not yet been published, and is subject to the same scrutiny and peer review as the OPERA folks, so we can’t accept van Elburg’s theory just yet. But it’s certainly a handy explanation. And it’s a lovely piece of irony, too — not only was Einstein’s special theory of relativity right all along, it even provides a reason why.

 by "environment clean generations"

Particles Faster Than Speed Of Light At CERN

Enormous underground detectors are needed to catch neutrinos, that are so elusive as to be dubbed "ghost particles".

A meeting at Cern, the world's largest physics lab, has addressed results that suggest subatomic particles have gone faster than the speed of light. 

The team presented its work so other scientists can determine if the approach contains any mistakes.

If it does not, one of the pillars of modern science will come tumbling down.

Antonio Ereditato added "words of caution" to his Cern presentation because of the "potentially great impact on physics" of the result.

The speed of light is widely held to be the Universe's ultimate speed limit, and much of modern physics - as laid out in part by Albert Einstein in his theory of special relativity - depends on the idea that nothing can exceed it.

Thousands of experiments have been undertaken to measure it ever more precisely, and no result has ever spotted a particle breaking the limit.

"We tried to find all possible explanations for this," the report's author Antonio Ereditato of the Opera collaboration told BBC News on Thursday evening.

"We wanted to find a mistake - trivial mistakes, more complicated mistakes, or nasty effects - and we didn't.

"When you don't find anything, then you say 'well, now I'm forced to go out and ask the community to scrutinise this'."

Friday's meeting was designed to begin this process, with hopes that other scientists will find inconsistencies in the measurements and, hopefully, repeat the experiment elsewhere.

"Despite the large [statistical] significance of this measurement that you have seen and the stability of the analysis, since it has a potentially great impact on physics, this motivates the continuation of our studies in order to find still-unknown systematic effects," Dr Ereditato told the meeting.

"We look forward to independent measurement from other experiments."

Neutrinos come in a number of types, and have recently been seen to switch spontaneously from one type to another.

The Cern team prepares a beam of just one type, muon neutrinos, and sends them through the Earth to an underground laboratory at Gran Sasso in Italy to see how many show up as a different type, tau neutrinos.

In the course of doing the experiments, the researchers noticed that the particles showed up 60 billionths of a second earlier than they would have done if they had travelled at the speed of light.

This is a tiny fractional change - just 20 parts in a million - but one that occurs consistently.

The team measured the travel times of neutrino bunches some 16,000 times, and have reached a level of statistical significance that in scientific circles would count as a formal discovery. 

But the group understands that what are known as "systematic errors" could easily make an erroneous result look like a breaking of the ultimate speed limit.

That has motivated them to publish their measurements.

"My dream would be that another, independent experiment finds the same thing - then I would be relieved," Dr Ereditato told BBC News.

But for now, he explained, "we are not claiming things, we want just to be helped by the community in understanding our crazy result - because it is crazy".

 by "environment clean generations"

Earth-Generated Panspermia

Jupiter's Moon Europa A new simulation found that high-velocity particles ejected from Earth could make their way to the Jupiter system, where they could conceivably land on a moon like Ganymede or Europa, shown here. Europa is thought to harbor a massive ocean.

Proponents of panspermia theory say life on Earth came from elsewhere, hitching a ride on rocks sheared from other worlds or from migratory asteroids. But what if life did originate here and then it left, hitching a ride on Earth-departed rocks? Earth could seed other worlds, instead of the other way around. A new analysis says the rocks could conceivably make it as far as Jupiter.

 

Scientists have found several meteorites that originated on Mars or the moon, after being ejected in asteroid collisions, forcefully thrown into space and finally arriving on Earth. It makes sense that the opposite could be true, and that after mega-collisions, some pieces of Earth could be thrown toward Mars or Venus.

But most simulations suggest very few Earth pieces would reach the fourth planet, because they would have a hard time overcoming the gravitational pull of both Earth and the sun. Lots of the ejected particles would actually wind up back on Earth, according to previous studies. Some scientists have even suggested these refugee particles would “re-seed” their home planet.

Now researchers in Mexico have a new simulation, and they say plenty of Earth bits would indeed make it to Mars — and beyond, all the way to the Jovian system. Mauricio Reyes-Ruiz and colleagues at the Universidad Nacional Autonoma de Mexico ran computer simulations of 10,242 test particles, following their predicted paths for 30,000 years. That’s about as long as scientists think life could survive in space, the authors note.

They ran simulations at five different ejection velocities, from 6.97 miles per second to 10.2 miles per second. They found that at faster velocities, particles are more likely to reach Jupiter than Mars, because of their great speed relative to Mars’ low gravitational pull. The particles also reach Jupiter more quickly, with half making the trip in 10,000 years, the authors write. In one simulation, just one particle reaches Mars, and it takes between 25,000 and 30,000 years to get there.

Even more bizarre, many particles end up traveling past 40 AU, which the authors describe as leaving the solar system. 

This is all theoretical, of course — the ejection velocity and the particles’ trajectory would be determined by variables like the size and velocity of the incoming object, not to mention the collision location relative to the spin of the Earth. But it’s an interesting concept — as KFC points out over at Technology Review, if life persists in space longer than astrobiologists think, life from Earth could still be speeding toward distant worlds.

 by "environment clean generations"