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Faster-than-Light Neutrino Puzzle Claimed Solved by Special Relativity

The relativistic motion of clocks on board GPS satellites exactly accounts for the superluminal effect, says physicist.

kfc 10/14/2011


It's now been three weeks since the extraordinary news that neutrinos travelling between France and Italy had been clocked moving faster than light. The experiment, known as OPERA, found that the particles produced at CERN near Geneva arrived at the Gran Sasso Laboratory in Italy some 60 nanoseconds earlier than the speed of light allows.

The result has sent a ripple of excitement through the physics community. Since then, more than 80 papers have appeared on the arXiv attempting to debunk or explain the effect. It's fair to say, however, that the general feeling is that the OPERA team must have overlooked something.

Today, Ronald van Elburg at the University of Groningen in the Netherlands makes a convincing argument that he has found the error.

First, let's review the experiment, which is simple in concept: a measurement of distance and time.

The distance is straightforward. The location of neutrino production at CERN is fairly easy to measure using GPS. The position of the Gran Sasso Laboratory is harder to pin down because it sits under a kilometre-high mountain. Nevertheless, the OPERA team says it has nailed the distance of 730 km to within 20 cm or so.

The time of neutrino flight is harder to measure. The OPERA team says it can accurately gauge the instant when the neutrinos are created and the instant they are detected using clocks at each end.

But the tricky part is keeping the clocks at either end exactly synchronised. The team does this using GPS satellites, which each broadcast a highly accurate time signal from orbit some 20,000km overhead. That introduces a number of extra complications which the team has to take into account, such as the time of travel of the GPS signals to the ground.

But van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

It's easy to think that the motion of the satellites is irrelevant. After all, the radio waves carrying the time signal must travel at the speed of light, regardless of the satellites' speed.

But there is an additional subtlety. Although the speed of light is does not depend on the the frame of reference, the time of flight does. In this case, there are two frames of reference: the experiment on the ground and the clocks in orbit. If these are moving relative to each other, then this needs to be factored in.

So what is the satellites' motion with respect to the OPERA experiment? These probes orbit from West to East in a plane inclined at 55 degrees to the equator. Significantly, that's roughly in line with the neutrino flight path. Their relative motion is then easy to calculate.

So from the point of view of a clock on board a GPS satellite, the positions of the neutrino source and detector are changing. "From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter," says van Elburg.

By this he means shorter than the distance measured in the reference frame on the ground.

The OPERA team overlooks this because it thinks of the clocks as on the ground not in orbit.

How big is this effect? Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observes.

That's impressive but it's not to say the problem is done and dusted. Peer review is an essential part of the scientific process and this argument must hold its own under scrutiny from the community at large and the OPERA team in particular.

If it stands up, this episode will be laden with irony. Far from breaking Einstein's theory of relatively, the faster-than-light measurement will turn out to be another confirmation of it.

Ref: arxiv.org/abs/1110.2685: Times Of Flight Between A Source And A Detector Observed From A GPS Satellite.

November 2011 Last updated at 06:42 ET

The "tractor beam" approaches depend on precise shaping of the intensities of laser beams

US space agency Nasa has funded a study of "tractor beams" to gather samples for analysis in future missions.

The $100,000 (£63,000) award will be used to examine three laser-based approaches to do what has until now been the stuff of science fiction.

Several tractor-beam ideas have been published in the scientific literature but none has yet been put to use.

Nasa scientist Paul Stysley says the approach could "enhance science goals and reduce mission risk".

"Though a mainstay in science fiction, and Star Trek in particular, laser-based trapping isn't fanciful or beyond current technological know-how," said Dr Stysley of Nasa's Goddard Space Flight Center, whose group was awarded the research funding.

High-beam profile

The team has identified three possible options to capture and gather up sample material either in future orbiting spacecraft or on planetary rovers.


The approach could be put to use in space and on planetary surfaces

One is an adaptation of a well-known effect called "optical tweezers" in which objects can be trapped in an area where two laser beams cross. However, this version of the approach would require an atmosphere in which to operate.

The other two methods rely on specially shaped laser beams - instead of a beam whose intensity peaks at its centre and tails off gradually, the team is investigating two alternatives: solenoid beams and Bessel beams.

The intensity peaks within a solenoid beam are found in a spiral around the line of the beam itself, while a Bessel beam's intensity rises and falls in peaks and troughs at higher distances from the beam's line.

Solenoid beams have already proven their "tractor beam" abilities in laboratory tests published in the journal Optics Express, but the pulling power of Bessel beams, presented on the preprint server Arxiv in February, remains to be proved experimentally.

In all three cases, explained Dr Stysley, the effect is a small one - but it could in some instances outperform existing methods of sample gathering.

"[Current] techniques have proven to be largely successful, but they are limited by high costs and limited range and sample rate," he said.

"An optical-trapping system, on the other hand, could grab desired molecules from the upper atmosphere on an orbiting spacecraft or trap them from the ground or lower atmosphere from a lander.

"In other words, they could continuously and remotely capture particles over a longer period of time, which would enhance science goals and reduce mission risk."

Tractor Beams in Space: The Next Awesome

By Jason Kennedy, PCWorld Oct 18, 2011 10:07 AM

I’m sure I don’t have to do much to describe to you a scene from a science fiction movie (pick one) where a tractor beam is utilized to save/capture our hapless victim/hero from certain death/escape, if you can pardon the choice of scenario. Though perhaps not in such a spectacular fashion, an engineer at Ohio State University has figured out the science to make it work.

Not to be confused with anti-pirate Bessel beam laser tractor beams that we covered earlier this year, the idea stems from the difficulty in minimizing the danger of being literally lost in space during “outside” walks. If an astronaut loses control and is somehow detached from the ship or station, the safety mechanisms only have a certain reach and thus a certain window to save him or her in. If the astronaut is incapacitated, such methods are futile as well(this method is, in this example, a gas or spring-loaded tether).

The solution is to have the astronaut wear a canister or two of propellant, with tubes pointing away from him or her that can be hit with a laser to achieve propulsion in the desired direction. Different propellant can be used, for instance, ones that ignite on different wavelengths to achieve propulsion and steering in different directions.

With the lack of atmosphere in space there’s very little drag, so care would have to be taken to not accelerate the astronaut to a point where impact would injure him or her, and the whole thing seems oddly laser-tag-ish to me, but the concept could be utilized to make space walks safer for astronauts out in the cold blackness of space.

2 November 2011 Last updated at 14:01 ET




Signs of ageing halted in the lab

By James Gallagher Health reporter, BBC News
[IMG]http://news.bbcimg.co.uk/media/images/56433000/gif/_56433033_c0102504-elderly_woman.gif[/IMG]
Elderly woman Will it one day be possible to stop ageing?


Unlocking the secrets of ageing
Do we all want to live to 100?
Genes reveal 'biological ageing'

The onset of wrinkles, muscle wasting and cataracts has been delayed and even eliminated in mice, say researchers in the US.

It was done by "flushing out" retired cells that had stopped dividing. They accumulate naturally with age.

The scientists believe their findings could eventually "really have an impact" in the care of the elderly.

Experts said the results were "fascinating", but should be taken with a bit of caution.

The study, published in Nature, focused on what are known as "senescent cells". They stop dividing into new cells and have an important role in preventing tumours from progressing.

These cells are cleared out by the immune system, but their numbers build up with time. The researchers estimated that around 10% of cells are senescent in very old people.

“Start Quote

I've never seen anything quite like it”

Dr James Kirkland

Cleanup

Scientists at the Mayo Clinic, in the US, devised a way to kill all senescent cells in genetically engineered mice.

The animals would age far more quickly than normal, and when they were given a drug, the senescent cells would die.

The researchers looked at three symptoms of old age: formation of cataracts in the eye; the wasting away of muscle tissue; and the loss of fat deposits under the skin, which keep it smooth.

Researchers said the onset of these symptoms was "dramatically delayed" when the animals were treated with the drug.

When it was given after the mice had been allowed to age, there was an improvement in muscle function.

One of the researchers, Dr James Kirkland, said: "I've never seen anything quite like it."

His colleague Dr Jan van Deursen told the BBC: "We were very surprised by the very profound effect. I really think this is very significant."

The treatment had no effect on lifespan, but that may be due to the type of genetically engineered mouse used.

Eternal youth?

The study raises the tantalising prospect of slowing the signs of ageing in humans. However, senescent cells cannot be just flushed out of human beings.

Dr Deursen said: "I'm very optimistic that this could really have an impact. Nobody wants to live longer if the quality of life is poor."

He argued that young people were already clearing out their senescent cells.

"If you can prime the immune system, boost it a little bit, to make sure senescent cells are removed, that might be all it needs.

"Or develop a drug that targets senescent cells because of the unique proteins the cells make."

Dr Jesus Gil, from the Medical Research Council's Clinical Sciences Centre, said the findings needed to be "taken with a bit of caution. It is a preliminary study".

However, he said it was a fascinating study which "suggests if you get rid of senescent cells you can improve phenotypes [physical traits] associated with ageing and improve quality of life in aged humans".