No, no, and no.
Experiments in the last decade have managed to slow light down, in some cases to as little as ten miles per hour...but the light at those slower speeds isn't bent by Gravity.
At all.
Posted on 06/30/2004 1:35:28 PM PDT by NukeMan
Speed of light may have changed recently
19:00 30 June 04
The speed of light, one of the most sacrosanct of the universal physical constants, may have been lower as recently as two billion years ago - and not in some far corner of the universe, but right here on Earth.
The controversial finding is turning up the heat on an already simmering debate, especially since it is based on re-analysis of old data that has long been used to argue for exactly the opposite: the constancy of the speed of light and other constants.
A varying speed of light contradicts Einstein's theory of relativity, and would undermine much of traditional physics. But some physicists believe it would elegantly explain puzzling cosmological phenomena such as the nearly uniform temperature of the universe. It might also support string theories that predict extra spatial dimensions.
The fine structure constant
The threat to the idea of an invariable speed of light comes from measurements of another parameter called the fine structure constant, or alpha, which dictates the strength of the electromagnetic force. The speed of light is inversely proportional to alpha, and though alpha also depends on two other constants (see graphic), many physicists tend to interpret a change in alpha as a change in the speed of light. It is a valid simplification, says Victor Flambaum of the University of New South Wales in Sydney.
It was Flambaum, along with John Webb and colleagues, who first seriously challenged alpha's status as a constant in 1998. Then, after exhaustively analysing how the light from distant quasars was absorbed by intervening gas clouds, they claimed in 2001 that alpha had increased by a few parts in 105 in the past 12 billion years.
Natural nuclear reactor
But then German researchers studying photons emitted by caesium and hydrogen atoms reported earlier in June that they had seen no change in alpha to within a few parts in 1015 over the period from 1999 to 2003 (New Scientist, 26 June) though the result does not rule out that alpha was changing billions of years ago.
Throughout the debate, physicists who argued against any change in alpha have had one set of data to fall back on. It comes from the world's only known natural nuclear reactor, found at Oklo in Gabon, West Africa.
The Oklo reactor started up nearly two billion years ago when groundwater filtered through crevices in the rocks and mixed with uranium ore to trigger a fission reaction that was sustained for hundreds of thousands of years. Several studies that have analysed the relative concentrations of radioactive isotopes left behind at Oklo have concluded that nuclear reactions then were much the same as they are today, which implies alpha was the same too.
That is because alpha directly influences the ratio of these isotopes. In a nuclear chain reaction like the one that occurred at Oklo, the fission of each uranium-235 nucleus produces neutrons, and nearby nuclei can capture these neutrons.
For example, samarium-149 captures a neutron to become samarium-150, and since the rate of neutron capture depends on the value of alpha, the ratio of the two samarium isotopes in samples collected from Oklo can be used to calculate alpha.
A number of studies done since Oklo was discovered have found no change in alpha over time. "People started quoting the reactor [data] as firm evidence that the constants hadn't changed," says Steve Lamoreaux of Los Alamos National Lab (LANL) in Albuquerque, New Mexico.
Energy spectrum
Now, Lamoreaux, along with LANL colleague Justin Torgerson, has re-analysed the Oklo data using what he says are more realistic figures for the energy spectrum of the neutrons present in the reactor. The results have surprised him. Alpha, it seems, has decreased by more than 4.5 parts in 108 since Oklo was live (Physical Review D, vol 69, p121701).
That translates into a very small increase in the speed of light (assuming no change in the other constants that alpha depends on), but Lamoreaux's new analysis is so precise that he can rule out the possibility of zero change in the speed of light. "It's pretty exciting," he says.
So far the re-examination of the Oklo data has not drawn any fire. "The analysis is fine," says Thibault Damour of the Institute of Advanced Scientific Studies (IHES) in Bures-sur-Yvette in France, who co-authored a 1996 Oklo study that found no change in alpha. Peter Moller of LANL, who, along with Japanese researchers, published a paper in 2000 about the Oklo reactor that also found no change in alpha, says that Lamoreaux's assumptions are reasonable.
The analysis might be sound, and the assumptions reasonable, but some physicists are reluctant to accept the conclusions. "I can't see a particular mistake," says Flambaum. "However, the claim is so revolutionary there should be many independent confirmations."
While Flambaum's own team found that alpha was different 12 billion years ago, the new Oklo result claims that alpha was changing as late as two billion years ago. If other methods confirm the Oklo finding, it will leave physicists scrambling for new theories. "It's like opening a gateway," says Dmitry Budker, a colleague of Lamoreaux's at the University of California at Berkeley.
Horizon problem
Some physicists would happily accept a variable alpha. For example, if it had been lower in the past, meaning a higher speed of light, it would solve the "horizon problem".
Cosmologists have struggled to explain why far-flung regions of the universe are at roughly the same temperature. It implies that these regions were once close enough to exchange energy and even out the temperature, yet current models of the early universe prevent this from happening, unless they assume an ultra-fast expansion right after the big bang.
However, a higher speed of light early in the history of the universe would allow energy to pass between these areas in the form of light.
Variable "constants" would also open the door to theories that used to be off limits, such as those which break the laws of conservation of energy. And it would be a boost to versions of string theory in which extra dimensions change the constants of nature at some places in space-time.
But "there is no accepted varying-alpha theory", warns Flambaum. Instead, there are competing theories, from those that predict a linear rate of change in alpha, to those that predict rapid oscillations. John Barrow, who has pioneered varying-alpha theories at the University of Cambridge, says that the latest Oklo result does not favour any of the current theories. "You would expect alpha to stop [changing] five to six billion years ago," he says.
Reaction rate
Before Lamoreaux's Oklo study can count in favour of any varying alpha theory, there are some issues to be addressed. For one, the exact conditions at Oklo are not known. Nuclear reactions run at different rates depending on the temperature of the reactor, which Lamoreaux assumed was between 227 and 527°C.
Damour says the temperature could vary far more than this. "You need to reconstruct the temperature two billion years ago deep down in the ground," he says.
Damour also argues that the relative concentrations of samarium isotopes may not be as well determined as Lamoreaux has assumed, which would make it impossible to rule out an unchanging alpha. But Lamoreaux points out that both assumptions about the temperature of the Oklo reactor and the ratio of samarium isotopes were accepted in previous Oklo studies.
Another unknown is whether other physical constants might have varied along with, or instead of, alpha. Samarium-149's ability to capture a neutron also depends on another constant, alpha(s), which governs the strength of the strong nuclear attraction between the nucleus and the neutron.
And in March, Flambaum claimed that the ratio of different elements left over from just after the big bang suggests that alpha(s) must have been different then compared with its value today (Physical Review D, vol 69, p 063506).
While Lamoreaux has not addressed any possible change in alpha(s) in his Oklo study, he argues that it is important to focus on possible changes in alpha because the Oklo data has become such a benchmark in the debate over whether alpha can vary. "I've spent my career going back and checking things that are 'known' and it always leads to new ideas," he says.
Eugenie Samuel Reich
The argument is of course about the speed of light in a vacuum. I assume you forgot your own </sarcasm>.
The "wrong sign" part is crushing. He should have been a Capricorn.
No, no, and no.
Experiments in the last decade have managed to slow light down, in some cases to as little as ten miles per hour...but the light at those slower speeds isn't bent by Gravity.
At all.
I actually sat down to do some calculations trying to figure that out assuming that light had changed speeds over history, i.e., c = c(t). I got up after my head started hurting. Ever since I went to an astronomy lecture about the red shift as a child, I have wondered whether there was another explanation for it and maybe this is it.
"The argument is of course about the speed of light in a vacuum. I assume you forgot your own </sarcasm>."
There is no vacuum. Not anywhere in the physical universe. Did you not learn that in your freshman physics class? An absolute vacuum is just a theoretical concept, which does not exist in nature.
Therefore, it is impossible to actually measure the speed of light in a vacuum, since no such vacuum exists. It stands to reason that estimations of the speed of light, in such a theoretical vacuum, might vary.
This article is silly, and misunderstand that science readjusts its constants, based on new information.
Do you really believe that the speed of light in a vaccum is actually known, down to the last decimal point? It is not, since no measurement can be taken in a medium that does not exist.
That said, the article misrepresents the actual findings, in my opinion. That's the trouble with popular science information.
Has the speed of light changed, or has the estimation of it changed?
I do not take this source as a scientific publication, any more than I take the National Enquirer as a news publication.
I remember telling my wife a few months ago that our flashlights seemed faster.
I have always thought there was another explanation. Makes my head hurt, too.
Not really. I had Chem, not Physics, in my freshman year back in 1967. I'm not sure they would have mentioned it in a 101 course then, anyway.
More importantly, changes in the dreaded Zero Point Energy, the quantum particle foam which exists in the absence of any "real" particles, are assumed to go with any change in c. The CDK-ers (Setterfield et al.) assume the vacuum used to be emptier when they say light was zipping around much faster. I'm sure this corresponds in some way to a fine-structure constant (alpha) being lower, except that from this study it seems to have been higher and light slower. Again, that's "if the find holds up."
Unknown Stuff Bump
LIGHT NORMALLY moves through a vacuum at about 186,000 miles per second. Nothing in the universe moves faster, and Albert Einstein theorized that nothing ever could. (Click here for some caveats.)
However, light waves can slow down as they pass through a medium. Last year, a research team at the Rowland Institute for Science and Harvard University, headed by Danish physicist Lene Hau, brought light waves down to a 1 mph crawl by putting them through a specially prepared haze of ultracold sodium atoms (http://www.msnbc.com/news/242698.asp)
Sounds interesting. A bit late tonight, I'll try and read it tomorrow. Thanks for the ping!
GOD BOUGHT A FASTER PROCESSOR... and ditched the windows OS...
We were getting too close, so He upgraded back a few centuries ago.
If you've seen one angstrom, you've seen them all.
The fact remains that everything we know about electric and magnetic fields requires electric charges, in other words, a medium, as a focus for the fields. If there is to be a wave, there must be something to wave!
We know that the “vacuum” of space is teeming with neutrinos. Countless trillions of the ghostly particles pass through each square centimetre every second. Maybe neutrinos constitute the medium of “empty” space? It makes sense if, as I suggest elsewhere on this site, all particles are composed of orbiting massless electric charges. And neutrinos are the most collapsed form of particle.
This brings us to the speed of light, “c.” We know from experiment that “c” varies depending on the medium. More particularly, “c” varies depending on the electrical characteristics of the medium. The speed of light in a vacuum cannot then be simply declared a universal constant, because a vacuum is not empty space it is filled with vast but varying numbers of neutrinos and some other particles.
It seems more reasonable to suggest that the speed of light is the speed with which an oscillating electrical disturbance is transmitted through a dielectric medium. The speed of light is highest in a medium where the rate of charge polarization in the particles of that medium is greatest. Neutrinos, having the lowest mass, or inertia, of any particle, have the fastest rate of internal charge polarization and response to an electric field. Therefore “c” is a maximum in a vacuum, paradoxically full of neutrinos.
The notion that c was considerably faster in the past has appeal to both cosmologists and creationists. Both camps have severe difficulties in explaining the observed universe, even with their vastly different time frames, unless things happened much faster initially. Cosmologists would like to see a near infinite speed of light immediately following the big bang and creationists about 10^11 times “c.” Both are misled by their misunderstanding of the creation myths. It was no accident that a Belgian priest, Georges LeMaitre, proposed the big bang theory, as it came to be known. Science is as much driven by culture and religion as any other human activity.
Proof that the cosmologists are mistaken both in their speculations about light-speed and the big bang hypothesis comes from the very source referred to in the above report the light from a quasar. The above-quoted article says that the quasar is 10 billion light years distant. That is based on the most peculiar big bang theory that the volume of the universe is increasing. It follows the observation that faint objects have their spectrum shifted towards the red. The discoverer of this phenomenon, Edwin Hubble, was careful to not attribute this “redshift” to the Doppler effect of the velocity of recession of the object, but theorists were not so circumspect. The redshift velocity - distance equation quickly became another of the many dogmatic assumptions of cosmology.
Thanks for the marshmallow demo!
I have to confess that the lead article boggled me severely.
Actually the speed of light (in a vacuum) is a fixed constant that is used as a reference for all other measurements.
-PJ
No strings attached? What's all this brouaha about String Theory then? Violin tunings?
Rule of debugging: Constants aren't; Variables don't.
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