Note: this topic is from 6/30/2004. Thanks NukeMan.
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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
You should check out Encyclopædia Britannica, 1768 edition. It's not illegal; it's not even bigamy; it's trigonometry.
I agree that there is some elements of it that have been linked with creationist theology.
But I did see a very long list of C values that was supposedely started from figures derived in the late 18th century. Now, if it was just a matter of "We're refining our measurementsand zomming in on the value" you would expect a deviation like someone learning how to throw horseshoes or something. But 9 out of ten of the figures showed a slight decrease from the previous figures.
I am interested in it from the philosophical side of science. The meaning of things, IMHO, has very little to do at all with what we're actually made of.
Eddington said as much a few times. He talks of physics as a kind of circular logic, a tautology, because there are no other ways of looking at say, an electron. There is no electron art, or electron poetry, or electron comedy.
In fact it seems to me unimportant whether we are made up of electrons and protons, or split peas and lentils.
It is the INTERACTIONS of these things that are important.
Physics is at a point where it must, by necessity, admit to something very large, and in fact to something that is (at least a small part) studiable by physics, but not contained by physics. I have coined the term "exscience" to represent things like that.
There seems to be little question that there is something underlying the physical world. The East Indians talk of the Maya, and other cultures have similar beliefs.
A decrease in C wouldn't hurt my feelings. Personally, I think if it is decreasing, it is probably somehow harmonic with whatever absolute value of T we have. At the big bang, C was infinate. Next clock tick, C was 2/1 Next clock tick, C was 3/2 next clock tick, C was 4/3 etc etc.
I also think that there is somehow a missing fundamental constant, or dimension. We need something to balance out the three dimensions (I mean the CGS or MKS dimensions) in the Lorentz invariablity theories.
When you look at the fine structure constant, something amazing pops out. The square root of a gram! What the hey is he square root of a gram? Same thing about length, we find the square root of a centimeter.
?????
So it's all very interesting.
Huh?
The c measurements actually start in the late 17th century with Roemer. Setterfield's initial list of early sightings was very skewed toward values above the modern one. Catching hell for this, he revised his theory so that c starts 11 million times modern at 6000 years ago, then crashes to a value well below modern a thousand or two years after that, then does a damped oscillation out to the present. That is to say, he accepted the below-the-line values he had once rejected and drew a squiggly line to connect them.
A decrease in C wouldn't hurt my feelings.
I'm sure, but there is no real evidence for such. With few exceptions all of the measurements made from Roemer on are within the error bars which shrink as you come forward.
When you look at the fine structure constant, something amazing pops out. The square root of a gram!
You are looking at it from a bad angle.
It was nice. I'm surprised at the lack of media coverage - NOT! clinton cut NASA's budget every year he was President.
I'm glad Cassini made it though. Otherwise it would be all over the news.
The phenomena you discuss is well known and is taken into account when examining intergalactic distances. Preferential scattering of shorter wavelength (blue) photons is the reason the sky is blue and the setting sun is red/orange. Red shift from stars and galaxies is usually associated with emission spectra of hydrogen, helium, lithium. The shift in these spectra is a Doppler-like effect. The red shift correlates with distances determined using the Cepheid variable stars and supernovae.
My point was that we launched those probes never having been in space before....we had no way of really knowing sure distances until we actually tried it, we only had mathematical extrapolations based on observations here on Earth!
Bring in this article when you want to fight a speeding ticket. "Now, officer, you are aware that radar is based on the Doppler principle and assumes a uniform speed of light, however, if the so-called fine structure 'constant' is not constant but exhibits secular variation..."
Thanks, you made my day.
In high school, the best way to get the physics teacher to go off on a tangent is to ask "What would happen to a monkey on a motor bike going close to the speed of light".
Not to mention the fact that his daughter was in the same class as I was, and didn't exactly have a stellar reputation...
Huh? placemarker
Nope...it didn't change...just checked it and it's still the same...FAST!
Actually, when we view the light from a galaxy 8 billion light-years away, we are there in the sense that we see the galaxy exactly as it was 8 billion years ago.God's word says nothing about the age of the universe. You're reading your own opinion into the Bible just as those who once claimed that the earth was the center of the universe read their own opinions into the Bible. The net result is that it makes Christianity look silly. People shouldn't leave their brains at the door when they become Christians.
Maybe, maybe not. Scripture records 17 TIMES that God "stretched" the heavens. So how do you know that galaxy was 8 billion years away when the light was generated that you are seeing?
My understanding is that triangulation has only been done on a few nearby stars. That most distances are determined by "red shift" in the light. But do we understand physics well enough to say that the only cause of that red shift is distance? I doubt it.
Also my understanding is that quantized red shifts have popped up again as an issue. I saw a recent 2004 article on it, that if memory serves me correctly said Hubble had confirmed quantized red shifts. I know this debate has gone back and forth as to whether the quantized red shifts were really statistically significant or whether more accurate measurements had dispelled them.
Without understanding how the universe came into being, I'm not convinced that the light we are seeing is 8 billion years old.
Not only are there unknowns due to our limitations in understanding physics pointed out in post 256.
But how do you know that God couldn't create the stars on the fourth day and have the rest of the universe age 14 billion years during a 24 hour period on earth?
I know there are people who say that if God allows anything to look old then He is guilty of deception. But I think it's entirely possible that he created the stars on the fourth day of creation some 6000-10,000 years ago, and that any apparent age is simply the by product of the processes God employed in order to make starlight for us. And imagination on the part of man that they know more than God and that God simply couldn't have created the universe some 6000 to 10000 years ago is simply arrogance combined with stupidity on behalf of man.
It's on the same intellectual level as accusing Levy of selling used Jeans (stonewashed) becaause everyone knows it takes 7 or 8 years and lots of washings for Jeans to fade.
Note: this topic is from 6/30/2004. Thanks NukeMan.
I have to admit to being a bit peeved that I have not heard of this study earlier...
‘Velly interesting ... but is it practical?’
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