Speed of light may have changed recently

New Scientist ^ | 6/30/04 | Eugenie Samuel Reich

[VadeRetro]

What? That's just silly. The speed of light has always been variable, depending on the medium through which it travels. If that were not so, there would be no rainbows.

The argument is of course about the speed of light in a vacuum. I assume you forgot your own </sarcasm>.

[VadeRetro]

Yeah, but other than that, a damm fine argument...

The "wrong sign" part is crushing. He should have been a Capricorn.

[Southack]

"The other good thing about the General Theory (okay, there are lots of them, but this is already a long note) is that it predicts that light itself obeys gravity, despite having no rest mass for the conventional Newtonian model to act upon. This is provable by lots of experimental data, so the General Theory gained a lot of credibility."

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.

[Rockitz]

The speed of light and the color of light are related. If the speed of light has increased, would the old light from galaxies long ago and far away appear to be redshifted?

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.

[MineralMan]

"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.

[O.C. - Old Cracker]

I remember telling my wife a few months ago that our flashlights seemed faster.

[RightWhale]

I have always thought there was another explanation. Makes my head hurt, too.

[VadeRetro]

Did you not learn that in your freshman physics class?

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."

[Gorjus]

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.

You'll have to provide a source for that before I'll buy it.

Here's a source for mine, just to be fair. Galaxy Cluster Abell 1689 Warps Space

By the way, I'll want that to be a credible source.

[DannyTN]

Unknown Stuff Bump

[Southack]

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)

Frozen Light (http://www.sciam.com/article.cfm?articleID=000BAEB1-B2AA-1C6F-84A9809EC588EF21)

Slowing a beam of light to a halt may pave the way for new optical communications technology, tabletop black holes and quantum computers

By Lene Vestergaard Hau

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Everyone knows of the speed of light as one of the unshakable properties of the universe. It's not surprising, then, that experiments to radically alter light's speed require some serious equipment and hard work. Running such an experiment requires first a careful tune-up and optimization of the setup and then a long period of painstaking data gathering to get a consistent set of measurements. At the Rowland Institute for Science in Cambridge, Mass., our original slow-light experiments typically took place in stints lasting 27 hours nonstop. Instead of breaking for meals, we learned to balance a slice of pizza in one hand, leaving the other clean to flip mirrors in and out on the optics table during 38 seconds of total darkness at a crucial stage of each run.

FREEZING OF LIGHT begins with a process in which a carefully tuned laser beam renders an opaque material transparent to a second laser beam.

Our goal was to drastically slow down light, which travels through empty space at the universe's ultimate speed limit of nearly 300,000 kilometers a second. We saw the first sign of light pulses slowing down in March 1998. As happens so often in experimental physics--because it can take so many hours to get all the components working together for the first time--this occurred in the wee hours of the morning, at 4 A.M. By July we were down to airplane speed. At that time I had to go to the Niels Bohr Institute in Copenhagen to teach a class. I remember sitting in the plane marveling that I was traveling "faster than light";--that I could beat one of our slow pulses to Denmark by a full hour.

Needless to say, I was restless during the week in Copenhagen and eager to get back to Cambridge to continue the light-slowing experiments. In the next month we reached 60 kilometers per hour and decided that it was time to publish. The real payoff for the hard work, prior to those results, was sitting in the lab in the middle of the night and observing the slow-light pulses, knowing that we were the first in the world to see light go so slowly that you could outpace it on a bicycle.

Late last year we took this process to its logical but amazing conclusion: we brought pulses of light to a complete halt within tiny gas clouds cooled to near absolute zero. We could briefly keep the pulses on ice, so to speak, and then send them back on their way.

As well as being of great intrinsic interest, slowing and freezing light have a number of applications. At sufficiently low temperatures the ultracold clouds of atoms used in our slow-light experiments form Bose-Einstein condensates, remarkable systems in which all the atoms gather in a single quantum state and act in synchrony. New studies of Bose-Einstein condensates will be made possible by, for example, sending a light pulse through a condensate as slowly as a sound wave, which we expect will cause a wave of atoms to "surf"; on the light pulse.

The slow and frozen light work also opens up new possibilities for optical communications and data storage and for quantum-information processing--that is, for quantum computers, which would utilize quantum phenomena to outperform conventional computers. The freezing-light system essentially converts between motionless forms of quantum information and photons flying around at the usual speed of light.

Getting Atoms into a State

Many ordinary materials slow down light. Water, for instance, slows light to about 75 percent of its velocity in a vacuum. But that type of speed reduction, associated with a material's refractive index, is limited. Diamond, which has one of the highest refractive indices of a transparent material, slows light by a factor of only 2.4. Reducing light's speed by factors of tens of millions requires new effects that depend on quantum mechanics. My group produces the conditions for these effects in a cigar-shaped cloud of sodium atoms--typically 0.2 millimeter long and 0.05 millimeter in diameter--trapped in a magnetic field and cooled to within a millionth of a degree of absolute zero.

[GrandEagle]

Sounds interesting. A bit late tonight, I'll try and read it tomorrow. Thanks for the ping!

[Robert_Paulson2]

GOD BOUGHT A FASTER PROCESSOR... and ditched the windows OS...
We were getting too close, so He upgraded back a few centuries ago.

[Old Professer]

If you've seen one angstrom, you've seen them all.

[Light Speed]

Article excerpts from:
The Remarkable Slowness of Light

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.

[headsonpikes]

Thanks for the marshmallow demo!

I have to confess that the lead article boggled me severely.

[RadioAstronomer]

Actually the speed of light (in a vacuum) is a fixed constant that is used as a reference for all other measurements.

[Political Junkie Too]

I guess that explains why I have to press the button on my remote a few times before the channel changes on my TV.

-PJ

[Doctor Stochastic]

And how does the sun manage to grab the earth and yank it around without a string between the two?

No strings attached? What's all this brouaha about String Theory then? Violin tunings?

[Doctor Stochastic]

Rule of debugging: Constants aren't; Variables don't.