Physicist suggests speed of light might be slower than thought

PHYS.ORG ^ | 07/01/2014 | Bob Yirka

[SeekAndFind]

Physicist James Franson of the University of Maryland, Baltimore County has captured the attention of the physics community by posting an article to the peer-reviewed New Journal of Physics in which he claims to have found evidence that suggests the speed of light as described by the theory of general relativity, is actually slower than has been thought.

The theory of general relativity suggests that light travels at a constant speed of 299,792,458 meters per second in a vacuum. It's the c in Einstein's famous equation after all, and virtually everything measured in the cosmos is based on it—in short, it's pretty important. But, what if it's wrong?

Franson's arguments are based on observations made of the supernova SN 1987A–it exploded in February 1987. Measurements here on Earth picked up the arrival of both photons and neutrinos from the blast but there was a problem—the arrival of the photons was later than expected, by 4.7 hours. Scientists at the time attributed it to a likelihood that the photons were actually from another source. But what if that wasn't what it was, Franson wonders, what if light slows down as it travels due to a property of photons known as vacuum polarization—where a photon splits into a positron and an electron, for a very short time before recombining back into a photon. That should create a gravitational differential, he notes, between the pair of particles, which, he theorizes, would have a tiny energy impact when they recombine—enough to cause a slight bit of a slowdown during travel. If such splitting and rejoining occurred many times with many photons on a journey of 168,000 light years, the distance between us and SN 1987A, it could easily add up to the 4.7 hour delay, he suggests.

If Franson's ideas turn out to be correct, virtually every measurement taken and used as a basis for cosmological theory, will be wrong. Light from the sun for example, would take longer to reach us than thought, and light coming from much more distant objects, such as from the Messier 81 galaxy, a distance of 12 million light years, would arrive noticeably later than has been calculated—about two weeks later. The implications are staggering—distances for celestial bodies would have to be recalculated and theories that were created to describe what has been observed would be thrown out. In some cases, astrophysicists would have to start all over from scratch.

Explore further: Does light experience time?

More information: Apparent correction to the speed of light in a gravitational potential, J D Franson 2014 New J. Phys. 16 065008 DOI: 10.1088/1367-2630/16/6/065008 . http://iopscience.iop.org/1367-2630/16/6/065008/

Abstract

The effects of physical interactions are usually incorporated into the quantum theory by including the corresponding terms in the Hamiltonian. Here we consider the effects of including the gravitational potential energy of massive particles in the Hamiltonian of quantum electrodynamics. This results in a predicted correction to the speed of light that is proportional to the fine structure constant. The correction to the speed of light obtained in this way depends on the gravitational potential and not the gravitational field, which is not gauge invariant and presumably nonphysical. Nevertheless, the predicted results are in reasonable agreement with experimental observations from Supernova 1987a.

[Hoodat]

Ever since Obama slapped that tax on tanning beds, light has lost a step.

[Fido969]

speed of light might be slower than we thought

I dunno. It gets here pretty early in the morning.

[353FMG]

Not only that, but how do they know the exact moment, where time = 0, that the explosion occurred? Saying that it took place in February 1987 doesn’t cut it.

[Vermont Lt]

Now it will take even longer to get to Cape Cod.

[centurion316]

That story was first told by or about Cool Papa Bell:

Numerous stories are told of his feats on the basepaths. Many no doubt are true, such as consistently hitting two hoppers to the infield and beating the throw to first for a hit, going from first to third on a bunt, scoring from second on a sacrifice fly, stealing two bases on one pitch, and once scoring from first base on a bunt against Bob Lemon and a team of major league all stars. Other stories are simply colorful exaggerations. Such accounts have Bell hitting a single up the middle and being declared out when hit by his own batted ball as he slid into second base; and, of course, the most repeated story of how he could switch off the light and get into bed before the room was dark.

[centurion316]

I believe that this finally explains why when you need your flashlight, it never works. All those photons have decayed.

[KarlInOhio]

If this is happening, then it will happen multiple times to some photons and not at all to others unless it happens so many times over the 168,000 light years that it causes a very tight bell curve. That means there should be some smearing of the wave front as the photons which didn't split into electron/positron pairs get in front of those which did split. Also, lower energy photons like radio waves should be far less likely (or even zero chance) to split and thus travel full speed all the way, while gamma rays with more energy would be more likely to split. Is there a frequency distribution with the radio waves getting here before the visible light, x-rays and gamma rays from the supernova?

Or is it possible that our theories about how light emerges from the last gasp of fusion from the supernova is wrong and it takes hours longer to make it through the star's outer shell?

[alexander_busek]

Methinks the author makes it much more dramatic sounding than it really is. 4.5 hours over 164,000 light years? What is the percentage error?

That's a discrepancy of one part in 3.13 billion - an incredibly huge discrepancy, considering the precision to which this important fundamental constant has been measured.

Having said that: I suspect that there is a logical explanation.

Regards,

[beethovenfan]

The photons were stuck in traffic.

[Lake Living]

Where’s the picture of Hillary Clinton exclaiming, “What difference does it make?”

[FredZarguna]

It should be noted that the author of this new theory is not an astrophysicist.

Nor was the author of my post, at one time a condensed matter theorist who makes no pretenses to expertness in cosmology. My comment did not deal with the origins of the discrepancy so much as the claims made that -- whatever their provenance -- these were potentially earth shattering discoveries.

Nope. Not.

As for the well-understoodness, is the delay accounted for entirely by the fact that it takes light from the core substantially longer to propagate to the surface than the weakly interacting neutrinos?

[CrazyIvan]

Probably just speedometer error from running the wrong tire size.

[SeekAndFind]

Where’s the picture of Hillary Clinton exclaiming, “What difference does it make?”

[FredZarguna]

He's not postulating the existence of real position-electron pairs, which would require either two γ's or a γ and a nucleus in order to conserve momentum; he's talking about virtual p-e pairs. Virtual pair production happens to all photons, all the time, regardless of energy. You don't need to conserve energy and momentum because the virtual particles don't exist long enough to have measurable physical effects. Essentially it's a quantum fluctuation in the electromagnetic field. It has to "exist" or the path integral doesn't work, and there are [presumably an infinite number of] Feynman diagrams describing it.

See, among many places, http://en.wikipedia.org/wiki/Virtual_particle.

[FredZarguna]

[FredZarguna]

Not incredibly huge.

The speed of light and second are now DEFINED, so you can no longer correctly say the "error in measuring the speed of light." But what amounts to the same thing is the length of a meter, which has been measured with an error of about 1/10 of this error. So larger than we would expect, but not incredibly large. And whether it would have cosmological significance, where most numbers [which are not just SWAG] range from order of magnitude estimates to no better than two significant figures is very doubtful.

[scrabblehack]

Does the special theory actually cite a number like that, or does it leave everything in terms of c?

[FredZarguna]

No, the actual value is one which would have been of little or no interest to Einstein [or any other theoretician] except to the extent that it's being "very large" [in some sense] explains why we were unaware of relativity for so long.

Here's one of the very first serious physicists' take on the matter:

"The speed of light, if not instantaneous, is extraordinarily rapid." -- Galileo

The symbol "c" itself was not used in Einstein's paper on Special Relativity. He used the symbol "v."

[ADemocratNoMore]

Question - c is the speed of light in a vacuum. I recall reading somewhere the the hardest vacuum in interstellar space has something like one atom per cubic meter, the article refers to the fact that space is not a “perfect” vacuum, but it's pretty darn close to one. On the other end of the scale, barionic matter is 99.99% empty space, the old analogy being an atomic nucleus being the size of a baseball, the electron (back in the days they were considered physical objects instead of probability clouds) would be the size of a grain of sand several hundred feet away from the nucleus and the next closest atom would be found a few miles away. This being the case, the space inside a glass lens at the scale of a photon would be as empty as the interstellar medium, to the photon it would be a vacuum, but it travels much slower through the glass than through “space”. Why do you suppose this is?

[Moonman62]

The speed of light is actually dependent on two other constants which describe the behavior of electricity and magnetism in a vacuum. The speed of light and most of the concepts of relativity were already known when Einstein wrote his paper. His great genius was due to two postulates:

From Wiki.

First, he applies the principle of relativity, which states that the laws of physics remain the same for any non-accelerating frame of reference (called an inertial reference frame), to the laws of electrodynamics and optics as well as mechanics. In the second postulate, Einstein proposes that the speed of light has the same value in all inertial frames of reference, independent of the state of motion of the emitting body.