The speed of light is slower than the speed of light?

[Ann]

I very much doubt that the tidbit I've come across here is correct.

Physicist James Franson of the University of Maryland 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.

It is the 4.7 hours arrival time difference between the neutrinos and the photons from Supernova 1987A that has led Franson to his radical conclusion.

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.

What would be the consequences if Franson is right?

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.

So, is cosmology doomed? I guess not, though. Chris, would you like to comment?

In the meantime, I can't resist quoting one of the comments on this article at http://phys.org/news/2014-06-physicist- ... ought.html:

h20dr wrote:
Wow, this could get interesting. I suppose the warp drive on the Enterprise will need to be re calibrated.

Ann

[neufer]

I very much doubt that the tidbit I've come across here is correct.

Physicist James Franson of the University of Maryland 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.

It is the 4.7 hours arrival time difference between the neutrinos and the photons
from Supernova 1987A that has led Franson to his radical conclusion.

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.

The Franson effect, if it exists, cannot possibly account for more than 2.5×10⁻¹¹ seconds of the SN 1987A 4.7 hour photon delay or else the observed 3×10²⁰ eV "Oh-My-God particle" would have suffered "supersonic shock" vacuum Cherenkov radiation all during it's interstellar space flight and would certainly never have made it all the way to Earth.

<<The Oh-My-God particle was an ultra-high-energy cosmic ray (most likely a proton) detected on the evening of 15 October 1991 over Dugway Proving Ground, Utah. Its observation was a shock to astrophysicists, who estimated its energy to be approximately 3×10²⁰ eV (3×10⁸ TeV, about 20 million times more energetic than the highest energy measured in radiation emitted by an extragalactic object); in other words, a subatomic particle with kinetic energy equal to that of 50 Joules, or a 5-ounce (142 g) baseball traveling at about 100 kilometers per hour (60 mph). The particle was traveling very close to the speed of light — assuming the particle was a proton, its speed was only about 1.5 femtometers (quadrillionths of a meter) per second less than the speed of light, translating to a speed of approximately 0.999 999 999 999 999 999 999 9951c. At that speed, in a year-long race between a photon and the particle, the particle would fall behind only 46 nanometers, or 0.15 femtoseconds (1.5×10⁻¹⁶ s); or one centimeter every 220 000 years.>>

[Ann]

Thanks, Art!

I think I remember reading about the Oh-my-God particle, too. Even though I don't remember that the nickname it received was so theological!

Ann

[Chris Peterson]

So, is cosmology doomed? I guess not, though.

I guess not, as well.

I'm not sure I agree with Art's comments, either his calculated timing or the issue of Cherenkov radiation. But that issue aside, it's not clear to me why photons traveling at very slightly less than c changes much about our observations. How does light arriving slightly later than we have assumed change our ideas about fundamental physics? It isn't like c is changing, after all. And practically nothing we observe depends on the actual time of flight, especially over cosmological distances. The difference between the arrival time of photons and neutrinos is a rare exception, but I don't think we understand the details of supernovas well enough to really explain that difference effectively yet.

[neufer]

So, is cosmology doomed? I guess not, though.

I guess not, as well.

I'm not sure I agree with Art's comments, either his calculated timing or the issue of Cherenkov radiation. But that issue aside, it's not clear to me why photons traveling at very slightly less than c changes much about our observations. How does light arriving slightly later than we have assumed change our ideas about fundamental physics? It isn't like c is changing, after all. And practically nothing we observe depends on the actual time of flight, especially over cosmological distances. The difference between the arrival time of photons and neutrinos is a rare exception, but I don't think we understand the details of supernovas well enough to really explain that difference effectively yet.

Mind you, I'm not stating that the Franson effect doesn't exist.

Perhaps photons do have an effective tiny mass
(or, perhaps, somehow or other have some constant velocity that is less than c).

All I'm saying is that it is totally irrelevant as regards to supernova delays on the order of hours.

[Markus Schwarz]

I'm not sure I agree with Art's comments, either his calculated timing or the issue of Cherenkov radiation. But that issue aside, it's not clear to me why photons traveling at very slightly less than c changes much about our observations. How does light arriving slightly later than we have assumed change our ideas about fundamental physics? It isn't like c is changing, after all.

If the speed of light were less than c in vacuum, it would mean that other charged particles, e.g. electrons or protons, could travel faster than light in vacuum. Thereby they would radiate Cherenkov radiation and lose energy until their speed is at least equal to the speed of light. You can cook up theories were this is indeed the case. But observations of ultra-high energy cosmic rays, such as the "Oh-My-God particle", put really tight constraints on the parameters of these theories.

[Chris Peterson]

If the speed of light were less than c in vacuum, it would mean that other charged particles, e.g. electrons or protons, could travel faster than light in vacuum.

Could, but not necessarily do.