Speed of light slower than previously thought.

[Manifestor_of_Light]

Re: 1987 supernova. Photons separating into subatomic particles and combining again.
My husbo the physicist confirmed this when I told him about this story.


http://phys.org/news/2014-06-physicist-slower-thought.html

[longship]

1. Hmmm!

Epsilon-nought times mu-nought equals 1 over C-squared.

The speed of light is not just something which takes on some arbitrary value that anybody wants it to. It is inextricably connected to other parameters in the universe. When one posits that we've got the speed of light -- a value measured centuries ago -- wrong one is not just saying that the speed of light is wrong. One is saying that a whole lotta other physics is also wrong.

Forgive me if I am skeptical.

[freshwest]

2. I could find some woo that would fix that right up, but I'm slowing down.

[Manifestor_of_Light]

3. I'm not a physicist, so read it for yourself.

If space can curve and there are gravity waves, why wouldn't other alleged constants have some sort of variability?

[longship]

4. Let's put it this way.

James Clerk Maxwell and Einstein kind of settled this issue some century and more ago.

Maxwell, who provided the first symmetric equations of electrodynamics, and Einstein who extended them to demonstrate that the speed of light is invariant for any observer in any inertial reference frame.

One has to climb a tall hill to make the claim to the contrary. And the universe would be an entirely different place if C were not invariant, or at least not too variant.

One cannot posit changes in physics ad hoc. There are always symmetries which bite one in the ass. Changing one parameter inevitably changes others. And quantum field theory as it stands now, commonly known as the standard model, is the most successful scientific theory in history. One does not just make a claim that the speed of light has changed without simultaneously making a claim that Maxwell was wrong, Einstein was wrong, Dirac was wrong, Feynman was wrong, Gell-Mann was wrong, Weinberg was wrong, Wilczek was wrong, etc.

I only have a BS in physics, but I try to keep up with it. Like you, I am not a physicist. But one must understand why this claim is extraordinary, and why one should be skeptical.

[caraher]

15. The Franson paper is worth reading

Jim Franson is no crank but a leading figure in quantum optics, and it's not an "Einstein (or Maxwell) was wrong" claim. Indeed, Einstein himself argued that the gravitational potential can affect the propagation speed of light, according to Franson:

Einstein was the first to predict that the velocity of light would be reduced by a gravitational potential [37]. According to general relativity [38, 39], the speed of light c as measured in a global reference frame is given by c=c0(1+2 Phi_g/c0^2) where c0 is the speed of light as measured in a local freely-falling reference frame.

According to Franson, the deviation he estimates from c0 is actually smaller than the neutrino-photon delay observed from the supernova, but his calculation also uses a lower limit on the value of the gravitational potentials the photons would experience. He says that this effect is in violation of the equivalence principle, but also notes that the paper represents an incomplete, approximate theory:

It should be emphasized that the model described in this paper is only intended to provide
an alternative and approximate description of the propagation of photons in a gravitational potential; it is not intended to represent a complete or consistent theory.

He promises a more rigorous treatment in a subsequent publication.

[longship]

16. I will wait for peer review on this one.

There are already questions on it. And the theoretical bar is quite high.

The main question... It's one case. Could there be a coincidence of neutrinos arriving at the detector? Or a measurement problem? It's one case! Hardly compelling.

Yawn!

[caraher]

18. This IS peer-reviewed

New Journal of Physics is not a pre-print server!

The supernova data are a well-documented, long-standing anomalous result. Franson would probably agree that we should be looking for more examples; indeed, his paper is largely a call for closer investigation of gravitational effects in other experimental contexts. The connection to the supernova is largely that this kind of calculation gives a result of the right order of magnitude to explain the supernova neutrino-photon arrival time delay.

If anything short of overthrowing Einstein or Maxwell is yawn-worthy to you, so be it. I can't set that bar for you! But this has been through peer review, which, as one delightfully cynical chemist says, means it's "not obviously wrong." And Franson is a big name in optics, so to me this isn't a random physicist's late-night musings.

New Journal of Physics is an online-only, open-access, peer-reviewed scientific journal covering research in all aspects of physics, as well as interdisciplinary topics where physics forms the central theme. The journal was established in 1998 and is a joint publication of the Institute of Physics and the Deutsche Physikalische Gesellschaft. It is published by IOP Publishing. The editor-in-chief is Eberhard Bodenschatz (Max Planck Institute for Dynamics and Self-Organization).

[longship]

20. We will see how it is received by others in the physics community.

That is peer review, too.

[BainsBane]

5. That's what I thought

Minus the knowing stuff about science part.

[DreamGypsy]

13. The speed of light was measured (accurately) 44 years ago, then redefined...

...according to Las Cumbres Observatory Global Telescope Network:

Galileo was the first person to attempt to measure the speed of light. In the early 1600s, he and an assistant each stood on a different hilltop with a known distance between them. The plan was for Galileo to open the shutter of a lamp, and then for his assistant to open the shutter of a lamp as soon as he saw the light from Galileo's. Using the distance between the hilltops and his pulse as a timer, Galileo planned to measure the speed of light. He and his assistant tried this with different distances between them, but no matter how far apart they were, Galileo could measure no difference in the amount of time it took the light to travel and concluded that the speed of light was too fast to be measured by this method. He was correct. We now know the speed of light very precisely, and if Galileo and his assistant were on hilltops one mile apart, light would take 0.0000054 seconds to travel from one person to the other. It is understandable that Galileo was unable to measure this with his pulse!

<snip>

In the 1850s, French physicist Jean Foucault measured the speed of light in a laboratory using a light source, a rapidly rotating mirror and a stationary mirror. This method was based on a similar apparatus built by Armand-Hippolyte Fizeau. For the first time the speed of light could be measured on Earth, and the speed of light was measured to very great accuracy.

In the 1970s, interferometry was used to get the most accurate value for the speed of light that had been measured yet: 299,792.4562±0.0011 km/s. Then, in 1983, the meter was redefined in the International System of Units (SI) as the distance traveled by light in vacuum in 1/299,792,458 of a second. As a result, the numerical value of the speed of light (c) in meters per second is now fixed exactly by the definition of the meter. <snip> For most calculations the value 3.00 x 105 km/s is used.

A couple of interesting points. First, note that the error range of the interferometry measurement was .0022 km/s for a measurement of 299,792.4562 km/s, or an percentage inaccuracy of 7.338410138420288e-9.

The Phys.org article reports that

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. <snip> 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.

However, the 4.7 hour delay is incorrectly stated. The research article says:

The observations made during Supernova 1987a are illustrated in figure 6, which is based on a review article by Bahcall and his colleagues [26]. A burst of neutrinos was observed by a detector underneath Mont Blanc followed 4.7 h later by a second burst of neutrinos that was detected in the Kamiokande II detector in Japan and the IMB detector in Ohio. The first observation of visible light from the supernova was then observed approximately three hours after the second burst of neutrinos, or 7.7 h after the first burst of neutrinos. As mentioned earlier, the usual interpretation of this data is that the first burst of neutrinos must not have been associated with the supernova for the reasons described below.

So, the actual delay of photon arrival is 7.7 hours in a journey of 168,000 light years. 168K light years is 1,472,688,000 light hours. The deviation of 7.7 hours over the total light hours traveled is 5.228534489314777e-9, so less than the accuracy of the interferometry measurement of the speed of light. Note also, of course, that the distance of 168K LY to the supernova is an approximation based on current understanding of red shift and the Hubble constant.

Three important conclusions from this consideration of the data:

First, the redefinition in 1983, of the meter as the distance traveled by light in vacuum in 1/299,792,458 of a second means that the speed of light doesn't change; the length of a meter changes.

Second, the attempt by Bob Yirka, the author of Phys.org article, to fulfill the MSM goal of instilling daily fear into the hearts of readers with crap like:

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.

are just the usual journalistic bullshit.

And, third, there may be some interesting events the occur during supernovas, relating to the emission of neutrinos and the electromagnetic output that we don't understand and need to explore further. Perhaps there are photon/virtual particle interactions that have not yet been observed. Science poses new questions; science will search for answers.

[Ghost Dog]

14. Nicely put. n/t

[defacto7]

6. Let's try this again...

it says,

Physicist suggests speed of light might be slower than thought.

It also says,"If Franson's ideas turn out to be correct... blah blah..."

The whole write up is a normal scientific exploration of ideas. It's not uncommon for scientists to brainstorm an anomaly. There's no big statement here.

[SheilaT]

7. I agree.

It's also suggesting that two weeks in 12 million years is a significant slippage. Don't have a calculator handy, but if I can still do pen and paper multiplication correctly, there are 625 million weeks in 12 million years. 2 weeks is an .00000052 percent of that enormous number of weeks. Hardly a significant amount.

[defacto7]

8. Your signature is great! love it.

but what is pen and paper?

[SheilaT]

10. I also love my signature line.

If I had a time machine I'd go back to 10th grade math -- great teacher and I loved that year -- and write it on the blackboard.

Pen and paper are these weird things, I know.

[Manifestor_of_Light]

9. Yes, it's a tiny amount.

But for people who live, breathe and think physics and math, any deviance is interesting and startling.

I know that because I live with someone who talks in equations. He's been reading a book about quarks lately and working the problems and telling me all about the symmetries of color, charm, up or down, and strangeness.

He also wanted to do his thesis on gravito-magnetism in 1970, and his advisor would have none of it "because black holes don't exist--you can cram a lot of stuff together--big deal".

He wanted to do that after reading a Sci Am article called "The Three Spectroscopies" by Victor Weisskopf back in 69.

Then I found an article on the internet a few years ago about Gravity Probe B which was a project of Stanford and they found evidence of gravito-magnetism. He was just 40 years ahead of the evidence.

[defacto7]

12. Science is like a wheel sometimes...

"and his advisor would have none of it "because black holes don't exist--you can cram a lot of stuff together--big deal"."

It's amazing how short sighted people choose to be, and statements like that are weak choices. What does your husband think about Planck stars?

[intaglio]

11. As I understand it, it's a bit more complicated

During it's travel a photon has a chance to change into an electron-positron pair; but mostly that pair recombine. so letting the (an identical) photon continue on its way. That e^-/e⁺ pair has mass and so travels at a bit less than c thus the average velocity of the photon is a bit less than c ...

It's at this point that I start to go "wibble"

[caraher]

17. The title is far too simplistic

Franson's suggestion does not, for instance, overthrow the value for c one gets from classical electrodynamics because classical electrodynamics "lives" in a flat spacetime without quantum effects. The term Franson introduces to the Hamiltonian is the result of a gravitational interaction with virtual particles, neither of which are elements of standard E&M a la Maxwell.

The "speed of light" as usually understood is unchanged by this proposal; rather, Franson argues that light may propagate more slowly in gravitational fields, because of interaction with those fields. Similarly, we know light travels more slowly in glass than vacuum, because of interactions (of a different nature!) between light and that medium.
Franson suggests that the most startling difference between this case and ordinary slowing of light in material media is that, if the result holds, it suggests a violation of Einstein's equivalence principle, which argues that the effects of gravity are indistinguishable (locally) from the effects of acceleration:

Based on the equivalence principle [38, 39, 56], one would expect that these effects should vanish in a local freely-falling reference frame. The calculations described above were performed using a coordinate frame that was assumed to be at rest with respect to mass M, where it seems reasonable to suppose that the effects of gravity can be represented by the Feynman diagrams of figures 2(b) or 3. In that reference frame, the photons and neutrinos would travel at different velocities according to equation (18). If we made a transformation to a local freely-falling coordinate frame where the laws of physics are assumed to be the same as in the absence of a gravitational field, then the photons and neutrinos would be expected to travel at the same velocity. This leads to a contradiction, since there can be no disagreement as to whether or not two particles are traveling at the same velocity. Thus the Hamiltonian of equation (4) leads to a small departure from the equivalence principle, which is closely related to the lack of gravitational gauge invariance noted above.

[Manifestor_of_Light]

19. The difference is one meter/sec in nearly 300 million.

Extremely small fraction.

I have no idea what a Planck star is.

[CanonRay]

21. We've all slowed down a little since '87

[Manifestor_of_Light]

22. Ain't that the truth!!