# High Energy Gamma Rays Go Slower Than the Speed of Light?

1. Oct 5, 2007

### SF

http://www.universetoday.com/2007/10/03/high-energy-gamma-rays-go-slower-than-the-speed-of-light/

2. Oct 5, 2007

### robphy

If the speed of light were to depend on frequency, then Einstein's Special Relativity would have to be re-worded to use "maximum signal speed" instead of "speed of light". Maybe some examples would have to be re-worded as well. But the theory itself [which used light because it was a convenient example] would largely remain in tact. The Maxwell Equations (for Electromagnetism and light) would probably require some revision, possibly the inclusion of additional terms.

Alternatively, there might be a different explanation that might point to some other mechanism at work between emission at the source and reception here on earth. Unfortunately, the article didn't provide any sources of literature to follow up with.
So, I tracked one down:
http://www.physics.ucdavis.edu/Text/Ferenc.html

Last edited: Oct 5, 2007
3. Oct 5, 2007

### neutrino

Why would it ever be bad news? Unless, of course, you belong the Church of Relativitians, it's good news for science.

4. Oct 5, 2007

### Mentz114

The paper is here -

http://www.arxiv.org/abs/0708.2889

It's still a moot point, this is from the abstract

5. Oct 5, 2007

### robphy

While I welcome new science, possibly correcting older science [like relativity],
it seems that some folks [e.g. that article writer] might be jumping to conclusions for publicity purposes. Some publicity is good [e.g. getting funding]... but I think it's more important to try to get science right... and that requires some care and some checking.

Some chatter:
http://blog.sciam.com/index.php?title=hints_of_a_breakdown_of_relativity_theor
http://www.math.columbia.edu/~woit/wordpress/?p=591
http://motls.blogspot.com/2007/08/magic-dispersion-of-gamma-rays.html

6. Oct 5, 2007

### Garth

From that website: Sci Am August 22 2007: Hints of a breakdown of relativity theory?
This could herald the breakdown of physics as we know it or it could have a mundane explanation.

Notice the higher energy group arrived later. This fact could be the significant one indicating a 'mundane' explanation.

It is thought these flares are generated as matter falls into a supermassive Black Hole.

The higher energy group came from a hotter region which is further into the SMBH potential well and therefore not only further away but deeper into its gravitational field.

Time dilation between the high and low energy emitting regions would not only lower the observed frequency of the high energy group, which means the photons would have to start out at even higher energies, but also it would increase their time of flight.

I haven't put in the exact numbers but I would have thought the light-time distance and time dilation could account for four minutes very nicely...

A rough calculation simply on light-time distance (ignoring time dilation) gives:
Mass of SMBH ~ 108 MSolar
Solar Schwarzschild radius ~ 1.5 km
SMBH Schwarzschild radius ~ 1.5 x 108 km
Typical inner accretion disk scale ~~ 3 x 108 km
speed of light = 3 x 105 km/sec
Typical photon times of flight in inner accretion disk ~~ 103 secs ~~ 4 minutes (OOM)

Garth

Last edited: Oct 6, 2007
7. Oct 5, 2007

### neutrino

Bad journalism, maybe. Also, if this turns out to be right, this will also "prove" many crackpots right, but for all the wrong reasons. In that way, it might be bad news.

8. Oct 5, 2007

### minorwork

Why can't two sources 45 million or so miles distance account for the temporal separation?

9. Oct 5, 2007

### Garth

They can and do, see my post #6 above.

Garth

10. Oct 5, 2007

### minorwork

Well OK. I thought mine the more mundane. Oversimplified and ignoring relativistic gravitational stuff and it seemed that 4 minutes was about half the solar-terran distance. Coal mines don't teach the differentials. I do see that the clock in the higher gravitation seems slower for us. The apparent distance, derived from the 4 minute time value seen, then would be the equivalent of about half that of the solar-terran.

I do not see the necessity of throwing out relativity theorems yet.

11. Oct 5, 2007

### Staff: Mentor

If the speed of some photons is less than c then that simply implies that photons have some small mass. I don't think this would be a major problem for special relativity, the existence of the invariant speed, c, is well established experimentally even if it does not exactly correspond to the speed of light. But my understanding is that it would be a problem for some quantum mechanical theories.

12. Oct 6, 2007

### SF

13. Oct 6, 2007

### Garth

That report, interesting in itself, is about distant supernovae not distant AGNs or Quasars.

The paper being reported would indicate we cannot be sure of the assumption that distant SNe Ia are standard candles, which if true would throw a lot of cosmological analysis leading to the standard $\Lambda$CDM model into doubt.

Garth

Last edited: Oct 6, 2007
14. Oct 6, 2007

### yuiop

Nice explanation Garth, in post #6