Experiment rules out a bunch of theories of gravity

[Humodour]

For those who've spent some of their spare time following developments in high-energy physics, you'd be aware that we currently have quite a few competing theories of physics (mainly related to gravity), almost all variations on eachother with no perceptible difference on a macroscopic (i.e. every-day) level and hence very hard to test.

 

Since the mid 1900's, scientists have been trying to tie all the forces together with a grand unified theory. Gravity has been the outlier. An experiment has been performed which rules out all of the group of alternate theories of physics which suggested the speed of EMR varied according to energy density, re-affirming the Einsteinian group of theories which posit that all EMR travels at the speed of light, regardless of energy density.

 

Basically, two photons sent from the same source at the same time (7.3 billion years ago) arrived here at almost exactly the same time. One photon was a million times more energetic than the other. Their arrival within tenths of a second of each other after 7.3 billion years essentially rules out the possibility that they travelled at different speeds.

 

http://www.physorg.com/news175965994.html

 

I felt this was newsworthy because while it's nice to see theories proposed it's also important to see theories disproved so that what you have remains science rather than metaphysical speculation.

[Moose]

Their arrival within tenths of a second of each other after 7.3 billion years essentially rules out the possibility that they travelled at different speeds.

 

I don't really follow that. If a car and a bicycle set off from some point at different speeds, then the reverse is possible - two entities travelling at different speeds can arrive at the same place at the same time, if one sets off first. How do they know these photons were emitted at the same time?

[Aristes]

Actually a very fun read, especially the science geek fight that ensured after the article. I don't have much of a science background myself, but it's always fun to read from an outsider's point of view.

[Aram]

God damn photons.

[Rostere]

And so Einstein was right in the end, as usual.

[alanschu]

Well that makes sense given it was established a long time ago. His theories built upon Newton's, so people are just trying to build upon his. It'd be pretty unfrakking believable if his theories were smashed in the process, but even then it'd probably be more of a "this is something that doesn't quite hold up true about this special case, so what's special about this special case? Which is kinda what Einstein did too

[Gorth]

Basically, two photons sent from the same source at the same time (7.3 billion years ago) arrived here at almost exactly the same time. One photon was a million times more energetic than the other. Their arrival within tenths of a second of each other after 7.3 billion years essentially rules out the possibility that they travelled at different speeds.

So, they missed the 3 photons that stopped by last year and probably wont even look at the delayed one that is due next year. They are getting sloppy...

[213374U]

Basically, two photons sent from the same source at the same time (7.3 billion years ago) arrived here at almost exactly the same time. One photon was a million times more energetic than the other. Their arrival within tenths of a second of each other after 7.3 billion years essentially rules out the possibility that they travelled at different speeds.

So, they missed the 3 photons that stopped by last year and probably wont even look at the delayed one that is due next year. They are getting sloppy...

Hmm, the idea is that since there is a huge energy difference between the two photons, and given the very short life of the GRB that emitted them (~2s), the high energy photon would need to have a substantial head start to reach us (almost) simultaneously, according to predictions that energy density affects the speed of light.

 

What I want to know is whether c is a constant no matter what, or the variations are too small to lend credibility to this "foam void medium" theory (but they exist and explain this 9/10 of a second difference) - or the difference is due to other causes.

[Aristes]

Seriously, you guys should read the nerd rage comments too. Some of those folks either cite their sources or link to blogs or other webpages. I found the argument fascinating, even if I could only understand it contextually, which meant a lot of it was above my head.

[Walsingham]

Hold on. Surely if gravity bends light, and Im pretty sure it does, then one could have gone a really bendy route, while the other zipped between competing fields by pure luck.