for science?

[lordofthewheel]

Okay LJ, I'm confused... So people have likely heard of the Nutrinos at CERN that have - allegedly - broken thge speed of lightIf this result is true, they say, then time travel may no longer be a theoretical impossibility. I shall now quote from an article from the BBC

The speed of light is the cornerstone in Einstein's theory of special

Comments

[luckykaa]

I think there's a certain amount of "from the point of view of an external observer" missing. My memory of how relativity actually works is a little bit hazy, but I think there are configurations where you're travelling at relativistic speed, and even if you take into account the propagation delay the light, the neutrons reach you before the event happened.

[fhtagn]

http://en.wikipedia.org/wiki/Closed_timelike_loop

As soon as anything becomes superluminal then, as we understand it, time travel and acausal events become possible. So, yes, effect can indeed come well before cause.

[kai_kay]

I don't understand the physics, but I think I'm with you Peter. The sequence is: supernova happens; neutrinos & light wave/particles rush out; neutrinos arrive; light arrives. No-one is suggesting the neutrinos arrive before they set out, are they? only that they seem to get somewhere a bit quicker than light would have done.

[weebleflip]

If the only implication of a particle being able to break the speed of light was that those particular particles could go faster than light, that would be the case.

However, a lot of modern physics (general relativity etc.) depends upon the speed of light (in a vacuum) being a fixed, maximum velocity that nothing can exceed.
As Fhtagn says, if this is not the case, causality breaks down, or at least our understanding of it does! Once causality is sufficiently bent or broken, the neutrinos could arrive before the supernova "kicks off".

That would completely over-throw all me know about cause and effect, and what we see happening around us in every-day life. I think it very unlikely to be true.

On the other hand, not all that long ago, space and time being relative was seen in the same way. And, not all that long before that (relatively speaking... :P), people thought the earth was flat. These notions were each thought similarly ridiculous!

Time (or space, or timey-wimey stuff) will tell...

[limpingdog]

From memory of my physics degree, without looking it up (as it's not something I use on a frequent basis):
1) Under general relativity, it's sometimes impossible to say which of two events happened first, given that two observers might disagree, depending on their acceleration. This is nothing new.
2) Two things that happen in the same place have a clear order: you can determine cause and effect as long as they're not too far apart or moving in weird ways.
3) The speed of light is central to general relativity, too, as a speed that can't be passed. It doesn't say that you can't start above it and stay above it, just that you can't cross it; unsurprisingly, there hadn't been any results consistent with that. (Also, you get imaginary numbers in the equations.)
4) If something travels faster than the speed of light, then from it's point of view time runs backwards