[dgottlieb]

The reason a particle would have infinite energy as it approaches the speed of light is because its mass (relativistic mass) would also approach infinite. Thus the understood reason a particle could not attain the speed of light is because most of the energy added into a particle going near the speed of light turns into relativistic mass instead of velocity.

If these neutrinos are indeed going faster than light, they clearly did not become infinitely massive.

[pbhjpbhj]

The concept behind tachyons is that whilst particles can't approach the speed of light they can be faster than the speed of light and not break relativistic equations (they couldn't then slow to the speed of light either). Similarly with time reversal.

Personally I think this is cool but probably also just difficult (if not impossible) to falsify and so hasn't yet been restricted. When you apply a mathematical model it's like applying a metaphor [so meta!], it has a limit at which it breaks down but that limit isn't always obvious and sometimes at the edges things look tantalisingly like they might work.

[sp332]

OK, either that or it violates relativity.

[jerf]

Relativity does not permit particles with mass to go the speed of light. However, the math works just fine with massive particles going faster than light. Further however, the effects are quite bizarre, even if well defined. You know how your physical intuition is basically useless when it comes to understanding relativity? It's even more useless when understanding what the math says about tachyons.

One of the more approachable discussions on the topic is actually http://www.theforce.net/swtc/hyperspace.html . Yes, I am aware of the context, but the author knows what he's talking about. http://www.mssl.ucl.ac.uk/~cjs2/

[JonnieCache]

My word. The star wars technical commentaries. What a blast from the past. Thanks for that.

[jerf]

Just to be clear, I did say "approachable". I've seen heavier duty explorations of what tachyons are like under real relativity theory, but I don't know of anything else that approachable.