Time travel: Light speed results cast fresh doubts

[dipsydoodle]

Physicists have confirmed the ultimate speed limit for the packets of light called photons - making time travel even less likely than thought.

The speed of light in vacuum is the Universe's ultimate speed limit, but experiments in recent years suggested that single photons might beat it.

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Now, a paper in Physical Review Letters shows that individual photons too are limited to the vacuum speed limit.

That means that photons maintain the principle of causality laid out in Einstein's theory of special relativity - that is, an event's effect cannot precede its cause by traveling faster than light. It is violation of this causality that would, in principle, permit time travel.

http://www.bbc.co.uk/news/science-environment-14289114

[Demeter]

1. And don't forget Gravity--It's not only a good idea, It's the Law!

[LARED]

2. Captain Kirk and Scotty disagree nt

[trotsky]

3. This would seem to rule out one type of travel into the past.

But it doesn't discount the idea of time travel into the future (just go very, very close to the speed of light), or other methods of travel into the past (wormholes, TARDISes). ;-)

[dipsydoodle]

4. Maybe ?

[trotsky]

5. Ooh, I'll make sure I don't miss that. n/t

[pokerfan]

6. TARDISes? TARDi?

Amy: Doctor, how come she can fly the TARDIS?
The Doctor: You call that flying the TARDIS? (scoffs) Ha!
River Song: Okay, I've mapped the probability vectors, done a foldback on the temporal isometry, charted the ship to its destination and... (presses a button, the cloister bell clangs) parked us right alongside.
The Doctor: Parked us? But we haven't landed!
River Song: Of course we've landed; I just landed her.
The Doctor: But it didn't make the noise.
River Song: What noise?
The Doctor: You know, the... (does an impression of the TARDIS materialisation sound)
River Song: It's not supposed to make that noise. You leave the brakes on.
The Doctor: Yes, well, it's a brilliant noise. I love that noise.

http://www.youtube.com/watch?v=__CQpbKZbcU

[trotsky]

7. Loved that scene. n/t

[Ready4Change]

9. We are already time travellers.

We are all traveling into the future.

[trotsky]

10. Great Scott! n/t

[hunter]

8. This is a single speed universe, the speed of light.

Everything IS light, there is no time, no fixed past or future. You yourself and all you know is an interference pattern written upon the light.

There's nothing mystical about it. It's all energy, it's all light.

E=mc² doesn't mean energy can be converted into mass or vice versa, it means mass IS energy.

If we could somehow effect a "violation of this causality" we'd never know it, never be able to see it or measure it. Our perceived pasts and futures would simply merge seamlessly into the everlasting here and now.