echo echo echo

[Magus]

Remus wants you to sign Remus up for the light-speed travel. Remus thinks destroying the fabric of the universe would finally put Remus' name in the history books (if they still existed for Remus' name to be put there, of course).

[Sithdarth]

If you could travel faster than the speed of light, from an outside perspective, you would get there before leaving here.

That depends. If you are following closed time like curves then maybe. Or you could just beat a light pulse to its destination.

Nah, when you slowed back down time would speed back up to normal (a basic error with people equating FTL with time travel). Basically the travel would appear to be instantaneous (if the distance were short enough)...or simply faster than light should be able to travel, which would make people scratch their heads, but you wouldn't have arrived at a time before you left. Uh, I think. Maybe if you went really faster than light...

Not even close really.

I think Loyal is right, though I cannot be sure. I was a poli sci/history major.

He's kinda right adjacent (though still not right) and the reasoning is way off.

Pyros will explain that in the event of someone traveling faster than the speed of light, the concept of 'here" would no longer apply, as the effect of moving at the speed of light means that a person would tear through the atoms within any matter between 'here' and 'there' causing a massive chain reaction that would completely obliterate 'here', and probably 'there' as well.

So as said by famed physicist lead singer of the goo goo dolls, "somehow Here is gone."

Not really.

[walkertexasdruid]

All right SithDarth, please explain it to us then.

[akaSM]

Ooo, is it Science Time with uncle Sith?

[Sithdarth]

Well for starters there is no possibility of traveling at the speed of light in flat spacetime. It's just not going to happen. The math and predictions of special relativity break down at exactly the speed of light. Quantities diverge leading to the prediction of zeros and infinities for things that should be observable which is impossible.

Closed time like curves are possible but only in curved spacetime. Properly curved spacetime allows for what is basically FTL travel. Basically you don't exceed the local speed of light in the bit of spacetime you are traveling through but you do exceed the speed of light in flatter spacetime some distance away. Tipler cylinders and Kerr blackholes are examples of solutions in general relativity with closed time like curves though people still dispute either their physical existence or that they are safely traversable.

Basically FTL travel is only possible in the context of general relativity and thus talking about it in terms of special relativistic effects like time dilation and length contraction is inappropriate. Besides that regardless of the whole time speeding back up thing when you slow down that doesn't necessarily mean that any difference in time accumulated would go away. If you could, and you really can't, travel faster than light in flat spacetime you really could travel back in time from the perspective of an outside observer. Unfortunately things aren't that simple.

So the take home is that no one is ever going to move through their local spacetime faster than light moves through their local spacetime. So there is no point in talking about what would or wouldn't happen. I mean the math of special relativity can deal with things that have always (and will always) moved faster than light but they basically look like a mirror version of sublight things and we can't even really prove their existence.

[RobinStarwing]

What about the hypothetical/theoritical Tachyon?

EDIT: Yes, well aware that nothing like this as been observed in nature but it bears asking.

[Sithdarth]

That would be this sentence:

I mean the math of special relativity can deal with things that have always (and will always) moved faster than light but they basically look like a mirror version of sublight things and we can't even really prove their existence.

Though to be slightly more clear what I mean by mirror version is that they travel backwards in time and might have negative mass depending on who you ask.

[RobinStarwing]

Originally Posted by Sithdarth

Though to be slightly more clear what I mean by mirror version is that they travel backwards in time and might have negative mass depending on who you ask.

Or because we have observed it, might then also be going forward in time + having positive mass/energy at the same moment it's traveling backwards in time while possessing negative mass/energy?

[Sithdarth]

Or because we have observed it, might then also be going forward in time + having positive mass/energy at the same moment it's traveling backwards in time while possessing negative mass/energy?

No superluminal particle has ever been observed. If anyone tells you anything to the contrary its probably faulty equipment. In fact I think all the physically possible Tachyonic theories require Tachyons to be impossible to observe in order to protect causality. Also, sometimes anything with negative or imaginary mass is called a Tachyon even if the actual propagation speed of the thing is less than the speed of light.

[RobinStarwing]

Originally Posted by Sithdarth

No superluminal particle has ever been observed. If anyone tells you anything to the contrary its probably faulty equipment. In fact I think all the physically possible Tachyonic theories require Tachyons to be impossible to observe in order to protect causality. Also, sometimes anything with negative or imaginary mass is called a Tachyon even if the actual propagation speed of the thing is less than the speed of light.

I was stating what would happen if we did try to observe it and succeeded. We wouldn't see it going backwards in time + having negative mass/energy. We would see it going forward in time + having positive mass/energy hence still preserving causality.

EDIT: To further add in, it maybe possible that the Tachyon transforms/undergoes a transition into all the other particles we observe. Hence, the very act of observing a Tachyon transforms it into other particles? This could mean the Tacyhon is the force carrier for Probability Wave Functions?

This is the ramblings of an idiot so don't take it too seriously. Just stating thoughts.