Open Thread, November 1 - 7, 2013

witzvo

If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

The energy blasts as usually depicted break conservation of energy; with a bit of physics trickery you can get time travel out of that.

Wait, explain that? What is "a bit of physics trickery" here?

I know in HPMOR, Harry points out that violations of conservation of mass in magic imply FTL signaling, and I know from relativity FTL implies time travel, but Harry doesn't even consider running off to get time travel from common spells. Assumed turning the theory into practice would be far from straightforward.

Heck, it's not even obvious to me how you turn FTL travel into time travel in practice, if you don't have control over what frame of reference you're FTL in.

To make a time machine out of an FTL drive, simply travel somewhere at near lightspeed and FTL back. Now you're where you started, before you left.

2[anonymous]13y

In the approximation of the True Laws Of Physics which is in use today --- The Relativistic Standard Model --- FTL (and subsidiarily time travel) is nonsense. Like, it's gibberish. It is a description of a situation which not only does not happen, but which is a mathematical falsehood. It is impossible. It is like violation of conservation of energy, or violation of entropic developments. The maths plainly states that assumptions like that leads to a contradiction, and we do in fact know that the Standard Model is complete and consistent (i.e. cannot encode formulas as objects). Any hypothetical scenarios involving time travel will invariably be contrite, non-causal, and require classical mechanics. It is fiction, make of it what you will.