David Kipping

You could be, you know, if you had a warp drive or a time machine, essentially, you could be, you know, you could be very conscious and careful of the way you use it so as to not to cause paradoxes or just do it in a local area or something.

But the real fundamental problem is you always have the ability to do it.

And so in a vast cosmic universe, if time machines are all over the place, there's too much risk of someone doing it, right?

Of somebody having the option of essentially breaking the universe with this.

So this is a fundamental problem.

Hawking has this chronology protection conjecture where he said that essentially it's...

This just can't be allowed because it breaks all our laws of physics if time travel is possible.

Correct, yeah.

And so we'd need to rip up relativity.

I mean, that's the point is the current laws of physics.

So you'd have to rip up our current law of relativity to make sense of how FTL could live in that universe because you can't have relativity, FTL, and causality sit nicely and play nicely together.

It's certainly not the full picture.

There must be more to go.

Is that warp drives?

Yeah, you're basically bending space-time.

You could also do it with a wormhole or tack.

Some of the hypothetical FTL systems doesn't have to necessarily be the Alcubierre drive, the warp drive.

It could be any faster-than-light system.

As long as it travels superluminarily, it will violate causality.

Presumably, that will be observable with LIGO.