Can one get trapped in the space/time continuum?

pnrjulius | Certified Educator

At one particular point in the spacetime continuum? No. That point would have to be a singularity, and they either don't exist at all or exist only at the cores of black holes. (We're still fuzzy on that point because black holes are weird and we still can't get General Relativity and quantum mechanics to work together consistently.)

But can you be stuck in the spacetime continuum? Well, yeah; everything is! The spacetime continuum is just... space and time. If something is somewhere at some time, that thing is in the spacetime continuum. And as far as we know, there is no way to make something not in space and time. (Abstract concepts such as "algebra" and "liberty" arguably aren't, but they aren't exactly things, either.)

The reason we use "spacetime" instead of just space and time has been alluded to above; based on Einstein's theories of Special and General Relativity we now know that time isn't the same for everyone everywhere. My time slows down, from your perspective, when I move relative to you. (Your time also slows down relative to my perspective---both can work because we don't actually agree on what constitutes "right now"!) My time also slows down relative to you (and we both agree on that) if I am under stronger gravity than you. Both of these effects are extremely weak at normal speeds and normal gravity, but as you approach the speed of light or get near a black hole they become very important.

As a result of these effects, time isn't something that's constant across all observers. Neither is space, which also changes with motion and gravity. But spacetime, it turns out, is. If you define the distance between two objects in spacetime as the usual Pythagorean distance `sqrt{x^2 + y^2+ z^2}` with one extra term for time, this is an invariant "distance" (the spacetime metric) that all observers agree on: `s = sqrt{x^2 + y^2 + z^2 - c^2 t^2}`

To clarify, no, as far as we know, time travel is impossible. If it is possible, it's not simply a matter of going faster than the speed of light (which is probably impossible) or going "really slowly" (which doesn't even make sense). It would most likely require some sort of wormhole, a connection between two distant points in spacetime that would allow instantaneous travel between them. And as far as we know, wormholes are either impossible or would destabilize in a billionth of the blink of an eye.