What are the reasons we think we can only move in one direction in time?

Question

I recently was told that we know there’s only one time dimension because otherwise we’d pivot between different dimensions of time, as we are able to do in space. But I still don’t understand, other than paradoxes and causality, why we can’t move backwards in time.

Even on a 1D spatial plane [edit to say yes… a line, not a plane.] we would be able to move forwards and backwards.

But we can’t with time. Why?

In: Physics

Answer 1

You’re not moving AT ALL in time. You’re riding the “present”, like the rest of the universe. You don’t have any organs (like legs) or devices (like cars or rockets) that would allow you to actually MOVE (to the future or to the past) independently of what the universe is doing. It’s not like space, where you CAN move because you have legs / spaceships.