system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 If time is a dimension, why can you only go in one direction?

I get that there are 3 dimensions of space and only one dimension of time, but it still seems like you should be able to go both forward and backward. It's like if you had a 1-dimensional space (which I assume would be an infinitely thin line, correct me if I'm wrong) you could still go both left and right.
gpt
We have yet to find a solid, physical explanation for it. All of the laws of physics we know work equally well in either direction so as far as we can tell nothing prevents it. It just... doesn't happen in any way we've observed.

The closest we can come is the observation that entropy in a closed system always increases. If you went backwards in time then the entropy would decrease, which violates the Second Law of Thermodynamics. There's a big gap between that and really understanding why you can't go backwards in time though (or even being entirely certain that you can't).