Memes

It's a bit more complicated than that. One of the consequences of theory of relativity was the realisation that time and space cannot be separated and it only make sense to speak of "spacetime", a four-dimensional continuum rather than just three as we thought until that point. As far as I understand it, time is not really different from the other dimensions, it just seems that way to us.

I heard an explanation that has to do with entropy - the total amount of entropy is always increasing (I'm not going to even try to explain this since I only barely understand that myself) and the act of encoding information (whether we're talking a brain forming a new memory, a computer storing some data, or me writing this comment) is a process that always increases entropy, therefore any kind of memories can only be of things in the past rather than the future, and so every moment of our lives feels like "now", the boundary between the written and the unwritten. I don't think we're actually moving in time. It's just an illusion.

That said, while my earlier explanation is simplified and probably contains a ton of inaccuracies, I'm fairly confident it's accurate in broad strokes. This comment though, I'm not nearly as confident this is the current scientific consensus. Just what makes sense to me, so take it with a grain of salt.

If you're interested in stuff like this, I cannot recommend The Elegant Universe by Brian Greene enough. Unlike me he's someone who actually knows exactly what he's talking about and he explains everything much better than I ever could.