Hi guys. Ever heard of a stasis box?. Like time travel, it's science fiction, but conceptually it's just a glorified refrigerator, and it tells you something important about "time travel".

No motion occurs inside a stasis box, so when I put you inside one, electromagnetic phenomena don’t propagate. So you can’t see, you can’t hear, and you can’t even think. Hence when I open the door 5 years later, to you it’s like I opened the door just as soon as I closed it. As far as you're concerned, you “travelled” to the future. But you did this by not moving. It wasn't you moving, it was everything else.

Ergo if you travel to the future by not moving, you aren't really travelling forward through time, hence there's no way you can travel backwards in time. For that to happen everything else in the universe would have to be subject to negative motion. And there's no such thing as negative motion. Motion is motion. You can reduce a rate of motion to zero, but you can't keep on reducing it.