Do you think it will ever be possible to go back in time?

[bradrn]

Maybe time travel is more like going by train. You have to build tracks and stations before you can go somewhere. This could mean that you cannot travel to a point in time where time travel was not invented yet. Et voila, no time travel to our present.

This is precisely what our current theories predict. (In fact, Ares Land already mentioned this point earlier.)

[Creyeditor]

I must have missed that.

[zompist]

My main problem with the idea of time travel is that you wouldn't just have a few people trying to kill Hitler... ...you'd have hundreds, or thousands, or perhaps even millions of people trying to kill, or prevent the killing of, basically every major or minor historical figure. Time travel stories rarely ever seem to account for this.

In fact it's a well-used trope!

[Xhin]

My thinking is something like this:

* Going back in time fundamentally changes the entire universe from that entry point moving forwards. From that universe's perspective a bunch of matter/energy just appeared fully assembled out of nowhere, displacing the matter/energy that was already there. This is going to have enormous effects on that universe via the butterfly effect, long before anything the time travelers themselves do. Unless causality converges or "heals", which is a roundabout way of saying that time travel isn't possible because time travelers wouldn't be able to actually change anything.

* If time travel is real, and major historical events have happened without interference, then it's pretty safe to say that there just exist multiple timelines (or "will exist", or "will have always had existed"). Anything where a historical event was altered would be in a different timeline, not this one.

* So this is just the timeline that invents time travel. Time travelers go out and interact with different timelines, which are interactable by virtue of them time traveling (and possibly always existed). This happens in our future but doesn't have any effect whatsoever on us in the present because we're not in the timeline that has time travelers appearing out of thin air in it. The time travelers then return to their time, which still doesn't affect us because it happens in our future.

* This doesn't rule out cross-timeline jumping. I'd argue there that the reason we don't see anyone jumping into this timeline is because it's really boring -- what, your AI can't even draw hands? What a bunch of fucking noobs.