time travel.

[Benny2guns]

i think as altezon does. the multiple time line theory but a slightly different.

if we travel in time we go to a new time line. when we go back we go back to a new time. after that we go back and forth along the two time lines that allow time travel.
A because in the first time people come to it from the past and
B in the second time line people travel from the future.
we actually only need three time lines.
this one to start from. one go back in and one to go forward from.

i say the other two because we know of no one going forward from here or coming back from anywhere else.

So that would imply that we do indeed know of someone going back to a previous line from this line. Do we?

nope. those who leave here go to one time line those who leave there go to another time line. both which are timelines where t/travel is possible.

when someone leaves here, they possibly cease existing to us.

It's possible but my idea, not mine really, lol, is more plausible to my mind. I really believe we will find there is truth in one version or another of it.