@freemo You can't come out the other end of a machine that doesn't exist yet.
@freemo The delorean method, maybe, but the terminator method seems exceedingly unlikely.
Even so, the only way it could possibly exist is with each travel backward forming a new timeline.
If there was only one timeline, then time travelers in our past or present would definitely leave some pretty obvious clues (hyper-resistant future illnesses, for one), even before you consider the timeless human need to be a shithead.
@freemo Also, I have a separate concern with both methods: What happens to the matter that used to be where you appear? When it's just air, nobody thinks about it, but landscapes change over time, so it won't always be just air.
I feel like we would have seen some time travelers fossilized halfway into a mountain by now.
@LouisIngenthron A portal would , it is a 1d surface that weakly interacts, by crossing through the portal you displace the air on the other side as you normally move.
@freemo Do you mean 2D? Struggling to picture how you'd cross a 1D barrier.
@LouisIngenthron sorry yes 2D
@LouisIngenthron That makes the assumption that a machine must exist on the receiving end at all.
Two counter possibilities... 1) your timemachine moves through time with you, like a car it doesnt need to exist at your destination 2) it "throws" you into the past, you just land there, with no machine anywhere to be seen. A bit like getting shot out of cannon.