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by nostrademons 3401 days ago
Out of all the branches of the space-time continuum, what's the chance that we are on the original one? Either we are improbably exceptional, or time travel is never invented. (This is the same argument as the "we are probably in a simulation", BTW.)

And if the past you visit is read-only, then you've invented history, not time-travel.
2 comments
Arizhel 3389 days ago
>Out of all the branches of the space-time continuum, what's the chance that we are on the original one?

None, because there's an infinite number of branches. And every time someone travels back in time, it creates a new branch.

What'd be interesting is to do an experiment to disprove this: invent a time machine that allows traveling both backwards and forwards in time. Use it to send two people back in time. Person A goes first, and the person B warps back to a time an hour later in the same place, and tells person A a secret. Then person B comes back, then person A comes back an hour later. Have person A repeat the secret, and see if they met each other in the past. With a new universe created every time someone goes back in time, will person B go back to the same new universe that was created when person A went back in time, or will they go back to the original universe that person A tried to go back to, and which still exists without person A which would change the course of history there? Does person B create a new universe? Will person A have met person B, and will they have seen person B go back to the future before them?

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krapp 3401 days ago
>Out of all the branches of the space-time continuum, what's the chance that we are on the original one?

It could be the case that time resembles a directed acyclic graph. Traveling "back in time" merely creates a new branch at a point on the graph in the past where that event (the presence of the time traveler) occurs, marking a divergence from the "original" past, in which where there was no time traveler. But you can't ever actually revisit your own timeline, forming a loop.

And, since every quantum interaction would create a new node in which all possible outcomes of that interaction are new branches (many worlds theory,) the concept of an "original" timeline wouldn't even make sense.

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