Time travel can't change history

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Originally Posted by Chuck

If the past can't be changed, could anything I do while visiting the past be considered to be unethical? If someone was shot dead at noon yesterday and I decide to time travel back and become the shooter, I didn't cut his life short. I'm just discovering that I pulled the trigger. If I decide not to time travel at all it just means that someone else did it. If the past can't be changed, no decision that I make now can have any effect on it and would be irrelevant, not unethical.

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Be a heck of a way to find out the theory was wrong! You'd be stuck in the Biff Tannen timeline with a murder rap dogging you.

There were possibly 42 assassination plots against Hitler. Maybe the time travelers finally got him in the bunker.

This is known as Hitler's Time Travel Exemption Act
https://tvtropes.org/pmwiki/pmwiki.p...elExemptionAct

While the paper is beyond me, the premise seems in my limited understanding to be, that a macro-scale human time traveler is subject to quantum laws rather than classical laws (I'm way oversimplifying) but that there's only one history to alter.

To me, all that's not a given. Many of the starting precepts of the scenario are not givens.

Even assuming for the sake of argument travel into the past could happen, the question as in fiction seems to come back to "how do the rules of time travel work in your universe?" Which is hardly clear even to the world's best physicists.

I can only see 3 logical scenarios that make any sense to me, and 1 that maybe possible but totally inconceivable.

1. Your example, where history is being changed constantly and we would/could never be aware
2. There are infinitely many universes and each event splices into another version, so that all that can happen does happen
3. Time travel to the past is impossible, therefore historical events cannot be changed
4. Time is not directional, in that it doesn't really "flow" into the future as we perceive. Therefore changing events: past, present and future would be feasibly possible.

My current opinion is that number 3 is the most likely scenario. I have yet to see anything to convince me otherwise, though new discoveries in the quantum world may change my view.

I'm also on number 3. Until any solid, tangible evidence says otherwise, there's no such thing as time travel into the past. It's a fantasy born of regret and imagination. "If only..."

3 for me as well.
But it's still fun!

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Originally Posted by nota

two things

one the current location of the time traveler is not the past location one wishes to be at
the earth moves as does the sun and the galaxy a LOT over long periods so one would need a space ship with a time machine

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There's no absolute reference frame in space. All motion is relative to something else.

So you can use the Earth as a reference point for your "time travel", and thus avoid popping out in empty space. You'd just have to make sure your wormhole doesn't open inside the planet.

Maybe the microwave background (or neutrino background) could be the reference frame?

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Originally Posted by Tom Mazanec

Maybe the microwave background (or neutrino background) could be the reference frame?

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Would that be better than using the Earth as a reference point? With a solid fix centered on Earth, at least you know you'd arrive in the vicinity of a livable planet. One small error in CMB calculations and you could materialize across the Universe, most likely in an intergalactic void. Navigating back from that might be... problematic.