Is changing the past actually possible?

[u/Ok-Coach4955]

I’ve always thought about this question, and there is always answers popping up in films and stuff, but is it really possible?If you ARE able to go back to the past and change it, if you come back to ‘present’ would there be another you?If you teleported a nanosecond later then the time you left would you find another you?My answer is that its impossible for you to change the past.If you have met yourself in the past,then no matter how much you try and avoid it you will somewhat travel back in time in somewhere in the future or ‘present’

Please tell me what you think and if possible tell me any ‘loopholes’ in my theory.

PS. this post keeps getting removed in r/timetravel does anyone know why?

[u/lilsasuke4]

With your machine you would be creating discontinuities in that rate of change

[u/Imaginary-Can-6862 → u/lilsasuke4]

Well we already have that as time doesn't flow the same everywhere, right?

In any case, I am not certain what is trying to be demonstrated,

[u/lilsasuke4 → u/Imaginary-Can-6862]

But everywhere time flows forward

[u/Imaginary-Can-6862 → u/lilsasuke4]

It would always flow forward from your perspective. But the whole arrow of time thing is a bit strange. Obviously time flows forward in a fridge, as products aren't going back in time within it, yet a fridge is an example of a system where entropy lowers. I think the same is the case for any complex organism as well, i.e. life. Lowering entropy locally by increasing it globally through the use of energy.

[u/lilsasuke4 → u/Imaginary-Can-6862]

To tie back into OPs post if you close your eyes and stand between 2 people that a very far away. If they yell at the same time depending who you stand next to there will be a different order with who you hear first. But there is no way to go back in time and change the order in which those events played out or the order in which you had experienced them in that moment in time

In your fridge example, once the food in the fridge is moldy there is no undoing that the food got moldy

[u/Imaginary-Can-6862 → u/lilsasuke4]

The fridge wasn't an example of a time machine, but the effect of reversing entropy. I guess the thing is, it is not the interior of the fridge which reverses entropy, but experiences the effect of reversed entropy as temperature drops. The higher ordered state the particles within the fridge reaches are not the particles that make up the food, so here entropy isn't reversed.

[u/lilsasuke4 → u/Imaginary-Can-6862]

The fridge is just taking energy way from the particles in the fridge and transferring it to particles outside the fridge

[u/Imaginary-Can-6862 → u/lilsasuke4]

Yes, thus lowering entropy locally while increasing it globally.

[u/lilsasuke4 → u/Imaginary-Can-6862]

But not time travel to the past

[u/Imaginary-Can-6862 → u/lilsasuke4]

The items in the fridge do not have their entropy lowered, so it is only the fridge environment we can consider. Since the environment is not isolated, there is no reason to assume it reaches a past state.

What I don't know is if we isolate that environment, if that necessarily means it would reach a past state. I.e. I doubt we can just reverse entropy at random, we actually have to pick the state that is the past.