> basically make people whatever age I want by varying my speed.
No more so than making the Earth change shape by moving your physical location.
> Since the same 1 hour passes for me no matter the age for them I chose, it seems like I'm selecting an already existent future from a stack, not fast-forwarding the present I left.
Yeah these are more philosophical questions rather than a testable hypothesis. It’s an interesting way of viewing the world, but if you’re talking about a future “existing” scientifically and materially in concert with the present, then you’d need to devise an experiment to be able to enter or interact with that future beyond just waiting for that future to exist.
Otherwise time travel isn’t even necessary for this thought experiment. You could say the morning already exists and fall asleep and wake up and boom it’s morning time. But in reality all of the ticks of time happened between when you fell asleep and when you woke up, you just weren’t able to observe all of them at the same speed as someone who stayed awake all night.
You can even make this clear in the "leave Earth in a fast ship and return" scenario - have the people on Earth send you a birthday card by radio every year that you're away, on your birthday in their reference frame. You'll receive those ticks of time as you travel (most of them on your way back).
> basically make people whatever age I want by varying my speed.
No more so than making the Earth change shape by moving your physical location.
> Since the same 1 hour passes for me no matter the age for them I chose, it seems like I'm selecting an already existent future from a stack, not fast-forwarding the present I left.
Yeah these are more philosophical questions rather than a testable hypothesis. It’s an interesting way of viewing the world, but if you’re talking about a future “existing” scientifically and materially in concert with the present, then you’d need to devise an experiment to be able to enter or interact with that future beyond just waiting for that future to exist.
Otherwise time travel isn’t even necessary for this thought experiment. You could say the morning already exists and fall asleep and wake up and boom it’s morning time. But in reality all of the ticks of time happened between when you fell asleep and when you woke up, you just weren’t able to observe all of them at the same speed as someone who stayed awake all night.