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time to think (lemm.ee)

submitted 23 hours ago by [email protected] to c/[email protected]

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[–] [email protected] 4 points 9 hours ago (1 children)

They could have forgotten about the position setting all together.

You're assuming that the time machine would just change the time and keep the position but there is no absolute reference frame, so the time machine should use some reference frame in which it keeps the position constant. It would then be common sense to have the time machine keep the position relative to the earth. Anything else would be pretty dumb, unless you want to use your time machine also for space travel to other planets.

why the suns position

That was just an example. It's either the sun or the center of our galaxy, or some other reference point so if it wasn't the earth then the sun is the next most logical option.

[–] [email protected] 7 points 9 hours ago (2 children)

What you're describing is a machine which moves both in time and space. A machine which only moves in time would result in this meme no matter how you twist it.

[–] [email protected] 1 points 2 hours ago

We can't really say that for certain. The word "space" as we know it means nothing without the idea of relativity. Earth orbits the sun, the sun orbits the center of the Milky Way, which exists in a nest of clusters and super clusters ... and then you get to the edge of the visible universe. My point is, if a universal frame of reference exists, we haven't found it. "Absolutely stationary" isn't something we can test for. Everything that we can observe appears to be moving around something, so can we even responsibly assume that there is a universal frame of reference? Or is it safer to assume that relativity all that there is (i.e. space-time has no boundaries)?

[–] [email protected] 1 points 5 hours ago (1 children)

please explain to me how do you think being stationary in space works?

[–] [email protected] 2 points 2 hours ago

There are two ways of looking at it.

The time machine is using itself as a point of reference to comply with general relativity. The only way to time travel is to move forward in time. The way to move through time would be to move a lot faster than the Earth, so that every minute for you inside the time machine would equal to many years for earthlings. And if you're moving that fast you'll fly away from Earth.
The time machine somehow has a knowledge of the whole universe, this way a Newtonian model applies and an absolute point of reference exists. That allows unrestricted travel both forwards and backwards in time, but that also means that the Earth will inevitably move from under the machine to follow its path across the universe.

No matter how you twist it you'll end up all alone in space. You need a machine which can move through both time and space at the same time.