this post was submitted on 13 Mar 2025
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[–] OhHiMarx@lemmygrad.ml 1 points 1 hour ago

This is not how general relativity works at all. If your coordinates are set to a spot on Earth (or some spot relative to Earth), you will appear at that same point. Spacetime exhibits something called diffeomorphism covariance which is a fancy way of saying you'd have to go out of your way in the dumbest way possible to get this outcome.

[–] MoonMelon@lemmy.ml 10 points 9 hours ago (2 children)

I was surprised when I read the OG time machine story by Jules Verne and this was a main plot point, and only later stories hand-waived it. You'd think it was something from later analysis of the idea. Almost like that Verne dude was clever.

[–] Bittle@lemmy.world 4 points 9 hours ago (1 children)

Clark Ashton Smith wrote a similar short story where the inventor failed to take it into account. Upon realizing his mistake he decided to just wait for another planet to reach him, turning his time machine into a spaceship.

[–] brognak@lemm.ee 3 points 9 hours ago

That's actually a fascinating idea. All interstellar travel is based on the movements of the planets through space time. I bet it alternates between being technically faster and slower than FTL travel since you may have to wait for a time when your destination to pass into the planets past location.

Wow that's a fun thought hole. Constraint certainly breeds creativity!

[–] AbsoluteChicagoDog@lemm.ee 1 points 9 hours ago

Classic sci-fi slaps hard

[–] FatsoJackson@lemmy.ml 13 points 13 hours ago (1 children)

that's why you build it like a spaceship 🤷 ez

[–] zod000@lemmy.ml 9 points 10 hours ago

I hear police boxes and phones booths are popular as well.

[–] polycrome@lemmy.world 2 points 9 hours ago

One way to resolve this is to have some kind of multiverse theory where you don't travel back in time to your universe, but to a narrow slection of parallel universes that are also shifted slightly so that it spits you out in an analogous location to your initial departure.

[–] stebo02@lemmy.dbzer0.com 30 points 18 hours ago* (last edited 17 hours ago) (3 children)

Position isn't absolute so if this happens this means you knowingly made the time machine memorize position relative to e.g. the sun rather than the earth.

[–] AngryCommieKender@lemmy.world 3 points 10 hours ago

Or relative to the galactic center. That would put you even further off.

[–] klay@lemm.ee 5 points 17 hours ago* (last edited 17 hours ago) (2 children)

incorrect, that is not what this means. They could have forgotten about the position setting all together. Also why the suns position? it is also moving and non absolute, just like earths. Makes no difference in this meme

[–] 1rre@discuss.tchncs.de 5 points 12 hours ago (1 children)

All of space is moving, you need to fix a reference point, there's nothing to stop you making it earth

[–] mexicancartel@lemmy.dbzer0.com 0 points 9 hours ago

Earth frame isn't inertial

[–] stebo02@lemmy.dbzer0.com 5 points 17 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.

[–] Aux@feddit.uk 6 points 17 hours ago (4 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.

[–] Fluke@lemm.ee 1 points 7 hours ago* (last edited 7 hours ago)

That isn't possible. Time is as part of space as the other dimensions. Time is distorted by mass, just like space.

You can't move "purely on the Y axis" any more than you can move "purely on the time axis", or vice versa.

Off topic: Why is it a new idea that the observed motion of the universe around us is affected by "faster time" in denser areas of space? Why is that not blindingly obvious? Bwuh?

[–] 0ops@lemm.ee 0 points 9 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)?

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[–] mexicancartel@lemmy.dbzer0.com 0 points 9 hours ago

Tine machine probably moved in its own inertial reference frame. That will actually get you lost in space because the inertial frame does not orbit around, which involves rotation(rotation is intrinsically non-inertial, i.e accelerating). Time machine's frame will be moving in a straight line if its inertial

[–] OddButNotReally@lemmy.world 14 points 20 hours ago

I remember reading about this concept as a kid in a short story Neal Shusterman wrote called Same Time, Next Year. Blew my mind

[–] Pilferjinx@lemmy.world 4 points 16 hours ago (1 children)

You've got to entangle the same machine first over a massive macro quantum space-time superposition.

[–] TokenBoomer@lemmy.world 2 points 10 hours ago

See, you get it.

[–] surph_ninja@lemmy.world 15 points 22 hours ago (8 children)

If space is always expanding, I’d really like to know if a time traveler would experience issues existing in a universe where the space between atoms is different from the one they left.

[–] MonkderVierte@lemmy.ml 3 points 12 hours ago

They are not, that would require changes in the strong force.

[–] BrainInABox@lemmy.ml 3 points 14 hours ago

They wouldn't; the expansion of space isn't strong enough to change the distance between atoms; the force holding them together overcomes it.

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[–] nucleative@lemmy.world 17 points 1 day ago (10 children)

I know we're in a meme community but this did get me thinking... Not only is the Earth spinning but it's also in an orbit around the Sun which is also orbiting around the center of the Milky Way which is moving through space relative to other galaxies and so on.

Do we have enough information to calculate a position in space in the future for Earth without a fixed reference other than current point?

[–] mexicancartel@lemmy.dbzer0.com 15 points 19 hours ago* (last edited 13 hours ago) (12 children)

That's what einstein said. There is no fixed reference frame, but only relative ones. Every "inertial"(meaning, motion without any external force) frame of reference is equally valid as any other inertial frame movibg with respect to it.

But for sure we can tell earth's orbit is not inertial since circular motion occur, which is due to external force of gravity.

Edit:typo

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