- cross-posted to:
- memes@lemmy.world
- cross-posted to:
- memes@lemmy.world
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This blew my mind. All those movies!
So, Back to the Future’s a bunch of bullshit?!
floating astronaut with pistol always has been
It could be explained as a time and space machine but just saying time machine is easier.
That’s how ive always thought of these things in my head.
but imagine if you could set it to the same time but different distance, it would allow you to teleport, that might be too strong.
Sounds like a good tech concept for a story
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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.
Or relative to the galactic center. That would put you even further off.
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
All of space is moving, you need to fix a reference point, there’s nothing to stop you making it earth
Earth frame isn’t inertial
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.
No, i am not assuming that. I was correcting you on ‘knowingly’ and ‘the sun rather than the earth’. When earth and suns position are relative to one another and can be calculated, therefore in a universal sense are both non-absolute, because as you correctly state, the suns position is non-absolute.
We can gladly discuss my assumption that we wouldn’t be able to tell a time machine what the position relative to the earth would be, as a time machine is in a universal sense rather than just earthly(?). Would that work like a rocket ship, starting form earth, going to places we can see from earth, or is it about dimensions the universe and so on?
Other than that you misunderstood my post.
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
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?
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
I don’t think we have a relative fixed point to go off unless you choose the centre of the big bang. It’s all relative to other things around us which are also moving lol
Isn’t everywhere kinda the center?
Effectively, yes
There actually isn’t a center of the big bang, every point is expanding away equally.
Here, that might be interesting to you.
I think you’ll run into the three body problem.
that’s why you build it like a spaceship 🤷 ez
I hear police boxes and phones booths are popular as well.
I remember reading about this concept as a kid in a short story Neal Shusterman wrote called Same Time, Next Year. Blew my mind
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.
I was under the impression that gravity was a constant force keeping the atoms closer together
More importantly it’s the electromagnetic force that keeps atoms together. Gravity only keeps planets and stars together and also solar systems and galaxies, but in ordinary objects it’s totally negligible.
“Weaker than Weak”.
Space itself is constantly expanding. Theories of the Big Rip predict the space between atomic particles could become vast enough to rip them apart.
The big rip concept comes into play when the expansion rate starts to become faster than the forces holding molecules and atoms together. As far as current cosmic expansion goes, it only applies to space between galaxies. The current expansion rate is so weak it’s not enough to overcome forces that hold galaxies together.
The big rip scenario happens in the case where the rate of space expansion is increasing. It’s possible, but we haven’t seen any evidence of it yet, so far the rate appears constant, which means a heat death scenario.
They are not, that would require changes in the strong force.
They wouldn’t; the expansion of space isn’t strong enough to change the distance between atoms; the force holding them together overcomes it.
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.
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.
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!
Classic sci-fi slaps hard
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And its not like there even is a same place. Position is relative, but to what in this case? Doesn’t even make sense
well it’s likely the big bang has a central point, no?
No central point there
Imagine the universe as the surface of a balloon. The Big Bang Theory stipulates that at one point, the balloon was extremely small, like a single point. But now that the balloon is bigger, you can’t find a particular spot on the balloon where that point was, because everywhere was that point. No matter where you are in the universe, if you turned back time and shrunk the balloon back down, you would be at the point of the Big Bang. Nowhere is closer or farther away from it.
would not the fact that blue shifted galaxies being rare, mean that in general all galaxies are red shifted from the perspective of all galaxies, thus they are expanding away from a point on a similar vector, and thus have a central point?
And a balloon does have a vector of direction: the mouth piece
would not the fact that blue shifted galaxies being rare, mean that in general all galaxies are red shifted from the perspective of all galaxies, thus they are expanding away from a point on a similar vector, and thus have a central point?
No, it means the opposite. They are expanding away from all points, because space itself is expanding. In fact, stars are able to move away from each other faster than the speed of light, which is only possible because space is expanding. Again, like the surface of a balloon, we can imagine that the further away two points are from each other, the faster they’ll move away from each other as the balloon expands, so even if there’s a certain maximum speed that you can move along the surface of the balloon, if two points are far enough away from each other the rate that distance is created between them can exceed that speed.
If there was a single, specific point in space where all the stuff came from, then we wouldn’t observe the same thing in every direction. Sure, we might see stuff ahead of us redshifted because it’s moving faster and stuff behind us redshifted because we’re moving faster, but we should also expect to see stuff to the sides moving alongside us at similar speeds that would not be redshifted. The fact that there’s consistent red shifting in every direction, getting more pronounced the greater the distance, leads us to the conclusion that space is expanding.
And a balloon does have a vector of direction: the mouth piece
It’s an analogy, don’t take it too literally.
It wasn’t matter that “banged”, it was space-time itself. We observe space expanding, and when we extrapolated backwards eventually we found the point when space-time (not necessarily the stuff inside it) was just a single point, and we called that point “the big bang”. That’s just what the current math says of course, but because of the rate of expansion and the speed of light, we can only observe so much of the universe, past and present. Even when we observe far out and way back to soon after the big bang, we don’t see it all, our scope is limited even within space-time. And from what we can observe, nothing indicates a center. For all we know, there isn’t one, just like you can’t paint a dot on the surface of a ball and call it the center of the surface, every point on the ball’s surface has equal claim to that. In that situation relativity is all that there is. Unless there’s a massive breakthrough, it’s looking like the laws of physics won’t permit us to know if a center exists, let alone find it.
Oooohh. Thanks for the tip, just added that into my time travelling port o pottie’s destination algorithms. Gotta respect the earth be moving and shit.
Also ghosts likely wouldn’t be affected by a gravitational pull, so the concept doesn’t make sense and there’d just be a trail of ghosts in space.
What is this comment in response to?
Glad I’m not the only one confused. Who’s talmbout ghosts
NGL, I don’t really feel confident assuming anything about the physics of ghost dynamics
It’s just another problem with the mechanics of the snap at the end of Avengers: Endgame
See, that’s a problem they always skip in time-travel movies.
You’ve got to entangle the same machine first over a massive macro quantum space-time superposition.
See, you get it.
I always wondered about this
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.
