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
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
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 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.
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.
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”.
They wouldn’t; the expansion of space isn’t strong enough to change the distance between atoms; the force holding them together overcomes it.
They are not, that would require changes in the strong force.
Should have watched Tom Scott
that’s why you build it like a spaceship 🤷 ez
I hear police boxes and phones booths are popular as well.
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.
See, that’s a problem they always skip in time-travel movies.
At least in Doctor Who, the T.A.R.D.I.S. can’t teleport through space as well as through time, solving that problem. But most time machines don’t
Wow, I never thought about that.
Math is hard.
It’s even cooler if you remember we send something to the moon even with all this variables and no calculators humans were able to know where the moon would be
Of course the moon is relatively close but still
Also, the earth will never be in the same place twice. So it’s not even like you can only jump increments of a solar year.
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?
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.
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.
I always wondered about this
This blew my mind. All those movies!
So, Back to the Future’s a bunch of bullshit?!
That’s why doctor who works, its very clear about the fact that TARDIS travels in spacetime, it can do only time, only space or both space and time and they can get away with time traveling and still staying on earth
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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It’s possible to assume that the professor did the math.
But yeah any time machine would also basically have to have space travel built in to compensate.
They knew that when they wrote Dr Who (IE the time travel machine is called a TARDIS (Time and Relative Dimension in Space).
Nah, this thing with the planet moving under you is stupid because it assumes a fixed reference frame which is not a thing in our universe. Any movement is always relative to something. You can’t just “stay in place”. Having the Earth move from under you is very arbitrary.
Even if you assume any frame is valid, you have to pick inertial frames. So even if you travel few days, you will be off from earths orbit into space since earth is in circular motion which is acceletared
Yeah, these jokes always assume a jump back in time, not some sort of rewinding for just the traveler.
There’s a ton of issues with time travel. That could be one, but most fictional time-travel devices can be said to accommodate for the difference in distance. It would just be boring to explain on-screen.
It should be illegal to remind people (me, particularly) about Steins;Gate while they’re at work
I can’t be fucking crying on the clock, dawg
It’s just another problem with the mechanics of the snap at the end of Avengers: Endgame
Magic exists in that universe though and they’re using some of the most powerful objects in the universe. So like if it’s granting a wish, you just wish that everyone comes back to earth or whatever. It’s not even really a suspension of disbelief. It feels more silly to think that genius scientists using wish granting artifacts wouldn’t remember to account for the movement of the earth through space.
I cant watch that movie without thinking of all the unintended consequences. Pilots on planes snapped out, plane goes down, when pilot is snapped back, where plane use to be, but is now free falling.
Maybe they just end up in the plane where it is now. You’re overthinking it. It’s not a monkey’s paw and they weren’t using it with intent to harm.
I remember reading about this concept as a kid in a short story Neal Shusterman wrote called Same Time, Next Year. Blew my mind
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.
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.
I also think about this a lot.
Can’t they just float and follow the Earth? Or would it be too fast? What’s the terminal velocity of a ghost?
NGL, I don’t really feel confident assuming anything about the physics of ghost dynamics
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Glad I’m not the only one confused. Who’s talmbout ghosts
