Ahummm, well actually, * adjusts monocle * time travel is not possible and since nobody has invented time machines yet, neither of these scenarios would happen in reality.
The time machine would use gravity so it can arrive at the same relative position in a different time. But that only gets you on the planet, not the same position on the planet.
How would rotational movement be accounted for in a generic way?
If the machine has the ability to jump in time and space (needed to land in the same spot) then it would be a real waste to use it only on earth.
So we would need a mathematical model of the entire universe that is accurate to the metre over all time. This N body is much harder than the 3 body problem.
Or we use gravity and other methods to track relative stationary position.
So, what other methods can be used to determine rotation?
So all travels to new planets require 2 jumps. One to get near and measure the rotation, and one to actually land. I’d prefer something more efficient.
Also there is the assumption that the surface rotational velocity is constant over time. This is only true for solid planets without gas or liquid centers. Insides can spin at different speeds than the surface.
When developing. You solve one problem a time. So you don’t spend time trying to calculate rotation from gravity.
The beauty of a time machine on earth. Is that we can imagine most of it, and add the time travel part with our imagination to make it “plausible”
You want to add instant teleportation to any point in space at any time, while knowing everything about every planet and star including their location. Instantly.
I have a magical spell that already does everything you want. It’s called “goannoyium-someoneelsium-fuckwad”.
You want to add instant teleportation to any point in space at any time, while knowing everything about every planet and star including their location. Instantly.
Teleportation is not being added by me. It’s the topic of this entire thread. Even calculating the rotation of just the earth at other points in time is not trivial because Earth has an unobservable liquid core.
I have a magical spell that already does everything you want. It’s called “goannoyium-someoneelsium-fuckwad”. I already solved your little problem
There is no space reference in time traveling only a time reference, the time traveler don’t change his start point, but the Earth and the whole solarsystem do. If you travel 6 month to the future, you are still in the point where you started, but the Earth will be on the other site of the Sun. A time machine must be a spaceship, otherwise you won’t survive. That is the error of almost all movies about time travel since H.G.Wells.
Kinda depends, doesn’t it? A travel that let’s you see glimpses of reality/earth implies you’re making smaller skips that may keep you somewhat held in place. Being able to establish a vector through time may also imply control of vectors in space.
Also, six months would likely take us farther than the other side of the sun. If we’re completely de-referenced we might be able to find a universal reference frame or some wild shit.
This is a huge assumption. Why is it necessary that time would not have a space reference? I’d actually say that based on relativistic physics there probably is a space reference because the dimensions are linked. I think it’s possible that the momentum of the current movement could remain constant and thus stick the time traveling device to the earth. Coming to a complete referential stop in space would require beyond immense energy and be inefficient if one only wants to travel in time
If you travel 6 month to the future, you are still in the point where you started, but the Earth will be on the other site of the Sun.
Why would you remain spatially locked to the sun? The solar system is moving around the milky way. The Milky way is traveling at around 370 miles per second if we use the universe as a frame of reference. A point is both a place and a moment. Everything is moving relative to everything else. Time travel is also space travel.
I mean, it’s the space-time continuum, it’s connected! As the documentary Stargate SG-1 shows, we’re well acquainted with spatial and chronological drift over interstellar distances.
the question is, what’s your frame of reference? if it’s the earth you’re good. if it’s the sun, you could presumably move forward any integer number of years because earth would be in the same place in its orbit relative to the sun (but try to move forward by a year and a day and you may have a bit of a chilling discovery about orbital mechanics). however, the position of our solar system (which, you’ll remember, includes the earth, the sun, me and presumably also you) is not static relative to the rest of the universe so if that’s your frame of reference then you’ll have to move in space and time instantaneously in order to move in time but seem stable in space to an observer whose frame of reference is the earth.
So either we would have to invent teleportation along with time travel/ have some sort of "magnet pad’ that must exist and not break at all times on earth, or its the time machine type where it just fast forwards everything around you until somehow you’re in a mall
I have yet to stumble across a sci-fi short story about space travelers finding an entire civilization’s worth of dead bodies floating round in space only to realize that they were all time travelers who only got part of the time traveling math correct. They figured out how to get through time but couldn’t figure out how to get through space, but since all their volunteers died, they never figured it out and just kept sending people to their doom.
something an awful lot like this happens with interdimensional travel in Pratchett and Baxter’s ‘The Long Earth’. The basic plot driver is humans discovering a way to travel to the different timelines predicted by the many worlds interpretation of quantum mechanics, and every once in a while as you’re bopping across dimensions from Earth to Earth you end up in a dimension or even a series of dimensions where, due to some sort of historical happenstance, Earthn’t.
There is a sci-fi short story whose name escapes me of a spaceship using some new FTL drive, but has largely been untested due to an impending doom. The math is said to be solid, however.
Anyway the drive powers up, and the spaceship jumps, and… all the crew and passengers are left behind, choking in space.
This. I like that Dr who actually has had this problem in universe. I don’t recall the episode, but he went to earth and ended up at the right time, but not the right place, since you know, earth is moving.
Even if you were to use the sun as a reference we orbit the sun (relative to the position of the sun) at some incredible speeds. Time of day factors in, since we’re rotating rather fast as well. So getting the right coordinates in space for a particular day, and a particular time in a particular year, for a specific place… Well, good luck.
Which isn’t to mention the fact that we’re in a galaxy, which is moving as well, so using a point of reference outside the solar system becomes insane to try and calculate; which is what you would have to do in order to enable travel outside of our solar system with something like a TARDIS.
Since relativity tells us there is no universal reference frame, then it having its reference tied to earth is perfectly valid.
Also sidenote: my favourite idea about time travel is that time travel is entirely possible, but will never be invented, because the timeline where its not invented is the only stable timeline. Because any timeline where it IS invented gets changed as soon as you use it, meaning the timeline changes over and over again every time time travel is invented repeatedly either infinitely or until someone accidentally creates a timeline where its never invented, only then does the timeline stop changing and we can actually experience it. So because we exist and can experience time, we can deduce that we will never invent time travel.
Yeah I think we don’t have to worry about it for the same reason why you don’t have to worry about getting thrown backwards when jumping in a moving train.
How much do you know about the “double slit” experiment and its subsequent variations? Because I think that’s a rabbithole you’ll enjoy. That first video is really just context; this next link is another video in that series, and this is the one that really pertains to the consequences of time travel: piped.video/watch?v=8ORLN_KwAgs
Rotational reference frames are out though! (Unless you want to deal with magic forces acting on your masses)
And since the earth rotates around itself and the sun, and the sun rotates around the center of the galaxy, you will always have to deal with a moving target.
Sure you can, but you need to adjust your position due to centrifugal forces all the time. A time machine would have to do that as well.
If a ball is flying in a straight line through space with a speed of 1m/s I can predict without much math where it will be at any point in time. In fact, if the reference frame is chosen such that the ball is stationary you don’t need any math at all, because the ball doesn’t move!
However, if you have a set of two balls orbiting each other you will always have to do math to calculate their position. I mean technically you could choose the reference frame that is rotating in sync with the balls. But still you need to do math to check that the centrifugal force, which is a real force coming from nowhere in this reference frame, exactly cancels out the gravitational pull between the two balls. Because rotating reference frames are not equivalent to each other!
I really don’t get why the time machine would have to do any calculations at all. The time machine is in this reference frame. You seem to assume that by going back through time you’d be teleporting through time, which leaves the open question of where you’d appear. However, I’d much rather assume that you’d actually be “going” through time. You wouldn’t cease to exist until you reappeared somewhere. Instead you’d be in the machine for some time until you’d get out of the machine again. That’d mean neither you nor the machine ever leave the reference frame.
There can be stable timelines with time travel - there’s actually 3 states:
Perpetual instability, where the timeline changes each time the time machine is used but never reaches the same state twice
Perpetual cyclic stability, where people’s actions in modifying the timeline lead to it eventually reaching the same state, eg. you go back in time to kill someone who becomes evil and oppresses you but the near death experience leads them capture you, so you can’t time travel any more, and to blame your people and start oppressing them, leading to the same actions
Stability without time travel, which is the default state but incredibly hard to get once time travel is invented as with nobody to stop time travel being invented it would probably get invented again, however parts of a cyclically stable timeline could have nobody having access to time travel, but any actions by time travellers to stop time travel would likely lead to the second rather than third option
I like the idea that time machines are like phones in that you need a receiver to pick up the signal. A consequence is that you can only travel back to the time that the machine was turned on.
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