Simple question. If you are on earth, say, and you go back in time, where do you end up? Are you still on earth? Because think about it. Earth is nowhere near where it was in in space, even a couple of moments ago.
And you can also see, I trust, why this then contradicts Einstein’s theory of relativity. Einstein said everything is relative. Space, time, velocity. If there is in fact absolute space, in this example, doesn’t that contradict Einstein then?
There is no factual answer to this question. As you’ve noted, the earth would not be in the same place if you magically transported back in time. But you can’t go back in time, so you won’t “end up” anywhere.
Your time machine will have to adjust for relative distance in space. If it can do that, then it would adjust for Time and Relative Distance in Space.
TARDIS seems like a catchy name.
ETA: Dangit, I just looked it up and the D is Dimension
What special relativity actually says is that space and time are inextricably interlinked. You cannot discuss two objects being separated in space without also considering their separation in time.
If they have solved how to travel backwards in time I am willing to bet they solved the travel to where you need to be in space too.
Just a WAG though.
Maybe it is like a balloon. It was once thought you could travel across the earth by rising in a balloon and letting the earth rotate under you. Come back down and you are in a different place.
Obviously it didn’t work like that. Maybe time travel is similar. Move in time but stay over the same spot in space even though that spot is moving. I have no way of testing that though but if you can I would be interested.
This was a plot point in a Superman comic episode, long time ago.
Of course, Supes can travel back in time by flying really, really fast.
And no-one ever raised the issue of how he stayed on Earth when he did that, considering Earth would be in a different position.
Until this one episode, where somehow he was put under a hex, or an alien space-warning, or something, that he couldn’t leave Earth.
So what does Supes do? He travels back in time, and explains in his thought bubbles that this time, he’s not going to make the routine adjustment he normally makes to his flight path to stay on Earth.
So he travels backwards, and when he comes out in the past, he’s no longer on Earth, because it’s in a different location in its orbit than it was when he left the present, but he didn’t leave the Earth, it left him, so he didn’t break the hex/alien curse/weird plot McGuffin. He didn’t leave the Earth; it left him.
Since discussions of time travel usually proceed along the lines of, “orbit your rocket ship around a nearly infinitely long massive cylinder made out of ???”, navigating back to the Earth should be a doddle by comparison.
The cylinder? Depends what you are doing, but e.g. the length measured along the axis, the radial distance, the angle, and a timelike coordinate.
I have yapped this a few times.
Time does not exist as something like mass, energy. It is not some physical thing that can be detected in itself or captured and put in a container. Time is a perceived thing. It is derived by us, who have memory and instruments that operate in the increments we design them to.
If you impart X amount of force to Y amount of mass, it will begin to move. It will then have some amount of kinetic energy. You did not add or subtract time to it. Somewhere out there is a thing that the mass may now hit. For us, with our ability to conceive the number of intervals of our timing devices, we can say it will take Z number of years for them to collide. But time does not matter. They are now destined to hit. It was mass, energy, angle of energy imparted that was real. Time is not an issue.
Time is always arbitrarily measured by us. Mass and energy are not arbitrary.
To travel back or forward in time is impossible, unless you have a device that can reverse or increase the velocity and reactions of all things in the Universe. For instance, push all the energy produced by the Sun back into it in a year, to travel back one year. All that energy is not existing forever in some weird static place in the Universe, waiting for you to come back and visit it.
Four dimensions, x, y, z, and t relative to a known reference point, such as the time machine itself. I don’t think coming up with a coordinate system is a problem, it’s how to travel in the negative direction on the t coordinate that is the problem.
The easiest way to make a time machine requires that you only make half of one. What you do is make a wormhole time machine where you make one half of it here and now and then the other half sometime and place in the future. You then jump through the future bit and come out the past bit. All you need to do is make the first half of it and if you suddenly jump out of it, you know the other half must get made somehow and you don’t need to bother with doing it yourself.
Yes you can use speed and the relativistic effect to do that.
But I was replying in the concept of a static time machine concept.
Also. In ways which my math limited knowledge cannot explain. It also comes down to applying energy, not time.
Also.
You are just applying extra energy to your local system, to get ahead of the energy mass interactions of other systems. But… does your system now change a little bit of the systems around your flight?
I am not clear on the functional reality of mass of you traveling at relativistic speeds, to the area around you.
So are you just traveling forward in time? Or altering time on the way.
Slowing your own time of course. Not moving forward.
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