Time travel doesn't work unless you also have teleportation. If you travel to the past/future, Earth will be in a different position in its orbit, and you'll die in space.

Alternatively teleportation doesn't work unless you also have time travel

In a different position relative to what?

Space and time are the same thing. Spacetime. Time travel would necessarily also by teleportation if you are traveling instantaneously through spacetime. Unless of course your travel is continuous like it is currently for all of us, just sped up, slowed down or reversed.

Also there is no objective point of reference for location in the universe, only relative points of reference. In other words, you are always some distance in some direction from some thing. But you never have objective stable coordinates relative to the universe itself. There is no "center" or other fixed point of the universe. So the earth is moving, yes, but only relative to other independent celestial bodies. And those bodies are moving, too, relative to other bodies. Their movement is always relative to a non-absolute frame of reference. No movement is objective to the universe, it's all relative.

So it would be illogical to expect the earth to have moved X miles away in Y direction if you teleported one second into the past/future because that would presuppose that your location was objective and absolute in the universe at the point of time traveling and the earth moved relative to your absolute location. It would break known physics if that were the case, as much as time travel itself would.

What sort of universal reference frame do you seem to be assuming? All location is relative to other things, and keeping your location relative to, say, the Earth would be a lot more convenient that making it relative to some arbitrary star or something.

Space is full of time travelers that forgot to include the Zed access into their calculations.

I get that people just refer to them as time machines, but they're actually space-time vehicles.

Before your first journey, you calibrate it to a reference point (mine already had Earth mapped out, with a gravity well depth monitor as a fail-safe) so that you lock your target coordinates in space and time.

But no, it's not teleportation. You're still just travelling to your destination, you just get there as quick as you want and without the need to be disintegrated.

You just need to maintain a relationship between Time And Relative Dimension In Space. 🟦

Tell me you didn’t pay attention in Spatial Distortion as Applied to Time Dilation class without telling me you didn’t pay attention in Spatial Distortion as Applied to Time Dilation class.

Just want to leave it here

That's correct. But if you've figured out how to travel through time, traveling through space should be easy.

Also, be sure to wear a hazard suit so you don't die from any ancient/future diseases your body has no protection from.

You're obviously the main character in this simulation so it's much more likely that all other coordinates are derived from your position in the simulation engine.

That’s why I always liked approaches that use a physical machine that has to stay in one place for an extended period of time. Quantum Break’s hard sci-fi approach to this was fascinating and kept making me reconsider how the time loop worked. Highly recommended for time loop nerds like me.

What if it works by reversing/fastforwarding time outside while preserving things within the time machine? Then as long as the time machine is grounded to the earth it would move with it

Forget the orbit... remember the song...

https://genius.com/Monty-python-the-galaxy-song-lyrics

"Just remember that you're standing on a planet that's evolving
And revolving
at 900 miles an hour.
It's orbiting at 19 miles a second,
so it's reckoned,
The sun that is the source of all our power.
Now the sun, and you and me,
and all the stars that we can see,
Are moving at a million miles a day,
In the outer spiral arm,
at 40,000 miles an hour,
Of a galaxy we call the Milky Way."

A wormhole type time machine would leave the travel points A and B physically independent of each other. This opens up the option to change destinations... step in at New York, exit in San Francisco.

This is interesting because the most "realistic" (i.e. still not realistic) depictions of time travel in fiction involve travelling through a singularity or wormhole. So you probably have to be in space to start with, but also both ends of the wormhole have mass so they can be orbiting a planet or star and stay within a stable distance of it. It solves this particular problem (just leaving the other usual problem of causality!) It also proves your point since it does allow travelling in space, in fact it allows travelling faster than light.

I think the converse is true as well, that if faster than light travel is possible then time travel must be possible, at least if you take relativity at face value. As others have pointed out there's no universal reference frame, and for any journey that is faster than light in one reference frame, there is another frame in which the journey goes backwards in time.

All my childhood i was scared about being stuck in a building that was there back then. If i knew that was my smallest problem i would have scratched that idea long ago.

That's why they used Delorean.

Yep, and not to mention the position of our solar system in the Milky Way or our galaxy in the local cluster. In fact, without a specific reference frame you would have to make corrections very rapidly for even a tiny jump in time.

Well, it depends. I mean the original story "The Time machine" I think very deliberately had a machine that was on the ground. I guess if you're "travelling" through time then you could follow your local location in the same way you do when it is moving forward at the normal rate.

The argument is more true for time machines that instantly move through time, like back to the future. Since yes it would need some way to account for planetary movement.