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.

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.

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.

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.

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.

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.

Just want to leave it here

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.

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

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.

I think it might depend on how the time travel is achieved. We all assume you're just instantly pooped out in your destination time but if you have to actually travel through time, it might be like just putting everything in reverse, and so you'd move alog with the earth as you move backwards through some kind of time tunnel.

Think Donnie Darko and not Looper.

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