Yeah but traveling in space takes time, so you can reason that traveling in time takes space.

So you're saying that, if you're traveling in space it seems like you could travel in time at the same space.

I think that's the joke. Media presents time travel as just inputting the date and off you go, but really you need to input time AND space because the two are interconnected.

Of course we could just imagine that all time machines somehow calculate the space itself just by knowing the current spacetime and the inputted time, but now we're giving writers too much benefit of doubt. In most cases time travel is used as plot device and very little thought is given to how it could work.

And an interesting sidenote. This also means that teleportation is a special case of time travel and if you've solved time travel you've probably also solved teleportation.

If they were really the same thing, traveling into the past would be trivial. Greg Egan's Orthogonal series explores the consequences of space and time actually being the same thing. You can also the the difference in formulas related to proper time, where terms for space and time have opposite signs. Space and time have the same relationship to each other as real and imaginary numbers, in a fairly literal sense.

What is time, if not curvy space?

So to travel into the future and be in the "same place" relative to your planet you'd need to solve the n-body problem for at least your local system to a suitable length of time. A slight error might mean you appear inside the planet or in outer space.

Or maybe I don't understand this stuff. :-)

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 prefer the H.G. Wells The Time Machine style of time travel , where you affect the flow of time instead of a discontinuous jump.

You're still attached to your current location, things just happen faster (in forwards or reverse). It also means that time travel takes time, which can be a handy plot tool.

Edit: grammatical swipe keyboard errors

Primer is one of my favourite movies ever. It was made on a budget of 3 peanuts and pocket lint, and it shows, but damn it's an interesting premise.

Great movie. I enjoyed the lofi feel of Primer as it handled a really fun concept.

I'm traveling forward in time right now.

Imagine building the first receiver, and immediately have 20 people spawn within the same space

You may enjoy Ted Chiang's The Merchant and the Alchemist's Gate, the short story.

The whole book is great if you like thought-provoking sci-fi premises I guess: https://www.goodreads.com/en/book/show/41160292

Rescue peepo from the nazis next.

Yeah, or if the time machine is genuinely a teleporter, then the invetor should at least know how to correct for drift.

That's probably the guy that offered people a few dollars and a chair to watch all of earth's history.