we live in an explosion

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?

Couldn't this be solved even if they weren't linked by just flickering in and out of phase or whatever to keep gravitationally relative with the earth

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. :-)

Time and Relative Dimension in Space, you say?

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

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.

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.

You might have better luck and accuracy using our galaxy' s black hole for reference marker depending on how much time you intend to traverse

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: https://piped.video/watch?v=8ORLN_KwAgs

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.

Same with The End of Eternity - they can travel to different times at which the machine existed.

In fact, isn't it a bit similar with the only 'real' possibility of time travel - you create a wormhole and take one end on a relativistic journey to create a time difference between the ends, but the only possible travel is between the two ends that you have created.

The name TARDIS is literally the solution, "Time And Relative Dimension In Space".

I feel like the scientists smart enough to invent time machines would have thought of that

I'm traveling forward in time right now.

I thought it was possible in relativity if only you could solve that pesky going faster than light problem. Only going to the speed of light is impossible. If you were to start out beyond the speed of light you should be traveling backwards in time. Mathematically that should be possible.

if you believe in the notion that the universe is cyclic then you can mimic time traveling backwards by traveling forwards, past the end of the universe, and stopping at just the right time in the new universe.

e.g., to get to 1700 you’d go (present time) -> (death of the universe) -> (1700 in next universe)

You need to add dimensions and relativity.

We are all space machines on this blessed day

🤯

Rescue peepo from the nazis next.

Hence how the artist was able to choose that the time machine in this context rewinds time while conserving the universal position(?)... Relative to the center of the universe(??)... assuming eucledian space(???)

I suppose you're going to tell me that the earth is flat too....

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

https://astronomy.stackexchange.com/questions/33514/how-fast-are-we-moving-relative-to-the-cmb#33515

Earth moves with somewhere between 230-500km/s, long term average should be 370 km/s

https://en.m.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System

https://en.m.wikipedia.org/wiki/History_of_Earth

The solar system and earth formed 4.6 billion years ago.

https://numbat.dev/?q=370+km%2Fs+*+4.6+billion+years+-%3E+ly%E2%8F%8E

That means the solar system travelled 3.45-7.67 million light-years (5.67 for the average speed) since then.

That plural form (millions of light years) is borderline, but actually not incorrect.

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

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.

Ooh, but what if the time machine came from Mars and uses that as its frame of reference?

Can you detect rotational velocity using gravity?

Ooh, new science fiction idea. We built a time machine and can only use it to reach other star systems. But just those that have been or will be at the same "spot" as earth.

This. It would have to be set as relative to something, why you would define that as any object not Earth or on Earth is a mystery to me

Since space and time are intertwined, we must travel both to achieve the desired goal

Maybe this is why Stephen Hawkings time travellor party never worked out lol

I should hope that if we had time travel landing pads, we'd have a pretty good log of maintenance times in the future.

The tough part to figure out, though, is that the more a pad is used, the more maintenance it requires, which in turn modifies the logs.

When I was a kid I thought that spacetime was created by mass. I thought that if you were to ever find the end of the universe you wouldn't be able to travel beyond because you would just create new spacetime everywhere you went.

And I thought that was scientific consensus. No idea where I got it from, though.

It'd be really interesting if time moves at different speeds in different bits of the galaxy, find out that none of the other solar systems have life because closer to the galactic center of someone dropped a teapot when the first life evolved on earth it still wouldn't have hit the floor.

Of course there's a lot of reasons this isn't the case but I dismiss them by saying they're all just an effect of distortion due to time variance.

Maybe we'll get s message from voyager saying 'arrived at a star 224 light years away, it was super quick because there's no time in the middle so you just skip that bit'

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.

Same as "7 days", they had to take the location shift into consideration.

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.