we live in an explosion

Time and space are the same thing, if you’re traveling in time it seems like you could travel in space at the same time.

Yeah but traveling in space takes time, so you can reason that traveling in time takes space.
- Right so have we tried putting the Time Machine in the middle of a football field or smthn?
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.
- 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.
  Alternately since we're Earthlings, someone designing a time machine might think it's a good idea to automatically calculate the location using the Earth as a reference point because that's likely to be the most common use case and doing so would prevent you from dying to the void of space if you make a tiny math error. At which point you would just need to input the destination time if the target is the same location relative to Earth.
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?

A time machine would necessarily need to have some way of defining what reference frame one is stationary in space relative towards, because there is no universal frame that everything moves relative to. This suggests that a time machine ought to let you move through space as well as time

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. :-)
- You'd also need to solve time travel.
- You'd just send a drone back, to say 100 years ago, first and have it send you exact coordinates into the future.
  Time paradox aside you'd probably have this data already, with all alternatives and can correctly time jump right away.
- Mass bends spacetime so one could assert that a time machine could anchor itself to a sufficiently large mass, just like how things in orbit are still bound to the earth's mass.
Time and Relative Dimension in Space, you say?

Since relativity tells us there is no universal reference frame, then it having its reference tied to earth is perfectly valid.

Also sidenote: my favourite idea about time travel is that time travel is entirely possible, but will never be invented, because the timeline where its not invented is the only stable timeline. Because any timeline where it IS invented gets changed as soon as you use it, meaning the timeline changes over and over again every time time travel is invented repeatedly either infinitely or until someone accidentally creates a timeline where its never invented, only then does the timeline stop changing and we can actually experience it. So because we exist and can experience time, we can deduce that we will never invent time travel.

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
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

In most media time machines are also teleporters - many are explicitly so, with the destination space needing to be chosen at the same time as the destination time, but even when that's not shown they still make the time traveller suddenly vanish and then just suddenly reappear elsewhen.

One movie I've seen with a more "realistic" time machine is Primer. It's not at all a teleporter or portal. Very slight spoiler:

It sidesteps the whole issue that OP presents because the place where you exit the machine after traveling is just where the machine is when it's turned on to begin with. You can't time travel outside the machine, including to before it exists, and your path (in all four dimensions) is contiguous.

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 move one end at a fraction of c to create an time difference between the two ends, but the only possible travel is between the two ends that you have created.

Guess this is why the TARDIS had to be a space ship as well.

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

Imagine building the first receiver, and immediately have 20 people spawn within the same space
- More like 2 million inconsiderate time tourists comming to gawk at the first reciver..

Well, since this was posted in Science Memes, I'll be so pedantic that science does not support the idea of travelling back in time.

It does support travelling forwards in time, at various speeds, but you'll constantly be aware of where you are (even if one method involves travelling really fast and therefore may still leave you in empty space).

I'm traveling forward in time right now.
- Big, if true
- Me too! What's your destination?
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)
- I mean, personally, I actually don't believe that the Big Bang created everything out of ~~thin air~~ vacuum, because much like travelling backwards in time, that would break causality.
  It makes much more sense for everything to just have always existed and the Big Bang is merely a very visible event + expansion afterwards.
  I'm open to the notion that expansion and contraction happen in some sort of cycle, because well, many things do.
  But for it to be cyclical to the point where it repeats precisely the same? Why?
  Can't we just let the universe flobber on its merry way without assigning some higher meaning to everything it does?
- But what if the absence of the atoms of your body affects how the universe collapses and in turn expands?

Time machines don't exist and (as far as we know) cannot exist. Therefore, we can say they work however we want. If you can travel back in time, surely you can do that while remaining close to an arbitrary point of reference.

Someone should build a space machine so we can travel through space freely

🤯

This meme format having a redemption arc is my favorite. It wasn’t super sexist, but it was just unnecessarily sexist.

Rescue peepo from the nazis next.

Time machines have been invented dozens of times since the 1800s; there's s trail of them drifting through deep space.

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

I have yet to stumble across a sci-fi short story about space travelers finding an entire civilization's worth of dead bodies floating round in space only to realize that they were all time travelers who only got part of the time traveling math correct. They figured out how to get through time but couldn't figure out how to get through space, but since all their volunteers died, they never figured it out and just kept sending people to their doom.

I feel like this could be a scene in Rick and Morty, with someone commenting, "Guess their Math was off"
There is a sci-fi short story whose name escapes me of a spaceship using some new FTL drive, but has largely been untested due to an impending doom. The math is said to be solid, however.
Anyway the drive powers up, and the spaceship jumps, and.... all the crew and passengers are left behind, choking in space.

How, uh, far back in time did you want to go?

Jokes on you, space doesn't exist

Use a space time machine. Problem solved.

You need to add dimensions and relativity.

Why would you time travel to a position relative to anything other than the earth?

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.

think this was in Issaacc Assimovv's Robot Visions

So either we would have to invent teleportation along with time travel/ have some sort of "magnet pad' that must exist and not break at all times on earth, or its the time machine type where it just fast forwards everything around you until somehow you're in a mall

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

Nah. Location is relative.

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.

It’s my belief that Time Machines aren’t immune to the effects of gravity. When time changes, the machine goes to the space it would be at if it was affect gravity for the whole time.

It's a shame we never invented a Space-Time machine

This is why you have to calibrate your time machine to track the relative gravity well.

I'd like to believe that mass (and then by extension the Earth) "defines" the spacetime around it as much as it distorts spacetime near it. I suspect this may even be the underlying cause for the observation of speed of light being constant in the presence of earth/solar/galactic movement.

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'

I think gravity is the solution to this problem. The time machine just has to be able to lock on to the earths gravitational force from across time

Can you detect rotational velocity using gravity?
- Earth rotates at about 460m/s around it's own axis.
  and I'm sure scientists have access to a more precise number than that.
  we dont have to detect what we can calculate

If I was writing a fiction and felt the need to address this, I would make it so where you wind up is based on the location of the time machine in the time you travel. But also I probably wouldn't and just handwave it

A time machine, at its very very core, is a literary device. You wouldn't bring up this nuance unless it was important to the plot of the story.
It's like warp drives. The point of warp or any FTL travel is to skip the boring parts. You only learn about warp drives when something goes wrong.
- Teleporters as well.
  I remember having access to one in an RPG (rogue trader, teleportarium), and almost every session was "why can't we use the teleporter for this?". Eventually we made a rule that we could only use it once per session, which meant functionally we saved it for emergencies or something really funny.
  There is an enjoyment to solving problems in the engineering sense, but in an oppositional sense you dont really tell any stories other than about how you solved a puzzle you yourself invented

did you travel millions of years into the past?

- Actually for me the conclusion from my math was that it's surprisingly possible to get millions of light years away from earth with just time travel. As such I consider the meme to be scientifically accurate.
  Seeing earth as a lava planet or the primordial soup of life would be pretty sick!