• BeefPiano@lemmy.worldEnglish
    1482·
    7 months ago

    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.

    • themeatbridge@lemmy.worldEnglish
      861·
      7 months ago

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

    • GoodEye8@lemm.eeEnglish
      161·
      7 months ago

      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.

      • Schadrach@lemmy.sdf.orgEnglish
        3·
        7 months ago

        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.

        • nilloc@discuss.tchncs.deEnglish
          1·
          7 months ago

          Or maybe the time travel happens by warping space in the first place (since you need to somehow overcome the speed of light problems anyway). Seems like a good job for a wormhole if someone wanted to write around the space/time/motion rules.

          • Schadrach@lemmy.sdf.orgEnglish
            1·
            7 months ago

            Wouldn’t matter, because the problem isn’t about space or motion, but about position. If you jump backwards in time but your position in the universe doesn’t change then you are probably no longer on earth because the Earth moves about the sun, etc. To land somewhere meaningful, you’d have to calculate the target location relative to some reference point with a predictable location and as Earthlings we’d probably pick the Earth itself unless this is a time traveling spacecraft.

    • walter_wiggles@lemmy.nzEnglish
      13·
      7 months ago

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

    • lolcatnip@reddthat.comEnglish
      91·
      7 months ago

      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.

    • Kowowow@lemmy.caEnglish
      1·
      7 months ago

      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

  • CarbonIceDragon@pawb.socialEnglish
    83·
    7 months ago

    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

    • essteeyou@lemmy.worldEnglish
      24·
      7 months ago

      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. :-)

      • Semi-Hemi-Lemmygod@lemmy.worldEnglish
        25·
        7 months ago

        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.

      • SomeGuy69@lemmy.worldEnglish
        5·
        7 months ago

        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.

        • Björn Tantau@swg-empire.deEnglish
          2·
          7 months ago

          But by the time you have collected and evaluated all the drone data you and all the masses around you would already be in a totally different configuration, making the data useless.

          But maybe a little jump to the time when you sent the drone out would be easier and then you could use the drone’s data.

  • gmtom@lemmy.worldEnglish
    752·
    7 months ago

    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.

    • 1rre@discuss.tchncs.deEnglish
      11·
      7 months ago

      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

    • Psythik@lemmy.worldEnglish
      51·
      7 months ago

      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.

    • Turun@feddit.deEnglish
      41·
      7 months ago

      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.

      • Opafi@feddit.deEnglish
        4·
        7 months ago

        Since I stay on earth now when I’m moving forward in time why wouldn’t I stay on earth when I move backward through time?

        • Turun@feddit.deEnglish
          21·
          7 months ago

          Sure you can, but you need to adjust your position due to centrifugal forces all the time. A time machine would have to do that as well.

          If a ball is flying in a straight line through space with a speed of 1m/s I can predict without much math where it will be at any point in time. In fact, if the reference frame is chosen such that the ball is stationary you don’t need any math at all, because the ball doesn’t move!

          However, if you have a set of two balls orbiting each other you will always have to do math to calculate their position. I mean technically you could choose the reference frame that is rotating in sync with the balls. But still you need to do math to check that the centrifugal force, which is a real force coming from nowhere in this reference frame, exactly cancels out the gravitational pull between the two balls. Because rotating reference frames are not equivalent to each other!

          • Opafi@feddit.deEnglish
            3·
            7 months ago

            I really don’t get why the time machine would have to do any calculations at all. The time machine is in this reference frame. You seem to assume that by going back through time you’d be teleporting through time, which leaves the open question of where you’d appear. However, I’d much rather assume that you’d actually be “going” through time. You wouldn’t cease to exist until you reappeared somewhere. Instead you’d be in the machine for some time until you’d get out of the machine again. That’d mean neither you nor the machine ever leave the reference frame.

    • Sam_Bass@lemmy.worldEnglish
      1·
      7 months ago

      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

  • davidgro@lemmy.worldEnglish
    49·
    7 months ago

    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.

    • Dave.@aussie.zoneEnglish
      15·
      7 months ago

      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

    • Barbarian@sh.itjust.worksEnglish
      12·
      7 months ago

      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.

    • perviouslyiner@lemmy.worldEnglish
      5·
      7 months ago

      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.

  • Etterra@lemmy.worldEnglish
    401·
    7 months ago

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

    • morrowind@lemmy.mlEnglish
      5·
      7 months ago

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

  • Ephera@lemmy.mlEnglish
    381·
    7 months ago

    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).

    • Björn Tantau@swg-empire.deEnglish
      3·
      7 months ago

      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.

      • Ephera@lemmy.mlEnglish
        2·
        7 months ago

        I have heard that notion before, but don’t know how the maths is supposed to work.

        I can tell you, though, that light would be going faster than light, if it could.

        Here’s a simple equation you probably know:
        F = m * a
        (F is force, m is mass, a is acceleration)

        Well, if you rearrange it, you get this:
        a = F / m

        We currently believe photons to have no mass.
        Insert that into the equation and you get a division by zero, but our closest approximation means acceleration is infinite, as soon as any non-zero force is applied.

        Infinite acceleration results in immediate infinite velocity. It makes no sense for light to only accelerate until 300,000 km/s and then take its foot off the gas pedal.

        This is why it’s instead believed that there is a speed limit to causality itself.
        The speed of light (as well as of gravitational waves and other massless things) just happens to be the same value, because they’re going as fast as is possible.

        Here’s a video about the speed of causality: https://www.pbs.org/video/pbs-space-time-speed-light-not-about-light/

    • affiliate@lemmy.worldEnglish
      31·
      7 months ago

      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)

      • EtherWhack@lemmy.worldEnglish
        6·
        7 months ago

        But what if the absence of the atoms of your body affects how the universe collapses and in turn expands?

        • Duamerthrax@lemmy.worldEnglish
          2·
          7 months ago

          If the universe is cyclic, then the version of you from the previous one is also jumping to a time before when you left. It works if the board gets reset to the exact same position and true randomness doesn’t exist. We’re talking down to the electron scatter of radioactive decay.

          • EtherWhack@lemmy.worldEnglish
            2·
            7 months ago

            If the universe is cyclic, then that would define it as a closed loop without any energy being removed or added. The very first instance of yourself traveling through time would break the loop by removing themselves from their iteration of the universe and reinsert into a future iteration. During those two points, the universe would now function with a deficit. This deficit could affect how it cycles to subsequent iterations.

            What if that discrepancy in energy affects when the universe starts to contract or it’s speed to the big crunch/bang and subsequently the time to, and speed of expansion. Maybe it could even prevent the big crunch from reaching critical mass, where it would normally trigger a big bang, and stop the cycle altogether.

      • Ephera@lemmy.mlEnglish
        4·
        7 months ago

        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?

  • Dalvoron@lemm.eeEnglish
    31·
    7 months ago

    I like the idea that time machines are like phones in that you need a receiver to pick up the signal. A consequence is that you can only travel back to the time that the machine was turned on.

  • BmeBenji@lemm.eeEnglish
    18·
    7 months ago

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

  • SuperSaiyanSwag@lemmy.zipEnglish
    213·
    7 months ago

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

  • AdrianTheFrog@lemmy.worldEnglish
    17·
    7 months ago

    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.

    • dQw4w9WgXcQ@lemm.eeEnglish
      2·
      7 months ago

      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(???)