203
Time travel doesn't work unless you also have teleportation. If you travel to the past/future, Earth will be in a different position in its orbit, and you'll die in space. (lemmy.world)
submitted 1 year ago by to c/showerthoughts@lemmy.world
59 comments fedilink hide all child comments
you are viewing a single comment's thread
view the rest of the comments
[–] 6 points 1 year ago (8 children)

But if you're in a moving car and "pop" back a few seconds while the car doesn't you won't be in the car anymore. If it worked more like rewinding a video you wouldn't need to do much, but I'm assuming OP means literally going "poof" and now you're back in time. If that's the case, you would still need to know how Earth is moving through spacetime. If you don't know your relativistic relationship to the Earth and every other object in the universe then how would you know where you are or your own relativity compared to the Earth?

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 8 child comments
    •
  • [–] 26 points 1 year ago (6 children)

    Their point is that (as per relatively), all movement is relative to something. So if the earth moved away then you must be measuring in relation to some other reference point. There is no absolute positioning system. So when you say the earth is moving, what is it moving in relation to? And why did you pick that reference point instead of having a time machine that uses earth itself as a reference point?

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 6 child comments
    •
  • [–] 0 points 1 year ago* (5 children)

    But that's the thing though. How can you determine the Earth as a reference point without knowing how it relates to other objects in space? "Here" is as useful a coordinated system as a fake absolute positioning system. "Here" is just your relation to other objects. If you don't know what your relation to those objects is you can't determine where "here" is, or the Earth for that matter. Whether it's the machine or the person operating it, something or someone has to calculate where the Earth is in order to use it as a reference point.

    If you are driving away from your friend at 20 mph, from your perspective they are moving away from you at 20 mph while you are the one that's stationary. The only thing determining your location, or reference point, is your relation to each other.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 5 child comments
    •
  • [–] 15 points 1 year ago (4 children)

    You're still thinking in a context where the earth is travelling around the sun, etc etc.

    If you assume the Earth as the reference point, then that is fixed, absolutely frozen, doesn't move at all. That's point zero.

    You cannot calculate where the earth is. What you do is calculate where everything else, the universe itself and even other dimensions, are with regards to your fixed point.

    This can feel counterintuitive, but here's a random visualization: https://youtube.com/shorts/UZyuZVvCE78

    Note that, in that video, only the perspective has changed. The solar system is moving as usual.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 4 child comments
    •
  • [–] 5 points 1 year ago (1 child)

    This is also demonstrated well in the show Travelers with T.E.L.L.

    Basically, a quantum AI from the future uses historical records to determine the time, elevation, latitude and longitude to send people back. Obviously the Earth itself is the reference point being used.

  • permalink
  • fedilink
  • source
  • parent
  • hideshow 1 child comment
    •
  • [–] 1 point 1 year ago*

    That video is super, super wrong, and nowhere even close to "just a different perspective". To demonstrate, Mercury and Venus should periodically come between the Sun and Earth, but that'll never happen in that model.

  • permalink
  • fedilink
  • source
  • parent
  • [–] 0 points 1 year ago

    But that's the point that I'm trying to make. It's probably my fault as I'm not very good at explaining things like this, and I'm not disagreeing with at all. I'm just saying that there is no way to have a machine or method of travel with a fixed point without knowing its relation to other objects. Just like you can't know the trajectory of the Earth through space without knowing its relation to other objects. What I'm saying is that regardless of your "fixed point" you will have to do the same math, just in a different order depending on your point of reference. We are dealing with relatively here so the only variable that changes is your point of reference while the math stays the same.

  • permalink
  • fedilink
  • source
  • parent