Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Movement and spacetime

  1. Jun 11, 2008 #1
    what would be the difference between the idea of being at point A and moving toward B in space-time; and being at point A and not moving and B not moving but the space-time between them moving and warping out of the way?
  2. jcsd
  3. Jun 11, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Didn't you just answer it yourself while asking the question? In the second case, space-time is curved. I assume that's not what you wanted to hear, since you said so yourself. What sort of answer are you looking for?
  4. Jun 11, 2008 #3


    User Avatar
    Gold Member

    The difference is that is scenario 1, the subject would have the epxreince of moving from A to B, whereas in scenario 2, the subject would ahve the experience of not moving while the two points would move to coincide.

    It would be easy to tell the difference merely by observing external reference points, such as distant stars.
  5. Jun 12, 2008 #4
    Particles have wordlines in spacetime and cross events which are points. In a curved spacetime worldlines can cross even if at some point the lines were parallel to each other.

    But spacetime itself is fixed, it does not change.
    Last edited: Jun 12, 2008
  6. Jun 12, 2008 #5

    would the idea change the way the motion, or lack thereof, of particles, is conceived; where as all particles are motionless, only space-time warps, muli-dimentionally. (i.e. - "my arm is not moving my fingers to my nose, but the amount of space time is curving or moving so there is less between them.) we would perceive in 3+1 dimentional space, as my arm is moving my fingers to my nose, using Einstein's perspective.


    fredrik, thank you sir, but this idea is theoretical. visible external reference other than point A and point B (the sight of my fingers and the feel of my nose) are not applicable in this theoretical scenario.

    Thank you MeJennifer, but your answer is based on part on Einstein's "Absolute Spacetime theory"in which this thread is written to challenge.

    thanks to you all for helping
  7. Jun 12, 2008 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I guess you can say that it changes the meaning of velocity. Consider e.g. the case of galaxies moving away from each other due to the expansion of the universe. I'm quoting myself from another thread:

    This speed is something very different from the speed an object has in a local inertial frame. That's why it can be >c.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Movement and spacetime
  1. On Movement (Replies: 33)

  2. Absolute movement (Replies: 28)

  3. Movement of mass (Replies: 6)