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

Spacetime elasticity

  1. Oct 24, 2011 #1
    I am curious if there has been any research in to the elasticity of spacetime in regards to mass. If we consider that a fabric is resistive to a degree to an object it could be said that an object must poses a certain amount of mass before it can cause a divet in spacetime.
  2. jcsd
  3. Oct 24, 2011 #2
    Einstein was the first such master. Or maybe Lorentz Fitzgerald for special relativity "elasticity"....

    More generally, you are asking about general relativity, how gravity "gravitational potential" "warps" spacetime....gravitational curvature causes tidal effects.

    A black hole is the "ultimate warper" crushing space and time and mass out of existance!
  4. Oct 24, 2011 #3
    i am curious as to something i heard about micro-gravity. If spacetime has a certian elasticity such that only objects of a "particular mass or graeter" have an effect on it.
    If i think of it as a bed sheet with a marble placed on it the sheet bends but if i put only a thin piece of plastic on it it would not move at all. I believe that maybe there is something to that in gravity is an effect of mass on spacetime but there is a minimum mass needed to begin effecting it.
  5. Oct 24, 2011 #4
    Are you talking about a 'quantum of curvature'?
  6. Oct 24, 2011 #5
    Einstein did not think of it as a sheet of rubber 'bending'. It's commonly used as a 2 dimensional analogue to the way gravity is space's 'metric' but I find it better to think of it as a 'Jello' that will adapt relative motion/mass/gravity/'energy'. And if you look out on the universe a dark night every star you see will have a (different) relative motion, relative you observing. That means that the universe you see is both time dilated and Lorentz contracted, which may seem weird :) but it's all a result of the invariant radiation describing what you look at.

    That's also why you can't really define a time dilation, other than the twin experiment, where the twin has to come home first to 'prove it'. But it is real, both the Lorentz contraction and the time dilation, and they must be different, relative different stars.

    But what communicates it all is that same 'propagating' light, coming at you at the same invariant 'speed', and that light paints the 'whole image' you obtain from observing that night sky. Think of that the next time you look up :)
    Last edited: Oct 24, 2011
  7. Oct 24, 2011 #6


    User Avatar
    Science Advisor

  8. Oct 26, 2011 #7
    before you reach a conclusion, you should decide what is your conception of mass and spacetime....are they continuous or discrete?? (Nobody really knows.)

    GR assumes a continuous spacetime; quantum gravity may end up with a quantized gravitational theory. So in the former there is no minimum, in the latter, maybe could be.

    Some references for consideration:

    I kept this for my own notes from another thread here:


    In this thread


    "argument for the discreteness of spacetime",

    Ben Crowell posted this question...
    some good discussion.
  9. Oct 28, 2011 #8
    nice :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook