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Space & time

  1. Jun 28, 2008 #1
    Are space & time same ,like two sides of a coin , one cannot exist without another ? Also does time exist for photons ?
  2. jcsd
  3. Jun 28, 2008 #2
    Wheeler(not sure) said matter tells spacetime how to curve, and spacetime tells matter how to move. Actually, if there were no objects in the universe, then the spacetime has no meaning. This contradicts to Newton's absolute concept of spacetime background. That's why the RHS of the Einstein equation is matter, the LHS of it is geometry. In some sense, the spatial space and temperal space cannot be separated. Because it's a spacetime continuum. What Einstein did is to bring space and time on equal footing.
    Althou the proper time doesn't flow on the photon, the worldline of photon is still in the spacetime continuum.
  4. Jun 29, 2008 #3
    Space and time have never been observed to exist without the other. Whether they can is a different story. For space to exist without time would mean that there has to be a space where there are objects present but for which nothing can happen, no motion no nothing.

  5. Jun 29, 2008 #4
    By the way, I come up with that I heard a talk which addressed the two-time physics, meaning, there are two temporal dimensions. They can prove that three-time physics or higher-time physics are impossible. I forgot the details, anyway, a crazy idea.
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