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How can it be that gravity can bend time and slow it down

  1. May 11, 2009 #1
    how can it be that gravity can bend time and slow it down, how can gravity influence a dimension of space?
     
  2. jcsd
  3. May 11, 2009 #2
    Re: time

    Anything with energy and momentum couples to the gravitational force/field thing and thus can bend spacetime inducing the effect we call gravity. Time dilation occurs because of the stretching and deforming of space in a non-euclidan metric.
     
  4. May 12, 2009 #3
    Re: time

    so it is space that is deformed and not time?
     
  5. May 13, 2009 #4
    Re: time

    gravity doesn't bend space or time. Gravity IS bent space and time. Or another way to look at it, bent space and time is what we call gravity. A better question is why does mass and energy bend space and time?
     
  6. May 13, 2009 #5
    Re: time

    Time does not exist nor does space.
    Space is not some sort of massive container with no walls. You can not bottle some of it up and take it to your lab. QT may say that objects are not truly separated because entangled particles are in unison even if they are in different parts of the universe. QM says that "empty space" is filled with particles and fields. Einstein's Relativity says that there is no absolute distance between objects because distances can mutate due to gravity and velocity.

    Time is only the sum of spatial states in your mind. Time is a word we use to measure change not some kind of invisible matrix/web in which these changes occur. Its the way we think to make sense of things.

    See: Heisenberg's uncertainty principle, Quantum Mechanics, Quantum Theory, John A. Wheeler's participatory principle, Einstein's relativity
     
  7. May 13, 2009 #6
    Re: time

    What a coincidence, that's exactly what Abraham Lincoln was telling me when we had lunch on the moon in 3018.
     
  8. May 13, 2009 #7
    Re: time

    thanks for the info. so then time is relevant only to the observer? and thus is suceptible to change from one one ''place'' to an other?
     
  9. May 14, 2009 #8
    Re: time

    Yes, and no because you can never be certain where anything is because there is no absolute distance between anything and anything else. Any measurement from different places will be different and any measurement from the exact same spot will be different. So time is not a "thing" it is a mental tool we use to measure the change of things.
     
  10. May 14, 2009 #9

    RUTA

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    Science Advisor

    Re: time

    Most textbooks will say that general relativity (GR) is a theory of gravity, but there is another way to view Einstein's eqns (EE) of GR, i.e., as a self-consistency criterion between spacetime measurements and the energy-momentum content therein. The LHS of EE contains the Ricci tensor, scalar curvature and metric tensor combined into what is called the Einstein tensor (G). G is a mathematical description of the geometry of spacetime. The RHS of EE contains the stress-energy tensor (SET), which is a mathematical description of the matter, energy and momentum content of spacetime. Typically, EE are solved for the metric (tensor that describes spatiotemporal distances) having made simplifying assumptions about the nature of the SET. But, the components of the SET require (tacitly or explicitly) a knowledge of how one makes spatiotemporal measurements so you can't input SET without tacit assumptions about the metric. Technically speaking, SET is the functional derivative of the matter-energy Lagrangian with respect to the metric. So, you can't put SET into EE to get the metric because you need the metric for SET. And, you can't figure out the metric without SET in EE. Thus, GR is telling you how space, time, matter, energy, and momentum are self-consistently co-related.
     
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