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

Time Dilation and Gravity

  1. Jul 8, 2004 #1
    We all know that velocity produces a time dilation, but gravity does too. My question is "Is the dime dilation produced by gravity the same as that produced by motion?"

    As you increase velocity your clocks (the clocks in your frame of reference) remain constant to you, but the clocks in other frames seem to slow, correct?

    In a gravitational feild do the clocks "outside" seem to slow or do they speed up relative to you? Do observers see your clocks slow or speed?

    Thanks.
    Moore1879

    Forgive any mis-spellings.
     
  2. jcsd
  3. Jul 8, 2004 #2

    russ_watters

    User Avatar

    Staff: Mentor

    GPS is a good example. The GR effect on the clocks in orbit is that they appear from the ground to be running faster than clocks on the ground.
     
  4. Jul 9, 2004 #3
    Yes, but the other half of my question was would the clocks on Earth seem to slow to the GPS satillites?
     
  5. Jul 9, 2004 #4
    "We all know that velocity produces a time dilation, but gravity does too. My question is "Is the dime dilation produced by gravity the same as that produced by motion?"

    Yes - the time retardation is the same if you consider an object that is moving (for example with circular motion) on a tether of radius r, at velocity v, as that which would be calculated if you considered the centripital acceleration (v^2/r). So since acceleration is equivalent to gravity, you get the same result if you calculate the acceleration that corresponds to a particular gravitational potential as you would get if you calculated the escape velocity at the same radius - - but the total time retardation is either one or the other, but not both. Those who are deciples of the inflow theory find important significance in this correlation in that they see it as a defacto unifaction of GR and SR.

    Your other question - in GR, the retardation is a one way phenomena in the sense that the situation is not reciprocal. Specifically, an observer on the surface of the earth does not see a high altitude clock running slow, but a high altitude observer would conclude that the surface clock is running slow when measured against his high altitude clock.
     
  6. Jul 9, 2004 #5
    "As you increase velocity your clocks (the clocks in your frame of reference) remain constant to you, but the clocks in other frames seem to slow, correct?"

    SR says you measure proper time in your own frame, so clocks at rest in your reference frame always measure the same time - no matter what your velocity with respect to whatever. When it is said in SR that you observe clocks running slow in the other frame, what is meant is that you have synchronized two or more clocks in your own frame and using these clocks you can calculate the rate of a single clock in the other frame that is in relative motion. It does not mean you can shine a light on the face of the other clock and make a measurement - it is a restricted procedure th defined by the interpretation to be accorded the Lorentz transforms.
     
  7. Jul 14, 2010 #6
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Time Dilation and Gravity
  1. Time Dilation+Gravity (Replies: 10)

Loading...