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Gravity and time, am I understanding this?

  1. Nov 21, 2003 #1
    [SOLVED] Gravity and time, am I understanding this?

    I am pretty new to physics in general. From what i've gotten so far, relativity states that time increases (or the increments of time become more closely spaced) when gravitational field is stronger. This is illustrated in black holes and the Big Bang. In the earlier moments of the Big Bang, the gravitational field of the early universe would be much greater than it is now, therefore, time would go by at a much quicker rate in the early stages of expansion. Now, correct me if I am wrong, but say my twin goes to a neutron star (or something with a much greater gravitaional field than the earth) and stays for what he perceives to be 10 years. He then returns to earth and meets up with me (who has stayed on earth the entire time). In this case, wouldn't my twin be younger than I? So isn't this stating that the greater gravitational field on the neutron star caused time (to the twin) to slow down and thus the twin stays younger for a longer amount of time in relation to me, on earth? Is this a contradiction of stronger gravitational fields speeding time up? Shouldn't the twin age faster than I in this case?
  2. jcsd
  3. Nov 21, 2003 #2


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    It's a question of perspective, as are most things in relativity. To any person inside a strong gravitational field, time appears to "speed up". That is, the rest of the universe (outside the strong gravitational field) seems to go by quickly like a videotape on "fast forward".

    However, if you were outside that gravitational field looking in at that person (your twin, for example), you would say that his time appears to "slow down". So your twin would indeed be younger than you, but you would dissagree as to the reason why. You would say that his time slowed down while he would say that your time sped up.
  4. Nov 21, 2003 #3


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    Everyone sees their own timepiece proceeding normally. It's only in comparisons of different gravitational fields/velocities that differences are detected.

    Time proceeds slower in a strong gravitational field as compared to a weaker gravitational field. So, it seems your premise is backwards and your twins example is correct.
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