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Relativity question

  1. Feb 12, 2016 #1
    I have no background in physics, but I understand the very basic concepts.
    I'm sorry if this is a stupid question, but it is searing in my head.

    Q: if time is relative to the observer, are there any cases where an observer perceives our ( meaning us on earth) space time to move slower, just as I would experience the time passed by an astronaut moving close the the speed of light as less?
    Is this dictated by the rate of speed and gravity of earth? Would our time on earth appear to pass slower to an observer on a body moving slower and with less gravity, say Pluto.

    I guess the basic question here is, what is the opposite of the speed of light, what is slow?

    I know this is serious forum, I'm sorry if this is a simple question,many thanks you for any answers,
  2. jcsd
  3. Feb 12, 2016 #2
    GPS systems clocks need to be time adjusted by microseconds due to time dilation.
    This arises because the satellite clocks are less deeply immersed in Earth's gravity field than are clocks on the surface.
    If this was not accounted for the apparent position of objects on Earth could by highly inaccurate.
  4. Feb 12, 2016 #3
    Hello Rootone
    Thank you very much for the answer.
    I guess what I want to know, is if the same extreme in time dilation can be encountered opposite the speed of light. Not merely microseconds, but on the level of the twin paradox. What conditions would need to exist on the opposite end. Is there anything in the universe that is influence in such a manner as to have its relative perception of our time seem as though we are our space time is moving slow relatively.
  5. Feb 12, 2016 #4


    Staff: Mentor

    There is no such thing as "opposite the speed of light". The speed of light is an invariant, but a speed of zero is not. If you are floating out in deep space, far away from all other objects, you will feel yourself to be at rest, but with respect to, say, a cosmic ray particle flying past you, you are moving at a speed very, very close to the speed of light. So there isn't any absolute sense in which you, at rest relative to yourself, are "opposite to the speed of light".
  6. Feb 12, 2016 #5
    Welcome to PF!
    Just to preface my answer, this is a good question. On PF we are here to answer people's questions about science, math, engineering and whatever else we have a forum for.
    I do believe, however, you don't quite get time intervals. Time intervals is the rate at which time passes. Larger time intervals makes time move slower, and vice versa. If you understand that, there are two answers to your question, the answer about relative velocities (which uses special relativity) and the answer about gravity (which uses general relativity). I feel like I can accurately explain the one using special relativity, however I don't feel completely confident in my general relativity answer, so I will not give it in great detail.
    If something moves with a relative velocity near c relative to you, it will think your time is moving slower, or your time intervals are larger. You will think the same thing except that you will think its time interval is larger. This is where you get the twin paradox. Until you invoke general relativity, in your frame of reference you will think that your time interval is less than or equal to all other time intervals. So (again, until you get the second answer), anything not at rest relative to the earth will think that our time interval is larger than their's. Of course, this means nothing as general relativity must be invoked when talking about massive bodies, so here's the short answer: time intervals are larger near massive bodies. So, on both counts (special and general relativity), an observer on pluto would find time on earth to move much slower.
  7. Feb 12, 2016 #6


    Staff: Mentor

    It actually wouldn't be "much" slower. The difference would be on the order of one part per hundred million or so.
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