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See far away objects in space in real time?

  1. Mar 8, 2013 #1

    I was asking myself if there is, or might be a way to see far away objects in space in real time? What I mean is that when we look even through the most powerful telescope we always see the past of the object we are looking at, and this past will depend on the distance the object is away from us, right?
    So, if a planet is 1000 light years away from us and we have a telescope powerful enough to see its surface like, let's say, in google maps we will see how this surface looked like 1000 years ago. Then, maybe we see life on a planet, a supernova exploded 500 years ago and killed everything and we will see this in 500 years only.
    Or maybe we don't see anything but there is life and the problem is that light still didn't reach us.
    Is it like this or am I completely wrong?
  2. jcsd
  3. Mar 8, 2013 #2


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    Yes, the only way to see what happened 500 years ago would be for the light that was emitted 500 years ago to travel at twice the speed of light which - more or less by definition - is not possible :)

    For a rigorous discussion, we should probably think about what "500 years ago" means... 500 years on whose clock? :)
  4. Mar 8, 2013 #3
    Thanks for your answer, you clarified something important!
    About the clock, I don't know, because that's also something I never understood :) I guess, my clock here on earth? But it's a mechanical device, and this is what confuses me even more! (in the same way that the ruler you leave in the drawer is not measuring anything...)
    By the way, you made me remember that I have to make a question about time, but in another place of the forum ;)
  5. Mar 8, 2013 #4


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    Yes, because you are saying that "the light is coming from a start 500 light years away", the distance is measured in your frame of reference, the time is measured in your frame of reference. In other words, by a clock sitting stationary next to you.
  6. Mar 8, 2013 #5


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    If there is any way to see light of later times (=not light emitted 1000 years ago for clocks on earth) here on earth, this allows time travel or completely ruins special relativity (or both).
    Well, you can use any clock here on earth, including radioactive decays, the orbit of earth around the sun and so on. You are not limited to a specific clock.
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