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Theory of Relativity VS. Relativity to placement

  1. Feb 21, 2013 #1
    Being new on this site I've decided to post a question that has echoed through my head for a while now. If Einstein's Theory of Relativity literally claims that all actions and reactions are relative to the observer, then how do we as humans measure anything at all without being at any constant? We know our constant speed around the sun, and even our universe's speed around the Super Giant Black Hole that supposedly resides at the center of our Universe, but as we have these constants wouldn't that make everything we see, feel and so on only relevant to us or our planet? In other words, if I were to travel to Mars and take measurements pertaining to vast distances across the Universe but based on measurements originally obtained from Earth would the entire aspect of all equations become different, or would I need to mover further out (lets say Alpha Centauri) before anything changed? We know (thanks to relativity) that we will always appear to be the center of "The Universe" except the measurements we have made that show the Universe is expanding, but we as a species have never identified (yet) where this actual center may be. I guess what I am asking is is there any other great all encompassing theroies besides relativity that can explain as much as Einstein did without relativity to the observer?

    Thanks very much,
  2. jcsd
  3. Feb 21, 2013 #2


    Staff: Mentor

    I'm not sure this is a good way of describing what relativity claims.

    If you mean the direct data we obtain, yes. If you mean the conclusions we draw from that data, combined with our scientific theories, not necessarily. We can use observations that depend on our particular state of motion to generate and test laws of physics that, as far as we can tell, apply everywhere.

    It would depend on what was being measured and how accurate the measurements were. We can detect some changes just from one side of the Earth to the other.

    If we choose to adopt such a coordinate system to describe our measurements, yes. But there's nothing that forces us to do this. Scientists often use coordinates that are not centered on the Earth; relativity says you can use whatever coordinates you want. It does not say you have to use coordinates centered on you.

    There is no "center" to the universe in any absolute sense.

    Not that I'm aware of.
  4. Feb 21, 2013 #3
    You seem to be discussing the principle of relativity per se, rather than Einstein's theory relativity. See this extract from Galileo:


    Einstein didn't invent relativity, he just used it, as does pretty much every physicist that I am aware of.
  5. Feb 21, 2013 #4


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    Staff: Mentor

    Don't confuse "relative" with random. Relativity makes testable predictions about how our measurements relate to each other.
  6. Feb 21, 2013 #5


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    Gold Member

    Whoever told you that there is a center to the universe OR that there is a black hole at the center is pulling your leg.

    There is a center to your OBSERVABLE universe, and you are it (so am I, of mine) but neither of us is a black hole.

    There IS a black hole at the center of the Milky Way but that's not at the center of anything other than the Milky Way
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