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Background radiation and intensity

  1. Sep 30, 2008 #1
    Hi all,

    Quick question. I'm reading through Stephen Hawking's a brief history of time (interesting even though I can only understand 1/10th of it).

    During this book he consistently mentions the fact the microwave radiation detected is near uniform in all directions, which is evidence that the universe is expanding as the wavelengths are red shifting.

    This leads me to the question, does this also mean that we are in the center of the universe? I'm modest enough to believe this is almost certainly not the case, however where is my thinking wrong. To me equal radiation says that the waves have traveled a roughly similar distance to get to us as they are red shifted the same amount, however lets say the universe stretched 1 million light-year's east of us, and 20 million light-years west of us (for want of a better way of describing it simply) wouldn't the microwave radiation coming from the west be red-shifted a further amount due to the fact is has traveled longer? Should there be different intensities if that was the case?

    I have no doubt my reasoning is wrong, however I'm looking to find out why it is wrong


    Edit: I think I just figured out the answer but I'll see if people respond with the same reason I'm thinking.
    Last edited: Sep 30, 2008
  2. jcsd
  3. Nov 6, 2008 #2


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    Think of the universe as being a loaf of bread, and the earth is a raisin. When you cook the bread, the dough expands in all directions. From the point of view of any raisin, it looks like all the other raisins are getting further away from you. From the raisin's perspective it may seem like it is in the center of the universe and everything else is expanding away from it. But the reality is that the distance between everything is increasing everywhere.
  4. Nov 6, 2008 #3


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    We are at the center of the universe. We are also at the furthest edge of the universe. The center and edge of the universe appears to be wherever [and whenever] you happen to be. It's like trying to find the center [or edge] of the surface of a sphere.
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