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    • Thread Starter

    The universe is observed to be filled wtih a highly isotropic blackbody background radiation.
    What does this tell us about conditions in the early universe??

    Well.... according to the mark scheme i have hear it tells us that there was thermal equilibrium/highly uniform

    Could anyone explain how the radtion relates to thermal equilibrium??

    I understand that the radiation is from the big bang and has been extreamly red-shifted... but what has all this got to do with thermal equilibrium??

    • Thread Starter

    Oh wait, sorry, just to answer my own question... Is it as simple as the fact that its isotropic (same in all directions) basically means the temperature must have been the same in all directions ie uniform ??

    yep, good call

    so how is this proof for the big bang? is it just the fact that its equal to 2.7K everywhere

    you could say that there are slight variations over the universe as a whole, but these variations in temperature are so far apart that the expansion of space would not allow them to arise from any event after a very early age of the universe. the variations are therefore attributed to the "quantum fluctuations" in the termperature of the universe when it was very small, so it provides evidence that the universe was in fact very small at one stage.

    although this is true I think it is greater detail than you need...

    The fact that there is the background radiation in the first place (and in every direction) is evidence of the big bang, becuase this radiation came from the big bang. Just like the light you see from a firework gives you evidence that a firework was there (although this is a huge simplification!)

    hope that helps..
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