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Astronomy and Cosmology
Cosmology
Question on the horizon problem
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[QUOTE="Nikolai01, post: 6843407, member: 635933"] I agree, which is why I wanted to bounce my thoughts off of others who have discussed the field in more depth and get feedback. ;-) Got it...I've been working mostly off Liddle's Intro to Modern Cosmology. When he presented the horizon problem, I read it as being a 2-fold problem: 1) How points of space too far apart to interact before decoupling could be at the same temperature, and 2) How irregularities/anisotropies would be introduced in the background. Because he had brought up problem 1 I had come from the perspective that there was some assumption within the field that they wouldn't start at the same temperature, but I'm reading from your statement that that isn't necessarily the case. Am I reading your statement correctly in that we cannot predict whether the universe would have come out of the singularity at the same temperature at all places, so that either: 1) The universe started at the same temperature everywhere, so inflation is not required to explane the relative isotropy of the CMB (though it obviously helps explain the anisotropies). or 2) The universe did not start at the same temperature everywhere, but inflation (or some other effect) expanded that inhomogeneity beyond our horizion, and also added the anisotropies. And we are not currently in a position to determine which of those two is the case? That was the crux of much of what I was wondering, whether the universe could have been thermally homogeneous at extremely early times, and it sounds like the answer is "Maybe, because we can't predict what comes out of a singularity." And so the end answer is that we're not sure whether inflation was required to explain the relative isotropy of the CMB, because we cannot know what emerged from the singularity? We thus can't use the relative overall isotropy of the CMB as necessary proof for the idea of inflation (although inflation does give an additional reason why it would be isotropic). Rather, it is the anisotropies and the science and modeling associated with them that supports the idea of inflation? [/QUOTE]
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Question on the horizon problem
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