The two edges of the visible universe are 28 billion light years apart. And yet our universe is only 14 billion years old.

Since nothing can travel faster than the speed of light and the CMBR temperature is even everywhere, there is no way temperature could have evenned out as there would be no time for the various regions to have 'seen' each other.

Thus, the 'horizon' problem.

The image is created by MK, publisher of Cosmology Curiosity -- http://woodside.blogs.com/cosmologycuriosity/ archive copy at the Wayback Machine

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