horizon problem

startswithabang.com reader Andy has a great follow-up to his question on the Age & Size of the Universe, and asks: why does the CBR “appear” to come from a light sphere that “appears” NOW to be larger than the universe WAS when it first set off in a straight line on its 13.4 billion year trip??? The "CBR" stands for "Cosmic Background Radiation," and it refers to the (presently) microwave background. Here's why Andy's question is actually profound, and was known for about 20 years as either the homogeneity problem or the horizon problem. The problem is that, when we look up at the sky,…