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But in the case of looking at the CMB and looking at the temperature change there and looking at inflation, two parts of the sky never came in contact. So you can look up any direction into the universe as far as you can see with telescope. And two sections of the sky were never in contact. So how is it that they managed to remain beautiful in temperature? They were always, right from the beginning, too far apart for light or even any info to pass between them. And any light from them is meeting constantly in the here and now for the first time. And how did the two points outside each other's observable universe get to be at exactly the same temperature? And this is what's called the horizon problem. And the best way to answer this is to introduce a period of extremely hot, fast expansion. So that refers to cosmic inflation.