The Cosmic Microwave Background in the Early Universe

By the mid-1950s, astronomers using radio telescopes were finding that the number density of really bright radio emitting objects was higher in the past than it was today. In a universe that's expanding, you could easily understand why there might have been more of these things per volume in the distant past than there are today. Fred Hoyle lived until 2001 and he died still rejecting the Big Bang theory. He didn't think it made real predictions, which he's just wrong about.