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Astronomy

How the Cosmic Microwave Background Reveals the Universe's Age

Quick fact

The cosmic microwave background is a snapshot of the universe when it was just 380,000 years old, and its temperature ripples—about one part in 100,000—encode the universe's composition and geometry, which together pin down its age to about 13.8 billion years.

Why this is interesting

When you tune an old TV to a channel with no signal, part of the static is the faint afterglow of the Big Bang. How can that glitch tell us the universe is 13.8 billion years old?