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Astronomy

How Do Astronomers Calculate the Age of the Universe?

Quick fact

The most precise measurement of the universe's age comes from the cosmic microwave background observed by the Planck satellite, giving 13.787 ± 0.020 billion years.

Why this is interesting

If you could rewind the expanding universe like a cosmic video, how far back would you go? Astronomers use two independent methods—one based on galaxies racing away from us, the other on the oldest light in the universe—to arrive at the same surprising number: 13.8 billion years.