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The Sky at Night
BBC Four

S69E06: The Expanding Universe

The Sky at Night · 2025
Aired 08 Sep 2025 at 9:00pm (UTC)
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The Expanding Universe

Synopsis

The team explores one of the greatest discoveries of modern astronomy - that our universe is expanding - and the new questions it raises about how the cosmos works. In the 1920s, astronomers studying galaxies realised they were moving away from us, with the most distant ones receding the fastest. The conclusion was revolutionary: space itself was stretching, and the universe was expanding in every direction. But once this discovery was made, a new challenge emerged – how fast is the universe expanding, and what could that tell us about its age, size and ultimate fate?

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