Astronomy › Section V · The Big Bang › Topic V.1
The age of the universe
If galaxies are moving apart today, they were closer together in the past. Running the expansion backwards gives the age of the universe, about 13.8 billion years, and the oldest stars give an independent check.
In this topic
- A universe that cannot stand still
- Running the film backwards
- The Hubble time
- Worked example: the Hubble time for H0 = 70
- The Hubble tension
- Slowing down, then speeding up
- Dark energy and the 13.8-billion-year age
- Checking with the oldest stars
- Worked example: a uranium clock
- Common mistakes to avoid
- Key takeaways
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