Happy birthday Universe! Unfortunately, its hard to see the cake beneath all 13.7 billion candles… [0:24m]
What’s the facts?
Yes, we actually know the age of our Universe! But how do we know? One helpful clue is that our Universe is expanding. We see this from the fact that distant galaxies in all directions are moving away from us, and the most distant galaxies are moving the fastest. Trace back all that motion to one point in space and time – the Big Bang – and you can figure out how long the Universe has been around. However, this type of age estimate makes an assumption as to how the Universe formed and how the expansion rate has changed over time – in astronomer-speak, it’s a “model-dependent” age. But other direct age estimates, such as the radioactive decay of heavy elements and the ages of the oldest stars and star clusters, give similar numbers. Astronomers now estimate that the Universe is 13,700,000,000 years old – now that’s a birthday cake!
Original air date 4 April 2009.