Season 1, Episode 4
In the last episode of Professor Brian Cox's epic journey across the universe, he travels from the fossils of the Burgess Shale to the sands of the oldest desert in the world to show how light holds the key to our understanding of the whole universe.
Brian Cox explores Andromeda - another galaxy roughly the size of our own.
Where does the sun get its energy?
Which chemicals make up our universe?
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