Thinking space

Martin Rees is sitting in the Master’s Lodge of Trinity College, Cambridge, with a laptop balanced on his knee. ‘I want to show you this,’ he says, tapping the keys with long, neat fingernails. Two red swirls appear on either side of the screen, gliding towards each other. When they meet it’s messy, like two ripe tomatoes smashing together in mid-air. We are watching one of the most violent events in the universe. ‘That’s two galaxies colliding,’ he explains.

In five billion years our own galaxy may be one of the exploding fruit. That’s when the Milky Way is predicted to crash into Andromeda, creating an intergalactic splatter known as ‘Milkomeda’. But like many things in our universe, it’s far from certain. Few people are better equipped to follow this cosmic food fight than Rees. The emeritus professor of cosmology and astrophysics at Cambridge has worked on more than 500 research papers, expanding our understanding of such celestial exotica as gamma ray bursts, redshifts, quasars and black holes. Astronomy, one of the oldest sciences, has advanced dramatically in the past half century, thanks in no small part to Rees.

We now understand the ‘ultra-early universe’, as astrophysicists call it, with some precision. At first, the cosmos was like a bad nightclub: exceedingly hot and densely packed. Then came the Big Bang. A nanosecond later every particle in the expanding universe carried as much energy as can be generated by the Large Hadron Collider. Our sun was formed 4.5 billion years ago and will begin to die in another five billion. Our bodies are the result of four billion years of evolution and are composed of the ashes of dead stars.

But there are plenty of things astronomers still don’t know. What came before the Big Bang? What banged and why? And does Ming the Merciless really live on the planet Mongo, or are we all alone in the universe? Astrophysics is a bustling bazaar of competing explanations.