It began in a moment of unimaginable violence, five billion years before humans walked the Earth.

There was a cloud, of gas and dust, slowly spinning. Much of it was the hydrogen and helium which had emerged from the Big Bang itself, but it was tainted by crystals of ice — ammonia, water and methane — and dust motes rich in iron, magnesium and silica, even some grains of pure metal. These were flotsam from older stars, stars already dead.

…And now another star died, a giant, in the conclusive spasm of supernova. A flood of energy and matter hammered into the cloud.

The cloud lost its stability, and began to collapse, to a spinning disc. The central mass shone cherry red, then gradually brightened to white, until — after a hundred million years — it burst into fusion life.

It was the protostar which would become the sun.

Within the disc, solid panicles began to crystallize. There were grains of rock — silicate minerals called olivines and pyroxenes — and minerals of iron and nickel, kamacite and taenite. The particles, stuck together by melting ice, formed planetesimals, muddy lumps which swarmed on looping, irregular orbits around the sun.