o princípio e o fim

Life begins with the process of star formation. We are made of stardust. Every atom of every element in your body except for hydrogen has been manufactured inside stars, scattered across the Universe in great stellar explosions, and recycled to become part of you.

I started this book with what may have seemed a metaphor, the idea of life on Earth as stardust, made from material forged inside the stars themselves. I end it with the discovery that this is not a metaphor at all - it is the literal truth. The raw material from which the first living molecules were assembled on Earth was brought down to the surface of the Earth in tiny grains of interplanetary material, preserved in the frozen hearts of comets from the interstellar debris of the giant molecular cloud from which the Solar System formed. Those grains themselves - literally, not metaphorically - formed from material ejected by stars. The 'manna from heaven' that carried the precursors of life down to the surface of the Earth was literally, not metaphorically, stardust. And so are we.