quantamagazine.orgAround 4.6 billion years ago, some 9 billion years after the birth of the universe, a cloud of gas and dust collapsed into the familiar blinding ball in our sky. Scraps of leftover material collided and accreted into the planets of the solar system, including our own. For the next few hundred million years, Earth was a hellish, molten landscape bombarded by meteorites. As it started to cool…