For decades, one question has haunted physics more stubbornly than almost any other: why does anything exist at all? According to the most basic laws of physics, the universe should never have made it past its first moments. Matter and antimatter should have been created in equal quantities during the Big Bang, instantly annihilating one another in a blinding flash of energy, leaving behind a smooth, empty cosmos filled only with radiation. And yet, here we are. Galaxies exist. Stars burn. Plan...