Earth's birth began around 4.6 billion years ago from a swirling cloud of gas and dust (the solar nebula) that collapsed under gravity, forming the Sun in the center and a spinning disk around it. Dust and rock particles within the disk collided and stuck together, growing into larger bodies called planetesimals and then protoplanets, one of which became Earth. Earth started as a molten ball, experiencing intense heat, frequent impacts, and volcanic activity, eventually cooling to form a solid crust, oceans from cometary water, and the Moon from a giant collision with a Mars-sized body named Theia.