Some 4.5 billion years ago, a Mars-sized world called Theia struck the young Earth, and from that violence the Moon was born — or so the story has long been told in the language of fluid dynamics and slow-assembling debris. New simulations from researchers at the Southwest Research Institute now suggest that the Moon's birth may have been far more sudden and whole, emerging intact within roughly five hours when the geological strength and temperature of the colliding bodies are properly accounted for. This shift in modeling — from treating planets as liquids to honoring the actual resistance o