What's the Earliest the Moon Could Have Formed?

Astronomers are pretty sure they know where the Moon came from. In the early Solar System, a Mars-sized object dubbed Theia smashed into Earth. This cataclysmic collision knocked a huge mass of material into orbit, which coalesced and cooled into the Moon. But establishing exactly when this occurred is a difficult task. At the 55th … Continue reading "What's the Earliest the Moon Could Have Formed?"