Imagine a planet that spins so fast a day lasts not 24 hours but only six. Daytime is brief, and nighttime is only long enough for a nap. The planet’s moon rushes across the sky so close it looks 10 times larger than our familiar Moon!
No, this is not one of the Earth-like planets astronomers have discovered around distant stars. It is Earth itself, 4.5 billion years ago, when the Moon was newly formed and orbiting less than 20,000 miles (32,200 kilometers) from Earth.
Since then, the power of the tides has slowed Earth’s spin and pushed the Moon’s
