Follow your curiosity

What discovery has been shared with you?

FACTREE gives you something interesting to discover every day — and something worth talking about together.

Start with one fact. Explore it, go deeper, then follow whichever branch catches your imagination.

Choose subjects for a surprise

Exploring any topic

Begin your discovery

Your next discovery is one click away.

Choose one or more subjects above, or leave Any Topic selected and let curiosity decide.

Astronomy

Gradual Slowing of Earth's Rotation and Day Length Increase

Quick fact

Fossil corals show that 370 million years ago, Earth had about 400 days per year, meaning each day was only about 22 hours long. The Moon is currently slowing Earth's rotation by about 1.8 milliseconds per century.

Why this is interesting

Earth takes 24 hours to spin once—but it hasn't always been that way. Billions of years ago, a day was only about 6 hours long. What has been putting the brakes on our planet?