At midnight, at the end of the year, Earth celebrates the completion of two cycles.

The first, of course, is Earth’s rotation, turning day to night and back again.

To complete this cycle, Earth rotates at 1,000 miles an hour, counterclockwise.

Not all planets spin this way. Venus rotates the opposite direction, and Uranus spins at 90 degrees to its orbit.

But pretty much everything in the universe spins.

The second cycle of course, is Earth orbiting the sun. The Solar System began as a cloud of dust and gas spinning around the sun 4.6 billion years ago, and should keep spinning for a few billion years more.

This rotation of Earth around sun is even faster: 67,000 miles an hour, and it takes 365-and-a-quarter days. This was recognized and set into a calendar by the Romans, but they overlooked that extra quarter day.

Meaning that, by the late 1500s, the calendar had drifted 10 days off. At that point, Pope Gregory added a leap day every 4 years, and the modern calendar was born.

Our Solar System is moving, too, and faster still. It’s in the Orion arm of the Milky Way galaxy, which orbits a supermassive black hole at 600,000 miles an hour.

And the black hole is spinning, too, even faster—more than 1,000 times a second.

So, if the New Year has your head spinning, well, now you know why.