Earth’s Place in the Universe


The reason for our seasons

Like all planets, Earth orbits its sun. It takes 365.25 days for Earth to make one complete trip around our sun. That’s what we call a year, of course. Every four years, we add an extra day, called Leap Day, to catch up with the extra quarter days.

At the same time that Earth is circling the sun, it is also rotating on its axis. The axis is a line from the north to the south pole, through the center of the earth. Each rotation is a day. So when you watch the sun “rise,” it’s really you that is moving, riding along as Earth spins around on its daily rotation.

The reason for our seasons

If a year is one orbit, and a day is one rotation on an axis, what is a season? Seasons occur because our planet is tilted on its axis. That tilt creates seasons. When the northern hemisphere is tilted away from the sun, it’s winter in the North America and other northern continents. When the southern hemisphere is tilted away from the sun, it is winter in South America and other continents in the southern hemisphere.

Written by Laura McCamy

Edited by Beth Geiger, MS Geology

Illustrated by Renee Barthelemy