Celebrate the first day of fall with this gorgeous animation that shows how the Earth changes with the seasons

• An animation showcases how the seasons change with Earth’s orbit around the sun.
• Earth’s axis tilt causes very specific weather patterns and daylight during the course of a year.
• Most places experience four seasons, but they’re not as pronounced near the equator.

Astronomers believe that billions of years ago, a Mars-sized object smashed into Earth, knocking our planet over and leaving it tilted at an angle.

That ancient bump is what caused the Earth’s seasons — times of the year that have very specific weather patterns and hours of daylight that vary depending on the latitude. It’s the reason Sunday is the first day of fall, also called the equinox.

Most places experience four noticeable seasons: spring, summer, autumn, and winter. Below, view how the seasons change with Earth’s orbit around the sun:

Earth is divided into a northern and southern hemisphere by an imaginary ring called the equator. When the northern hemisphere is leaning toward the sun in June, it experiences summer. That’s when the sun’s rays hit that part of Earth more directly, heating Earth’s surface. When it’s summer in the northern hemisphere, it’s winter in the southern hemisphere.

Six months later, in December, the situation is reversed: the northern hemisphere is tilted away from the sun, and it experiences winter weather.

The tilt of the Earth’s axis also defines the length of daylight hours, which are shortest in each hemisphere’s winter. This is most dramatic at the planet’s poles, above the Arctic Circle.

In Utqiaġvik, Alaska, the northernmost town in the US, the darkness lasts from mid-November until mid-January.

Near the equator, the seasons are less pronounced, because each day the sun strikes at about the same angle. There, the duration of daytime remains almost 12 hours throughout all of the seasons.

The angle of the Earth’s tilt is relatively stable, but there are some slight shifts over large time scales (tens of thousands of years). According to NASA, the angle is slowly decreasing.

This story was originally published on December 21, 2022, and most recently updated on September 20, 2024.