Why do we have seasons?

In summer you splash in the pool, and in winter you build snowmen. Why does the weather change so much through the year? The answer is hiding in the way Earth leans.

Earth leans to one side

As Earth travels around the Sun, it doesn’t sit up straight. It is a little bit tilted, like a top that leans as it spins. That small lean makes a big difference.

It takes Earth a whole year to travel all the way around the Sun, and the lean always points the same way.

Leaning toward the Sun means summer

When your half of Earth leans toward the Sun, the sunlight hits it strong and straight from high in the sky. The days are long and warm — that’s summer.

Half a year later, your side leans away. Now the sunlight arrives weak and slanted, the days are short, and it feels cold. That’s winter. Spring and autumn are the gentle in-between times.

Two sides, two seasons

Here is something funny: when it is summer where you live, it is winter on the other half of the world at the same time, because they are leaning the opposite way!

Wonder fact: Earth is actually a tiny bit closer to the Sun in January — so the seasons come from the tilt, not from being nearer or farther away.