Why is summer hot and winter cold? Some people say Earth is closer to the sun in summer. That is not true. The distance to the sun does not make summer hot or winter cold.

Earth goes around the sun. One trip takes about a year, or about 365 days. Earth is also tilted, so it does not stand up straight.

The tilt is about 23 and a half degrees. As Earth goes around the sun, its tilt always points the same way in space. Earth does not wobble back and forth.

In June the north half of Earth is tilted toward the sun. It is summer there. In December the north half is tilted away from the sun.

In summer the sun is higher in the sky. Its rays hit the ground more directly. That makes summer warmer.

In winter the rays hit the ground at a slant. They spread out over more ground. They warm it less. That is part of why winter is cold.

Summer days have more hours of sunlight. Winter days have fewer hours of sunlight.

When it is summer in the north, it is winter in the south. The seasons are opposite.

In fall, many tree leaves lose their green color. Then you can see yellow, orange and red.

Some animals migrate when the seasons change. They travel a long way to a winter home.

So the seasons do not come from distance. They come from the tilt of Earth.

Words to know

• tilted: leaning, not straight
• degrees: units for angles
• migrate: travel far
• opposite: the other way