Earth is tilted by about 23 and a half degrees, and the tilt always points the same way in space as Earth goes around the Sun once a year. That tilt gives us the seasons, not the distance to the Sun. But the seasons are not the same everywhere on the planet.

How does a tilt change the heat? In summer, the Sun is higher in the sky and its rays hit the ground more directly, which makes summer warmer. In winter, the rays hit the ground at a slant. They spread out over more ground and warm it less.

The tilt also changes the length of the day. Summer days have more hours of sunlight, and winter days have fewer hours of sunlight. The summer solstice is the longest day of the year in the north part of Earth. The winter solstice is the shortest day and the longest night in the north.

The two halves of Earth have opposite seasons. When the north part leans toward the Sun, the south part leans away from it, and when it is summer in the north part of Earth, it is winter in the south part.

Seasons show up in living things too. In late summer the days get shorter, and that tells trees to make less green chlorophyll. Less chlorophyll lets other colors show, and some animals migrate when the seasons change and travel a long way to a winter home.

Near the equator it stays warm all year. There the seasons are wet and dry instead of warm and cold, but near the poles the amount of daylight changes dramatically between summer and winter. At the South Pole the Sun stays up all summer and stays down all winter, so days and nights last half a year.

Earth's orbit is slightly squashed, so Earth is a little closer to the Sun at some times of year and a little farther at others. Earth is closest in early January, in the middle of northern winter, as of November 2026. That changing distance is too small to cause the seasons. The seasons come from the tilt of Earth's axis.

Words to know

• equator: middle line
• orbit: path around
• migrate: travel far
• chlorophyll: leaf's green