Earth has seasons because its axis is tilted about 23.5 degrees relative to its orbit around the Sun. This tilt causes different parts of Earth to receive varying amounts of solar energy throughout the year. When one hemisphere is tilted toward the Sun, it experiences summer with more direct sunlight and warmer temperatures. Conversely, when that hemisphere is tilted away from the Sun, it experiences winter with less direct sunlight and cooler temperatures. The tilt remains pointed in the same direction as Earth orbits, so the amount and angle of sunlight change over the course of the year, producing the seasons. Earth's distance from the Sun during its orbit plays a much smaller role and is not the cause of seasonal changes.
How the tilt causes seasons
- The tilt causes one hemisphere to lean toward the Sun for part of the year (summer), receiving sunlight more directly.
- The other hemisphere tilts away at that time, receiving sunlight at a shallower angle (winter).
- This alternates as Earth orbits the Sun, causing opposite seasons in the Northern and Southern Hemispheres.
Additional notes
- Regions near the equator receive relatively consistent sunlight year-round and have less variation in seasons.
- The tilt and Earth's orbit produce varying day lengths and sun angles, further contributing to seasonal temperature differences.
- The Moon stabilizes Earth's tilt, helping maintain relatively consistent seasonal patterns over long periods.
Thus, the primary reason Earth has seasons is its axial tilt and the resulting change in solar angle and daylight intensity as it orbits the Sun.
