The seasons on Earth are caused primarily by the tilt of Earth's axis. Earth's axis is tilted about 23.4 to 23.5 degrees relative to its orbital plane around the Sun. This tilt means that as Earth orbits the Sun during the year, different parts of the planet receive varying amounts of sunlight and solar energy
. Key points explaining the cause of seasons:
- Earth's axis is tilted, not perpendicular to its orbit, so the Northern and Southern Hemispheres alternatively tilt toward or away from the Sun at different times of the year
- When a hemisphere tilts toward the Sun (e.g., Northern Hemisphere around June), it receives more direct sunlight and experiences summer. When it tilts away (e.g., Northern Hemisphere around December), it receives less direct sunlight and experiences winter
- The tilt causes the length of daylight and the intensity of sunlight to change throughout the year, leading to seasonal temperature changes and weather patterns
- Earth's orbit is slightly elliptical, but the variation in distance from the Sun has minimal effect on seasons. For example, Earth is closest to the Sun during the Northern Hemisphere's winter, so distance is not the cause of seasons
- The equinoxes (around March 21 and September 23) occur when the tilt of Earth's axis is such that both hemispheres receive equal sunlight, marking the start of spring and autumn
In summary, the axial tilt of Earth and the consistent orientation of this tilt as Earth orbits the Sun cause the changing seasons by altering the distribution and intensity of sunlight received by different parts of the planet throughout the year
