Seasons on Earth are caused primarily by the tilt of Earth's axis relative to its orbit around the Sun. Earth's axis is tilted about 23.4 to 23.5 degrees from perpendicular to its orbital plane. This tilt means that as Earth orbits the Sun over the course of a year, different parts of the planet receive varying amounts of sunlight at different times
. Key points explaining the cause of seasons:
- Earth's axis is tilted, so it does not stand straight up relative to its orbit around the Sun. This tilt remains pointed in the same direction in space throughout the year
- Because of this tilt, when the Northern Hemisphere is tilted toward the Sun (around June), it receives more direct sunlight, resulting in warmer temperatures and summer. At the same time, the Southern Hemisphere is tilted away from the Sun and experiences winter
- Conversely, when the Southern Hemisphere tilts toward the Sun (around December), it experiences summer, while the Northern Hemisphere experiences winter
- The amount of sunlight and its angle change throughout the year, causing the variation in temperature and daylight hours that define the seasons
- Earth's elliptical orbit does cause some variation in distance from the Sun, but this has little effect on the seasons. For example, the Northern Hemisphere's winter occurs when Earth is closest to the Sun, showing that distance is not the main factor
- Equinoxes occur around March 21 and September 23, when both hemispheres receive equal sunlight, marking the start of spring and autumn. Solstices mark the longest and shortest days, occurring when Earth's tilt is most extreme relative to the Sun
In summary, the axial tilt of Earth and its consistent orientation during its orbit cause seasonal changes by altering the intensity and duration of sunlight different regions receive throughout the year.
Summary:
- Earth's axis tilted ~23.4° causes seasons.
- Tilted hemisphere receives more direct sunlight → summer.
- Opposite hemisphere receives less → winter.
- Earth's distance from the Sun has minimal effect.
- Equinoxes and solstices mark seasonal transitions
