The seasons, solstices, and equinoxes

Earth has seasons because its axis is tilted about 23.5 degrees relative to its orbit, not because its distance from the Sun changes much; Earth is actually closest to the Sun in early January, during Northern Hemisphere winter. When a hemisphere is tilted toward the Sun, sunlight hits it at a steeper, more direct angle, concentrating the same energy on a smaller area, and its days are longer, so it has summer; tilted away, it gets slanting, spread-out sunlight and short days, so it has winter. At the solstices, around June 21 and December 21, one hemisphere is tilted most toward the Sun, giving the longest and shortest days of the year. At the equinoxes, around March 20 and September 22, neither hemisphere tilts toward the Sun, and day and night are about equal everywhere. Near the equator, day length stays close to 12 hours all year; the difference grows toward the poles, where there can be 24-hour daylight in summer and 24-hour darkness in winter. A planet with almost no tilt, like Jupiter, has very weak seasons, while Uranus, tilted about 98 degrees, has extreme ones.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report