Understanding Earth's Seasons and Axial Tilt

Earth's axis is tilted 23.5 degrees relative to its orbit around the Sun. This tilt is responsible for the changing seasons as different parts of Earth receive varying sunlight intensity throughout the year.

Contrary to popular belief, seasons are not caused by Earth's varying distance from the Sun but by its axial tilt. Earth's orbit is elliptical, with distance changes having a lesser effect on seasons than the axial tilt.

Seasons are marked by solstices and equinoxes. Solstices occur when Earth's poles are at maximum tilt toward or away from the Sun, resulting in the longest and shortest days. Equinoxes happen when the tilt is neutral, leading to equal day and night.

Earth reaches perihelion, the closest point to the Sun, in January, during Northern Hemisphere's winter. Aphelion, the farthest point, occurs in July, during Northern Hemisphere's summer. This counterintuitive phenomenon further emphasizes that distance does not dictate seasons.

If you photograph the Sun at the same time over a year, the resulting shape is an analemma. This figure-eight pattern is due to Earth's axial tilt and elliptical orbit, demonstrating the complex motion resulting in our experience of time and seasons.

Over 26,000 years, Earth's axis precesses or wobbles, like a spinning top. This slow movement alters the orientation of the axis in space and shifts the timing of the seasons, a cycle known as the Great or Platonic Year.

Earth's orbital changes over tens of thousands of years, known as Milankovitch cycles, affect climate and seasons. These cycles include variations in tilt, orbit shape (eccentricity), and precession, and are thought to influence long-term natural climate change patterns, like Ice Ages.

Uranus has a 98-degree axial tilt, causing extreme seasonal changes where each pole experiences 42 years of continuous sunlight or darkness.