Tilt Definition //top\\ - Axis

It is a common pedagogical error to define axis tilt as "the angle of the Earth's axis from the vertical." While functionally equivalent, the precise astronomical definition references the orbital plane (the ecliptic). Thus, Earth’s axis is tilted 23.44° away from the perpendicular to its orbital path.

| Planet | Axis Tilt (Obliquity) | Notable Effect | | :--- | :--- | :--- | | Mercury | ~0.03° | No seasons | | Earth | | Temperate seasons | | Mars | 25.19° | Similar seasons, but more extreme due to eccentric orbit | | Jupiter | 3.13° | Negligible seasonal variation | | Saturn | 26.73° | Pronounced seasons (7+ years each) | | Uranus | 97.77° | Extreme seasons; poles face Sun directly |

1. Formal Definition

For Earth, the current mean obliquity is approximately (or 23°26′). This value is not constant; it varies between 22.1° and 24.5° over a cycle of approximately 41,000 years due to gravitational perturbations from other planets (a Milankovitch cycle).