Axial Tilt
The axial tilt or obliquity is the angle between the orbital plane and the equatorial plane of a planet. It can also be described as the angle between the rotational axis and a perpendicular line to the orbital plane. The Earth's axial tilt is currently 23.44°. This angle varies between 22.1° and 24.5° in a period that lasts 41000 years.
The axial tilt is responsible for the existence of seasons because it allows one hemisphere to receive more sunlight than the other hemisphere for a determined amount of time in a year (orbital period).
Previous Posts
Concepts in Astronomy #1. Introduction
Concepts in Astronomy #2. The Ecliptic
Concepts in Astronomy #3. The Celestial Equator
Concepts in Astronomy #4. Right Ascension
Concepts in Astronomy #5. Declination
Concepts in Astronomy #6. The Celestial Sphere
Concepts in Astronomy #7. Azimuth
Concepts in Astronomy #8. Altitude
Concepts in Astronomy #9. The Equatorial Coordinate System
Concepts in Astronomy #10. The Topocentric Coordinate System
Concepts in Astronomy #11. Equinox
Concepts in Astronomy #12. Solstice
Concepts in Astronomy #13. Rotation Period
Concepts in Astronomy #14. Orbital Period
Concepts in Astronomy #15. Axial Precession