Seasons and sky
Season Length Asymmetry
Direct answer
Season Length Asymmetry is the unequal duration of the four astronomical seasons caused mainly by Earth's changing orbital speed along its elliptical orbit.
Season Length Asymmetry is the unequal time between successive equinoxes and solstices.
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At a glance
- Found in
- Seasons & Earth Almanac
- Related
- Earth-Sun Distance Cycle, Equilux, Astronomical Season, Equinox
Season Length Asymmetry is the unequal time between successive equinoxes and solstices.
A Sun-Earth orientation for seasonal, atmospheric, tidal, and terrestrial terms.
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The story behind Season Length Asymmetry
Kepler second law supplied the dynamical explanation for unequal seasonal intervals already visible in careful solar calendars.
Why Season Length Asymmetry matters
Earth moves faster near perihelion and slower near aphelion, so seasonal quarters are not all the same number of days.
How to read Season Length Asymmetry
Season Length Asymmetry comes up when comparing equinox-to-solstice intervals or explaining why calendar seasons differ in duration.
Season Length Asymmetry in practice: an example
Northern Hemisphere spring and summer together currently last longer than autumn and winter because aphelion falls during northern summer.
Where readings of Season Length Asymmetry go wrong
It is a mistake to infer warmer weather from a longer astronomical season; climate response depends on many local and planetary factors.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory: The Seasons and the Earth's Orbit - Official explanation of axial tilt, solstices, equinoxes, perihelion, aphelion, and seasonal sunlight.
- U.S. Naval Observatory: Astronomical Almanac Glossary - Reference definitions for astronomical periods, coordinates, dates, and time scales.
- Source
- The Great Almanac Dictionary
- Category
- Seasons & Earth Almanac
- Last updated
- 2026-09-26
Compare the four seasonal intervals
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Common questions
What is Season Length Asymmetry?
Season Length Asymmetry is the unequal duration of the four astronomical seasons caused mainly by Earth's changing orbital speed along its elliptical orbit.
What do people get wrong about Season Length Asymmetry?
It is a mistake to infer warmer weather from a longer astronomical season; climate response depends on many local and planetary factors.
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