An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The period during which the Sun is close enough to one of the → lunar orbit nodes so that an eclipse can take place. This time window lasts for 37 days for → solar eclipses and almost 24 days for → lunar eclipses. These seasons occur every 173.31 days. Two eclipse seasons make up an → eclipse year.

→ eclipse; → season.

One of the four periods of the year astronomically defined by the position of the Sun with respect to the equator. As a result of the obliquity of the ecliptic, the angular distance between the Sun and the equator varies in the course of the year. This circumstance gives rise to seasons. The current lengths of the astronomical seasons, around the year 2000, are about: spring 92.76 days, summer 93.65 days, autumn 89.84 days, and winter 88.99 days. The seasons are unequal because the Earth's orbit is slightly elliptical and the Sun is not exactly at the center of the orbit. Moreover, the Earth moves faster when it is close to the Sun than when it is farther away, so the seasons that occur when the Earth is close to the Sun pass more quickly.

M.E. sesoun, seson, from O.Fr. seison "a sowing, planting," from L. sationem (nominative satio) "a sowing," from p.p. stem of serere "to scatter seed over land."

Fasl, from Ar. faSl "cutting, dividing; section."