The inclination of the earth's equatorial plane to the plane of the earth's orbit around the sun, termed the obliquity of the ecliptic by astronomer's, is approximately equal to 23º27' of arc. If this inclination were 0º the sun would remain directly overhead the Equator throughout the year and there would be no seasons. In reality, the directly overhead point of the sun moves north and south with the seasons.
Beaman, Ralph G.
Word Ways: Vol. 3
, Article 15.
Available at: http://digitalcommons.butler.edu/wordways/vol3/iss2/15