What is equinox?

Ans. On 21^st March & September 23^rd, direct rays of the sun fall on the equator. At this positions neither of the poles is tilted towards the sun so, the whole earth experiences equal days & equal nights. We have 12 hours of day & 12 hours of night. This is called an equinox. On 23^rd September it is autumn season in the southern Hemisphere & is called autumn equinox. The opposite is the case on 21^st March When it is spring in the Northern Hemisphere & called spring & equinox autumn in the Southern Hemisphere.