SOLSTICE
Solstice occurs twice a year, around 21 June and 22 December. On solstice day, the sun appears
to have reached its highest or lowest annual altitude in the sky above the horizon at local solar
noon. Summer solstice is the day of the year with the longest period of daylight or when the
length of time between sunrise and sunset is the longest of the year and Winter solstice is the
day of the year with the longest period of night or when the length of time between sunrise and
sunset is the shortest of the year. They signify the start of summer and winter respectively in the
Northern hemisphere. The word solstice is derived from the Latin sol (sun) and sistere (to stand
still), because at the solstices, the sun stands still in declination; that is, the seasonal movement
of the sun's path (as seen from the Earth) comes to a stop before reversing direction.
EQUINOX
An equinox occurs twice a year around 20 March and 22 September, when the tilt of the Earth's
axis is inclined neither away from nor towards the sun, the centre of the sun being in the same
pla e as the Ea th’s e uato . The a e e ui ox is derived from the Latin aequus (equal) and
nox (night), because around the equinox, the night and day have approximately equal length. The
days of equinox are known as Autumnal equinox which marks the first day of the season of
autumn and Spring equinox which marks the first day of the season spring in the Northern
hemisphere.
The tilt of the Earth creates seasons and solstice/equinox as the Earth moves around the
sun: