An equinox is a day when the sun is in its apex over the Equator, and the Earth experiences days and nights of generally equal length. There are two equinoxes in a year: around March 21 and around Sept 22. Equinox is an astronomical event, caused by Earth’s tilt on its axis and ceaseless orbit around the sun. Only during an equinox is the Earth’s 23.5-degree axis not tilting toward or away from the sun: the center of the sun is in the same plane as the Equator. From here on, nights are longer than days and days continue to get shorter.

                    In the Northern Hemisphere, March 21 is the spring or vernal equinox. September 22 is the autumnal equinox. March and September are spring and fall in the Northern Hemisphere, but it’s the opposite in the Southern Hemisphere. The Southern Hemisphere’s “spring” equinox takes place in autumn.


The equator is located at zero degrees latitude. The equator runs through Indonesia, Ecuador, northern Brazil, the Democratic Republic of the Congo, and Kenya, among other countries. The equator divides the planet into the Northern and Southern Hemispheres. On the equator, the length of day and night is equal every day of the year – day is always twelve hours long and night is always twelve hours long.

Axis is an imaginary line going right through the planet between the north and south poles. The axis is tilted somewhat off the plane of the earth’s revolution around the sun. The tilt of the axis is 23.5 degrees; thanks to this tilt, we enjoy the four seasons. For several months of the year, one half of the earth receives more direct rays of the sun than the other half.

When the axis tilts towards the sun, as it does between June and September, it is summer in the northern hemisphere but winter in the southern hemisphere. Alternatively, when the axis points away from the sun from December to March, the southern hemisphere enjoys the direct rays of the sun during their summer months.