What is an equinox ?

An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latin aequus (equal) and nox (night), because around the equinox, the night and day have approximately equal length.

in every fourth year, february has 29 days instead of 28 days is called a leap y6ear

sorry girshu i have forget wrote about  aleap year and the answer is

an equinox is a day  when the duration of day and night is of equal lenght in both the hemispheres

21st march and

23 september

 Equinox is the position of the earth on 21st March and 23rd September.Both the Hemispheres experience equal day and nights?

when the midday sun falls vertically on the equator and the duration of day & night are equal it is called equinox.the word 'equinox' stands for equal nights

great effort by all , keep answering.

position 1and 3.

Equinox is one of the two moments when the sun appears overhead at the eqator.(21 march and23 september) On the day of eqinox day and night are equal in length.

equinox is the day when in both the northern and southrn hemispheres day and night are equal.

HOPE IT HELPS!!!!!!!!!

Equinox is the position of the earth when the rays of the sun fall directly on the equator. At this position,neither of the poles is tilted towards the sun.As a result,the entire Earth has equal days and equal nights.........Hope it is helpful to you!

Anequinoxoccurs twice a year, when the tilt of the Earth 's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth 's equator. The termequinoxcan also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latinaequus(equal) andnox(night), because around the equinox, the night and day have approximately equal length.

Either of two times of the year when the sun crosses the plane of the earth's equator and day and night are of equal length. There are 2 equinoxes spring equinox autumn equinox.

equinox means equal days and nights

Anequinoxoccurs twice a year (around 20 March and 22 September), when the plane of the Earth'sequatorpasses the center of the Sun. At this time thetiltof theEarth's axis is inclined neither away from nor towards theSun. The termequinoxcan also be used in a broader sense, meaning the date when such a passage happens. The name "equinox" is derived from the Latinaequus(equal) andnox(night), because around the equinox, night and day are about equal length.

At an equinox the Sun is at one of two opposite points on thecelestial spherewhere thecelestial equator(i.e. declination 0) andeclipticintersect. These points of intersection are calledequinoctial points: classically, thevernal point(RA=00^h00^m00^sand longitude = 0º) and theautumnal point(RA=12^h00^m00^sand longitude = 180º). By extension, the termequinoxmay denote an equinoctial point.

The equinoxes are the only times when thesubsolar point(the place on the Earth's surface where the center of the Sun is exactly overhead) is on the Equator. The subsolar point crosses the Equator moving northward at the March equinox and moving southward at the September equinox. (Since the sun's ecliptic latitude isn't exactly zero it is not exactly above the equator at the moment of the equinox, but the two events usually occur less than 30 seconds apart.)

The equinoxes are the only times when theterminatoris perpendicular to the Earth's Equator. Thus the Northern and Southern hemispheres are illuminated equally. (At the solstices, that angle reaches its minimum of 66.5, corresponding to 90 minus Earth's axial tilt).^[2]

Another meaning ofequinoxis the date when day and night are the same length.^[3]The equinox is not exactly the same as the day when day and night are of equal length for two reasons. Firstly, because of the size of the sun, the top of the disk rises above the horizon (constituting 'sunrise' which is the start of 'daytime') when the center of the disk is still below the horizon. Secondly, the Earth's atmosphere refracts sunlight which means that an observer can experience light (daytime) even before the first glimpse of the sun's disk has risen above the horizon. To avoid this ambiguity the termequiluxis sometimes used in this sense.^{[4][note 1]}Times of sunset and sunrise vary with an observer's location (longitude and latitude), so the dates when day and night are of exactly equal length likewise depend on location. For places near the equator the daytime is always longer than the night, so they would never experience an equinox by this definition.