What is the exact time of the spring equinox 2010?”
An equinox occurs twice a year, when the tilt of the Earth’s axis is inclined neither away from nor towards the Sun, the Sun being vertically above a point on the 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 are approximately equally long. It may be better understood to mean that latitudes +L and -L north and south of the equator experience nights of equal length. The word is also used for the same event happening on other planets and in setting up a celestial coordinate system; see equinox (celestial coordinates). At an equinox, the Sun is at one of two opposite points on the celestial sphere where the celestial equator (i.e. declination 0) and ecliptic intersect. These points of intersection are called equinoctial points: the vernal point and the autumnal point. By extension, the term equinox may den
During the course of a year the Earth completes one orbit around the Sun. To us on Earth we see this as the Sun moving against the background of stars through the year, along an imaginary line which we call the ecliptic. This defines the plane in which the Earth and most of the other planets orbit around the Sun. The directions to the north and south ecliptic poles are at right angles to this. The Zodiac is the band of constellations running along the ecliptic. The Earth’s orbit around the Sun takes 365.25 days, and a ‘day’ is, of course, defined as the Earth spinning once on its axis. The Earth’s axis of rotation, tilted at 23.5 degrees to the line of the poles of the ecliptic, gives us the directions to the north and south celestial poles. The bright star Polaris is currently showing us the direction of the north celestial pole. Like a spinning top this axis is precessing around the ecliptic pole with a period of 26,000 years. The celestial equator is the projection of the Earth’s eq
