At the winter solstice in December (point A in the diagram) the North Pole is tilted furthest away from the Sun than at any other time of the year, and the South Pole is tilted nearest the Sun.However the precise astronomical definition of an equinox is slightly different.īecause the axis of the Earth is tilted rather than perpendicular to its orbit around the Sun, different parts of the Earth are closer to the Sun at different times of the year. The origin of the word equinox comes from two Latin words aequus (equal) and nox (night), suggesting that at an equinox the length of the day and night are equal. In fact, at the equinoxes there is actually nowhere on the Earth where there are exactly 12 hours of daylight and 12 hours of darkness. March 21 can sometimes be the date on which the spring equinox falls but its precise date varies from year to year and also depends upon where you are located. In fact, as I’ll explain later, this is only approximately correct. There is a commonly held view that March 21 is the spring equinox and that the equinoxes are the two days in the year when all places on the Earth have exactly 12 hours of daylight and 12 hours of darkness. In addition, in 2001 the United Nations declared 21 March as the International Day for the Elimination of Racial Discrimination (United Nations 2016). March 21 is also the first day of the astrological calendar, although as a scientist I am unconvinced of astrology’s usefulness for anything other than entertainment. ![]() Traditional German Easter postcard – Image from Wikimedia Commons ![]() Early Christian decision makers in the fourth century established that Easter would be held on the first Sunday after the first full moon occurring on or after March 21, and this definition is still used today. For one thing, it is used as the basis for the calculation of Easter. ![]() Now that we are in the month of March, for most of us in the northern hemisphere the worst of the winter is over, and it is only a couple of weeks until 21 March, the first day of spring.Ģ1 March is an important date for other reasons, too.
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