Sunday 20 March 2016

March Equinox, 2016.

The March Equinox fell on 20 March this year. The Earth spins on its axis at an angle to the plain of the Solar System. This means that the poles of the Earth do not remain at 90° to the Sun, but rather the northern pole is tilted towards the Sun for six months of the year (the northern summer), and the southern pole for the other six months (the southern summer). This means that twice a year neither pole is inclined towards the Sun, on days known as the equinoxes.

The tilt of the Earth relative to the Sun at the planet's equinoxes and solstices. Astronomy Group/University of St Andrews.

The equinoxes fall each year in March and September, with the March Equinox being the Spring (or Vernal) Equinox in the Northern Hemisphere and the Autumn Equinox in the Southern Hemisphere, while the September Equinox is the Autumn Equinox in the Northern Hemisphere and the Spring Equinox in the Southern Hemisphere. On these two days the day and night are both exactly twelve hours long at every point on the planet, the only days on which this happens.

See also... 2015 December Solstice.                      The December (or Southern) Solstice this year falls on Tuesday 22 December, when the Sun is at its southernmost point in the sky. This is the shortest day of the year in the Northern Hemisphere, where it is known as the Winter Solstice and the longest day in... of the Supermoon.                              A total Lunar Eclipse will occur on 28 September 2015, starting at about ten minutes past midnight GMT. It will be visible across much of Western Europe and... Equinox 2015.                              The September Equinox will fall on Friday 23 September 2015, when the day and night will be of equal length in both of the Earth's hemispheres. The Earth's seasons are driven by the tilt of the planet, but the planet does not, as is generally assumed, tilt back and forth over the course of a year. Rather it remains at a constant angle of 23½° to the plane of its orbit throughout the year...

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