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Sun, Moon and Earth

9 8 In between the two solstices, the longest and shortest days in the year normally 21st June and 22nd December, lie the two equinoctial periods in the spring and the autumn. The equinoxes 21st March and 23rd September deliver equal lengths of day and night everywhere on the planet, with the Sun rising exactly due east and setting exactly due west, on a level horizon. These equinoctial dates are accompanied by the maximum rate of change in the length of the day. In temperate latitudes, this creates the impression that the year is divided into two distinct halves, a light, warm, summer half, and a dark, cold, winter half. During the summer half the Sun rises and sets north of an east west line in the winter half always south of it. The solstices and equinoxes naturally divide the year into four quarters, defining the four seasons. Each season is about 91 days in length see page 5 and opposite page 1, caused by the tilt of the Earth on its own axis currently 23 o with respect to its orbital plane. This angle may be constructed using a right triangle, base 13 and height 30, or more approximately 3 and 7. The crossquarter days, halfway between equinoxes and solstices, are still celebrated as the Celtic festivals of Samhain November, Imbolc February, Beltane Mayday and Lughnasadh August. The Earth orbits the Sun at the incredible speed of 66,666 miles per hour and at a distance of 108 solar diameters. SolStIceS equInoxeS the four natural divisions of the year 1 2 9
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