Sun Stopping

by Rosalind

The latin word for Solstice is Solstitium and it means "sun stopping". At the June Solstice the sun appears to stop heading north and begins to head south again.

What this means is that the Earth's North Pole is pointed directly towards the sun: a great time to head north to the Arctic Circle see the midnight sun, but a near impossible time to go travelling to Antarctica which is going through the long dark frozen season.

For those in the Northern Hemisphere this can only mean one thing - summer has arrived! For those in the Southern Hemisphere it is the winter solstice: the time of the longest night.

At the same time the sun passes directly over the Tropic of Cancer (the latitude line at 23.5° north, passing through Mexico, Saharan Africa, and India).

Mostly this furthest point of our star's apparent journey occurs on June 21st but occasionally the date of the solstice varies slightly ; the last time this happened was June 22nd 1975, the next time will be June 20th 2012.

If the Earth was not slightly tilted(23.5 degrees), there would be no seasons as the same amount of sunlight would hit our planet throughout the year. Between the Tropic of Cancer and the Tropic of Capricorn (23.5° latitude south) there really are no seasons as the Sun is never very low in the sky so it stays warm and humid ("tropical") year-round. Only those people in the upper latitudes north and south of the tropics experience seasons.

The Earth does not move at a constant speed in its elliptical orbit. Therefore the seasons are not of equal length: the times taken for the Sun to move from the March equinox to the June solstice, to the September equinox, to the December solstice, and back to the March equinox are roughly 92.8, 93.6, 89.8 and 89.0 days respectively. The consolation in the northern hemisphere is that spring and summer last longer than autumn and winter.

Image credits:
From Wikimedia Commons