| Autumnal Equinox | + The sun is directly overhead, on the autumn equinox, at the equator and if the earth was a perfect sphere, there would be 12 hours of day and 12 hours of night. + The sun sets at the north pole and will not rise again until the next equinox around March 21. + In contrast, on the south pole the sun rises and will not set until March 21. |
Whether one considers that the summer consists of June, July and August, or whether it really only begins three months after the vernal equinox, the irrefutable fact is that the autumn will soon be with us and summer will be well and truly over. At 1729 BST on Wednesday 22nd September 2004, the sun will cross the celestial equator - the autumn equinox will be here. The significance of this is that every point on Earth will, for one day, experience 12 hours of darkness and 12 hours of daylight. At the South Pole the penguins will be celebrating the first appearance of the sun in six months. By the same token, at the North Pole the polar bears will be bracing themselves for six months of darkness.
 | | South Pole penguins get ready for sun |
The occurrence of the autumn equinox and its counterpoint the vernal (or spring) equinox (around March 21st) is a consequence of the Earth’s movement around the sun. The axis of this orbit is inclined at an angle of 23.5 degrees. So at the winter solstice the sun is 23.5 degrees south over the Tropic of Capricorn. The vernal equinox sees the sun crossing the celestial equator whilst the summer solstice is the point at which the sun is over the Tropic of Cancer. When the sun then begins its journey into the southern hemisphere, the autumn equinox is here. It is sometimes claimed that this event has an effect on our weather. Mariners often talk of equinoctial gales. But evidence for this is, at best, debatable. The long nights will soon be with us and so, for many, will the winter blues. But cheer up, there will then be just around 90 shopping days left to Christmas. | 
