Sunday is the 23rd September, which is the Autumnal Equinox in the northern hemisphere (of course it is the Spring or Vernal Equinox in the southern hemisphere), and to mark the occasion here are a few fun facts about equinoxes:
- We tend to say that a particular day is the equinox, when in fact the equinox is a moment in time when the sun is directly overhead at the equator - technically the celestial equator.
- This also means that the equinox will be on different days in different parts of the world, depending on your time zone. Those countries in the east (just to the west of the International Date Line) often have the equinoxes during the day after those countries further west. The equinox is at the same time, it just happens to be after midnight in those countries.
- Most other planets in the solar system have equinoxes. On Saturn the rings align with the sun's rays and they cast virtually no shadow.
- Equinox comes from the Latin for equal night, but this doesn't mean that everywhere gets a day and night of the same length. Because of diffraction in the atmosphere, most places will have more than twelve hours of daylight on the equinox.
This last point leads to an interesting question: In any given year, does everywhere on the surface earth get the same amount of daylight (and thus the same amount of darkness) as every other place? We don't mean sunshine, we mean daylight hours between sunrise and sunset.
This question gets more involved the more that you think about it. Try it with your friends at work or in the pub, and you are guaranteed a "lively" discussion. It fact shall we have a lively discussion on here.
We want more than just Yes or No.
Answer at 9.00 on Monday