The equinoxes are the two days of the year, usually March 21 and September 21, that day and night are the same length all over the Earth. This happens because the sun is exactly above the equator on those days. The word equinox means "equal night"
After the spring (vernal) equinox and until the fall (autumnal) equinox, the days are longer than the nights in the Northern Hemisphere and shorter in the Southern Hemisphere. In fact, during this time of the year the sun never sets at the North Pole and never rises at the South Pole.
After the fall (autumnal) equinox and until the spring (vernal) equinox, the days are longer than the nights in the Southern Hemisphere and shorter than the nights in the Northern Hemisphere. During this time of the year the sun never sets at the South Pole and never rises at the North Pole.
On the spring and fall equinoxes, day and night are exactly the same length all over the world.
Do eggs balance on the days of the equinox?
There is a common idea, often raised at the time of each equinox, that eggs can stand on their ends unaided on the day of an equinox - something they cannot do at other times.
"Actually, the sun's gravity force could not 'pull upward' on an egg as suggested. A person standing next to an egg produces a 'pulling gravity' force 50,000 times greater than the sun, but even this force has a negligible effect on the balancing of an egg. A steady hand can indeed make an egg balance, but it has nothing to do with the equinox."
Use the equinox to find the date of Easter
The date for Easter varies from year to year, but can be worked out using a formula established by Constantine the Great and the Council of Nicaea in AD 325. (This formula also appears in Donald DeYoung's book Astronomy and the Bible.)
First, find the date of the vernal (spring) equinox on a calendar that lists basic astronomical information (the date will be around March 21).
Second, find the date of the next full moon (usually shown in the corner of a date box on the calendar). Easter will fall on the following Sunday.
In this formula, the earliest date that Easter can fall is March 22. The next time Easter falls on this date is in the year 2285. The latest date for Easter is April 25. The next time this will happen is in 2038.
- Equinox and the Iron Sun Astronomy Picture of the Day, Accessed 23 September 2010.