Ten things you never knew about... equinoxes

This is the day of the Autumnal Equinox which marks the meteorological start of autumn.

1. The spring and autumn equinoxes (from the Latin for “equal” and “night”) occur when there is 12 hours between sunrise and sunset.

2. To be precise, that means 12 hours from the moment the centre of the Sun moves over the horizon to the moment its centre disappears again.

3. Daylight begins when the edge of the Sun peeks over the horizon and goes on until all the sun has set, so we have more than 12 hours of light today.

4. The Equilux (equal light), when daylight and dark both equal 12 hours, will fall on September 27.

5. The precise time of today’s equinox is 8.02pm (British Summer Time), when the plane of our Equator passes through the centre of the Sun.

6. The autumn equinox is usually on September 22 or 23 (using GMT for dating it) but very rarely it is on the 21 or 24.

7. The next September 21 equinox will be in 2092 but a September 24 equinox is not until 2303.

8. The full moon closest to the autumn equinox is known as a harvest moon.

9. That was seen by farmers as the best day for harvesting as the full moon let them work late.

10. On the day of the autumn equinox, the Sun rises exactly due East and sets exactly due West.