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Equinox: Day & Night Not Equal This Week
21 Sep
Summary
- The autumnal equinox occurs precisely at 1:05 AM BST on September 23rd.
- Day and night are not truly equal during the equinox, contrary to popular belief.
- The closest approach to equal day and night in the UK is expected around September 25th.
The autumnal equinox is set to occur precisely at 1:05 AM British Summer Time on September 23rd. This event signifies the astronomical commencement of autumn in the Northern Hemisphere and spring in the Southern Hemisphere.
While the name 'equinox' suggests equal day and night, this is not strictly accurate. An equinox happens when the sun crosses the celestial equator. Earth's atmospheric refraction and the sun appearing as a disc mean daytime is slightly longer than 12 hours during this period.
For those in the UK, the day when daylight and darkness are closest to being equal will be around September 25th. This specific day is referred to as the equilux, derived from 'equal light'.
