The Autumn Equinox is a captivating event which commences in the Northern Hemisphere as the sun crosses directly over the equator.
Set to take place at 7:19pm this evening, the sun will shine vertically above a location in the Pacific Ocean.
The Southern Hemisphere simultaneously welcomes spring at this exact instant.
The term equinox derives from Latin, signifying "equal night," suggesting that daylight and darkness should balance perfectly across the globe.
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However, this widespread understanding proves misleading, as the actual duration of daylight today exceeds 12 hours throughout most locations.
Two factors explain why daylight persists longer than 12 hours during an equinox.
Atmospheric refraction bends sunlight, elevating the solar disc by more than its apparent width when near the horizon.
When the sun appears as an orange sphere resting on the horizon, it has already dipped completely below it - an optical illusion created by our atmosphere.
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The term equinox derives from Latin, signifying 'equal night', suggesting that daylight and darkness should balance perfectly across the globe
|GETTY
Additionally, sunrise and sunset times are calculated from when the sun's upper edge first appears or finally vanishes, rather than its centre.
In London today, daylight spans 12 hours and 12 minutes, with genuine day-night equality not arriving until October 12.
The widespread belief that Arctic regions plunge into six months of darkness following the equinox misrepresents reality.
Twilight continues illuminating the sky whenever the sun remains less than 18C below the horizon.
At the North Pole, whilst the sun vanishes from view on September 24, civil twilight - when outdoor activities remain possible - persists until October 8.
The definition of darkness often overlooks these twilight periods, treating nightfall as simply the sun's absence below the horizon.
This misconception appears repeatedly in geography textbooks and travel guides, yet twilight provides substantial illumination for weeks after the sun disappears from polar skies.
Two distinct twilight phases follow the sun's disappearance at polar latitudes.
The UK will soon have less than 12 hours of daylight
| PANautical twilight, ending when the sun drops 12C below the horizon, concludes at the North Pole on October 24, marking when most people perceive true nightfall.
Astronomical twilight, which means complete darkness from horizon to horizon, doesn't commence until November 13 when the sun sinks 18C below.
This absolute darkness continues until January 28, when twilight gradually returns.
Therefore, the North Pole experiences merely 11 weeks of total darkness annually, far from the mythical six months often cited.