SouthParkMe

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Vernal Equinox 2026

Vernal Equinox 2026

Murk
Space

At 2:46, UTC, 20th March 2026, the Earth’s axis was neither pointed toward or away from the sun, this means that it is officially the Equinox, in the North this is the first day of spring.

This is odd, because the sunrise and sunset times for London today are 6:03am and 6:13pm. That this isn’t exactly centred around noon is part to do with timezones, and part to do with the ‘equation of time’ meaning noon drifts back and forth over the year due to the Earth’s orbit being elliptical.

Much more puzzling is that the duration of light and dark is not equal! Should it not be 12 hrs each? Daylight is 12hrs and 10 minutes? What’s going on?

One effect is the dawn and dusk are changing times by about 2 minutes per day, each - so over 12 hour period, we only have about an 8 minute discrepancy.

This is largely as our atmosphere bends the light from the sun. So when the sun is low in the sky, we see it higher than it actually is - by about the diameter of the sun. Given the sun appears to move 15 degrees an hour, and half a degree wide, that means the dawn we see is about 2 minutes ‘early’, and the sunset about 2 mins ‘late’. That is a four minute discrepancy. Also, we count sunset as when the sun is visible, when the top edge appears or disappears - not the centre - that also makes a correction.

In short:

  • dawn is continually getting earlier, and dusk later. Even over the course of a day, this is noticeable.

  • We don’t measure to the middle of the sun, but to the ‘top’ of the sun - increasing our error

  • We also have refraction to contend with

  • And EQUINOX is NOT when we get equal day and night (despite the name), it is when the angle between the Earth’s axis and the direction to the sun is 90 degrees. If you were stood on the equator, the sun would stop being south of you, and start being north of you.

  • EQUILUX, - 12 hours day, 12 hours night, was a few days ago - and the exact date depends on your location. Equinox is defined by the orbit, and is an instant in time, the same for everyone.

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