This cosmic event marks the beginning of astronomical autumn…
The UAE’s Autumnal Equinox is set for Monday, September 23.
What is the Autumnal Equinox?
There are two equinoxes each year: one in March, known as the Vernal or Spring Equinox, and one in autumn. The term “equinox” translates to “equal night,” referring to the moment in Earth’s orbit around the sun when day and night hours are approximately equal—around 12 hours each.
Why is it important for me?
The Autumnal Equinox marks the beginning of astronomical autumn, serving as a celestial benchmark indicating that cooler weather is approaching. However, regional weather patterns, like the Asian monsoon seasons, suggest we may still experience some lingering high humidity for a while.
Why do the Equinoxes happen?
This is where things get a bit complex…
It relates to Earth’s axial alignment—the north-south axis, which currently sits at a 23.5º tilt (though this changes over a 40,000-year cycle) in relation to the sun’s orbit.
Throughout the solar year, the sun’s focus, known as the subsolar point, shifts along the north-south axis, reaching its peak at the June Solstice and hitting its lowest point at the December Solstice.
Equinoxes occur when the solar declination is at 0º, meaning the sun is directly overhead at midday, aligned with the equator, and the Earth’s axis is neither tilted towards nor away from the sun. During these times, most of the planet experiences roughly equal daylight hours.
Is it on the same date every year?
Fun fact: The exact timing of the equinox varies slightly but typically falls between September 22 and 24. This discrepancy arises because our calendars can’t perfectly account for the Earth’s orbit around the sun, which takes about 365.24 days. This is also why we have leap years!
