The autumn equinox 2022 in the northern hemisphere is on Friday 23
September. The autumn equinox marks the first day of astronomical autumn, and
the precise time of the autumn equinox in 2022 will be at 3:04am BST.
For the two hemispheres, the equinoxes are opposite each other. When
it’s the autumn equinox in the northern hemisphere, it’s the spring equinox in
the southern hemisphere. For the purposes of this article, when we refer to the
autumn equinox, it is from the perspective of the northern hemisphere, and we
are referring to the September equinox, unless stated otherwise.
What exactly happens during the autumn equinox? Put simply, the autumn
equinox is when the Sun crosses the celestial equator (this being an imaginary
line in the sky above Earth’s equator), going from the northern hemisphere to
the southern hemisphere. It's caused by the cyclical tilt of Earth's axis, and
at the equinoxes, this tilt aligns with the orbit around the Sun.
At the equinoxes, the Sun is exactly above the equator, and both
hemispheres receive (nearly) equal amounts of sunlight. In other words, day and
night are (almost) equal in both hemispheres. After the autumn equinox, we
start to receive more darkness and less daylight.
The word ‘equinox’ derives from the Latin words aequi, meaning ‘equal’,
and nox, meaning ‘night’. Taken together, 'equinox' translates as ‘equal
night’.
The September equinox denotes the start of astronomical autumn in the northern hemisphere, and the start of spring in the southern hemisphere. From our perspective, the Sun moves to be south of the equator, in the western portion of the constellation Virgo.
Link:
https://www.sciencefocus.com/planet-earth/autumn-equinox/
