In climatology, the fall season begins on 1st September. However, the September (or fall) equinox gives us the green signal in order to welcome the astronomical fall season. This is in the Northern Hemisphere (and lunar spring season in the Southern Hemisphere). The event takes place on 22nd September 2021, at 19:21 UTC (2:21 p.m. CDT) North America.
Along with indicating the start of astronomical fall, the Sun will be just above Earth’s equator. It moves from north to south, making day and night almost equal in length – about 12 hours – all over the globe.
At the North Pole, over the forthcoming days, the Sun will drop below the horizon for a kind of twilight from now. This is until sometime in October when it will be entirely dark, as per NASA solar scientist Mitzi Adams. Spring twilight at the North Pole starts a few weeks before the vernal, or spring, equinox in March. This is when the sun comes above the horizon again.
This only occurs twice in Earth’s year-long trip across the Sun. The rest of the year, the Sun shines irregularly over the Northern and Southern Hemispheres. That is due to Earth’s axis is bent with respect to the Sun-Earth plane.
However, on these special days (names below) the Sun shines roughly evenly on the Northern and Southern hemispheres –
- The spring
- Fall equinoxes
In the Northern hemisphere, the September equinox indicates the beginning of a period giving us –
- Late sunrises
- Early sunsets
We will also feel cooler days with –
- Chillier winds
- Dry, falling leaves
The people of archaic traditions make use of the sky as a clock and calendar. They saw that the Sun’s path around the sky, length of daylight, and location of sunrise and sunset all changed in a regular way through the year.
Furthermore, previous civilizations made the first observatories, like –
Today, we commemorate the equinox as an exorbitant event set off by Earth’s incline on its axis and its movement in orbit around the Sun.