The changing seasons are split between the two annual equinoxes and the two solstices. In September and March respectively, the Autumn Equinox and the Spring Equinox usher in the new seasons. Then the Winter Solstice and the Summer solstice take place in December and June respectively. The Autumn Equinox is just around the corner and the last days of summer are quickly coming to an end.
What is the Autumn and Spring Equinox?
As the Earth races around the Sun, it’s north and south poles tilt towards and away from the Sun at a 23.5-degree angle.
When the North Pole is most tilted towards the Sun, we experience the Summer Solstice in the Northern Hemisphere.
When the South Pole is most tilted towards the Sun, we experience the Winter Solstice in the Northern Hemisphere.
The equinoxes are different in this regard and mark the midway points between the solstices.
During an equinox, the planet’s tilt in relation to the Sun is at a right angle, which should produce 12 hours of day and 12 hours of night.
Space agency NASA said: “Equinox means ‘equal night’ in Latin, capturing the idea that daytime and nighttime are equal lengths everywhere on the planet.”
READ MORE: How is the September Equinox celebrated?
When is the Autumn Equinox this year?
The Autumn Equinox falls every year on one date between September 21 and September 24.
Similarly, the Spring Equinox always falls on a date between March 19 and March 21.
Last year, the Autumn Equinox fell on Sunday, September 23.
Next year, the equinox will arrive on Tuesday, September 22, followed by Wednesday, September 22, 2021.
This month, the equinox will arrive on Monday, September 23, around 8.53am BST (7.53am UTC).
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Is the Autumn Equinox the last day of summer and the first day of autumn?
There are two ways in which you can determine the changing seasons.
Firstly, you can look at your calendar and decide autumn has already begun on September 1.
Meteorologists employ this method of determining the changing seasons.
Astronomers, however, prefer to look at the celestial movements of the Earth to mark the changing seasons.
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NASA said: “As our planet orbits around the Sun, that tilt means that during half of the year, the Northern Hemisphere receives more daylight — its summertime — and during the other half of the year, the Southern Hemisphere does.
“Twice a year, Earth is in just the right place so that it’s lined up with respect to the Sun, and both hemispheres of the planet receive the same amount of daylight.
“On these days, there are almost equal amounts of day and night, which is where the word equinox — meaning “equal night” in Latin — comes from.”
After the Autumn Equinox peaks, the days will grow shorter and the nights will grow longer.