(CNN) — Twice a year, everyone on Earth is seemingly on equal footing — at least when it comes to the distribution of light and dark.
But during equinoxes, everyone from pole to pole gets to enjoy a 12-hour split of day and night. Well, there’s just one rub — it isn’t as perfectly “equal” as you may have been told.
There’s a good explanation (SCIENCE!) for why you don’t get precisely 12 hours of daylight on the equinox. More on that farther down in the article.
But first, here are the answers to your other fall equinox questions:
Where does the word ‘equinox’ come from?
Precisely when does the fall equinox happen?
The sun rises behind the Washington Monument in the US capital.
J. David Ake/AP
For people in places such as Toronto and Washington, that’s 3:21 p.m. local time. Out West in Los Angeles and Vancouver, that means it arrives at 12:21 p.m.
For residents of Madrid, Berlin and Cairo, it comes precisely at 9:21 p.m. Going farther east, Dubai marks the exact event at 11:21 p.m.
Is the autumn equinox the official first day of fall?
Autumn in northern Germany shows its beautiful side at the Ludwigslust Canal at Ludwigslust Palace. This photograph was taken on November 2, 2020, which lands within astronomical fall and meteorological fall.
Jens Büttner/picture alliance/Getty Images
Yes. Fall officially begins on the autumn equinox.
Allison Chinchar, CNN meteorologist, explains the differences:
“Astronomical fall is essentially the time period from the autumnal equinox up to the winter solstice. Those dates can vary by a day or two each year, but this year are September 22 though December 21,” she says.
“Meteorological fall is different … in that the dates never change and are based on climatological seasons rather than Earth’s angle relative to the sun. These are perhaps the seasons that more people are familiar with,” Chinchar says.
Meteorological seasons are defined as the following: March 1 to May 31 is spring; June 1 to August 31 is summer; September 1 to November 30 is autumn; and December 1 to February 28 is winter.
“This makes some dates tricky,” Chinchar says. “For example, December 10, most people would consider winter, but if you are using the astronomical calendar, technically that is still considered autumn because it is before the winter solstice.”
She said that “meteorologists and climatologists prefer to use the ‘meteorological calendar’ because not only do the dates not change — making it easy to remember — but also because it falls in line more with what people think traditional seasons are.”
Why does fall equinox happen?
The Earth rotates along an imaginary line that runs from North Pole to South Pole. It’s called the axis, and this rotation is what gives us day and night.
The effect is at its maximum in late June and late December. Those are the solstices, and they have the most extreme differences between day and night, especially near the poles. (That’s why it stays light for so long each day during the summer in places such as Scandinavia and Alaska.)
But since the summer solstice three months ago in June, you’ve noticed that our days have been progressively becoming shorter in the Northern Hemisphere and the nights longer. And now here we are at the fall equinox!
What did our ancestors know about all this?
Stonehenge has been fascinating tourists for a long time, as this photo dated to 1875 attests.
Here are just a few of the sites associated with the equinox and the annual passage of the sun:
What are some festivals, myths and rituals still with us?
All around the world, the fall equinox has weaved its way into our cultures and traditions.
Great Britain’s beloved harvest festivals have their roots in fall equinox since pagan times.
Autumn leaves put on a show at Showa Kinen Park in Tokyo.
courtesy Takashi Hososhima, creative commons
Are the Northern Lights really more active at the equinoxes?
Yes — they often put on more of a show this time of year.
It turns out the autumnal equinox and spring (or vernal equinox) usually coincide with peak activity with the aurora borealis.
So why isn’t the equinox exactly equal?
It turns out you actually get a little more daylight than darkness on the equinox, depending on where you are on the planet. How does that happen? The answer is a bit complicated but fascinating.
This bending of light rays causes the sun to appear above the horizon when the actual position of the sun is below the horizon. The day is a bit longer at higher latitudes than at the equator because it takes the sun longer to rise and set the closer you get to the poles.
Nairobi, the capital of Kenya, lies only 89 miles (143 miles) south of the equator and sees very little variation between daylight and darkness.
Peter Macdiarmid/Getty Images
So on fall equinox, the length of day will vary a little depending on where you are. Here are a few breakdowns to give you an approximate idea:
— At the equator: About 12 hours and 6 minutes (Quito, Ecuador; Nairobi, Kenya; and Singapore are all close to the equator)
— At 30 degrees latitude: About 12 hours and 8 minutes (Houston, Texas; Cairo, Egypt; and Shanghai, China)
— At 60 degrees latitude: About 12 hours and 16 minutes (Helsinki, Finland, and Anchorage, Alaska)