(CNN) — Twice a year, everyone on Earth is seemingly on equal footing — at least when it comes to the distribution of daytime and nighttime.
Folks right along the equator have roughly 12-hour days and 12-hour nights all year long, so they won’t really notice a thing.
But during the equinox, everyone from pole to pole gets to enjoy a 12/12 split of day and night. Well, there’s just one rub — it isn’t as perfectly “equal” as you may have thought.
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.
Here are the answers to some of your fall equinox questions:
Where does the word ‘equinox’ come from?
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.)
Since the summer solstice in June, days have been progressively becoming shorter in the Northern Hemisphere and the nights longer for the past three months. Welcome to fall equinox!
What did our ancestors know about all this?
A ‘superhenge’ discovered near Stonehenge in England is believed to have been built 4,500 years ago. CNN’s Erin McLaughlin reports.
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 celebrations.
Harvest festivals in Great Britain have their roots in fall equinox since pagan times.
Are the Northern Lights really more active at the equinoxes?
In a word, yes.
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?
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. So on fall equinox, the length of day will vary a little according to where you are:
— At the equator: About 12 hours and 6 and half minutes (Quito, Ecuador, or Kampala, Uganda)
— At 30 degrees latitude: About 12 hours and 8 minutes (Austin, Texas, or Cairo, Egypt)
— At 60 degrees latitude: About 12 hours and 16 minutes (Helsinki, Finland)