The fall equinox is Wednesday: 8 things to know about the first day of autumn

The autumnal equinox is upon us: On Wednesday, September 22, the Northern and Southern hemispheres will expertise an equal quantity of daylight.

For these in the Northern Hemisphere, it marks the starting of astronomical fall, with daytime persevering with to shorten till the winter solstice in December. For these south of the equator, it’s the starting of spring. This week’s full moon — the closest to the fall equinox, and this 12 months the final full moon of summer time — happens on Tuesday and is often known as the harvest moon.

Technically talking, the equinox happens when the solar is straight in keeping with the equator. This will occur at 3:21 pm Eastern on Wednesday (for some elements of the world, it is going to be Thursday morning presently).

Below is a brief scientific information to the most equal day and evening of the season.

1) Why do we now have equinoxes?

The fall and spring equinoxes, the seasons, and the altering size of daytime all through the 12 months are all due to one truth: Earth spins on a tilted axis.

The tilt — probably attributable to an enormous object hitting Earth billions of years in the past — implies that for half the 12 months, the North Pole is pointed towards the solar (as in the image under). For the different half of the 12 months, the South Pole will get extra gentle. It’s why we now have seasons.

Here’s a time-lapse demonstration of the phenomenon shot over the course of an entire 12 months from house. In the video, you may see how the line separating day from evening (known as the terminator) swings backwards and forwards from the poles throughout the 12 months.

A enjoyable truth about the terminator: It’s not the case that it splits the Earth into even halves of gentle and darkish. That’s as a result of our environment bends daylight a bit, basically stretching it over a barely better space of land. This “results in the land covered by sunlight having greater area than the land covered by darkness,” the National Oceanic and Atmospheric Administration (NOAA) explains.

So dangle on to this straightforward, candy thought: There’s all the time a bit extra daylight than darkness on Earth, as an entire.

And right here’s one more cool manner to visualize the seasons. In 2013, a resident of Alberta, Canada, took this pinhole digicam {photograph} of the solar’s path all through the 12 months and shared it with the astronomy web site EarthSky. You can see the dramatic change in the arc of the solar from December to June.

(You can simply make the same picture at residence. All you want is a can, photograph paper, some tape, and a pin. Instructions right here.)

2) Is the equinox actually the first day of autumn?

Well, relies upon: Are you asking a meteorologist or an astronomer?

Meteorologically talking, summer time is outlined as the hottest three months of the 12 months, winter is the coldest three months, and the inbetween months are spring and fall.

Here’s how NOAA breaks it down:

Astronomically talking, sure, fall begins when the Southern Hemisphere begins to obtain extra daylight than the Northern Hemisphere. And that begins on the autumnal equinox.

3) How many hours of daylight will I get on the equinox?

Equinox actually means “equal night.” And throughout the equinox, most locations on Earth will see roughly 12 hours of daylight and 12 hours of darkness.

But not each place will expertise the very same quantity of daylight. For occasion, on Monday, Fairbanks, Alaska, will see 12 hours and 14 minutes of daylight. Key West, Florida, will see 12 hours and 7 minutes. The variations are due to how the daylight will get refracted (bent) because it enters Earth’s environment at totally different latitudes.

You may additionally discover that each of these areas have daylight instances longer than 12 hours. Aren’t day and evening supposed to be equal? Daylight time is barely longer than nighttime on the equinox as a result of of how we measure the size of a day: from the first trace of the solar peeking over the horizon in the morning to the final glimpse of it earlier than it falls under the horizon in the night. Because the solar takes a while to rise and set, it provides some additional daylight minutes.

Check out to see what number of hours of daylight you’ll get throughout the equinox.

4) Can I actually solely stability an egg on its tip throughout on the equinox?

Perhaps you have been informed as a toddler that on the equinox, it’s simpler to stability an egg vertically on a flat floor than on different days of the 12 months.

The apply originated in China as a convention on the first day of spring in the Chinese lunar calendar in early February. According to the South China Morning Post, “The theory goes that at this time of year the moon and earth are in exactly the right alignment, the celestial bodies generating the perfect balance of forces needed to make it possible.”

This is a fantasy. The quantity of daylight we get throughout the day has no energy over the gravitational pull of the Earth or our skills to stability things on it. You can stability an egg on its finish any day of the 12 months (when you’re good at balancing things).

5) When do the leaves begin altering colours?


When days start to develop shorter, deciduous (inexperienced leafy) bushes begin signaling to their leaves to cease producing chlorophyll, the inexperienced pigment accountable for the leaves’ shade and photosynthesis.

Because the shade change is extra depending on gentle than temperature, it takes place at principally the identical time 12 months after 12 months, in accordance to the US National Arboretum.

Temperature and climate situations, although, can impression the depth of fall colours and the way lengthy they linger. They can even subtly have an effect on the timing of when the leaves begin to change. And drought can change the fee at which the leaves flip.

Because of all the variables at play, it may be powerful to predict exactly when fall colours will peak and the way lengthy they’ll final in a selected space. But right here’s an admirable effort: The web site (a web site selling Smoky Mountains tourism) created this interactive map (click on the hyperlink to play with it) to decide peak fall colours throughout the United States by county.

6) What is really in “pumpkin spice”?

“Pumpkin spice” is not a single spice however a mix of them. And it accommodates no pumpkin.

This recipe from Epicurious contains cinnamon, ginger, allspice, nutmeg, and cloves. It’s autumn — go forward and sprinkle it on no matter you want.

7) Is there an historic monument that does one thing cool throughout the equinox?

During the winter and summer time solstices, crowds flock to Stonehenge in the United Kingdom. During the solstices, the solar both rises or units in keeping with the structure of the 5,000-year-old monument. And whereas some flock to Stonehenge for the autumnal equinox too, the actual place to be is Mexico.

That’s as a result of on the equinox, the pyramid at Chichen Itza on the Yucatan Peninsula places on a wondrous present. Built by the Maya about 1,000 years in the past, the pyramid is designed to solid a shadow on the equinox outlining the physique of Kukulkan, a feathered snake god. A serpent-headed statue is situated at the backside of the pyramid, and as the solar units on the day of the equinox, the daylight and shadow present the physique of the serpent becoming a member of with the head.

This is simpler to see in a video. Check it out under.

8) Are there equinoxes on different planets?

Yes! All the planets in our photo voltaic system rotate on a tilted axis and subsequently have seasons. Some of these tilts are minor (like Mercury, which is tilted at 2.11 levels). But others are extra like the Earth (23.5 levels) or are much more excessive (Uranus is tilted 98 levels!).

Below, see an exquisite composite picture of Saturn on its equinox captured by the Cassini spacecraft (RIP) in 2009. The fuel big is tilted 27 levels relative to the solar, and equinoxes on the planet are much less frequent than on Earth. Saturn solely sees an equinox about as soon as each 15 years (as a result of it takes Saturn 29 years to full one orbit round the solar).

During Saturn’s equinox, its rings develop into unusually darkish. That’s as a result of these rings are solely round 30 toes thick, and when gentle hits them head-on, there’s not a lot floor space to mirror.

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