Magnolia blossoms begin to bloom at the US National Arboretum in Washington, DC.
The vernal equinox is upon us: On Thursday, March 19, both the Northern and Southern hemispheres will experience roughly an equal amount of daylight. For those of us in the Northern Hemisphere, it marks the beginning of spring, with daylight hours continuing to lengthen until the summer solstice in June. For those south of the equator, it’s the beginning of autumn.
Technically speaking, the equinox occurs when the sun is directly in line with the equator. This will happen at 11:49 pm Eastern on Thursday. (With the equinox occurring so close to midnight, I’d argue to can choose to celebrate either today or tomorrow.)
This year’s equinox comes at a tough time, with a pandemic forcing many people to stay away from the people and activities they love. Maybe it helps to know that nature will still go on as planned. Flowers will still bloom, temperatures will still rise, and sunsets will creep later and later into the evening.
Below is a short scientific guide to the equinox.
1) Why do we have an equinox?
The equinox, the seasons, and the changing length of daylight hours throughout the year are all due to one fact: The Earth spins on a tilted axis.
The tilt — possibly caused by a massive object hitting Earth billions of years ago — means that for half the year, the North Pole is pointed toward the sun (as in the picture below). For the other half of the year, the South Pole gets more light. It’s what gives us seasons.
Here’s a time-lapse demonstration of the phenomenon shot over the course of a whole year from space. In the video, you can see how the line separating day from night swings back and forth from the poles during the year.
And here’s yet another cool way to visualize the seasons. In 2013, a resident of Alberta, Canada, took this pinhole camera photograph of the sun’s path throughout the year and shared it with the astronomy website EarthSky. You can see the dramatic change in the arc of the sun from December to June.
This is a 6 month pinhole photo taken from solstice to solstice, in Medicine Hat, Alberta, Canada. We are one of the sunniest cities in Canada, and this shows it nicely.
Posted by Ian Hennes on Saturday, December 21, 2013
(You can easily make a similar image at home. All you need is a can, photo paper, some tape, and a pin. Instructions here.)
2) How many hours of daylight will I get Thursday?
Equinox literally means “equal night.” And during the equinox, most places on Earth will see approximately 12 hours of daylight and 12 hours of night.
But not every place will experience the exact same amount of daylight. For instance, on Thursday, Fairbanks, Alaska, will see 12 hours and 13 minutes of daylight. Key West, Florida, will see 12 hours and six minutes. The differences are due to how the sunlight gets refracted (bent) as it enters Earth’s atmosphere at different latitudes.
That daylight is longer than 12 hours on the equinox is also due to how we commonly measure the length of a day: from the first hint of the sun peeking over the horizon in the morning to the last glimpse of it before it falls below the horizon in the evening. Because the sun takes some time to rise and set, it adds some extra daylight minutes.
Check out TimeAndDate.com to see how many hours of sunlight you’ll get during the equinox.
3) Is the equinox really the first day of spring?
- Well, depends: Are you asking a meteorologist or an astronomer?
- Meteorologically speaking,summer is defined as the hottest three months of the year, winter is the coldest three months, and the in–between months are spring and fall.
- Here’s how the National Oceanic and Atmospheric Administration breaks it down:
Meteorological spring includes March, April, and May; meteorological summer includes June, July, and August; meteorological fall includes September, October, and November; and meteorological winter includes December, January, and February.
Astronomically speaking, yes, winter begins on the winter solstice.
Meteorologically speaking, spring for many parts of the US came very early this year (due to that other crisis):
4) Over the entire year, does every spot on Earth get an equal number of daylight hours?
In the summer months, the northernmost latitudes get a lot of daylight. Above the Arctic Circle, during the summer, there’s 24 hours of daylight. In the winter, the Arctic Circle is plunged into constant darkness.
So does this mean the number of daylight hours — in total, over the course of the year — equal out to places where the seasonal difference is less extreme?
The answer to this question is somewhat surprising: Roughly speaking, everywhere on Earth sees a similar number of daylight hours every year. But the equator actually gets slightly fewer daylight hours than the poles.
As astronomer Tony Flanders explained for Sky & Telescope magazine, sunlight at the poles gets refracted more than sunlight at the equator.
That refracting results in the visible disk of the sun being slightly stretched out (think of when the full moon is near the horizon and looks huge — it’s being refracted too). And the refracted, stretched-out sun takes slightly longer to rise and set.
Flanders estimated that the equator spends around 50.5 percent of its year in sunlight, while the poles spend between 51.5 and 53 percent of their years in sunlight.
And, of course, this is how much sunlight these areas could potentially receive if the weather were always perfectly clear; it’s not how much sunlight they actually see, nor the strength of the sunlight that hits their ground. “Where are the places on Earth that receive the largest amount of solar radiation?” is a slightly different question, the answer to which can be seen on the chart below.
US Energy Information Administration
5) Can I really only balance an egg on its tip during on the equinox?
Perhaps you were told as a child that on the equinox, it’s easier to balance an egg vertically on a flat surface than on other days of the year.
The practice originated in China as a tradition 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 myth. The amount of sunlight we get during the day has no power over the gravitational pull of the Earth or our abilities to balance things upon it. You can balance an egg on its end any day of the year (if you’re good at balancing things).
This man is very good at balancing eggs.
6) Is there an ancient monument that does something cool during the equinox?
What is the spring equinox? | CBC Kids
Image by armennano from Pixabay
The spring equinox is the first day of spring — astronomically speaking, that is!
It’s also a day where there is almost 12 hours of light and 12 hours of darkness because the sun is passing directly over the equator. It’s also called the vernal equinox.
Since daytime is measured from the time any part of the sun is visible over the horizon to when the last part of the sun has set, there's actually a little bit more than 12 hours of light.
What does the word equinox mean?
Equinox comes from the Latin words for equal (aequus) and night (nox) because the day and night were thought to be equal in all parts of the world on this day. After that, we begin to get longer and sunnier days.
When is the spring equinox?
It actually changes but it’s always around the end of March — either the 19th, 20th or 21st. In 2020, the spring equinox falls on March 19th.
The old equinox egg trick
There is an old story that says that on the spring equinox, you can stand a raw egg upright instead of on its side.
Why not try it and see if it's true?
4 things you can do to celebrate the spring equinox:
Image by Myriams-Fotos from Pixabay
- Go for a walk and see if you find signs of spring! Look for buds on the trees and flowers starting to poke through the ground. Are the birds flying back yet?
- If you have a front yard or backyard, spring is the perfect time to clean up any trash that has made its way into the yard. If you don’t have a yard, maybe you can hit the sidewalk or your local park.
March equinox: All you need to know
This photo was the Earth Science Picture of the Day for March 19, 2020, from the Universities Space Research Association. It shows the path of the sun across our sky – from about noon to sunset – on 3 different days of the year, an equinox and the summer and winter solstices. Photographer Marcella Giulia Pace said: “I made these observations from Gatto Corvino village, Sicily, Italy. To show as much of the path as possible, I chose a field where the western horizon was clearly visible and always shot from the same spot, every 10 minutes, beginning at true local noon.”
Although there’s nothing official about it, many say the March or vernal equinox signals the start of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. The equinox is a hallmark of the seasons.
At this equinox, the sun crosses the celestial equator, moving from south to north. The March 2020 equinox falls on March 20 at 03:50 UTC. That’s March 19 at 10:50 p.m.
Central Daylight Time for us in North America; translate to your time zone.
In the Northern Hemisphere now, the March equinox will bring earlier sunrises, later sunsets, softer winds, sprouting plants. Meanwhile, you’ll find the opposite season – later sunrises, earlier sunset, chillier winds, dry and falling leaves – south of the equator.
The equinoxes and solstices are caused by Earth’s tilt on its axis and ceaseless motion in orbit. You can think of an equinox as happening on the imaginary dome of our sky.
The Earth-centered view is that the celestial equator is a great circle dividing Earth’s sky into northern and southern hemispheres. The celestial equator wraps the sky directly above Earth’s equator. At the equinox, the sun crosses the celestial equator, to enter the sky’s Northern Hemisphere.
The Earth-in-space view is that, because Earth doesn’t orbit upright, but is instead tilted on its axis by 23 1/2 degrees, Earth’s northern and southern hemispheres trade places in receiving the sun’s light and warmth most directly as Earth orbits the sun. We have an equinox twice a year – spring and fall – when the tilt of the Earth’s axis and Earth’s orbit around the sun combine in such a way that the axis is inclined neither away from nor toward the sun.
Cherry blossoms opening in Japan, via EarthSky community member Beverly Fish.
What Exactly Is The Spring Equinox?
We get pretty excited about the spring equinox bringing us out of winter and officially starting the season of spring. But what exactly is the spring equinox? And does an equinox happen at the start of every season?
First, let’s get into the equinox, which actually occurs just twice a year. The word equinox comes from Latin and means “equality of night and day.” So, the equinox occurs at two specific moments in time when the sun is exactly above the equator (contrary to popular belief, the equinox doesn’t last for 24 hours).
What are the dates of the two equinoxes?
In the northern hemisphere, the spring, or vernal equinox happens around March 21, when the sun moves north across the celestial equator.
The autumnal equinox occurs around September 22nd, when the sun crosses the celestial equator going south. But if you want to be truly egalitarian, opt for saying March equinox and September equinox instead.
After all, in the southern hemisphere, March represents the beginning of autumn and spring comes along in September!
The equinox has inspired a number of interesting false beliefs, including that the event causes a massive disruption of communication satellites, or that on the equinox an egg can effortlessly be balanced on its end (egg balancing is a skill you can practice any day of the year).
What is a solstice?
So what about the beginning of summer and winter? Well, the equinox is often confused with the solstice, which is either of the two times a year when the sun is at its greatest distance from the celestial equator. Solstice derives from the Latin solstitium, which literally means “the standing still of the sun.” The solstice occurs around June 21 and December 22.
Whether you’re celebrating spring or autumn, the March equinox represents an interesting moment in our latest journey around the sun.
What is the spring equinox and when does summer start?
- Today is the vernal equinox which means that, no matter how you look at it, spring has officially sprung.
- Even though it might not quite feel like it, the vernal or spring equinox brings with it the changing of the seasons.
- As we prepare to welcome warmer weather at last, here’s a quick look at what the spring equinox is and when summer is set to start.
What is the spring equinox?
The spring equinox is an event which happens once a year.
It occurs in March when the sun crosses the earth’s equator, and day and night are equal lengths of time.
There is also an autumn equinox which marks the start of – you guessed it – autumn. This year it will fall on 22 September.
When does summer start?
- The date on which summer begins varies depending on how you prefer to look at it.
- From a meteorological perspective, summer begins when we get to the month of June, and carries on through until the beginning of September.
- If you prefer to look at things from an astrological point of view however, then summer won’t start until the summer solstice, which marks the longest day of the year and falls on 20 June this year.
In 2020 the summer solstic will occur on Saturday 20 June 2020 at 21:43 GMT (22:43 BST). As the solstice is independent of the specific rotation of the Earth, it can occur even during the middle of the night, as it will this year.
What is the summer solstice?
The summer solstice is often referred to as the longest day of the year. On this day, the number of hours of daylight are at their maximum, while the number of hours of night are at their minimum. However, while most people consider the summer solstice to be a day, it is in reality an exact moment in time that falls upon that day.
The summer solstice occurs in June in the Northern Hemisphere and marks midsummer: the longest day and shortest night.
What is a solstice?
Our Earth rotates on its axis once each day, producing the cycle of day and night.
At the same time, the Earth moves around the Sun on its orbit over the course of a year. However, the axis of rotation of the Earth is not lined up with the axis of motion around the Sun. Instead, it is tilted slightly at 23.44°. This is sometimes referred to as the 'ecliptic'.
This tilt means that during one half of the year the North side of the Earth is tilted slightly towards the Sun and the South is tilted away. For the other half of the year the reverse is true.
At the exact moment that the northern hemisphere is most tilted towards the Sun, the northern hemisphere experiences its summer solstice while the southern hemisphere has its winter solstice. About six months later, the northern hemisphere has its winter solstice while the southern hemisphere is at its summer solstice.
These key points in the year, along with the equinoxes, help to determine the seasons on Earth.
What is the winter solstice?
The winter solstice occurs in December in the Northern Hemisphere and marks midwinter: the shortest day and longest night. Find out more about the winter solstice.
When is the winter solstice 2020?
In 2020 the winter solstice will occur on 21 December.
When do the solstices occur?
The times when the Sun is at its furthest from the celestial equator are called the summer and winter solstices. These occur at midsummer and midwinter.
The world 'solstice' comes from the Latin solstitium meaning 'Sun stands still', because the apparent movement of the Sun's path north or south stops before changing direction.
|2020||20 June, 9.44pm||21 December, 10.02am||Yes|
|2021||21 June, 4.31am||21 December, 3.58pm|
|All times are UTC (GMT)|
Why do people celebrate the solstice at Stonehenge?
Since humans began using the Sun as a timekeeper, particularly when it came to the cycle in farming, the summer solstice has been marked with varying degrees of importance.
Perhaps most famously, the ancient monument Stonehenge has for some time been the centre of a ritual celebration.
This comes from the fact the stones are lined up to frame the rising of the Sun on the solstice, perhaps suggesting a connection to the day and as a celebration of Sun. However it isn’t clear if marking summer solstice was indeed its purpose.
The stones also mark the position of sunset on the winter solstice, and so may instead indicate a place to request the return of the summer months.
- In any case, many modern day religions gather at the site to mark the occasion: it is also one of the rare times visitors are allowed to walk right up to the stones themselves.