Why April Fools Day in France Involves Fish Pranks

It’s a long and fishy history.

BY AMELIA PARENTEAU

MARCH 31, 2024

"Allow me to address to you / With my deepest tenderness / This beautiful fish, fresh and discreet / To which I have confided my secret," says this April Fish card in French. 

IF YOU FIND YOURSELF IN France on April 1, don’t be surprised if something seems fishy. Maybe someone gives you a chocolate or a pastry in the shape of a cod? Perhaps you find a paper haddock stuck to your back, and then everyone erupts into laughter and starts pointing and shouting “poisson d’avril”? Don’t be alarmed, you’ve simply immersed yourself in the centuries-long French tradition of April Fool’s Day, known as poisson d’avril or “April Fish.”

“The idea of April Fool’s Day, or April 1, as a special day is murky,” says Jack Santino, a folklorist and Professor Emeritus at Bowling Green State University in Ohio. “Every country has its own historical event they think gave rise to it.” But France’s tradition is the only one that involves aquatic life. Historians have many theories about the origins of this piscine tradition, but no overall consensus. The most common theories are connected to pagan celebrations of the vernal equinox, Christianity, a 16th-century calendar change, and the start of the French fishing season.

April fools may trace back to Ancient Rome, but France’s fish part is harder to pin down. 

Some historians date this tradition back to the Ancient Roman pagan festival of Hilaria, a celebration marking the vernal equinox with games and masquerades. Santino says ancient Roman and Celtic celebrations of the vernal equinox are likely forerunners. Connections to those rituals “provide a kind of cultural vocabulary that people can draw on,” according to Santino. However, he believes they probably don’t have a direct connection to the fish part.

For some, that’s where Christianity comes in. The “ichthus” fish—an ancient Hellenic Christian acronym for “Jesus Christ, Son of God, Savior”—is nowadays widely recognized as a symbol of Christianity, but was originally used as a secret marker of Christian affiliation. Moreover, the Lenten forty-day period between Ash Wednesday and Easter Sunday prohibits the consumption of meat, so fish is often served as a substitute protein during this period.

The depiction of Lent from 1893 shows how long fish has been a major part of the Christian tradition. 

As the end of Lent often occurs on or near April 1, celebrations including fish imagery would be apt to mark the end of the fasting season. Some even go so far as to surmise that poisson d’avril is a corruption of the word “passion,” as in “passion of the Christ,” into “poisson,” the French word for fish. Despite these cultural associations, Santino points out there is no actual evidence for this link to Christianity.

Then there’s the popular calendar change theory that has been widely discounted by experts today, but still comes up. In 1564, King Charles IX of France issued the Edict of Roussillon, which moved the start of the calendar year from somewhere in the period of March 25 and April 1 (different provinces kept their own calendars) to January 1.


Pope Gregory XIII standardized January 1 as the beginning of the calendar year throughout the entire Christian empire with the adoption of the Gregorian calendar in 1582. One might surmise that those who still observed the start of the new year on April 1 rather than January 1 were the “April Fools” in question and therefore subject to pranks. However, references to poisson d’avril predate the 1564 edict, occurring in print as early as 1466, which debunks this explanation.

Now paper, people used to hook real dead fish onto the backs of fishermen.

 JACK GAROFALO/GETTY IMAGES

Another plausible theory involves actual fishing. As the days get longer in the northern hemisphere, the return of spring also marks the beginning of the fishing season in France, on or near the first day of April. Some posit that the prank of offering a fish was to tease fishermen who, at this time, either had no fish or an incredible abundance. They would either have to wait around for spawning fish to be of legal size before catching them or, once it was finally time, they would be overwhelmed by catching so many fish rushing upstream. According to this theory, real herrings were the original sea critter of choice for the prank, and the trick was to hook a dead herring onto a fisherman’s back and see how long it took him to notice, as the fish began to progressively stink over the course of the day.

The poisson d’avril tradition took another turn in the early 20th century, when friends and lovers would exchange decorative postcards featuring ornate images of fish. The majority of these cards were inscribed with funny rhyming messages that were often flirtatious and suggestive, but cloaked in humor. While most cards depict young women, flowers, and fish, the ocean and other marine animals are occasionally featured, as well as references to advances in technology, such as airplanes and automobiles. Pierre Ickowicz, chief curator of the Château de Dieppe Museum in Normandy, which houses an impressive collection of these cards, says the card exchange tradition seems to have died out shortly after World War I. The museum’s 1,716 postcards are mainly from the 1920s-1930s

.

Poisson d’avril postcards from the 1920s and ’30s were full of flirtation and fish. WELLCOME COLLECTION/PUBLIC DOMAIN; FOTOTECA GILARDI/GETTY IMAGES

These days in France, the most common observers of poisson d’avril are schoolchildren, who delight in taping paper fish to the backs of their siblings, classmates, and teachers. Although the execution has varied over time, from dead herring accessories to postcards to paper fish, the prankster nature has been consistent.

“This idea of playing pranks on people is something that would be obnoxious if it weren’t socially condoned on certain days,” says Santino. He notes that times of transition are often connected to rites of passage where societal rules can be broken. “If poisson d’avril has to do with a recognition of springtime, I would link it to the idea of a celebratory transition into a new period of time, and part of that celebration means we can do things that are not usually allowed.”

Today, people celebrate poisson d’avril in both neighboring Italy and in Quebec, Canada, a former colony of France. The exact origins remain murky, but the fish endures. Whether or not you participate in any kind of trickster behavior on the first of April, there’s surely some relief today that an actual dead, stinky fish is no longer a regular part of April Fool’s day—or at least hopefully that bit of history doesn’t plant any devilish ideas.

Children are the main culprits today, but anyone can end up with a paper fish on their back on April 1. KEYSTONE-FRANCE/GETTY IMAGES; LAURENT SOLA/GETTY IMAGES

Patrick in the Anthropocene

 BY LEE HALL

MARCH 15, 2024



Image source: Dave (CC BY-ND 2.0 Deed)

Ah, March! Relief. Renewal. Green beer, so we can get merry and forget about the ancestors.

NAVVIES

U.S. canal and railroad developers put Irish migrants to work in the 1850s. Workers who succumbed to injuries, exhaustion, and disease were buried without ceremony. In Malvern, Pennsylvania, grave researcher Frank Watson spoke of teenaged and adult workers buried in a human “trash heap.” A Chicago-area mass-grave marker observes:

“They arrived sick and penniless, and took hard and dangerous jobs building the Chicago & Alton Railroad. Known but to God, they rest here in individual anonymity – far from the old homes of their heirs – yet forever short of the new homes of their hopes.”

Some years ago I came across my father’s family name in an old news story about Irish workers buried near a railway. And I wondered: Were we related? My father’s family swore they came from French nobility, not from the shanty Irish like your mother.

But JFK became president the year I was born and the narrative was bound to shift. JFK too had forebears who fled the potato famine. (We say “famine” so we can forget it was deliberate starvation. As Sinéad O’Connor reminded everyone, Ireland’s food was shipped to England; Irish people caught eating anything except potatoes could be shot dead.)

The Fitzgeralds and Kennedys first worked in Boston as common tradespeople. Eventually, they’d run shops and bars, and make successful bids for political posts. Who, in the all-encompassing quest for Standard of Living, had time to look back?

Noel Ignatiev explored the way Irish Catholics climbed up the U.S. class ladder in How the Irish Became White. That book might have been a user’s manual for my forebears as it explains how they did in fact become white. Meanwhile, JFK publicly vowed that the USA would be first on the moon. And it was. JFK’s key project leader was Wernher von Braun, who’d developed Nazi Germany’s “vengeance weapons”—the V-2 rockets.

Humans had entered some new phase, some kind of hyper-self-domestication. Trains weren’t built so much to move ordinary people as to deliver freight and luxury goods. Apollo 11 got resources that could have funded vital social networks. Gil Scott-Heron called it. Making a nation (for some) Number One eclipsed real values.

But getting back to the shamrocks and beer…Now comes Saint Patrick’s Day in all its whiskey-soaked and dollar-shop green glory.

A Star Performance

Patrick—the bishop Patricius—claimed credit for converting Ireland to Catholicism in the 5th century:

“Never before did they know of God except to serve idols and unclean things. But now, they have become the people of the Lord, and are called children of God. The sons and daughters of the leaders of the Irish are seen to be monks and virgins of Christ!”

Now, if the Anthropocene Awards are ever produced for star-quality performances, nominate Patrick. Why bother to learn from others when you can stamp out their knowledge instead? And this was superhero-level stamping-out. Unless, more likely, Patrick is just a diversion, superimposed on history to blot out the druidic take on the universe.

The Collins Dictionary traced the root meaning of the word druid to the term oak-wise. We need more oak wisdom.

But a 5th-century Roman Catholic “patron saint of Ireland” had no use for it. And in a later century—Sinéad told us all about this, too—the British pope Adrian IV handed Ireland to England, setting the stage for the British to eventually starve the Irish people and ban the Irish language, forcing them to leave, die, or live with no memory of their cultural story.

Of course, the Anthropocene epoch is riddled with crimes against humanity; who was Patrick, but one of history’s common tormentors? Patrick, like any other conqueror, could have championed a different route, guided by the connections humans knew before the times of nations and borders, before we authorized some to routinely confine and control others.

Point of Contention

Naomi Klein, a few years ago, objected to the term Anthropocene:

“Diagnoses like this erase the very existence of human systems that organised life differently: systems that insist that humans must think seven generations in the future; must be not only good citizens but also good ancestors; must take no more than they need and give back to the land in order to protect and augment the cycles of regeneration.”

So at essence, Klein has a “Not all humans…” take. There’s an idea that indigenous communities have no connection to human-driven extinctions or geological crises. Is that so? Indigenous humans set out to domesticate living communities more than 10,000 years ago.

Now, a quest to declare the Anthropocene an official geological epoch has stalled as experts debate just how far back they’ll pin the starting point. The official working group focuses on measurable, physical evidence of human-caused changes—microplastics, coal, pesticides—and situates the start of the Anthropocene in 1952, pointing to the global plutonium fallout from nuclear weapon testing.

Wait, though. We were deep into the Anthropocene by the 1950s. I Love Lucy was already on in 1952. It was the year Hasbro unveiled Mr. Potato Head, that breakthrough use of plastic which turned children into TV advertising consumers. The first patent for a bar code product was issued that year. In 1952, according to a study guide from the Michigan Farm Bureau: “The first Herringbone parlor is used. This helped farmers move a row of cows in together for milking in one clean space.”

Cows, you might remember, are the descendants of some of Earth’s most formidable animals—the aurochs. Living in their natural habitat, carrying out their evolution on their terms, was their birthright. But we humans developed breeding technologies to make them smaller, turn them into our underlings, fence them in, kill them, eat their flesh and drink what we could pull from their teats. By the 1600s we had killed off the last of their free-living ancestors.

We could say humans entered our current, late stage of hyper-self-domestication by the time petkeeping became popular, back in the Elizabethan era. The Anthropocene was fully fledged much earlier. Never mind. As my friend Patricia Fairey emailed, “At the current rate the Anthropocene won’t last long.”

And now, the vernal equinox approaches. Let’s turn off our computers, go out to the oaks, and welcome it.


Lee Hall holds an LL.M. in environmental law with a focus on climate change, and has taught law as an adjunct at Rutgers–Newark and at Widener–Delaware Law. Lee is an author, public speaker, and creator of the Studio for the Art of Animal Liberation on Patreon.

Spring equinox 2024: When it is and why it's also called the vernal equinox

Tiffany Acosta
Arizona Republic


Spring is blooming and with it comes the spring equinox. This celestial event occurs annually, marking the moment when the Earth's axis is neither tilted away from nor toward the sun, resulting in nearly equal lengths of day and night across the globe.

This phenomenon symbolizes the transition from winter to spring in the Northern Hemisphere and from summer to autumn in the Southern Hemisphere.

Beyond its astronomical significance, the spring equinox holds cultural, spiritual and metaphorical importance for many people worldwide. Throughout history, cultures have marked this occasion with festivals and ceremonies.

Here is everything you need to know about the spring equinox.

When is the spring equinox 2024?

The spring equinox officially starts at 8:06 p.m. Arizona time on Tuesday, March 19.
What is the difference between spring equinox and vernal equinox?

According to NASA, the terms "spring equinox" and "vernal equinox" refer to the same astronomical event and are used interchangeably. Both terms describe the moment when the sun crosses the celestial equator, moving from south to north.

Why is it called vernal equinox?

The term "vernal equinox" originates from Latin, where "vernal" means spring and "equinox" denotes the equal length of day and night. The term "vernal equinox" specifically emphasizes the seasonal aspect while "spring equinox" is more generic, referring to the equinox that occurs in springtime.
Is spring equinox always March 21?

No. The spring equinox does not always occur on March 21. While March 21 is often cited as the date of the spring equinox, it can occur on March 20 or 21st, depending on the year and time zone, according to Almanac.com. This variation is due to the complexities of Earth's orbit around the Sun and the adjustments made in the calendar system to account for these movements.

What happens at the spring equinox?

The spring equinox marks the moment when the sun crosses the celestial equator, heading northward. On this occasion, day and night are approximately of equal duration all over the Earth, according to the National Weather Service.

The spring equinox is considered the beginning of spring in the Northern Hemisphere. Cultures around the world have celebrated this event for centuries through various rituals, festivals and traditions, often focusing on themes of fertility, growth and the balance between light and dark.

Will spring come early 2024?

Sorry, Punxsutawney Phil, but predicting whether spring will come early in a specific year depends on numerous factors such as weather patterns, atmospheric conditions and regional climate dynamics.

While the spring equinox occurs at a fixed point in time each year, the arrival of warmer temperatures, the blooming of flowers and other signs of spring can vary.


Some years may experience earlier spring due to warmer weather patterns or climate variability, while others may see colder temperatures lingering longer.

The spring equinox typically falls on March 20 or 21, but in a leap year like 2024, when February has an extra day, the equinox may occur a bit earlier.
What are the 4 equinox dates?

Here are the 2024 equinox and solstice dates, according to the National Weather Service:
Spring (vernal) equinox: March 19, 2024, at 9:06 p.m.
Summer solstice: June 20, 2024, at 2:51 p.m.
Autumn equinox: Sept. 22, 2024, at 6:43 a.m.
Winter solstice: Dec. 20, 2024, at 2:20 a.m.

All times are Arizona time.
What does the spring equinox symbolize?

The spring equinox symbolizes renewal and rejuvenation, the transition from darkness to light as nature emerges from the dormancy of winter.

Many cultures observe the spring equinox with festivals and rituals centered around fertility, abundance and the renewal of life, according to the almanac.com.

Ancient monuments such as the Sphinx in Egypt and Angkor Wat in Cambodia align with the equinox, showcasing humanity's historical reverence for this celestial event.

The spring equinox is also regarded as a time for balance, harmony and personal growth.
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Why is it called equinox?

The term "equinox" comes from the Latin words "aequus," meaning equal, and "nox," meaning night. It is called so because during the equinox, day and night are approximately equal in length.

It's a moment of balance and symmetry in the Earth's orbit around the sun, symbolizing the cyclical nature of time and the changing of seasons.

Leap of imagination: how February 29 reminds us of our mysterious relationship with time and space

THE CONVERSATION

Published: February 27, 2024 

If you find it intriguing that February 28 will be followed this week by February 29, rather than March 1 as it usually is, spare a thought for those alive in 1582. Back then, Thursday October 4 was followed by Friday October 15.

Ten whole days were snatched from the present when Pope Gregory XIII issued a papal bull to “restore” the calendar from discrepancies that had crept into the Julian calendar, introduced by Julius Caesar in 45 BCE.

The new Gregorian calendar returned the northern hemisphere’s vernal equinox to its “proper” place, around March 21. (The equinox is when the Earth’s axis is tilted neither toward nor away from the sun, and is used to determine the date of Easter.)

The Julian calendar had observed a leap year every four years, but this meant time had drifted out of alignment with the dates of celestial events and astronomical seasons.


In the Gregorian calendar, leap days were added only to years that were a multiple of four – like 2024 – with an exception for years that were evenly divisible by 100, but not 400 – like 1700.

Simply put, leap days exist because it doesn’t take a neat 365 days for Earth to orbit the Sun. It takes 365.2422 days. Tracking the movement of celestial objects through space in an orderly pattern doesn’t quite work, which is why we have February – time’s great mop.

Father Time: statue of Pope Gregory XIII in Bologna, Italy. Getty Images

Time and space

This is just part of the history of how February – the shortest month, and originally the last month in the Roman calendar – came to have the job of absorbing those inconsistencies in the temporal calculations of the world’s most commonly used calendar.

There is plenty of science, maths and astrophysics explaining the relationship between time and the planet we live on. But I like to think leap years and days offer something even more interesting to consider: why do we have calendars anyway?

And what have they got to do with how we understand the wonder and strangeness of our existence in the universe? Because calendars tell a story, not just about time, but also about space.

Our reckoning of time on Earth is through our spatial relationship to the Sun, Moon and stars. Time, and its place in our lives, sits somewhere between the scientific, the celestial and the spiritual.

Read more: Why does a leap year have 366 days?

It is notoriously slippery, subjective and experiential. It is also marked, tracked and determined in myriad ways across different cultures, from tropical to solar to lunar calendars.

It is the Sun that measures a day and gives us our first reference point for understanding time. But it is the Moon, as a major celestial body, that extends our perception of time. By stretching a span of one day into something longer, it offers us a chance for philosophical reflection.

The Sun (or its effect at least) is either present or not present. The Moon, however, goes through phases of transformation. It appears and disappears, changing shape and hinting that one night is not exactly like the one before or after.

The Moon also has a distinct rhythm that can be tracked and understood as a pattern, giving us another sense of duration. Time is just that – overlapping durations: instants, seconds, minutes, hours, days, weeks, months, years, decades, lifetimes, centuries, ages.

Rhythm of the night: the Moon is central to our perception of time passing. Getty Images

The elusive Moon

It is almost impossible to imagine how time might feel in the absence of all the tools and gadgets we use to track, control and corral it. But it’s also hard to know what we might do in the absence of time as a unit of productivity – a measurable, dispensable resource.

The closest we might come is simply to imagine what life might feel like in the absence of the Moon. Each day would rise and fall, in a rhythm of its own, but without visible reference to anything else. Just endless shifts from light to dark.

Nights would be almost completely dark without the light of the Moon. Only stars at a much further distance would puncture the inky sky. The world around us would change – trees would grow, mammals would age and die, land masses would shift and change – but all would happen in an endless cycle of sunrise to sunset.

Read more: Scientists are hoping to redefine the second – here's why

The light from the Sun takes eight minutes to reach Earth, so the sunlight we see is always eight minutes in the past.

I remember sitting outside when I first learned this, and wondering what the temporal delay might be between me and other objects: a plum tree, trees at the end of the street, hills in the distance, light on the horizon when looking out over the ocean, stars in the night sky.

Moonlight, for reference, takes about 1.3 seconds to get to Earth. Light always travels at the same speed, it is entirely constant. The differing duration between how long it takes for sunlight or moonlight to reach the Earth is determined by the space in between.

Time on the other hand, is anything but constant. There are countless ways we characterise it. The mere fact we have so many calendars and ways of describing perceptual time hints at our inability to pin it down.

Calendars give us the impression we can, and have, made time predictable and understandable. Leap years, days and seconds serve as a periodic reminder that we haven’t.

Author

Emily O'Hara
Senior Lecturer, Spatial Design + Temporary Practices, Auckland University of Technology

ICYMI

The fall equinox is here. What does that mean?

by Maddie Burakoff

The sun sets beyond the downtown skyline of Kansas City, Mo., as the autumnal equinox 

marks the first day of fall Saturday, Sept. 23, 2023

During the equinox, the Earth’s axis and its orbit line up so that both hemispheres get an equal amount of sunlight. Credit: AP Photo/Charlie Riedel, File

Fall is in the air—officially. The equinox arrives on Saturday, marking the start of the fall season for the Northern Hemisphere. But what does that actually mean? Here's what to know about how we split up the year using the Earth's orbit.

What is the equinox?

As the Earth travels around the sun, it does so at an angle.

For most of the year, the Earth's axis is tilted either toward or away from the sun. That means the sun's warmth and light fall unequally on the northern and southern halves of the planet.

During the equinox, the Earth's axis and its orbit line up so that both hemispheres get an equal amount of sunlight.

The word equinox comes from two Latin words meaning equal and night. That's because on the equinox, day and night last almost the same amount of time—though one may get a few extra minutes, depending on where you are on the planet.

The Northern Hemisphere's spring—or vernal—equinox can land between March 19 and 21, depending on the year. Its fall—or autumnal—equinox can land between Sept. 21 and 24.

What is the solstice?

The solstices mark the times during the year when the Earth is seeing its strongest tilt toward or away from the sun. This means the hemispheres are getting very different amounts of sunlight—and days and nights are at their most unequal.

During the Northern Hemisphere's summer solstice, the upper half of the earth is tilted in toward the sun, creating the longest day and shortest night of the year. This solstice falls between June 20 and 22.

Meanwhile, at the winter solstice, the Northern Hemisphere is leaning away from the sun—leading to the shortest day and longest night of the year. The winter solstice falls between December 20 and 23.

What's the difference between meteorological and astronomical seasons?

These are just two different ways to carve up the year.

Meteorological seasons are defined by the weather. They break down the year into three-month seasons based on annual temperature cycles. By that calendar, spring starts on March 1, summer on June 1, fall on Sept. 1 and winter on Dec. 1.

Astronomical seasons depend on how the Earth moves around the sun.

Equinoxes, when the sun lands equally on both hemispheres, mark the start of spring and autumn. Solstices, when the Earth sees its strongest tilt toward or away from the sun, kick off summer and winter.

© 2023 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed without permission.

It's the first day of spring: Here's what that really means

Why the first day of autumn is later than usual this year

Glenn Roberts · Columnist | Posted: a day ago 

An illustration of the March (spring) and September (fall or autumn) equinoxes. During the equinoxes, both hemispheres receive equal amounts of daylight. - NASA/JPL-Caltech

You might be wondering why the autumnal equinox is on Sept. 23 this year – it officially starts at 3:50 a.m. ADT (4:20 a.m. NDT) – and not on the usual date, Sept. 21 or 22.

The date of the autumnal equinox – like the vernal equinox, summer and winter solstices – can vary yearly.

Its date is not determined by the calendar but is an astronomical moment in time when the sun crosses the celestial equator (the plane of the Earth's equator extended out into space), moving from north to south.

While equinoxes and solstices occur at the same moment in time across the globe, due to varying time zones, the actual date of the equinox or solstice may vary, depending on geographical location.

Autumnal equinoxes can occur between Sept. 21-24; in 2024, it's on Sept. 22

Equal day and night

On the date of the autumnal equinox, the sun is directly overhead at local solar time (as seen from Earth's equator).

The word "equinox" comes from the Latin words aequs (meaning "equal") and nox (meaning "night"), referring to equal daylight and nighttime.

There are two equinoxes each year: autumnal and spring here in the Northern Hemisphere. In the Southern Hemisphere, Sept. 23 marks the southern vernal equinox or the beginning of their spring.

On the vernal and autumnal equinoxes, the Earth's axis is neither tilted towards or away from the sun (as it is during the summer and winter solstices in the Northern Hemisphere). The amount of sunlight striking both hemispheres of the Earth's surface is pretty much the same: every latitude across the planet receives approximately the same amount of daylight as it does darkness as the sun is directly over the equator.

Day and night are only relatively equal in length for areas close to the equator; the length of day and night for non-equatorial regions depends on latitude.

For example, on Sept. 23, in Charlottetown, P.E.I., (latitude 46.23824 degrees north), the sun will rise at 7 a.m. and set just after 7:08 p.m., giving a day length of 12 hours, eight minutes, and nine seconds.

On the day of both equinoxes, the sun will rise almost due east and set almost due west, depending on your exact latitude. Charlottetown, on Sept. 23, will see the sunrise at 89 degrees east and set at 271 degrees west.

Decreasing light

Except for tropical regions, most locations in the Northern Hemisphere see a slow but steady decrease in daylight after the summer solstice (the longest day of the year), with the day-to-day differences greatest around the date of the autumnal equinox.

The same is true for the spring equinox, except the daylight period steadily grows longer.

After the autumnal equinox, the daylight period continues to shorten at an ever-decreasing rate until the winter solstice (the shortest period of daylight of the year), when it reaches zero.

Regions closer to the poles experience larger day-to-day differences than those closer to the equator.

Equilux

The moment when daylight and nighttime hours are equal is known as an "equilux," occurring a few days before the spring equinox and after the autumnal equinox in both hemispheres.

For Charlottetown, the equilux is Sept. 25. If you would like to find out when an equilux will occur where you live (you will need to know your approximate latitude), go to timeanddate.com/astronomy/equilux.html.

Astronomy vs. meteorology

The astronomical definition of when seasons begin differs from the meteorological definition.

While astronomical autumn begins Sept. 23, meteorological autumn (which defines the start of the seasons as occurring on the first day of the month that includes the equinox or solstice) occurred Sept. 1.

As the Earth doesn't move at a constant speed in its orbit around the sun, the actual timings of equinoxes and solstices can change each year, meaning the length of astronomical seasons also varies.

On average, the autumnal season in the North Hemisphere lasts about 89.8 days; in the Southern Hemisphere, it's approximately 92.8 days.

Differences

Not all countries use the astronomical definition of when the seasons change.

Australia and New Zealand use the meteorological definition to mark seasons, with spring starting Sept. 1. Some Southeast Asian cultures divide the year into six seasons.

Finland and Sweden base the date of seasons not on a calendar, but on temperature. Seasons within these two countries start and end on different dates, depending on each region's climate.

Global climate change will, no doubt, dramatically alter how these countries determine the start of their seasons.

This week's sky

Mercury (magnitude +2.5, in Leo - the Lion) has emerged from inferior solar conjunction and will reach its highest point in the morning sky 16 degrees above the eastern horizon on Sept. 23, before fading from view as the sun rises.

Venus (magnitude -4.5, in Cancer - the Crab), now at its brightness morning apparition, rises around 3:35 a.m., reaching an altitude of 29 degrees above the eastern horizon, before fading from view around 6:30 a.m.

Saturn (magnitude +0.5, in Aquarius - the Water Bearer) becomes accessible shortly before 8 p.m., 12 degrees above the southeast horizon as darkness falls, reaching a height of 31 degrees above the southern horizon by 11:40 p.m., and remaining visible until about 3:35 a.m. when it drops below 10 degrees above the southwest horizon.

Jupiter (magnitude -2.7, in Aries - the Ram) is visible by about 10 p.m., seven degrees above the eastern horizon, reaching its highest point of 58 degrees in the pre-dawn, southern sky around 4:15 a.m., then becoming lost in the dawn twilight 47 degrees above the southwest horizon by 6:30 a.m.

Mars, two degrees below the western horizon at dusk, is not observable this week.

Comet C/2023 P1 Nishimura reached perihelion (its closest passage of the sun) on Sept. 17 and is too close to the sun to be observed in the western, post-sunset twilight. It will pull away from the sun over the coming weeks, and, although fading in brightness, may still be visible.

Until next week, clear skies.

---

Events:

• Sept. 18 – Venus at greatest brightness in morning sky; mag, -4.5
• Sept. 22 – First Quarter Moon
• Sept. 23 – Autumnal Equinox; start of autumn season in Northern Hemisphere
• Sept. 23 – Mercury at its highest altitude in the morning sky; 16 degrees above the eastern horizon

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Glenn K. Roberts lives in Stratford, P.E.I., and has been an avid amateur astronomer since he was a small child. He welcomes comments from readers at glennkroberts@gmail.com.

IS THE DAY 12 HOURS LONG ON THE EQUINOX? IT'S COMPLICATED

BY: BOB KING SEPTEMBER 20, 2023  

Denser air near the horizon acts like a lens and refracts (bends) the Sun's bottom half upward into the top, compressing the solar disk into a bean. Refraction also "lifts" the Sun into view at the horizon about 2 minutes before the real Sun arrives there. Both effects increase the amount of daylight we experience at the equinoxes.
Bob King

Astronomical cycles acquaint us with the inevitable. That's what I'm thinking right now as we approach the first official day of fall (spring in the southern hemisphere), also known as the autumnal equinox. At 2:49 a.m. EDT, the Sun will cross the celestial equator going south and won't stop its descent until it bumps into the winter solstice on December 21st.

The celestial equator is a projection of Earth's equator on the sky. On that special day, the Sun will pass directly overhead at noon for residents living along the equator, from Nairobi to Quito to Singapore. At local noon, when the Sun passes overhead, residents won't be able to avoid stepping on their shadows. On the same day at the North and South Poles the Sun scrapes completely around the horizon. And no matter where you live except the poles it rises due east and sets due west.

At both the spring and fall equinoxes, the Earth's axis tilts neither toward nor away from the Sun but sidelong. Day and night momentarily strike a balance, each of them 12 hours long on this day, so neither one of them has the upper hand. That's why we call it the equinox, which literally means "equal night." Right?

Don't believe it. There's more to daylight on the equinox than you might think.

THE SUN'S DISK

Venus, pictured here at dawn on September 14, 2023, is essentially a point source compared the Sun's disk.
Bob King

Even on the equinox, daylight still edges out night for two reasons. First, the Sun is a disk, not a point source. If the Sun were simply a more brilliant version of Venus, all of it would rise in one pop. Instead, sunrise is defined as the moment when the Sun's upper edge breaches the horizon. Since the solar disk is about ½° in diameter, its full disk takes between 2.5 and 3 minutes at mid-latitudes to clear the horizon. Similarly, sunset is the moment the trailing limb finally touches the western horizon. That adds another 2.5 to 3 minutes of sunshine at day's end. The result is a total of approximately 5 to 6 minutes of additional daylight. By the way, this is true for every day of the year, not just on the equinox.

As one approaches the Arctic at the time of the fall equinox, the Sun's angle of ascent becomes shallower and shallower. In Alert, Nunavut, the northernmost continuously inhabited place in the world, it takes more than 16 minutes from the moment of sunrise until the Sun clears the eastern horizon! At the equator — the opposite extreme — the Sun rockets straight up from the due-east horizon and extricates itself in just over 2 minutes.

THE EARTH'S AIR

Adding to the complexity is the fact that Earth has air. Consider atmospheric refraction, in which light rays are bent when they pass from a less dense medium (outer space) into a more dense medium (Earth's atmosphere). A familiar example is the "broken" straw sticking out of a glass of water. Light from the top of the straw travels directly to our eyes, while light from the underwater part is refracted (bent) and travels in a slightly different direction, making it look as if it's fractured.

A pencil in a glass of water looks broken because we see the top part through air and the bottom part through the denser medium of water, which bends or refracts the light in a different direction to our eyes. Refraction effects also magnify the submerged half.
Bob King

As the Sun approaches the horizon, air density rapidly increases, making refraction effects much stronger along the bottom edge of the solar disk compared to the top. The difference bends or "lifts" the bottom half of the solar disk into the top half, flattening an otherwise circular Sun into an oval.

You can see the Sun several minutes before it actually rises due to strong refraction at the horizon which bends light rays upward into view.
Sciencia58 / CC BY-SA 4.0

Even before the Sun has physically risen in the morning, refraction elevates its upper edge, causing it to appear nearly 3 minutes (at mid-latitudes) beforehand. Likewise, the actual Sun sets several minutes before its refracted light does. If you were to remove Earth's atmosphere at sunset, sunlight would disappear the moment the entire solar disk sets.

So, we'll need to add another 5 to 6 minutes of daylight to the equinox due to Earth's atmosphere. Even if we were to imagine a hypothetical point at the center of the solar disk instead of the full Sun, atmospheric refraction would also lift it into view earlier and hold onto it later just like all celestial sources.

On an airless Earth, we could watch the solar corona precede the sunrise by blocking the glaring white solar disk from view. All would proceed unaffected by refraction.
Stellarium

EQUAL LIGHT ON THE EQUILUX

Are days and nights ever 12 hours apiece? Yes! Well, close. This occurs at the equilux, a delightful word that derives from the Latin equi (equal) and lux (light). While the equinox occurs across the planet at the same moment, the equilux varies according to latitude.

In the Northern Hemisphere, it occurs several days after the autumnal equinox (on September 25th or 26th at mid-northern latitudes) and several days before the vernal equinox; in the Southern Hemisphere, it's the other way around.

At the equator, day and night are never exactly equal — daylight always exceeds night by 6 to 8 minutes due to the Sun's large apparent size. At the same time, though, day and night are nearly equal every day of the year.

City Latitude Approximate date of equilux

Anchorage, Ak. 61° Sept. 25

Calgary, Alberta 51° Sept. 25

Champaign, Ill. 40° Sept. 26

New Orleans, La. 30° Sept. 27

Honolulu, Hawai'i 21° Sept. 28

San José, Costa Rica 10° Oct. 4

Bogotá, Colombia 5° Oct. 19

Quito, Ecuador 0° Never

Traveling south, equilux dates increasingly part from the equinox date.

Data from Stellarium and other sources

While the equilux concept is great in principle, a perfect balance of day and night isn't possible from many locations because daylight is decreasing at the rate of 2 to 3 minutes per day, not minute by minute. For that reason day and night lengths often differ by about a minute. For example, in Detroit the equilux occurs on September 25th, when the time between sunrise and sunset is only about 13 seconds shy of 12 hours. In Phoenix it occurs on the same date, but daylight is a little more than a minute longer than night.

Isn't splitting hairs fun?

Fall leaves frame the waning gibbous Moon in early October 2020.
Bob King

The equinox is a happy time to be a night-sky watcher. Insects retreat, and evening temperatures are cool and pleasant. To stand under a dark sky before 9 o'clock is a joy. During the summer many of us start observing at the very time we should be getting to bed. These chances occur because of Earth's tilted axis. As the Sun hastens south, the curtain of darkness drops incrementally earlier. Before you know it, the insatiable night will make sunshine a prized commodity.

Happy equinox and equilux indeed!

Bpl.org

https://www.bpl.org/blogs/post/the-origins-and-practices-of-mabon

The Origins and Practices of Mabon | Boston Public Library 

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En.wikipedia.org

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History.co.uk

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Cosmopolitan.com

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Diversity.iu.edu

https://diversity.iu.edu/cultural-involvement/holiday-religious-observances/description/autumn-equinox-mabon.html

Autumn Equinox (Mabon): Description: Religious Holidays and ... 

Autumn Equinox (Mabon) (Mah-bon or May-bon). While Mabon is not one of the four major sabbats in Wicca, it is one of the eight and is thus significant. It ...