Maybe you were expecting the equinox on the 21st. Did you realize how wrong you were?
Anyway, the fall equinox this year is on the 23d. That seemed oddly late to me, but I see that it's not.
২০ সেপ্টেম্বর, ২০২৩
"While the September equinox usually occurs on September 22 or 23, it can very rarely fall on September 21 or September 24."
"A September 21 equinox has not happened for several millennia. In the 21st century, it will happen twice—in 2092 and 2096. The last September 24 equinox occurred in 1931, the next one will take place in 2303.... The equinox dates vary because of the difference between how the Gregorian calendar defines a year (365 days) and the time it actually takes for Earth to complete its orbit around the sun (about 365 and 1/4 days)."
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So the Gregorian calendar has chosen a gender of 365 days, and we're all bound to acknowledge their personal truth.
I always remember as the 21st. I know it varies a bit, sometimes falling on the 22nd, but I thought that was less common. And never the 23rd or 24th.
Does the equinox tend to arrive earlier in leap years?
Boom! Right here folks is the exact timestamp of when we were just Mandela Effected. New rule that's always existed just popped into our universe.
Equinox has always been 21/22 in my timeline. Can't be rused into thinking otherwise.
If only June had 31 days.
And so the cosmic dance continues.
Sadly, I shall not live long enough to see an equinox that falls on 9/21. I'll take my loss philosophically and muddle through. You don't experience much perfection in a single lifetime.
Sadly, I shall not live long enough to see an equinox that falls on 9/21. I'll take my loss philosophically and muddle through. You don't experience much perfection in a single lifetime.
Yet another example of our global climate crisis
Well, it’s a good thing that both July and August have 31 days, but there I go thinking about the Roman Empire again.
TIMING: I was just ran across this a few hours ago
In D.C., our 12-hour day is not until September 26. Right now, we are losing 2.5 minutes of sunlight a day.
In March, you are ecstatic that sunset is 7 p.m. In September, a 7 p.m. sunset starts getting depressing. Soon it will be dark when you leave work.
I know the shortest day of the year. All the other equinoxes and solstices I've no clue when they come. I guess I just never thought to absorb that information.
21st is the norm. Rarely on 22nd because of calendar issues. I call BS on any other date.
'Weather forecast for tonight: dark. Continued dark overnight, with widely scattered light by morning.' ~ George Carlin
Looking forward to ski season.
Since I was born on the 23rd – in a year when that day was the equinox (1949) – it doesn't seem late to me at all.
As usual, CBS News mangles science and history just enough to sound plausible while leaving the reader less informed.
Yes, the solar year is about 365 1/4 days long. No, the Gregorian calendar does not define the year as 365 days. Whoever wrote that for CBS News is earning far too much money. Obviously, he/she just assumed the fraction was a recent discovery. Read the goddamned sources, you news-maven monkeys, you flea-picking apes!
365 days and some fraction of day -- everyone who bothered to look and to measure since ancient times, including the Greeks and the Maya, knew that and proposed calendrical systems to compensate. The question was the fraction. Hipparchus, a 2nd-century BC Greek astronomer reckoned the year to be 365 days, 5 hours, and 12 seconds (365.24667). The Julian calendar, the ecclesiastical default throughout Christendom for over 1500 years, was invented to compensate for that fraction of a day by adding leap years to distribute the fractional day over several years. Unfortunately, a regular system of leap years is not mathematically possible. (More on that later) Consequently, the Julian calendar came to be about ten full days out of sync with the solar year by the mid-16th century. A new system with the correction and a new formula for distributing the fraction, recalculated to be 0.2425 days, was decreed by Pope Gregory XIII in 1582. For religious reasons, the English didn't adopt it until the 18th century, consequently, Washington's birthday is celebrated on the wrong date. For religious reasons, the Russians didn't use the Gregorian system until the Tsars were deposed in 1917. (The military, diplomatic, and agricultural implications of that obstinate adherence to an increasingly flawed calendar are tragicomic.) For political reasons, the ruling Jobins ditched the Gregorian system for their barking-mad Revolutionary calendar.
But there's a snag. The length of the solar year isn't the whole story. For religious reasons, Christian scholars pictured the Earth as a perfect sphere, but it's not. You see, God created a perfect universe because He is perfect. All the fuck ups are our fault, which is why we're damned and why Jesus was executed, yaddah, yaddah, yaddah. In addition to measuring the year, Hipparchus also discovered the precession of the equinoxes, one of the consequences of our non-spherical planet and having a moon. Hipparchus reckoned the precession factor to be about 1º of arc per century. It's a bit more than that, currently reckoned as about 50.4 arc seconds per year. And the year is getting longer. These little snags mean that a consistent and invariable system of leap years isn't possible. The accumulated error must be dealt with by occasional ad hoc corrections to the calendar and to official clocks applied by consensus. Precession is why the true equinoxes creep around those assumedly fixed dates, the calendar has little to do with it.
Trust the MSM -- NEVER.
"Maybe you were expecting the equinox on the 21st. Did you realize how wrong you were?"
It's due to Global Warming, of course. Is there anything it can't do?
Jacobins. (damed fingers)
Quaestor said...
"... These little snags mean that a consistent and invariable system of leap years isn't possible. The accumulated error must be dealt with by occasional ad hoc corrections to the calendar and to official clocks applied by consensus..."
With all of the conflict and disagreement in the world, it's good to see that we humans can at least agree on somethi- Wait, what was Ann saying in her original blogpost abouit the date again?
"Season of mists and mellow fruitfulness."
Probably my favorite.
“Maybe you were expecting the equinox on the 21st. Did you realize how wrong you were?“
Were we expecting the equinox on the 21st, or the end of summer and beginning of fall?
The idea that we now have to compute the exact day and time of the equinoxes and solstices to know when the seasons begin and end sounds scientific, but smells religious.
The first day of spring, summer, fall, and winter being March 21, June 21, September 21, and December 21 every year was an easy-to-remember convention. That results in 90 or 91 days of winter, 92 days of spring, 92 days of summer, and 91 days of fall.
Using the dates 12/21/2022, 3/20/2023, 9/23/2023, and 12/22/2023 results in 89 days of winter, 93 days of spring, 94 days of summer, and 90 days of fall. Perhaps someone who understands this could explain why the seasons computed this way have such different lengths, and why that’s a better convention. OK, more spring and summer, I get that as a selling point.
The equinox is racist and only exists because of the patriarchy, so it's not real anyway...
Then there's the sidereal year. Not the same as the solar year.
Years are composed of days, but what's a day? The time between one sunrise and the following sunrise is one reasonable answer, but what's a sunrise? We've got a consensus definition of sunrise and optics that allow us to check. The ancients didn't.
The evidence supports the assumption that the Egyptians defined the day by the stars, probably Sirius. The reason is simple, glare. Imagine trying to determine sunrise with a rigorous degree of certitude with your naked eyes. Hurts, don't it?
Defining the day as the interval between the rising or setting of a particular star has advantages and disadvantages. The advantage is a star is a point source of light. Though bright stars give the illusion of being bigger than the dimmer ones, they're all points. Even today we still don't have an instrument capable of resolving the disc of even a nearby star like we can see the disc of our sun. When a star reaches the horizon it winks off faster than an incandescent lightbulb can go dark. There's no interval of half up and half down like a sunset or sunrise. This is good for precision. The disadvantage? What you get by using a star rather than our sun is a sidereal day, a bit longer than a solar day by about 3.285 seconds -- an additional complication to matters calendrical when we realize that calendars are fundamentally about agriculture and agriculture is about plants and plants are about the sun.
Food production in Egypt depended on the yearly inundation of the Nile. Predicting it was therefore crucially important. Working from the basis of a sidereal year may have complicated that prediction enough that by the 4th century BC Egyptian grain output had been sufficiently compromised to allow Alexander's comparatively small Macedonian army to overrun the most populous nation of the ancient West. Alexander brought with him a bunch of Greek smartypants (smartytogas?) who fixed the Egyptian calendar enough to restore the output, which attracted the Romans, yaddah, yaddah. yaddah.
Micheal McNeil- same w/my daughter.
1993. Pregnant w/her 1st child.
I named her: guess?
It fits her.
You say tomato,
I say tomAHto,
You say equinox,
I say solstice,
Tomato, TomAHto,
Equinox, Solstice,
Let's call the whole thing off ...
"Does the equinox tend to arrive earlier in leap years?"
You noted, obviously, that the two instances of it occurring on September 21st are in 2092 and 2096. The more important thing to note, however, is that those are the last two leap years before the omission of a leap day in 2100 which will have the effect of moving the equinox forward a day on the calendar for 2100 from what it was in 2092 and 2096. The leap day is added every four years because the year is approximately 365 and 1/4 days- you make up for that extra 1/4 of day every 4 years by adding February 29th. However, the year isn't exactly 365.25 days either- it is very slightly less than that, so that over many decades you end up adding one too many leap days, which is made up for by omitting a leap day during century years that aren't exactly divisible by 400.
So, answer your question- yes it is probably (I don't know for absolute certain) that it occurs only during leap years, but it makes sense to me that it would as it is the addition of the extra day in a leap year at the end of a long period before a leap day omission where the equinox would occur a day early.
On the other hand, it should occur a day late on September 24th in a year just prior to the addition of leap day always, but I have to think about why is occurred specifically in 1931, for example, rather than, say 1903. It probably has something to do with the additional day that would get added in 2000, but has to occur after the omission of 3 days for 1700, 1800, and 1900.
Now for some math:
The year as of right now is on average 365.2422 days, so adding a leap day every four years adds a full day to the calendar, but the Earth has only gone through .2422 x 4, or 0.9688 days. So each leap day adds 0.0312 too many days every 4 years, or an extra 3.12 days every 4 centuries- this is why the system omits 3 leap days every 400 years. However, this still leaves an extra 0.12 days every 4 centuries added. I honestly don't know how this accounted for- maybe another omitted leap day every 4 millenia.
Culturally in the U.S., summer runs from the Saturday of Memorial Day weekend through the Monday of Labor Day weekend, which this year was 101 days.
Here is a good image from Wikipedia that probably better illustrates (than my attempted explanation above) why 2092 and 2096 have equinoxes on September 21st rather than the 22nd or 23rd- it is a graph for the Summer solstice, but the effect is the same- 2092 and 2096 are the last two leap years spanning the 200 years from the omitted leap day of 1900 (those years the sawtooth bottoms since February 29th comes before September in those years) across the true leap year of 2000 and the omitted leap day of 2100. Because the leap years add too many days, the solstice occurs earlier and earlier- the general trend from 1900 to 2100- the sawtooth is the effect of the each added leap day, and the reset at 2100 occurs because of the omitted leap day that year shifting the cycle up.
"Precession is why the true equinoxes creep around those assumedly fixed dates, the calendar has little to do with it."
That's what I've always thought.
I am happy the nights are lengthening. This dark window I got in three all-nighters of observing. Summer nights are so short (only 3ish hours of full darkness) it's barely worth the effort to travel to a dark site and set up the telescope.
Kinda on topic: Nice aurora in northern Wisconsin Monday night. Even saw STEVE (Strong Thermal Emission Velocity Enhancement).
Is this going to delay the new Prime Day in October?
Please God, tell me it's not.
My goodness. Quaestor continues to amaze. It seems he knows everything about everything. I'm totally in awe. (Not sarc)
Holidays in general are arbitrary. I like the equinox and the solstice because they refer to actual measurable things.
Precession, the main cycle, doesn't cause the date of the equinox/solstice to bounce around- it literally moves it along the calendar in one general direction. Over a timescale of millenia, the Summer solstice for the northern hemisphere will eventually occur around December 21-22 in about 13,000 years. Our present calendar was developed, what, about 500 years ago? I assume we can add new adjustments to the calendar to keep the solstices and equinoxes on about the same dates, but have we done this yet?
Yancy Ward writes, "The year as of right now is on average 365.2422 days, so adding a leap day every four years adds a full day to the calendar, but the Earth has only gone through .2422 x 4, or 0.9688 days."
Your problem arises from an assumption that's not quite correct. Leap years aren't added every four years. If that were true your math would account for a substantial error, that would have produced a revised calendar by now. However, the leap year rule is slightly more complex than evenly divisible by four
According to the Royal Observatory at Greenwich, to be a leap year, the year number must be divisible by four – except for end-of-century years, which must be divisible by 400.
You may also have noticed the famous Times Square Big Ginormous Ball occasionally seems to get stuck. The madding crowd chants 5... 4... 3... 2... 1 Happy New Year!!! but the big luminous sphere doesn't immediately comply. Well it's not stuck, it's adding leap seconds, giving the calendar a bit more correction. This wasn't practical before the atomic clocks, the internet, and NTP (network time protocol) and the correction eventually gets forwarded to your devices. Occasionally, December 31st isn't a 24-hour day.
"Even today we still don't have an instrument capable of resolving the disc of even a nearby star like we can see the disc of our sun."
That's no longer true; hasn't been true for awhile. Betelgeuse was the first. There are others, but I don't have a list.
"When a star reaches the horizon it winks off faster than an incandescent lightbulb can go dark."
Similar phenomenon is observing stellar occultations by the moon. One instance it's there, then it's gone. Blink of an eye. They're fun to observe in a telescope.
The time between one sunrise and the following sunrise is one reasonable answer, but what's a sunrise? We've got a consensus definition of sunrise and optics that allow us to check. The ancients didn't.
I thought a little clarification was in order. By "the ancients" I meant the Bronze Age. Hellenistic Age astronomers were not so encumbered. They could observe and time sunrises and sunsets with astonishing accuracy by using the simplest optical instrument imaginable, the pinhole lens. If you've ever watched a solar eclipse with that box-over-your-head thing, you've crudely replicated one of the most significant astronomical apparatuses in history. If the length of your box and the size of your hole are just right, the projected image of the sun is good enough to show sunspots, which many Greek astronomers saw and commented on.
More on our current imaging capabilities: Recently watched a NASA TV program discussing the imaging of other stellar systems. They showed a MOVIE! made from several years of images of 4 planets revolving around their sun. Was taken using adaptive optics and a stellar coronagraph to block out the light of the star. Mind-blowing. We are an amazing species when we aren't doing stupid stuff.
According to the Royal Observatory at Greenwich, to be a leap year, the year number must be divisible by four – except for end-of-century years, which must be divisible by 400.
The rule I learned getting my masters was: leap year if it is divisible by 4 UNLESS it is divisible by 40 UNLESS it is divisible by 400.
So the year 2200 is divisible by 4 and 40 but not 400, so it is NOT a leap year, however 2000 is divisible by 4, 40, and 400 so it was a leap year.
I, personally, would much rather deal with adding leap seconds, similar to how I would prefer to get rid of the time change.
Farmgirl: At a guess: Equi (or Equy)? I might name such a child Fall. But, more seriously, perhaps Autumn?
Quaestor, did you read the rest of that comment? I actually explained why you don't have leap days added in, for example, 1700, 1800, 1900, but you do add one in 2000. I even showed that that isn't enough to compensate for all the extra time added, I just don't know if that extra 1.2 days/4000 years is accounted for in some other way.
The day on the Earth is slowly getting longer- if I have calculated it right, in 200 million years, the day will be 25 hours long at the present rate of decrease (1.8 milliseconds/100y, which probably isn't a constant either and has its own rate of change, though I don't know it.)
Aught Severn,
1900 isn't divisible by 40 or 400 and it was also not a leap year (same for 1700 and 2100). I think all you need is 4 and 400, or am I missing something here?
9/20/23, 10:44 AM
Blogger Left Bank of the Charles said...
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Perhaps someone who understands this could explain why the seasons computed this way have such different lengths, and why that’s a better convention. OK, more spring and summer, I get that as a selling point.
9/20/23, 10:53 AM
The Earth's orbit is an ellipse. It's closest to the Sun in early January (6th), so it's moving faster than in summer, where it's farthest from the Sun on July 6th. So the time to move 90-deg in its orbit is slightly different depending on the season.
Ok, I see it now, Aught Severn- nevermind.
“Oh no!
Anyway.”
The years 2000 +? Call them the Noughties, or Double-Noughties.
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