I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets first sunday after first full moon after 25th march ... Easter is a holy day for procrastinators
I'm not religious either, I think I learned that in my 40s -
@grb090423 Backwards compatibility. It's tied to a Jewish holiday, and the Jewish lunisolar calendar is built radically differently from the solar-dominant Roman calendars that grew dominant in the Christian parts of Europe.
@riley @grb090423 @sundogplanets
Though it doesn't always (nearly) coincide with Pesach.
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@sundogplanets What shocks me most of all is how the dude was born at Christmas and they nailed him to a cross 4 months later.
@rozeboosje
Growth hormones /j
@sundogplanets -
@rozeboosje
Growth hormones /j
@sundogplanets -
Thanks for illuminating this!
I remembered from childhood education that the date of Easter was determined by some mysterious calculus, performed in some faraway place by some select cognoscenti using some ancient methodology that little boys in the backwoods of North Carolina will never be able to master. I also learned that I should not waste time on things I can't influence and don't care enough to understand. Now I just look at the calendar and the problem is solved!
@oldclumsy_nowmad @sundogplanets My grandmother had something called the Book of Common Prayer (Church of England) and it was all spelled out in the back of there.
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets Hilda of Whitby says "hold my beer"
"Bede present[s] the synod as a victory for the Roman party...[but doubted their use in Rome]. He produced his own version based on the Alexandrian tables, as amended by Dionysius...in his De Temporibus (703) and in more detail in his De Temporum Ratione (716–25). The Bedan tables came to be accepted in the British Isles and the Carolingian Empire in the ninth century and in Rome in the tenth."
https://en.wikipedia.org/wiki/Synod_of_Whitby -
@psneeze Oh, and there's a famous book by Isaac Asimov in which 'Computer' is a job title for humans, and not even by clever pun: The End of Eternity. In it, The Eternity is an organisation for manipulating Teh One Timeline, and it employs people known as Computers to figure out which way the timeline should be manipulated. Computers as we know them are notoriously missing from throughout the book (except, possibly, a seldom-referenced hand-held device that might be interpreted more like a PDA or a calculator), which kind of makes sense, because the book came out in 1955, when the early ancestors of our kind of computers were exotic experimental mathematics things that militaries sometimes gave maths departments a lot of money for.
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@psneeze Oh, and there's a famous book by Isaac Asimov in which 'Computer' is a job title for humans, and not even by clever pun: The End of Eternity. In it, The Eternity is an organisation for manipulating Teh One Timeline, and it employs people known as Computers to figure out which way the timeline should be manipulated. Computers as we know them are notoriously missing from throughout the book (except, possibly, a seldom-referenced hand-held device that might be interpreted more like a PDA or a calculator), which kind of makes sense, because the book came out in 1955, when the early ancestors of our kind of computers were exotic experimental mathematics things that militaries sometimes gave maths departments a lot of money for.
@riley Computers is what NASA called the mathematicians (mainly women) who did the calculations for space flight so I suppose Asimov was influenced by that. @sundogplanets
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@psneeze Oh, and there's a famous book by Isaac Asimov in which 'Computer' is a job title for humans, and not even by clever pun: The End of Eternity. In it, The Eternity is an organisation for manipulating Teh One Timeline, and it employs people known as Computers to figure out which way the timeline should be manipulated. Computers as we know them are notoriously missing from throughout the book (except, possibly, a seldom-referenced hand-held device that might be interpreted more like a PDA or a calculator), which kind of makes sense, because the book came out in 1955, when the early ancestors of our kind of computers were exotic experimental mathematics things that militaries sometimes gave maths departments a lot of money for.
@psneeze I don't know for sure, but Asimov's inspiration might have been the Manhattan Project's practice of arranging human 'computers' into systolic arrays to perform complex simulations before the time of automatic computers and spreadsheets. Reportedly, these computers could use mechanic calculators, though.
The Manhattan Project's practice might, in turn, be derived from the New Deal initiative of the "Mathematical Tables Project", which employed unemployed office clerks and tasked them to 'compute' look-up tables for a bunch of useful transcendental functions. Importantly, the Tables Project was relatively public from the beginning; the Manhattan Project, obviously, was very, very classified, in order to properly ensure that only Russian spies would know exactly what was going on in it. But ten years after the war, the organisational lessons of the project might possibly have started to seep out of the military.
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@riley Computers is what NASA called the mathematicians (mainly women) who did the calculations for space flight so I suppose Asimov was influenced by that. @sundogplanets
@psneeze There was no NASA in 1955. It was still two years until the Sputnik Moment that caused NASA to be established.
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@psneeze There was no NASA in 1955. It was still two years until the Sputnik Moment that caused NASA to be established.
@riley Maybe I'm confusing it with the NACA. @sundogplanets
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@psneeze There was no NASA in 1955. It was still two years until the Sputnik Moment that caused NASA to be established.
Incidentally, a major plot twist of the book is that future humans find it to be a problem that the early Eternity's meddlement didn't let Terrans develop space travel technologies.
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@riley Maybe I'm confusing it with the NACA. @sundogplanets
@psneeze Maybe. I don't know for sure, but NACA would probably have been into some fancy fluid dynamics calculations by its latter years, and a systolic array of human computers is a feasible way of doing it.
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@riley @grb090423 @sundogplanets I didn't know he was called Dennis (sorry).
Anyway, thanks for sharing.
@nxskok He probably wasn't, in his days. He lived in the 'Civilised World'(tm); the still-chugging-on Roman Empire, where both Greek-speaking Romans and Latin-speaking Romans would have used some recognisable form of 'Dionysios' or 'Dionysius'. The 'Dennis' form probably only arose as the name got exported into the 'Barbarian World', probably starting from the semi-"wild", semi-Roman, Gaul of the day, where the two had some of the relatively friendliest encounters. Old Greek is a bit weird, as languages go, in that it has a marker suffix for the nominative case; most other European languages don't, and as the Greek and Latin words started to seep into the developing European languages, many of them kind of bulk-snapped the -os and -us nominative suffixes off from Roman words, and names. With that, and some vowel merging, Dionysios became Dennis for English (and Denis / Денис for Bulgarian). It's the same process that made 'Mathaios' into 'Matthew', 'Petros' into 'Peter', and 'Ioannes' into English 'John' and German 'Hans' and Slavic 'Ivan'.
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RE: https://telescoper.blog/2026/04/03/finding-easter/
I'm an astronomer, and I teach at a Catholic college (though I'm not religious myself).
I had absolutely no idea how complicated the date of Easter is. Wow.
@sundogplanets Perhaps more bizarre is that in Norway the deadline to take studded tyres off your car is the week after Easter.
Which is completely daft as the dates that Easter can fall on is in a range of a month.
The weather here can vary enormously between late March and late April.
We just had two nights where snow fell. It would make a lot more sense to just pick a date that reflects the change in the weather such as the 15th of April for the deadline.
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@sundogplanets What shocks me most of all is how the dude was born at Christmas and they nailed him to a cross 4 months later.
@rozeboosje @sundogplanets Wait till you learn that he was likely born in 5 BC
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@rozeboosje @sundogplanets Wait till you learn that he was likely born in 5 BC
@SamantazFox @sundogplanets I thought he was imaginary
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@nxskok He probably wasn't, in his days. He lived in the 'Civilised World'(tm); the still-chugging-on Roman Empire, where both Greek-speaking Romans and Latin-speaking Romans would have used some recognisable form of 'Dionysios' or 'Dionysius'. The 'Dennis' form probably only arose as the name got exported into the 'Barbarian World', probably starting from the semi-"wild", semi-Roman, Gaul of the day, where the two had some of the relatively friendliest encounters. Old Greek is a bit weird, as languages go, in that it has a marker suffix for the nominative case; most other European languages don't, and as the Greek and Latin words started to seep into the developing European languages, many of them kind of bulk-snapped the -os and -us nominative suffixes off from Roman words, and names. With that, and some vowel merging, Dionysios became Dennis for English (and Denis / Денис for Bulgarian). It's the same process that made 'Mathaios' into 'Matthew', 'Petros' into 'Peter', and 'Ioannes' into English 'John' and German 'Hans' and Slavic 'Ivan'.
@riley @grb090423 @sundogplanets thank you for the much better explanation than I deserved after all I did was almost-quote a line from Monty Python and the Holy Grail.
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@riley @grb090423 @sundogplanets thank you for the much better explanation than I deserved after all I did was almost-quote a line from Monty Python and the Holy Grail.
@nxskok Anyway, it turns out that there's a Saint Dionysios of Paris, also known as Saint Denis of Paris, who lived somewhen in the middle of the 200s, was, as the legend goes, beheaded in Lutetia the 250s, moved into his own abbey in the 600s, and as his career progressed, eventually rose to be a patron saint of France and headaches. Unfortunately, reliable data about his life is scarce; we don't even know for sure if the root cause of his final headache was Valerian.
But he lived about two centuries before Dionysios Exiguus, and moved from Rome to Lutetia, so odds are, if Dennis the Geek was discussed in Gaul in a local vernacular during his lifetime, he would already have been called 'Denis'.
St. Denis | France, Biography, Feast Day, & Facts | Britannica
St. Denis was allegedly the first bishop of Paris and an early Christian martyr. He is a patron saint of France and Paris. St. Denis is also venerated as one of the 14 Holy Helpers, a group of saints who were especially popular in the Middle Ages for their powers of intercession.
Encyclopedia Britannica (www.britannica.com)
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@nxskok Anyway, it turns out that there's a Saint Dionysios of Paris, also known as Saint Denis of Paris, who lived somewhen in the middle of the 200s, was, as the legend goes, beheaded in Lutetia the 250s, moved into his own abbey in the 600s, and as his career progressed, eventually rose to be a patron saint of France and headaches. Unfortunately, reliable data about his life is scarce; we don't even know for sure if the root cause of his final headache was Valerian.
But he lived about two centuries before Dionysios Exiguus, and moved from Rome to Lutetia, so odds are, if Dennis the Geek was discussed in Gaul in a local vernacular during his lifetime, he would already have been called 'Denis'.
St. Denis | France, Biography, Feast Day, & Facts | Britannica
St. Denis was allegedly the first bishop of Paris and an early Christian martyr. He is a patron saint of France and Paris. St. Denis is also venerated as one of the 14 Holy Helpers, a group of saints who were especially popular in the Middle Ages for their powers of intercession.
Encyclopedia Britannica (www.britannica.com)
@nxskok The world in which, if you had questions about the Computus Arguments in Paris, you couldn't just pick up your phone and call the abbot in Rome who knew the Easter stuff for clarification, was so weird. @grb090423 @sundogplanets
Yes! 
