Author Archives: gmcdavid

About gmcdavid

Retired IT professional with a wide range of interests. Married. Three sons, two with autistic-spectrum disorders and the third being transgender with Ehlers-Danlos syndrome. From Chicago but now living in the Twin Cities metro, Minnesota. Episcopalian. Carleton College (BA 1972, physics) and Stanford University (MS 1974, Applied Physics; MS 1976 Statistics).

Science Fiction got there first (again)

Back in High School (1964-68) I read a lot of science fiction by Mack Reynolds. His Joe Mauser series is set in a world where the cold war continues into the 21st century, but, to avoid catastrophe, the West and the “Sov-world” have agreed to restrict all military forces to pre-1900 technology. There is still lots of fighting going on at that level.

Recently I was reading about the decades old border dispute between between China and India countries, which actually led to war in 1962. The conflict still simmers on, but a 1996 agreement states that

Neither side shall open fire, cause bio-degradation, use hazardous chemicals, conduct blast operations or hunt with guns or explosives within two kilometers from the line of actual control.

Neither side wants to get the blame for starting a shooting war, so both sides are following the letter of the agreement. However, nobody is backing down. There have been reports that “Chinese troops have used improvised edged weapons, such as nail-studded clubs, in … skirmishes with Indian forces.” and both sides have martial artists in their border forces.

It seems that the Chinese are escalating. We now have Chinese soldiers armed with new devices for hand-to-hand combat with Indians in Tibet. Actually the “new device”, the guan dao, is quite old. It similar to a a western medieval halberd. It will be interesting to see how Indian army responds. They have a rich tradition of edged weapons to draw upon.

Calculating a limit

Today I saw this problem on Medium: Compute the limit

Followed by “Pause the article and attempt a solution now.” (Don’t cheat and look ahead)

So I did. I do not really like factorials, so I immediately thought of Stirling’s approximation:

ln n! ≃ n ln nn as n → ∞

and all of the n‘s cancelled, leaving the result 1/e. I then looked at the author’s solution. My answer was correct, but he used a completely different approach, as you can see. I posted my solution, and got a nice complement from him.

This is Thanksgiving day in the USA. I am thankful that my calculus skills are still pretty good decades after my last formal course in that or any related field .

Rang Gaeilge, 24ú lá Mí na Samhna 2020

Duinnín agus an Cat (tuilleadh)

  • ‘Tá an gloine briste i ndoras uimhir a 33,’ arsa Eleanór, ‘díreach mar a bheadh i ndoras Mharia murach gur imir tú cleas ar an nglas.’
    ‘Féach an sneachta os comhair an dorais [g],’ ar sise. ‘B’é go raibh cruinniú poiblí ar an táirseach?’
    ‘Dráma, seachas cruinniú, déarfainn,’ arsa an Duinníneach. ‘An rian is tábhachtaí ná an ceann sin ar clé ar fad.’
    ‘Is geall le rian coise eilifint é.’

    ‘The glass is broken in door number 33,’ Eleanor said , ‘just like it would be in Maria’s door if you hadn’t played a trick on the lock.’
    ‘Look at the snow in front of the door,’ she said. Was there a public meeting on the threshhold?’
    ‘Drama, rather than a meeting, I would say,’ said Dineen. ‘The most important track is that one on the far left. It is like an elephant’s footprint.’

    cruinniúGathering, Meetingm
    poiblípublie
    táirseachthreshhold
    rianCourse, path; Mark, trace, track; Power of movement, vigorm
    geallPledge, security; Wager, bet; promisem
    Is geall leIt is like

  • ‘Cuimhnigh go raibh bróga tí á gcaitheamh ag Maria. Faoin am seo, bheidís báite fliuch agus éadach na n-uachtar ag sliobarnaíl thar na boinn. Tá na coiscéimeanna eile anuas ar na cinn aici siúd.’
    ‘An méid atá iontu!’ arsa Eleanor go himníoch. ‘Fiú agus méadú le linn leá a chur san áireamh! . . . Feicim fathaigh, abominable snowmen, dosaen garraíodóir ar thóir Mharia.’
    ‘Siúil anseo i lár an chosáin mar a bhfuil an sneachta leáite.’
    ‘Fuil!’ arsa Eleanór agus uafás uirthi.
    ‘Braonta ar fud na háite,’ a d’aontaigh an Duinníneach.
    Chuir sé lámh trín bpoll agus d’oscail sé an doras.

    Remember Maria was wearing house shoes. By this time, they would be drenched wet and the cloth on top drooping over the soles. The other footsteps are on top of hers.
    ‘The size of them!’ said Eleanor anxiously. ‘Even considering the increase during melting! . . . I see giants, abominable snowmen, a dozen gardeners in search of Maria.’
    ‘Walk here in the middle of the path where the snow has melted.’
    ‘Blood!’ said Eleanor in horror.
    ‘Drops all over the place,’ agreed Dineen.
    He put his hand through the hole and opened the door.

    báitedrowned
    éadachclothm
    uachtartop, upper part; creamm
    ag sliobarna = ag liobarnahanging loose, drooping
    bonnsolem
    méadúincreasem
    leámelting, dissolutionm
    áireamhcounting, reckonning
    fathachgiantm
    ar thóirin search of
    cosán Path; Footway, track; Way, passage; directionm
    fuilbloodf
    uafásHorror, terrorm
    aontaighunite; agree

  • Léigh tuilleadh

Water on the Moon

It’s confirmed. There is water on the Moon. OK, what’s the big deal? Water is very common in the cosmos and has been seen on the moon before. The difference is that previously it had been been only in craters near the lunar south pole, perpetually in darkness. Now, as the updated NASA announcement said, NASA’s SOFIA Discovers Water on Sunlit Surface of Moon, which will be much more accessible to future explorers.

How significant this is remains to be seen, but it has provided Katie Mack with some inspiration.

Rang Gaeilge, 27ú lá Mí Dheireadh Fómhair 2020

Duinnín agus an Cat

Féirín . . . a reward, a present, a keepsake . . . in a bad sense, a lasting complaint, an affliction ; f. Nodlag, a Christmas box.

Deireadh an scéil
End of the story

Oíche Lae Nollag atá ann. Tá an tAthair Pádraig Ó Duinnín ar an traein dheireanach ó Shráid Amiens ar a shlí abhaile go dtí an bungaló beag cois farraige i bPort Mearnóg mar a bhfuil cónaí air. Tá a hata ard dubh síoda leagtha béal in airde ar a ghlúine mar a mbíonn lámhscríbhinn éigin de ghnáth. Tá sé ag cáitheadh sneachta. Ó am go chéile ardaíonn an Duinníneach an nuachtán atá leagtha ar an hata aige agus féachann sé arís ar an bpiscín cait atá ina chodladh istigh. Agus é ag druidim le stáisiún Phort Mearnóg, crochann sé an ruidín beag dubh san aer le súil go mbeadh cat ó dhuine éigin. Ní fhéachann ceachtar den bheirt eile sa charráiste air féin ná ar an bpiscín. Ligeann sé osna agus cuireann sé síos ina phóca é. Póca doimhin é a shíneann go bun a chóta – maintín, a bhfuil sé cairdiúil léi, a réitigh an póca seo, in aisce, dó – le gur féidir leis rudaí ilghnéitheacha a iompar thart go discréideach. Sháigh an piscín ingne ina láimh agus é á stiúrú isteach go cneasta. ‘Féirín!’ arsa an Duinníneach go grod.

It is Christmas Eve. Pádraig Ó Duinnín on the last train from Amiens Street on his way home to the small seaside bungalow in Portmarnock where he lives. His tall black silk hat is set mouth-high on his knees where some manuscript is usually. It is snowing [lit. “throwing snow”]. Occasionally Dineen raises the newspaper set on his hat and he looks again at the kitten who is sleeping inside. Approaching Portmarnock station, he lifts the little black thing in the air with the hope it be someone’s cat. Neither of the other two in the carriage looks at him or the kitten. He lets out a sigh and puts it down in his pocket. It is a deep pocket that stretches to the bottom of his coat, – a seamstress, with whom he is a friend, made this pocket, for nothing, for him – so that he can carry various things around discreetly. The kitten pushed a claw into his hand while while he was politely steering it in. ‘Gift!’ Said Dineen abruptly.

either, neither [with neg.]
síodasilkmgs síoda
leagthalaid
béalmouthm
de ghnáthas a rule
lámhscríbhinnmanuscriptf
féachlookv
piscínkittenm
druidclose, shut; Move close to, draw near, approach [with le
crochhang; raise up; lift, carryv
ceachtar
osna a ligeansighv
doimhin = domhaindeep
sínstretchv
maintínseamstress
aisceRequest, favour; gift, present.f
in aiscefor nothing, gratis
ilghnéitheachaDiverse, various, heterogeneous
discréideachdiscreet
SáighThrust; stab; push, press; dart, lunge
iongaclaw; fingerf pl ingne
stiúrústeering, directing, guiding
cneastaHonest, sincere; Decent, seemly; Mild-mannered
grodShort, sudden; prompt, abrupt

Tus an scéil
Beginning of the story
Léigh tuilleadh

Phosphine on Venus: Not so fast

Last month I posted about a Possible Sign of Life on Venus, which reported on Phosphine gas in the cloud decks of Venus. Earlier this month I mentioned More about phosphine on Venus. The story is not over yet.

A Question of Phosphine links to Re-analysis of the 267-GHz ALMA observations of Venus: No statistically significant detection of phosphine. This team re-analyzed the same data used in the first Phosphine gas paper, but came to the opposite conclusion. So it comes down to a very complicated question of statistical analysis.

Professor Coles also linked to A stringent upper limit of the PH3 abundance at the cloud top of Venus by another team which included Jane Greaves, first author of Phosphine gas in the cloud decks of Venus.

The Archaeology of Armageddon

From 1925 until 1939 The University of Chicago’s Oriental Institute (OI) conducted an archaeological expedition at Tel Megiddo, in what is now northern Israel. This was literally the Biblical Armageddon and has an archaeological record going back to c. 3500 BCE. Eric Cline’s Digging Up Armageddon: The Search for the Lost City of Solomon is a fascinationg account of these excavations. The author interleaves descriptions of the discoveries with the story, which Cline describes as a soap opera, of the participants in the dig.

I discovered the OI back in the 1960’s and it has been a part of my life ever since. However, I had no idea it was such an important player in the archaeological work between the world wars. It is amazing what could be done with Rockefeller money in those days.

The site was occupied almost continuously from about 3500 BCE until about 586 BCE, but a direct connection to King Solomon has yet to be found. What were thought to be Solomon’s stables now seem date from the reign of Ahab, about 870-850 BCE. Ahab and his father Omri get a terrible press in the Biblical book of 1 Kings, but unlike their predecessors in both Israel and Judah, they are mentioned in contemporary Moabite and Assyrian records. We do not yet have such a verification of the Biblical account for David and Solomon.

Columbus and the Flat Earth

Inventing the Flat Earth: Columbus and Modern Historians, by Jeffrey Burton Russell, is the book for the day. Columbus did not show the world that the Earth was round. No educated European in 1492 believed that the Earth was flat. They all knew it was round. As all math geeks know, Eratosthenes of Cyrene had made a good calculation of the circumference of the Earth about 200 BCE.

Catholic church authorities did not say that the plan of Columbus to reach the orient by sailing westward was impossible because the Earth was flat. Their scholastic theology was based on the philosophy of Aristotle, who understood perfectly well that the Earth was round.

There are passages in the Bible that suggest a flat Earth, but almost all theologians of ancient and medieval times knew the evidence for a round Earth was overwhelming, and understood the Bible was not to be taken literally in this and similar cases.

The objection to the plans of Columbus was that, thanks to Eratosthenes, people had a good idea of the distance from the west coast of Europe to the east coast of China, and could easily calculate that no ship of the day could possibly carry enough supplies for the voyage.

Columbus, acting like a 21st century Republican, rejected the best science of the day and chose a smaller alternative value for the circumference that suited his purposes. He was just lucky that the Americas happened to be there. As a result their inhabitants were then horribly unlucky.

The story about Columbus and the flat Earth is a 19th century invention, not history.

Also posted on Facebook.

The Fall of the Western Roman Empire

Some quotes from The Fall of the Roman Empire: A New History of Rome and the Barbarians, by Peter Heather.

“…this book will argue that the view that Rome’s own internal transformations had so weakened it by the fourth century that it was ready to collapse under its own weight in the fifth, has become unsustainable. The roots of fifth-century collapse must be sought elsewhere.” [pp. 14-15]
“‘What we call the fall of the Roman Empire was an imaginative experiment that got a little out of hand.’ You can only argue this, it seems to me, if you don’t let narrative history dirty your hands. Any attempt to reconstruct fifth-century events brings home just how violent the process was. In my view, it is impossible to escape the fact that the western Empire broke up because too many outside groups established themselves on its territories and expanded their holdings by warfare.” [p. 436]
“All the evils identified in the western system applied equally, if not more, to the eastern. If anything, the Roman east was more Christian, and more given to doctrinal argument. Also, it operated the same kind of governmental system over the same kind of economy. Yet the east survived, when the west fell. This alone makes it difficult to argue that there was something so inherently wrong with the late imperial system that it was bound to collapse under its own weight.” [pp. 443-444]

This reminded that I had seen a similar argument in Arther Ferrill’s The Fall of the Roman Empire: The Military Explanation. As I noted in my Amazon review of that book:

“There is a lot of nonsense in circulation about the Fall of the Western Empire. Ferrill gets past all of it by starting from one obvious but often neglected criterion: Any explanation of the Fall of the Western Roman Empire must also account for the survival of the Byzantine East.”