Showing posts with label astrolabe. Show all posts
Showing posts with label astrolabe. Show all posts

Monday, September 5, 2022

Who Invented the Mechanical Clock?

In researching the previous post, I came across a reference to Pope Sylvester II (formerly Gerbert d'Aurillac, c.946 - 1003) inventing the mechanical clock. The source of this was the William Godwin's final book, Lives of the Necromancers, An Account of the Most Eminent Persons in Successive Ages Who Have Claimed for Themselves, or to Whom Has Been Imputed by Others, The Exercise of Magical Powers [1834]:

This generous adventurer, prompted by an insatiable thirst for information, is said to have secretly withdrawn himself from his monastery of Fleury in Burgundy, and to have spent several years among the Saracens of Cordova. Here be acquired a knowledge of the language and learning of the Arabians, particularly of their astronomy, geometry and arithmetic; and he is understood to have been the first that imparted to the north and west of Europe a knowledge of the Arabic numerals, a science which at first sight might be despised for its simplicity, but which in its consequences is no inconsiderable instrument in subtilising the powers of human intellect. He likewise introduced the use of clocks. He is also represented to have made an extraordinary proficiency in the art of magic; and among other things...

The italics are mine. A little further along, Godwin adds a footnote that tells us his information comes from William of Malmesbury. William (c.1095 - c.1143) was the foremost English historian of the 12th century. Not exactly a contemporary, but maybe near enough that the memories and stories were still fresh? It would be difficult to determine the accuracy of this report, especially in the context of a brief blog post. Fortunately, I don't have to.

As it turns out, Marek Otisk of the University of Ostrava (Czechoslovakia) published an article on this very topic in September 2020, Gerbert of Aurillac (Pope Sylvester II) as a Clockmaker. He examines the reports from William of Malmesbury, the Chronicle of Thietmar of Merseburg (died c.1018), and a much later record (someone who died in 1610). Among his detailed examination of these and other historical records we learn that although William claims Gerbert built a clock in Reims, a friend of Gerbert's (Richest of Reims), writes about Gerbert's stay in Reims in detail and never mentions a clock. Otisk concludes that William's ascribing of the creation of a clock to Gerbert cannot be trusted.

The later report by the Benedictine monk Arnold Wion, who died about 1610, claims Gerbert built a clepsydra, a water clock, in Ravenna. What we know of Gerber's time in Ravenna, however, is that it was very short; again, no contemporary accounts support this story.

Thietmar of Merseburg tells a different story, that Gerbert created a clock in Magdeburg. Thietmar was a bishop and close friend of Holy Roman Emperor Henry II, who succeeded Otto III, credited with making Gerbert into Pope Sylvester II. Thietmar's Chronicle includes a specific detail about Gerbert creating, in Magdeburg, "created clocks (horologium) which he correctly calibrated according to the Polar star (stella, dux nautarum) which he observed through an observation tube (fistula)." [Otisk, p.32] Otisk likes this account because both Thietmar and Gerbert were in Magdeburg in the late 990s, and very likely crossed paths several times.

The use of the word horologium is misleading, however. We use it for the word "clock," but it is more likely that Gerbert was creating a calibrated armillary, or possible even an astrolabe, which he knew about from his exposure to science being done by Islamic philosophers.

So I can't tell you who created the first mechanical clock. But the question of horologium remains: when long-ago writers refer to "clocks," what exactly did they mean? What constituted a clock? There were several ways to measure time without staring at the sun and judging, and I'll talk about those devices tomorrow.

Sunday, September 4, 2022

Armillary Spheres

The "wooden terrestrial spheres" mentioned here are what we now call "armillary spheres." An armillary is a spherical arrangement of rings designed to mimic the orbits of the sun and planets around the Earth—or around the Sun, depending on the prevailing theory at the time. If the Earth is the center, it is a Ptolemaic sphere; if the Sun is at the center, it is a Copernican sphere. China and Greece each invented them BCE. Hipparchus credited Eratosthenes (276 - 194BCE) as the inventor.

An early Christian philosopher, John Philoponus, wrote the earliest extant treatise on the armillary sphere and the astrolabe. The oldest example of one we have today dates to the 11th century.

Gerbert d'Aurillac (946 - 1003), who became Pope Sylvester II in 999, had brought the armillary sphere to Western Europe. He was also responsible for introducing Western Europe to the abacus, the Hindu-Arabic numeral system we use today, and (possibly) the mechanical clock.

Sylvester used the armillary sphere and sighting tubes to determine the definitive position of the pole star and to record measurements for the tropics and the equator. His work was improved upon in the Renaissance by Tycho Brahe (1546 - 1601). Public figures would have an armillary sphere incorporated into their portraits to indicate their wisdom and knowledge.

I've written about clocks before, but I don't recall learning that Gerbert d'Aurillac invented it. I want to check that out; I'll let you know what I find.

Tuesday, January 28, 2014

Abd al-Rahman al-Sufi, Astronomer

MS. Marsh 144, fol. 135v, Bodleian
The contributions of the Muslim world to astronomy are many, and I have only briefly touched on some of them (such as here). There were nine Muslim astronomers in particular who made major contributions. One of them was the Iranian Abd al-Rahman al-Sufi (7 December 903 - 25 May 986). His name indicates that he was a Sufi Muslim, like Rumi.

al-Sufi translated and expanded on the work of the Greeks, especially attempting to reconcile the Greek and Arabic star charts and constellations. In 964 he published Suwar al-Kawakib al-Thabitah, the "Book of Fixed Stars."* In it he gave the latitude and longitude of hundreds of stars for the year 964 from two views: from both the exterior and interior of a celestial globe. The oldest surviving manuscript known is in the Bodleian Library and was created about 1009 by al-Sufi's son. There was no English translation of this book until 2013.

Among the "firsts" that can be credited to al-Sufi's work are the following identifications:
Ursa Major
  • "the little cloud" that we call the Andromeda Galaxy.
  • the Large Magellanic Cloud*
  • the Omicron Velorum star cluster
  • a "nebulous object" in Vulpecula, now called "Al Sufi's Cluster"
He also describes the astrolabe and lists a thousand uses of it.

The significance of al-Sufi's work led the astronomical community to name other objects after him, such as a a lunar crater (Azophi) and 12621 Alsufi, a minor plant in the asteroid belt with a period of 2000 days.

*There is an argument that he could not have known of the Magellanic Cloud until the same time as Western European astronomers in the 15th century because of its position in the Southern Hemisphere.

Monday, September 24, 2012

Hermann of Reichenau

Hermann, with crutch & Salve Regina
Hermann of Reichenau (1013-1054) was born to Count Wolverad II and his wife Hiltrud in Upper Swabia. He was severely disabled at birth, and had to be carried around in a specially built chair. A 1999 article tried to diagnose him based on contemporary reports.
Using the biography written by his disciple Berthold, [an] unbiased analysis of the symptoms described [...] is worked out: [...] Intellectual functions were unaffected. [...] Muscle disease is considered possible, but motor neuron disease - either amyotrophic lateral sclerosis or spinal muscular atrophy - seems to be the most convincing diagnosis. [C Brunhölzl, Thoughts on the illness of Hermann von Reichenau]
Because of his condition, he was nicknamed "Contractus" or "the Lame." When he was seven years old, his parents handed him over to the cloister school of the nearby Benedictine monastery on Lake Constance, where he studied under Abbot Berno. Berno was a well-known figure at the time for, among other things, his reforms in liturgical music. Hermann became a monk in 1043 and, upon Abbot Berno's death in 1048, became Berno's successor as abbot.

Despite Hermann's extreme difficulty in moving and even speaking, he was considered a devoted monk and brilliant scholar. He wrote a great deal on music, mathematics, and astronomy. As well as a treatise on the science of music, he wrote two of the best-known of the medieval liturgical songs, the Alma Redemptoris Mater (Loving Mother of the Redeemer), and the Salve Regina (Hail Holy Queen).*

Among his other accomplishments, he is credited with speaking Arabic, because through his writings he made available to the Latin West many scientific discoveries that were previously only widely known in the Arab world. This knowledge of Arabic, however, is only an assumption. His biographer, Berthold, never mentions knowledge of Arabic, which would be unusual omission for such an accomplishment. The monastery was a center of learning in the area, and very likely held copies of works by Gerbert of Aurillac, who learned much from Arabic sources in Spain.

Hermann wrote two works on the astrolabe, previously unknown in Europe, and described a portable sundial. His works on mathematics used Roman numerals. Although this precluded the use of decimals, he still achieved some remarkable results. In his Epistola de quantitate mensis lunaris (Letter on measurement of lunar months), he tries to find the average length of a lunar month. In decimal notation, it is 29.530851 days. Hermann did not only not have decimal notation, he didn't have minutes and seconds. In his time, the hour was divided into "moments" and "atoms." He calculates the length of the lunar month to be 29 days, 12 hours, 29 moments, 348 atoms, which turns out to be exactly right.

He also wrote a history called Chronicon ad annum 1054 (Chronicle to the year 1054). The original is lost, but a 1529 edition saved the unique historical knowledge inside. After Hermann's death, it was continued by Berthold; Berthold died in 1088, but the duty was taken up by others up until 1175.

Hermann died on 24 September. In 1863, he was beatified (a step toward being recognized as a saint). As Blessed Hermann of Reichenau, he is considered the patron of unborn babies, and his Feast Day is celebrated on 25 September.

*A popular English version of Salve Regina was prominent in the Whoopi Goldberg film "Sister Act."