Michael Wright made a study of the original fragments of the Antikythera mechanism, an Ancient Greek brass mechanism, together with Allan George Bromley. They used a technique called linear X-raytomography which was suggested by retired consultant radiologist, Alan Partridge. For this, Wright designed and made an apparatus for linear tomography, allowing the generation of sectional 2D radiographicimages.[2] Early results of this survey were presented in 1997, which showed that Price's reconstruction was fundamentally flawed.[3]
Further study of the new imagery allowed Wright to advance a number of proposals. Firstly he developed the idea, suggested by Price in "Gears from the Greeks", that the mechanism could have served as a planetarium. Wright's planetarium not only modelled the motion of the Sun and Moon, but also the Inferior Planets (Mercury and Venus), and the Superior Planets (Mars, Jupiter and Saturn).[4][5]
Wright proposed that the Sun and Moon could have moved in accordance with the theories of Hipparchus and the five known planets moved according to the simple epicyclic theory suggested by the theorem of Apollonius. In order to prove that this was possible using the level of technology apparent in the mechanism, Wright produced a working model of such a planetarium.[6][7]
Wright also increased upon Price's gear count of 27 to 31[5] including 1 in Fragment C that was eventually identified as part of a Moon phase display.[8] He suggested that this is a mechanism that shows the phase of the Moon by means of a rotating semi-silvered ball, realized by the differential rotation of the sidereal cycle of the Moon and the Sun's yearly cycle. This precedes previously known mechanisms of this sort by a millennium and a half.
More accurate tooth counts were also obtained,[9] allowing a new gearing scheme to be advanced.[10] This more accurate information allowed Wright to confirm Price's perceptive suggestion that the upper back dial displays the Metonic cycle with 235 lunar months divisions over a five-turn scale. In addition to this Wright proposed the remarkable idea that the main back dials are in the form of spirals, with the upper back dial out as a five-turn spiral containing 47 divisions in each turn. It therefore presented a visual display of the 235 months of the Metonic cycle (19 years ≈ 235 Synodic Months). Wright also observed that fragmentary inscriptions suggested that the pointer on the subsidiary dial showed a count of four cycles of the 19-year period, equal to the 76-year Callippic cycle.[11]
Based on more tentative observations, Wright also came to the conclusion that the lower back dial counted Draconic Months and could perhaps have been used for eclipse prediction.[12]
All these findings have been incorporated into Wright's working model,[11] demonstrating that a single mechanism with all these functions could be built, and would work.
Despite the improved imagery provided by the linear tomography, Wright could not reconcile all the known gears into a single coherent mechanism, and this led him to advance the theory that the mechanism had been altered, with some astronomical functions removed and others added.[11]
Finally, as an outcome of his research,[2][11][13][14][15][16][17] Wright also conclusively demonstrated that Price's suggestion of the existence of a differential gearing arrangement was incorrect.[8][11]
In 2006, Wright completed what he believed to be an almost exact replica of the mechanism.[18] With that came a paper dated 2007 entitled "The Antikythera mechanism reconsidered",[19] recapitulating most of the points made above. In a footnote to that paper dated 29 November 2006, Wright acknowledges details explained by the Antikythera Mechanism Research Program since his publication:
Note added 29 November 2006: This paper was submitted on 2 September 2006 and accepted for publication on 26 October 2006. Since then the Antikythera Mechanism Research Project Group has published interesting findings [citation:[20]]. Their independent survey has included study of the newly discovered fragment F, a part of the lower back dial which was not available to me. Their reading of the inscriptions on this dial reveals that the function displayed on it was the eclipse cycle of 223 synodic months, distributed around the four-turn spiral scale. (As eclipses of the Sun are rare events, the engraved sequence may, in principle, afford means for dating the Mechanism.) One revolution of the pointer thus represented (223÷4) synodic months, not one draconitic month as I have suggested. The Group offers a modification of my gear train which achieves this function and also incorporates exactly those mechanical features that I characterised as having probably been made redundant by alteration of the instrument. The satisfactory way in which the Group’s suggestions for these parts fall in with my own observations of the artefact itself, and remove residual difficulties with my reconstruction, lead me to believe that they are correct. I have no hesitation either in adopting the Group’s revisions of the function of the lower back dial and of the internal mechanism or in withdrawing statements concerning these features that conflict with them. The changes, though important, are physically quite slight, and do not affect my arguments for other significant features of my reconstruction. I stand by the conclusions of my paper.
Michael Wright's research on the mechanism has continued in parallel with the efforts of the Antikythera Mechanism Research Project (AMRP). On 6 March 2007, he presented his model in the National Hellenic Research Foundation in Athens, Greece.[citation needed]
An orrery is a mechanical model of the Solar System that illustrates or predicts the relative positions and motions of the planets and moons, usually according to the heliocentric model. It may also represent the relative sizes of these bodies; however, since accurate scaling is often not practical due to the actual large ratio differences, a scaled-down approximation may be used instead. The Greeks had working planetaria, but the first modern example was produced c. 1712 by John Rowley. He named it orrery for Charles Boyle, 4th Earl of Orrery. The plaque on it reads "Orrery invented by Graham 1700 improved by Rowley and presented by him to John [sic] Earl of Orrery after whom it was named by at the suggestion of Richard Steele."
The Antikythera mechanism is an Ancient Greek hand-powered orrery, described as the oldest known example of an analogue computer used to predict astronomical positions and eclipses decades in advance. It could also be used to track the four-year cycle of athletic games similar to an Olympiad, the cycle of the ancient Olympic Games.
An exeligmos is a period of 54 years, 33 days that can be used to predict successive eclipses with similar properties and location. For a solar eclipse, after every exeligmos a solar eclipse of similar characteristics will occur in a location close to the eclipse before it. For a lunar eclipse the same part of the earth will view an eclipse that is very similar to the one that occurred one exeligmos before it. The exeligmos is an eclipse cycle that is a triple saros, three saroses long, with the advantage that it has nearly an integer number of days so the next eclipse will be visible at locations and times near the eclipse that occurred one exeligmos earlier. In contrast, each saros, an eclipse occurs about eight hours later in the day or about 120° to the west of the eclipse that occurred one saros earlier.
A differential is a gear train with three drive shafts that has the property that the rotational speed of one shaft is the average of the speeds of the others. A common use of differentials is in motor vehicles, to allow the wheels at each end of a drive axle to rotate at different speeds while cornering. Other uses include clocks and analogue computers. Differentials can also provide a gear ratio between the input and output shafts. For example, many differentials in motor vehicles provide a gearing reduction by having fewer teeth on the pinion than the ring gear.
An epicyclic gear train is a gear reduction assembly consisting of two gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates, to carry the planet gear(s) around the sun gear. The planet and sun gears mesh so that their pitch circles roll without slip. If the sun gear is held fixed, then a point on the pitch circle of the planet gear traces an epicycloid curve.
In astronomy, an octaeteris is the period of eight solar years after which the moon phase occurs on the same day of the year plus one or two days.
Various ancient Greek calendars began in most states of ancient Greece between autumn and winter except for the Attic calendar, which began in summer.
The Prague astronomical clock or Prague Orloj is a medieval astronomical clock attached to the Old Town Hall in Prague, the capital of the Czech Republic.
An astronomical clock, horologium, or orloj is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the Sun, Moon, zodiacal constellations, and sometimes major planets.
Meton of Athens was a Greek mathematician, astronomer, geometer, and engineer who lived in Athens in the 5th century BC. He is best known for calculations involving the eponymous 19-year Metonic cycle, which he introduced in 432 BC into the lunisolar Attic calendar. Euphronios says that Colonus was Meton's deme.
Callippus was a Greek astronomer and mathematician.
Chronometry or horology is the science studying the measurement of time and timekeeping. Chronometry enables the establishment of standard measurements of time, which have applications in a broad range of social and scientific areas. Horology usually refers specifically to the study of mechanical timekeeping devices, while chronometry is broader in scope, also including biological behaviours with respect to time (biochronometry), as well as the dating of geological material (geochronometry).
Allan George Bromley was an Australian historian of computing who became a world authority on many aspects of early computing and was one of the most avid collectors of mechanical calculators.
The Antikythera wreck is a Roman-era shipwreck dating from the second quarter of the first century BC.
An astrarium, also called a planetarium, is a medieval astronomical clock made in the 14th century by Italian engineer and astronomer Giovanni Dondi dell'Orologio. The Astrarium was modeled after the solar system and, in addition to counting time and representing calendar dates and holidays, showed how the planets moved around the celestial sphere in one timepiece. This was its main task, in comparison with the astronomical clock, the main task of which is the actual reading of time. A complex mechanism, it combined the functions of a modern planetarium, clock, and calendar into a singular constructive device. Devices that perform this function were known to have been created prior to the design of Dondi, though relatively little is known about them. It is occasionally erroneously claimed by the details of some sources that the Astrarium was the first mechanical device showing the movements of the planets.
An equatorium is an astronomical calculating instrument. It can be used for finding the positions of the Moon, Sun, and planets without arithmetic operations, using a geometrical model to represent the position of a given celestial body.
St Mark's Clock is housed in the Clock Tower on the Piazza San Marco in Venice, Italy, adjoining the Procuratie Vecchie. The first clock housed in the tower was built and installed by Gian Paolo and Gian Carlo Rainieri, father and son, between 1496 and 1499, and was one of a number of large public astronomical clocks erected throughout Europe during the 14th and 15th centuries. The clock has had an eventful horological history, and been the subject of many restorations, some controversial.
The concept of engineering has existed since ancient times as humans devised fundamental inventions such as the pulley, lever, and wheel. Each of these inventions is consistent with the modern definition of engineering, exploiting basic mechanical principles to develop useful tools and objects.
Decoding the Heavens: A 2,000-Year-old Computer and the Century Long Search to Discover Its Secrets by Jo Marchant is an exploration of the history and significance of the Antikythera Mechanism, an ancient mechanical calculator designed to calculate astronomical positions. Technological artifacts of similar complexity did not reappear until a thousand years later.
The astronomical clock of Messina is an astronomical clock constructed by the Ungerer Company of Strasbourg in 1933. It is built into the campanile of Messina Cathedral.
1 2 Wright, M T.; Bromley, A. G.; Magkou, E (1995). "Simple X-ray Tomography and the Antikythera Mechanism". PACT. 45: 531–543.
↑ Wright, M T.; Bromley, A. G. (4–7 September 1997). "Current Work on the Antikythera Mechanism". Proc. Conf. Αρχαία Ελληνική Τεχνολογία (Ancient Greek Technology). Thessaloniki. pp.19–25.
↑ Wright, M T.; Bromley, A. G. (August 2001). "Towards a New Reconstruction of the Antikythera Mechanism". Proc. Conf. Extraordinary Machines and Structures in Antiquity. Ancient Olympiai. pp.81–94. ed. S.A. Paipetis, Peri Technon, Patras 2003.
1 2 Wright, M T. (July 2002). "In the Steps of the Master Mechanic". Proc. Conf. Η Αρχαία Ελλάδα και ο Σύγχρονος Κόσμος (Ancient Greece and the Modern World). Ancient Olympiai. pp.86–97. University of Patras 2003.
↑ Wright, M T. (2002). "A Planetarium Display for the Antikythera Mechanism (a)". Horological Journal. 144 (5 (May 2002)): 169–173.
↑ Wright, M T. (2002). "A Planetarium Display for the Antikythera Mechanism (b)". Horological Journal. 144 (6 (June 2002)): 193.
1 2 Wright, M T. (2005). "The Antikythera Mechanism and the early history of the Moon Phase Display". Antiquarian Horology. 29 (3 (March 2006)): 319–329.
↑ Wright, M T. (2004). "The Scholar, the Mechanic and the Antikythera Mechanism". Bulletin of the Scientific Instrument Society. 80 (March 2004): 4–11.
↑ Wright, M T. (2005). "The Antikythera Mechanism: a New Gearing Scheme". Bulletin of the Scientific Instrument Society. 85 (June 2005): 2–7.
1 2 3 4 5 Wright, M T. (2005). "Counting Months and Years: the Upper Back Dial of the Antikythera Mechanism". Bulletin of the Scientific Instrument Society. 87 (December 2005) (1 (September 2005)): 8–13.
↑ Wright, M T. (October 2005). "Understanding the Antikythera Mechanism". Proc. Conf. Αρχαία Ελληνική Τεχνολογία (Ancient Greek Technology). Athensi. in preparation ()
↑ Wright, M T. (2005). "Epicyclic Gearing and the Antikythera Mechanism, part 2". Antiquarian Horology. 29 (1 (September 2005)): 54–60.
↑ Wright, M T., "Il meccanismo di Anticitera: l'antica tradizione dei meccanismi ad ingranaggio" (The Antikythera Mechanism: evidence for an ancient tradition of the making of geared instruments), in: E. Lo Sardo (ed.), Eureka! Il genio degli antichi, Naples, July 2005 – January 2006, Electa Napoli 2005, pp. 241 – 244.
↑ Wright, M T. (2004). "Il meccanismo di Anticitera: l'antica tradizione dei meccanismi ad ingranaggio (The Antikythera Mechanism: evidence for an ancient tradition of the making of geared instruments)". Αρχαιολογία & Τέχνες. 95 (June 2005): 54–60.
↑ Wright, M T. (2005). "Ο Μηχανισμός των Αντικυθήρων (The Antikythera Mechanism)". Αρχαιολογία & Τέχνες. 95 (June 2005): 54–60.
↑ Wright, M T. (2003). "Epicyclic Gearing and the Antikythera Mechanism, part 1". Antiquarian Horology. 27 (March 2003) (3): 270–279.
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
