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Orrery

From Wikipedia, the free encyclopedia
This article is about the mechanical device. For the Irish peerage, see Earl of Orrery.
A small orrery showing Earth and the inner planets

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, it may use a scaled-down approximation. The Greeks had working planetaria, but the first modern example was produced c. 1712 by John Rowley.[1] He named it "orrery"[2] for his patron Charles Boyle, 4th Earl of Orrery (in County Cork, Ireland). 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 at the suggestion of Richard Steele."[3][4]

Orreries are typically driven by a clockwork mechanism with a globe representing the Sun at the centre, and with a planet at the end of each of a series of arms.

History

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Ancient

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Antikythera mechanism, main fragment, c. 205 to 87 BC
Carlo G Croce, reconstruction of Dondi's Astrarium, originally built between 1348 and 1364 in Padua

The Antikythera mechanism, discovered in 1901 in a wreck off the Greek island of Antikythera in the Mediterranean Sea, exhibited the diurnal motions of the Sun, Moon, and the five planets known to the ancient Greeks. It has been dated between 205 to 87 BC.[5][6][7] The mechanism is considered one of the first orreries.[8] It was geocentric and used as a mechanical calculator to calculate astronomical positions.

Cicero, the Roman philosopher and politician writing in the first century BC, has references describing planetary mechanical models. According to him, the Greek polymaths Thales[9] and Posidonius[10] both constructed a device modeling celestial motion.

Early Modern

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Astronomical clock (Venus-Mercury side) by Eberhard Baldewein, 1563–1568. Exhibit in the Mathematisch-Physikalischer Salon of Dresden, Germany.

In 1348, Giovanni Dondi built the first known clock driven mechanism of the system. It displays the ecliptic position of the Moon, Sun, Mercury, Venus, Mars, Jupiter and Saturn according to the complicated geocentric Ptolemaic planetary theories.[11][12] The clock itself is lost, but Dondi left a complete description of its astronomic gear trains.

As late as 1650, P. Schirleus built a geocentric planetarium with the Sun as a planet, and with Mercury and Venus revolving around the Sun as its moons.[13]

At the court of William IV, Landgrave of Hesse-Kassel two complicated astronomic clocks were built in 1561 and 1563–1568. These use four sides to show the ecliptical positions of the Sun, Mercury, Venus, Mars, Jupiter, Saturn, the Moon, Sun and Dragon (Nodes of the Moon) according to Ptolemy, a calendar, the sunrise and sunset, and an automated celestial sphere with an animated Sun symbol which, for the first time on a celestial globe, shows the real position of the Sun, including the equation of time.[14][15] The clocks are now on display in Kassel at the Astronomisch-Physikalisches Kabinett and in Dresden at the Mathematisch-Physikalischer Salon.

In De revolutionibus orbium coelestium, published in Nuremberg in 1543, Nicolaus Copernicus challenged the Western teaching of a geocentric universe in which the Sun revolved daily around the Earth. He observed that some Greek philosophers such as Aristarchus of Samos had proposed a heliocentric universe. This simplified the apparent epicyclic motions of the planets, making it feasible to represent the planets' paths as simple circles. This could be modeled by the use of gears. Tycho Brahe's improved instruments made precise observations of the skies (1576–1601), and from these Johannes Kepler (1621) deduced that planets orbited the Sun in ellipses. In 1687 Isaac Newton explained the cause of elliptic motion in his theory of gravitation.[16]

Modern

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The Orrery inside the Sphaera Copernicana, designed by Joseph of Gottorp and built by Andreas Bösch, 1653
A Philosopher Lecturing on the Orrery (c. 1766) by Joseph Wright of Derby
Modern working reconstruction of a grand orrery at Derby Museum and Art Gallery (England)
The orrery built by wool carder Eise Eisinga from 1774 to 1781 in his living room, the oldest functioning planetarium in the world

There is an orrery built by clock makers George Graham and Thomas Tompion dated c. 1710 in the History of Science Museum, Oxford.[17] Graham gave the first model, or its design, to the celebrated instrument maker John Rowley of London to make a copy for Prince Eugene of Savoy. Rowley was commissioned to make another copy for his patron Charles Boyle, 4th Earl of Orrery, from which the device took its name in English.[18][19] This model was presented to Charles' son John, later the 5th Earl of Cork and 5th Earl of Orrery. Independently, Christiaan Huygens published in 1703 details of a heliocentric planetary machine which he had built while living in Paris between 1665 and 1681. He calculated the gear trains needed to represent a year of 365.242 days, and used that to produce the cycles of the principal planets.[13]

Joseph Wright's painting A Philosopher giving a Lecture on the Orrery (c. 1766), which hangs in the Derby Museum and Art Gallery, depicts a group listening to a lecture by a natural philosopher. The Sun in a brass orrery provides the only light in the room. The orrery depicted in the painting has rings, which give it an appearance similar to that of an armillary sphere. The demonstration was thereby able to depict eclipses.[20]

To put this in chronological context, in 1762 John Harrison's marine chronometer first enabled accurate measurement of longitude. In 1766, astronomer Johann Daniel Titius first demonstrated that the mean distance of each planet from the Sun could be represented by the following progression:

That is, 0.4, 0.7, 1.0, 1.6, 2.8, ... The numbers refer to astronomical units, the mean distance between Sun and Earth, which is 1.496 × 108 km (93 × 106 miles). The Derby Orrery does not show mean distance, but demonstrated the relative planetary movements.

The Eisinga Planetarium was built from 1774 to 1781 by Eise Eisinga in his home in Franeker, in the Netherlands. It displays the planets across the width of a room's ceiling, and has been in operation almost continually since it was created.[21] This orrery is a planetarium in both senses of the word: a complex machine showing planetary orbits, and a theatre for depicting the planets' movement. Eisinga house was bought by the Dutch Royal family who gave him a pension.

A 1766 Benjamin Martin Orrery, used at Harvard

In 1764, Benjamin Martin devised a new type of planetary model, in which the planets were carried on brass arms leading from a series of concentric or coaxial tubes. With this construction it was difficult to make the planets revolve, and to get the moons to turn around the planets. Martin suggested that the conventional orrery should consist of three parts: the planetarium where the planets revolved around the Sun, the tellurion (also tellurian or tellurium) which showed the inclined axis of the Earth and how it revolved around the Sun, and the lunarium which showed the eccentric rotations of the Moon around the Earth. In one orrery, these three motions could be mounted on a common table, separately using the central spindle as a prime mover.[8]

Workings

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All orreries are planetariums. The term orrery has only existed since 1714. A grand orrery is one that includes the outer planets known at the time of its construction. The word planetarium has shifted meaning, and now usually refers to hemispherical theatres in which images of the night sky are projected onto an overhead surface. Orreries can range widely in size from hand-held to room-sized. An orrery is used to demonstrate the motion of the planets, while a mechanical device used to predict eclipses and transits is called an astrarium.

An orrery should properly include the Sun, the Earth and the Moon (plus optionally other planets). A model that only includes the Earth, the Moon, and the Sun is called a tellurion or tellurium, and one which only includes the Earth and the Moon is a lunarium. A jovilabe is a model of Jupiter and its moons.[22]

Planet Average distance from Sun (AU) Diameter (in Earth diameters) Mass (in Earth masses) Density (g/cm3) No. of moons Orbital period (years) Inclination to ecliptic (degrees) Axial tilt (degrees) Rotational period
(sidereal)
Mercury 0.39 0.38 0.05 5.5 0 0.24 7.0° 0° 59 days
Venus 0.72 0.95 0.82 5.3 0 0.62 3.4° 177° -243 days
Earth 1.00 1.00 1.00 5.5 1 1.00 0° 23° 23.9 hours
Mars 1.52 0.53 0.11 3.9 2 1.88 1.9° 25° 24.5 hours
Jupiter 5.20 11.21 317.9 1.3 95 11.9 1.3° 3° 10 hours
Saturn 9.54 9.45 95.2 0.7 146 29.5 2.5° 27° 11 hours
Uranus 19.2 4.01 14.5 1.3 28 84 0.8° 98° -17 hours
Neptune 30.1 3.88 17.1 1.6 16 165 1.8° 28° 16 hours

A planetarium will show the orbital period of each planet and the rotation rate, as shown in the table above. A tellurion will show the Earth with the Moon revolving around the Sun. It will use the angle of inclination of the equator from the table above to show how it rotates around its own axis. It will show the Earth's Moon, rotating around the Earth.[23] A lunarium is designed to show the complex motions of the Moon as it revolves around the Earth.

Orreries are usually not built to scale. Human orreries, where humans move about as the planets, have also been constructed, but most are temporary. There is a permanent human orrery at Armagh Observatory in Northern Ireland, which has the six ancient planets, Ceres, and comets Halley and Encke. Uranus and beyond are also shown, but in a fairly limited way.[24] Another is at Sky's the Limit Observatory and Nature Center in Twentynine Palms, California; it is a true to scale (20 billion to one), true to position (accurate to within four days) human orrery. The first four planets are relatively close to one another, but the next four require a certain amount of hiking in order to visit them.[25] A census of all permanent human orreries has been initiated by the French group F-HOU with a new effort to study their impact for education in schools.[26] A map of known human orreries is available.[27]

A normal mechanical clock could be used to produce an extremely simple orrery to demonstrate the principle, with the Sun in the centre, Earth on the minute hand and Jupiter on the hour hand; Earth would make 12 revolutions around the Sun for every 1 revolution of Jupiter. As Jupiter's actual year is 11.86 Earth years long, the model would lose accuracy rapidly.

Projection

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Many planetariums have a projection orrery, which projects onto the dome of the planetarium a Sun with either dots or small images of the planets. These usually are limited to the planets from Mercury to Saturn, although some include Uranus. The light sources for the planets are projected onto mirrors which are geared to a motor which drives the images on the dome. Typically the Earth will circle the Sun in one minute, while the other planets will complete an orbit in time periods proportional to their actual motion. Thus Venus, which takes 224.7 days to orbit the Sun, will take 37 seconds to complete an orbit on an orrery, and Jupiter will take 11 minutes, 52 seconds.

Some planetariums have taken advantage of this to use orreries to simulate planets and their moons. Thus Mercury orbits the Sun in 0.24 of an Earth year, while Phobos and Deimos orbit Mars in a similar 4:1 time ratio. Planetarium operators wishing to show this have placed a red cap on the Sun (to make it resemble Mars) and turned off all the planets but Mercury and Earth. Similar approximations can be used to show Pluto and its five moons.

Notable examples

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An orrery made by Robert Brettell Bate, c. 1812. Now in Thinktank, Birmingham Science Museum.

Shoemaker John Fulton of Fenwick, Ayrshire, built three between 1823 and 1833. The last is in Glasgow's Kelvingrove Art Gallery and Museum.

The Eisinga Planetarium built by a wool carder named Eise Eisinga in his own living room, in the small city of Franeker in Friesland, is in fact an orrery. It was constructed between 1774 and 1781. The base of the model faces down from the ceiling of the room, with most of the mechanical works in the space above the ceiling. It is driven by a pendulum clock, which has 9 weights or ponds. The planets move around the model in real time.[28]

An innovative concept is to have people play the role of the moving planets and other Solar System objects. Such a model, called a human orrery, has been laid out at the Armagh Observatory.[24]

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  • The construction system Meccano is a popular tool for constructing highly accurate orreries. Model 391, the first Meccano Orrery, was described in the June 1918 Meccano Manual.[29][30]
  • In Dune Messiah, the 1969 sequel to Dune, there is a description of a desktop orrery representing the two moons of the fictional planet Arrakis and its sun.
  • In the backstory of the 1982 film The Dark Crystal, the UrSkek TekTih made a giant automatic orrery, with the help of his fellow UrSkek ShodYod, for Aughra, in the mountaintop observatory where she lives.
  • In the 1999 version of Tarzan, the title character studies an orrery with planets on it.
  • In the 2000 science fiction film Pitch Black, an orrery was used to demonstrate a pending eclipse of the planet.
  • In the 2020 historical novel A Room Made of Leaves by Kate Grenville, a makeshift orrery is made from scraps found in the early colony of New South Wales by its first astronomer, William Dawes.

See also

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References

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  1. ^ "Orrery made by John Rowley for the Earl of Orrery | Science Museum Group Collection".
  2. ^ "Oxford English Dictionary". oed.com. Retrieved 11 July 2024.
  3. ^ King, Henry C.; Millburn, John R. (1978). Geared to the Stars: The Evolution of Planetariums, Orreries, and Astronomical Clocks. Toronto: University of Toronto Press. p. 382. ISBN 9780802023124. Retrieved 1 November 2024. [...] inscription on a brass plaque attached to Rowley's orrery, which reads: 'Orrery invented by Graham 1700. Improved by Rowley and presented by him to John Earl of Orrery, after whom it was named at the suggestion of Richard Steele.'
  4. ^ Compare: Buick, Tony (26 October 2013). Orrery: A Story of Mechanical Solar Systems, Clocks, and English Nobility. Astronomers' Universe. New York: Springer Science & Business Media. pp. 87–88. ISBN 9781461470434. Retrieved 1 November 2024. While the model was with Rowley, he was commissioned by the Earl of Orrery to make a copy for him, and Rowley then named the model an orrery after his patron. [...] It had been suggested that Sir Richard Steele (Irish essayist, 1672-1729) came across Rowley's model in a presentation delivered by Rowley and, knowing nothing of the Graham model, named it an orrery in honor of the Earl of Orrery to popularize it. [...] the lecturer and writer Desaguliers (1683-1744) [...] attribute[d] the actual naming of the orrery to Steele when it was, quite possibly, Rowley [...].
  5. ^ de Solla, Price, Derek (1974). "Gears from the Greeks. The Antikythera Mechanism: A Calendar Computer from ca. 80 BC". Transactions of the American Philosophical Society. 64 (7): 1–70 (page 19). doi:10.2307/1006146. JSTOR 1006146. S2CID 222364275.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  6. ^ Carman, Christián C.; Evans, James (15 November 2014). "On the epoch of the Antikythera mechanism and its eclipse predictor". Archive for History of Exact Sciences. 68 (6): 693–774. doi:10.1007/s00407-014-0145-5. hdl:11336/98820. S2CID 120548493.
  7. ^ Markoff, John (24 November 2014). "On the Trail of an Ancient Mystery – Solving the Riddles of an Early Astronomical Calculator". The New York Times. Retrieved 25 November 2014.
  8. ^ a b Calvert, H. R. (1967). Astronomy: Globes Orreries and other Models. London: H.M.S.O. ASIN B001A9C9SQ.
  9. ^ Cicero, Marcus. de Re Publica I (in Latin). dicebat enim Gallus sphaerae illius alterius solidae atque plenae vetus esse inventum, et eam a Thalete Milesio primum esse tornatam, post autem ab Eudoxo Cnidio, discipulo ut ferebat Platonis, eandem illam astris quae caelo inhaererent esse descriptam;
  10. ^ Cicero, Marcus. De Natura Deorum [Treatises On The Nature Of The Gods]. Translated by Yonge, Charles. p. 253. But if that sphere which was lately made by our friend Posidonius, the regular revolutions of which show the course of the sun, moon, and five wandering stars, as it is every day and night performed, were carried into Scythia or Britain, who, in those barbarous countries, would doubt that that sphere had been made so perfect by the exertion of reason?
  11. ^ King, Henry C.; Millburn, John R. (1978). Geared to the stars : the evolution of planetariums, orreries, and astronomical clocks. Toronto: University of Toronto Press. pp. 28–41. ISBN 0-8020-2312-6.
  12. ^ Lloyd, H. Alan (1958). Some Outstanding Clocks Over Seven Hundred Years. London: Leonard Hill Books Limited. pp. 9–24.
  13. ^ a b Brewster, David (1830). "Planetary Machines". The Edinburgh Encyclopedia. Vol. 16. Edinburgh: William Blackwood et al. p. 624.
  14. ^ Lloyd (1958), pp. 46–57.
  15. ^ Poulle, Emmanuel; Sändig, Helmut; Schardin, Joachim; Hasselmeyer, Lothar (2008). Die Planetenlaufuhr : ein Meisterwerk der Astronomie und Technik der Renaissance geschaffen von Eberhard Baldewein 1563 - 1568 (1ª ed.). Stuttgart: Dt. Gesellschaft für Chronometrie. ISBN 978-3-89870-548-6.
  16. ^ Ronan, Colin (1992) [First published 1981]. The Practical Astronomer. London: Bloomsbury Books. pp. 108–112. ISBN 1-85471-047-8.
  17. ^ "Orrery, by Thomas Tompion and George Graham, London, c. 1710". Retrieved 29 June 2021.
  18. ^ "orrery". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  19. ^ Ley, Willy (February 1965). "Forerunners of the Planetarium". For Your Information. Galaxy Science Fiction. pp. 87–98.
  20. ^ "Revolutionary Players". Search.revolutionaryplayers.org.uk. Archived from the original on 2011-07-24. Retrieved 2010-02-09.
  21. ^ "Welcome - Planetarium Friesland". www.planetarium-friesland.nl.
  22. ^ Pentz, M.J. (1971). The Earth, Its Shape, Internal Structure and Composition. Vol. OU_S100_22. Bletchley: Open University Press. ISBN 978-0-335-02034-8.
  23. ^ "Adler Planetarium:Research Collections". 1300 South Lake Shore Drive • Chicago IL 60605: Adler Planetarium. 2010. Archived from the original on 27 January 2012. Retrieved 22 June 2011.{{cite web}}: CS1 maint: location (link)
  24. ^ a b "Human Orrery". Armagh Observatory and Planetarium. Archived from the original on 2023-04-02.
  25. ^ "Orrery". Sky's The Limit Observatory & Nature Center.
  26. ^ "The Human Orrery". planetaire.over-blog.com.
  27. ^ "Emmanuel Rollinde's "Planetaires Humains - Human Orreries" List". Emmanuel Rollinde's "Planetaires Humains - Human Orreries" List.
  28. ^ Sixma, H (November 1934). "The Franeker Planetarium". Popular Astronomy. XLII (9). SAO/NASA ADS: 489–495. Bibcode:1934PA.....42..489S. Retrieved 2011-06-22.
  29. ^ "Analysis of Meccano Manuals - Manual Models Listings". www.meccanoindex.co.uk.
  30. ^ Whiting, Michael (2007). "Orrery Developments:The Use of Meccano in Constructing Planetaria" (PDF). Bulletin of the Scientific Instrument Society (94): 26–30. CiteSeerX 10.1.1.694.9199. Archived from the original (PDF) on 21 December 2014. Retrieved 2017-05-03.

Further reading

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  • Buick, Tony (2020). Orreries, Clocks, and London Society: The Evolution of Astronomical Instruments and Their Makers, 2nd Ed. Cham, Switzerland: Springer. ISBN 978-3-030-61776-9.
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