Orrery
An orrery is a mechanical
History
Ancient versions
The
Early versions
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.[7][8] 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.[9]
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.[10][11] The clocks are now on display in Kassel at the Astronomisch-Physikalisches Kabinett and in Dresden at the Mathematisch-Physikalischer Salon.
In
Modern orreries
There is an orrery built by clock makers George Graham and Thomas Tompion dated c. 1710 in the History of Science Museum, Oxford.[13] 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.[14][15] 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.[9]
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.[16]
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
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.[4]
Explanation
All orreries are planetariums (alternative plural planetaria). The term orrery has only existed since 1714. A grand orrery is one that includes the
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
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
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.[20] 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.[21] 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.[22] A map of known human orreries is available.[23]
A normal mechanical clock could be used to produce an extremely simple orrery 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. Jupiter's actual year is 11.86 Earth years long, so this particular example would lose accuracy rapidly. A real orrery would be more accurate and include more planets, and would perhaps make the planets rotate as well.
Projection orreries
Many planetariums (buildings) 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
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.[24]
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.[20]
In popular culture
- 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.[25][26]
- 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 made from scraps found in the early colony of New South Wales by the first astronomer of the colony, William Dawes, serves as the metaphor for the desire of human love in general, and the evolving fictional relationship of Elizabeth Macarthur to Dawes in particular.
See also
References
- S2CID 222364275.)
{{cite journal}}
: CS1 maint: multiple names: authors list (link - S2CID 120548493.
- ^ 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.
- ^ ASIN B001A9C9SQ.
- ^ 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;
- ^ 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?
- ISBN 0-8020-2312-6.
- ^ Lloyd, H. Alan (1958). Some Outstanding Clocks Over Seven Hundred Years. London: Leonard Hill Books Limited. pp. 9–24.
- ^ a b Brewster, David (1830). "Planetary Machines". The Edinburgh Encyclopedia. Vol. 16. Edinburgh: William Blackwood et al. p. 624.
- ^ Lloyd (1958), pp. 46–57.
- ISBN 978-3-89870-548-6.
- ISBN 1-85471-047-8.
- ^ "Orrery, by Thomas Tompion and George Graham, London, c. 1710". Retrieved 29 June 2021.
- ^ "orrery". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ Ley, Willy (February 1965). "Forerunners of the Planetarium". For Your Information. Galaxy Science Fiction. pp. 87–98.
- ^ "Revolutionary Players". Search.revolutionaryplayers.org.uk. Archived from the original on 2011-07-24. Retrieved 2010-02-09.
- ^ "Welcome - Planetarium Friesland". www.planetarium-friesland.nl.
- ISBN 978-0-335-02034-8.
- ^ "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) - ^ Armagh Observatory and Planetarium. Archivedfrom the original on 2023-04-02.
- ^ "Orrery". Sky's The Limit Observatory & Nature Center.
- ^ "The Human Orrery". planetaire.over-blog.com.
- ^ "Emmanuel Rollinde's "Planetaires Humains - Human Orreries" List". Emmanuel Rollinde's "Planetaires Humains - Human Orreries" List.
- Bibcode:1934PA.....42..489S. Retrieved 2011-06-22.
- ^ "Analysis of Meccano Manuals - Manual Models Listings". www.meccanoindex.co.uk.
- CiteSeerX 10.1.1.694.9199. Archived from the original(PDF) on 21 December 2014. Retrieved 2017-05-03.