View source for Orrery

{{short description|Mechanical model of the Solar System}}
{{About|the mechanical device|the Irish peerage|Earl of Orrery|the Irish kingdom and barony|Orrery and Kilmore}}[[File:orrery small.jpg|thumb|upright=1.2|A small orrery showing Earth and the inner planets]]
An '''orrery''' ({{IPAc-en|'|ɒr|.|ə|.|r|i|audio=LL-Q1860 (eng)-Vealhurl-orrery.wav}}) is a mechanical [[Solar System model|model of the Solar System]] that illustrates or predicts the relative positions and motions of the [[planet]]s and [[natural satellite|moon]]s, 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. [[Ancient Greek astronomy|The Greeks]] had working [[planetarium|planetaria]], but the first modern example was produced {{circa | 1712}} by John Rowley.<ref>{{cite web | url =https://collection.sciencemuseumgroup.org.uk/objects/co56970/orrery-made-by-john-rowley-for-the-earl-of-orrery-demonstration-models-orreries-planetaria-models | title =Orrery made by John Rowley for the Earl of Orrery &#124; Science Museum Group Collection }}</ref>  He named it "orrery"<ref>{{cite web |title =Oxford English Dictionary |url =https://www.oed.com/dictionary/orrery_n |website =oed.com |access-date =11 July 2024}}</ref> 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}}{{efn|[[John Boyle, 5th Earl of Cork|John Boyle]] was Charles Boyle's son, and succeeded him as [[Earl of Orrery]].}} Earl of Orrery, after whom it was named at the suggestion of [[Richard Steele]]."<ref>
{{cite book
 |last1                = King
 |first1               = Henry C.
 |author-link1         = Henry C. King
 |last2                = Millburn
 |first2               = John R.
 |year                 = 1978
 |title                = Geared to the Stars: The Evolution of Planetariums, Orreries, and Astronomical Clocks
 |url                  = https://books.google.com/books?id=0gJAAQAAIAAJ
 |publication-place    = Toronto
 |publisher            = University of Toronto Press
 |page                 = 382
 |isbn                 = 9780802023124
 |access-date          = 1 November 2024
 |quote                = [...] 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.'
}}

Alternative url https://archive.org/details/gearedtostarsevo00king
</ref><ref>
Compare:
{{cite book
 |last1                = Buick
 |first1               = Tony
 |date                 = 26 October 2013
 |title                = Orrery: A Story of Mechanical Solar Systems, Clocks, and English Nobility
 |url                  = https://books.google.com/books?id=lU24AQAAQBAJ
 |series               = Astronomers' Universe
 |publication-place    = New York
 |publisher            = Springer Science & Business Media
 |pages                = 87–88
 |isbn                 = 9781461470434
 |access-date          = 1 November 2024
 |quote                = 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 [...].
}} 
</ref>

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==
===Ancient===
[[File:Antikythera Fragment A (Front).webp|thumb|[[Antikythera mechanism]], main fragment, {{circa}} 205 to 87&nbsp;BC]]
[[File:Carlo G Croce Astrarium.jpg|thumb|upright|Carlo G Croce, reconstruction of [[Astrarium of Giovanni Dondi dell'Orologio|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 motion]]s of the [[Sun]], [[Moon]], and the five [[planet]]s known to the [[Ancient Greece|ancient Greeks]]. It has been dated between 205 to 87&nbsp;BC.<ref>{{cite journal | last= de Solla| first=Price, Derek |author-link=Derek J. de Solla Price| title=Gears from the Greeks. The Antikythera Mechanism: A Calendar Computer from ca. 80 BC| journal= Transactions of the American Philosophical Society| volume=64 | issue=7 | pages=1–70 (page 19)| year=1974| doi=10.2307/1006146 | jstor=1006146| s2cid=222364275}}</ref><ref name="Carman Evans">{{cite journal|last1=Carman|first1=Christián C.|last2=Evans|first2=James|title=On the epoch of the Antikythera mechanism and its eclipse predictor|journal=Archive for History of Exact Sciences|date=15 November 2014|volume=68|issue=6|pages=693–774|doi=10.1007/s00407-014-0145-5|s2cid=120548493|hdl=11336/98820|hdl-access=free}}</ref><ref name="NYT-20141124-JM">{{cite news |last=Markoff |first=John |title=On the Trail of an Ancient Mystery – Solving the Riddles of an Early Astronomical Calculator |url=https://www.nytimes.com/2014/11/25/science/solving-the-riddles-of-an-early-astronomical-calculator.html |date=24 November 2014 |work=[[The New York Times]] | access-date=25 November 2014 }}</ref> The mechanism is considered one of the first orreries.<ref name="HMSO">{{cite book|last=Calvert|first=H. R.|title=Astronomy: Globes Orreries and other Models |publisher=H.M.S.O|location=London|date=1967|asin=B001A9C9SQ}}</ref> 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]]<ref>{{Cite book |last=Cicero |first=Marcus |url=http://www.thelatinlibrary.com/cicero/repub1.shtml |title=de Re Publica I |language=la |quote=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;}}</ref> and [[Posidonius]]<ref>{{Cite book |last=Cicero |first=Marcus |url=https://www.gutenberg.org/ebooks/14988 |title=De Natura Deorum |pages=253 |language= |translator-last=Yonge |translator-first=Charles |trans-title=Treatises On The Nature Of The Gods |quote=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?}}</ref> both constructed a device modeling celestial motion.

===Early Modern===
[[File:Astronomical clock (Venus-Mercury side), Eberhard Baldewein et al, Marburg-Kassel, 1563-1568 - Mathematisch-Physikalischer Salon, Dresden - DSC08057.jpg|thumb|upright|Astronomical clock (Venus-Mercury side) by Eberhard Baldewein, 1563&ndash;1568. Exhibit in the [[Mathematisch-Physikalischer Salon]] of [[Dresden, Germany]].]]
In 1348, [[Giovanni Dondi dell'Orologio|Giovanni Dondi]] built the first known clock driven mechanism of the system. It displays the [[Ecliptic coordinate system|ecliptic position]] of the Moon, Sun, [[Mercury (planet)|Mercury]], [[Venus]], [[Mars]], [[Jupiter]] and [[Saturn]] according to the complicated [[Geocentrism|geocentric]] Ptolemaic planetary theories.<ref>{{cite book|last1=King|first1=Henry C.|last2=Millburn|first2=John R.|title=Geared to the stars : the evolution of planetariums, orreries, and astronomical clocks|date=1978|publisher=[[University of Toronto Press]]|location=Toronto|isbn=0-8020-2312-6|pages=[https://archive.org/details/gearedtostarsevo00king/page/28 28–41]|url-access=registration|url=https://archive.org/details/gearedtostarsevo00king/page/28}}</ref><ref name=Lloyd>{{cite book|last1=Lloyd|first1=H. Alan|title=Some Outstanding Clocks Over Seven Hundred Years|date=1958|publisher=Leonard Hill Books Limited|location=London|pages=9–24}}</ref> The clock itself is lost, but Dondi left a complete description of its astronomic [[gear train]]s.

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 [[Natural satellite|moon]]s.<ref name="EE">{{cite book|last=Brewster|first=David|title=The Edinburgh Encyclopedia |publisher=William Blackwood et al.|location=Edinburgh|date=1830|volume=16|pages=624|chapter=Planetary Machines|chapter-url=https://books.google.com/books?id=q2tTt_NNr2YC&pg=PA646}}</ref>

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]].<ref name=Lloyd2>Lloyd (1958), pp. 46–57.</ref><ref>{{cite book|last1=Poulle|first1=Emmanuel|author1-link=Emmanuel Poulle|last2=Sändig|first2=Helmut|last3=Schardin|first3=Joachim|last4=Hasselmeyer|first4=Lothar|title=Die Planetenlaufuhr : ein Meisterwerk der Astronomie und Technik der Renaissance geschaffen von Eberhard Baldewein 1563 - 1568|date=2008|publisher=Dt. Gesellschaft für Chronometrie|location=Stuttgart|isbn=978-3-89870-548-6|edition=1ª|ref=Poulle}}</ref> 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 [[epicycle|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 [[ellipse]]s. In 1687 [[Isaac Newton]] explained the cause of elliptic motion in his [[Newton's law of universal gravitation|theory of gravitation]].<ref name="Ronan">{{cite book|last=Ronan|first=Colin |title=The Practical Astronomer|publisher=Bloomsbury Books|location=London|orig-year=First published 1981|date=1992|pages=108–112|isbn=1-85471-047-8}}</ref>

===Modern===
[[File:Frederiksborg slot - Museum 20090818 28.JPG|thumb|The Orrery inside the Sphaera Copernicana, designed by Joseph of Gottorp and built by Andreas Bösch, 1653]]
[[File:Wright of Derby, The Orrery.jpg|thumb|''[[A Philosopher Lecturing on the Orrery]]'' ({{circa|1766}}) by [[Joseph Wright of Derby]]]]
[[File:Two Orreries (Derby Museum & Art Gallery).webm|thumb|Modern working reconstruction of a grand orrery at [[Derby Museum and Art Gallery]] (England)]]
[[File:Planetarium Eise Eisinga in Franeker.jpg|thumb|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 (clockmaker)|George Graham]] and [[Thomas Tompion]] dated {{circa|1710}} in the [[History of Science Museum, Oxford]].<ref>{{cite web|url=http://www.mhs.ox.ac.uk/object/inv/97810|title=Orrery, by Thomas Tompion and George Graham, London, c. 1710|access-date=29 June 2021}}</ref> 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.<ref>{{OED|orrery}}</ref><ref name="ley196502">{{Cite magazine
 |last=Ley
 |first=Willy
 |date=February 1965
 |title=Forerunners of the Planetarium
 |department=For Your Information
 |url=https://archive.org/details/Galaxy_v23n03_1965-02/page/n87/mode/2up
 |magazine=Galaxy Science Fiction
 |pages=87–98
}}</ref> 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.<ref name="EE"/>

[[Joseph Wright of Derby|Joseph Wright]]'s painting ''[[A Philosopher Lecturing on the Orrery|A Philosopher giving a Lecture on the Orrery]]'' ({{circa|1766}}), which hangs in the [[Derby Museum and Art Gallery]], depicts a group listening to a lecture by a [[natural philosophy|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 [[eclipse]]s.<ref>{{cite web |url=http://www.search.revolutionaryplayers.org.uk/engine/resource/exhibition/standard/child.asp?txtKeywords=&lstContext=&lstResourceType=&lstExhibitionType=&chkPurchaseVisible=&txtDateFrom=&txtDateTo=&x1=&y1=&x2=&y2=&scale=&theme=&album=&resource=5230&viewpage=%2Fengine%2Fresource%2Fexhibition%2Fstandard%2Fdefault%2Easp&originator=&page=&records=&direction=&pointer=&text=&exhibition=1652&offset=0 |title=Revolutionary Players |publisher=Search.revolutionaryplayers.org.uk |access-date=2010-02-09 |url-status=dead |archive-url=https://web.archive.org/web/20110724091137/http://www.search.revolutionaryplayers.org.uk/engine/resource/exhibition/standard/child.asp?txtKeywords=&lstContext=&lstResourceType=&lstExhibitionType=&chkPurchaseVisible=&txtDateFrom=&txtDateTo=&x1=&y1=&x2=&y2=&scale=&theme=&album=&resource=5230&viewpage=%2Fengine%2Fresource%2Fexhibition%2Fstandard%2Fdefault.asp&originator=&page=&records=&direction=&pointer=&text=&exhibition=1652&offset=0 |archive-date=2011-07-24 }}</ref>

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:

<math>\frac{4+0}{10},\frac{4+3}{10},\frac{4+6}{10},\frac{4+12}{10},\frac{4+24}{10},...</math>

That is, 0.4, 0.7, 1.0, 1.6, 2.8,&nbsp;... The numbers refer to [[astronomical unit]]s, the mean distance between Sun and Earth, which is 1.496 × 10<sup>8</sup> km (93 × 10<sup>6</sup> 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.<ref>{{cite web|url=http://www.planetarium-friesland.nl/en|title=Welcome - Planetarium Friesland|website=www.planetarium-friesland.nl}}</ref> 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.
[[File:Planetarium in Putnam Gallery 2, 2009-11-24.jpg|thumb|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.<ref name="HMSO"/>
<!-- [[File:Planetaire Vatican.jpg|thumb|upright|Orrery ([[Vatican Museums]]).]]
[[File:Wilhelm Schickard.jpg|thumb|upright|Portrait of [[Wilhelm Schickard]] (1592–1635) holding a "hand planetarium" (orrery) of his own invention]]  -->

== Workings ==
All orreries are ''[[planetarium]]s''. The term ''orrery'' has only existed since 1714. A ''grand orrery'' is one that includes the [[outer planet]]s 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 [[Astronomical transit|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.<ref name="OU_S100_22">{{cite book|last=Pentz|first=M.J.|title=The Earth, Its Shape, Internal Structure and Composition|publisher=[[Open University Press]]|location=Bletchley|date=1971|volume=OU_S100_22|isbn=978-0-335-02034-8}}</ref>
{{table alignment}}
{| class="wikitable plainrowheaders" style=text-align:right;
|+Key statistics of planets
|-
! scope="col" | Planet
! scope="col" style="max-width: 6em;" | Average distance from Sun<br>({{abbrlink|AU|Astronomical unit}})
! scope="col" style="max-width: 6em;" | Diameter<br>(in Earth diameters)
! scope="col" style="max-width: 6em;" | Mass<br>(in [[Earth mass]]es)
! scope="col" | Density<br>(g/cm<sup>3</sup>)
! scope="col" style="max-width: 5em;" | No. of known moons
! scope="col" | Orbital period<br>(Earth years)
! scope="col" style="max-width: 7em;" | Inclination to ecliptic<br>(degrees)
! scope="col" | Axial tilt<br>(degrees)
! scope="col" style="max-width: 6em;" | Rotational period<br />[[Sidereal orbital period|(sidereal)]]
|-
! scope="row" | [[Mercury (planet)|Mercury]]
|0.39||0.38||0.05||5.5||0||0.24||7.0°||0°||59 days
|-
! scope="row" | [[Venus]]
|0.72||0.95||0.82||5.3||0||0.62||3.4°||177°||–243 days{{efn-lg|name=retrograde}}
|-
! scope="row" | [[Earth]]
|1.00||1.00||1.00||5.5||1||1.00||0°||23°||23.9 hours
|-
! scope="row" | [[Mars]]
|1.52||0.53||0.11||3.9||2||1.88||1.9°||25°||24.5 hours
|-
! scope="row" | [[Jupiter]]
|5.20||11.21||317.9||1.3||97||11.9||1.3°||3°||10 hours
|-
! scope="row" | [[Saturn]]
|9.54||9.45||95.2||0.7||274||29.5||2.5°||27°||11 hours
|-
! scope="row" | [[Uranus]]
|19.2||4.01||14.5||1.3||29||84||0.8°||98°||−17 hours{{efn-lg|name=retrograde}}
|-
! scope="row" | [[Neptune]]
|30.1||3.88||17.1||1.6||16||165||1.8°||28°||16 hours
|}
{{notelist-lg|refs=
{{efn-lg|name=retrograde|A negative figure indicates retrograde rotation.}}
}}

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 [[Barycenter|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.<ref name="Adler">{{cite web|url=http://64.107.216.64/research/collections/instruments/orreries.shtml|title=Adler Planetarium:Research Collections|date=2010|publisher=Adler Planetarium.|access-date=22 June 2011|location=1300 South Lake Shore Drive • Chicago IL 60605|url-status=dead|archive-url=https://web.archive.org/web/20120127045601/http://64.107.216.64/research/collections/instruments/orreries.shtml|archive-date=27 January 2012}}</ref> A lunarium is designed to show the [[Orbit of the Moon|complex motions of the Moon]] as it revolves around the Earth.

Orreries are usually not built to [[scale model|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 (dwarf planet)|Ceres]], and comets [[Halley's Comet|Halley]] and [[Comet Encke|Encke]]. Uranus and beyond are also shown, but in a fairly limited way.<ref name="Armagh Observatory">{{cite web |title=Human Orrery |url=https://www.armagh.space/planetarium/attractions/human-orrery |url-status=live |archive-url=https://web.archive.org/web/20230402022124/https://www.armagh.space/planetarium/attractions/human-orrery |archive-date=2023-04-02 |website=[[Armagh Observatory and Planetarium]]}}</ref> 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.<ref>{{Cite web|url=https://www.skysthelimit29.org/orrery.html|title=Orrery|website=Sky's The Limit Observatory & Nature Center}}</ref> 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.<ref name="Site des planétaires humains">{{Cite web|url=http://planetaire.over-blog.com/en|title=The Human Orrery|website=planetaire.over-blog.com}}</ref> A map of known human orreries is available.<ref name="Carte des planétaires humains">{{Cite web|url=https://www.google.com/maps/@2.5507389,-77.2359853,3z/data=!3m1!4b1!4m3!11m2!2sk4G9ui5ZqmKbfaYxNOVoKuqmMKqjow!3e3|title=Emmanuel Rollinde's "Planetaires Humains - Human Orreries" List|website=Emmanuel Rollinde's "Planetaires Humains - Human Orreries" List}}</ref>

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===
Many [[planetarium]]s have a [[Planetarium projector|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 (moon)|Phobos]] and [[Deimos (moon)|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==
[[File:Thinktank Birmingham - object 1956S00682.00001(1).jpg|thumb|An orrery made by [[Robert Brettell Bate]], c. 1812. Now in [[Thinktank, Birmingham Science Museum]].]]

Shoemaker [[John Fulton (instrument maker)|John Fulton]] of [[Fenwick, East Ayrshire|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 [[Carding|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.<ref name="Sixma">{{cite journal|last=Sixma|first=H|date=November 1934|title=The Franeker Planetarium|journal=Popular Astronomy|publisher=SAO/NASA ADS|volume=XLII|issue=9|pages=489–495|url=http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1934PA.....42..489S&db_key=AST&page_ind=0&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES|access-date=2011-06-22|bibcode=1934PA.....42..489S}}</ref>

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.<ref name="Armagh Observatory"/>

In 2024, the LEGO Group commercially produced an orrery of the Sun, Earth, and Moon. The model is assembled exclusively from LEGO elements and reproduces solar and lunar orbits, as well Earth's rotation about a tilted axis.<ref>{{Cite web |title=Planet Earth and Moon in Orbit 42179 |url=https://www.lego.com/en-us/product/planet-earth-and-moon-in-orbit-42179?gclid=Cj0KCQjwkN--BhDkARIsAD_mnIq1xZ5X49Q46KjbhKb5HQH43ubXZRHTVqy-FjkgKG_HdKiSseOpx58aAm9WEALw_wcB&ef_id=Cj0KCQjwkN--BhDkARIsAD_mnIq1xZ5X49Q46KjbhKb5HQH43ubXZRHTVqy-FjkgKG_HdKiSseOpx58aAm9WEALw_wcB:G:s&s_kwcid=AL!790!3!!!!x!!!19932189580!&cmp=KAC-INI-GOOGUS-GO-US_GL-EN-RE-SP-BUY-CREATE-MB_ALWAYS_ON-SHOP-BP-PMAX-ALL-CIDNA00000-PMAX-LOW_PRIORITY&gad_source=1 |access-date=2025-03-17 |website=www.lego.com |language=en}}</ref>

==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.<ref>{{Cite web|url=https://www.meccanoindex.co.uk/Mmanuals/Mmodels.php?page=2&Smotor=&Tsearch=&Soutfit=&Sdate=&M_era=16&Srow=37&Edate=&id=1493837531|title=Analysis of Meccano Manuals - Manual Models Listings|website=www.meccanoindex.co.uk}}</ref><ref name="Meccano">{{Cite journal |last=Whiting |first=Michael |date=2007 |title=Orrery Developments:The Use of Meccano in Constructing Planetaria |url=http://www.sis.org.uk/bulletin/94/meccano.pdf |journal=Bulletin of the Scientific Instrument Society |issue=94 |pages=26–30 |citeseerx=10.1.1.694.9199 |archive-url=https://web.archive.org/web/20141221065757/http://www.sis.org.uk/bulletin/94/meccano.pdf |archive-date=21 December 2014 |access-date=2017-05-03}}</ref>

==See also==
{{div col|colwidth=22em}}
* [[Apparent retrograde motion]]
* [[Armillary sphere]]
* [[Astrarium]]
* [[Astrolabe]]
* [[Astronomical clock]]
* [[Celestial globe]]
* [[Clockwork universe]]
* [[Eidouranion]]
* [[Ephemeris]]
* [[Equatorium]]
* [[Eratosthenes]]
* [[John Fulton (instrument maker)]]
* [[List of astronomical instruments]]
* [[Orbit of the Moon]]
* [[Stability of the Solar System]]
* [[Tellurion]]
* [[Torquetum]]
{{div col end}}

==Notes==
{{notelist}}

==References==
{{Reflist}}

==Further reading==
*{{cite book 
|last1=Buick|first1=Tony
|title=Orreries, Clocks, and London Society: The Evolution of Astronomical Instruments and Their Makers, 2nd Ed.
|date=2020 
|publisher=Springer 
|location=Cham, Switzerland
|isbn=978-3-030-61776-9}}

==External links==
{{wiktionary | orrery}}

{{Commons category|Orreries}}
* [http://space.jpl.nasa.gov/ JPL Solar System Simulator]
* [http://www.longnow.org/projects/clock/orrery/ Long Now Foundation Orrery]
* [https://web.archive.org/web/20100406030718/http://www.library.upenn.edu/exhibits/pennhistory/orrery/orrery.html University of Pennsylvania Orrery]

{{Solar System models}}
{{Portal bar|Astronomy|Stars|Outer space|Solar System|Science}}

[[Category:Historical scientific instruments]]
[[Category:Astronomical instruments]]
[[Category:Solar System models]]
[[Category:Scale modeling]]
[[Category:1704 in science]]
[[Category:Science education materials]]