An Iconic Image Not so Newtonian After All
Image 1: Engraved print of A philosopher giving a lecture on the orrery, after the painting by Joseph Wright of Derby. Image © the Whipple Museum (Wh.1602).
A number of images created by Joseph Wright (1734-1797) of Derby are very familiar to us, and are often seen as presenting an archetypical vision of “popular” science in 18th-century England. Wright is well known for his “candlelight” paintings – incorporating the chiaroscuro effect utilizing strongly contrasting light and darkness – and his work is taken to represent the power of Enlightenment science (image 1). In particular, his representation of A Philosopher giving that lecture on the Orrery, in which a lamp is put in place of the Sun has been characterized by a number of art historians as “Newtonian.” (The painting was exhibited at the Society of Artists in 1766, and is currently in the collection of the Derby Museum and Art Gallery, Derby, England.) The centerpiece of the image is the orrery, a form of planetary model; the painting (and associated prints) are the means whereby many people first see an orrery. However, in its own period, the orrery was not conceived of as a specifically Newtonian object; in fact, it was associated most strongly with Copernicus, and his Sun-centered cosmology. The effect of the illuminating lamp, demonstrating the power of the Sun on the people gathered around the orrery depicted in Wright’s image, emphasizes the continuing importance of the Copernican conception, even in the age of Newton.
Planetary Models in the 18th Century
During the 18th century, instrument makers, lecturers, and demonstrators made, sold, and used a variety of devices that were designed to teach natural philosophy and astronomy. Indeed, there was a proliferation of planetary models marketed by instrument makers with commercial interests, anxious to promote products for the growing consumer market. Particularly in London, instrument makers developed a variety of models, in a range of prices.
Lecturers, including John Theophilus Desaguliers (1683-1744), used planetary models as part of their demonstrations; these models often served as the centerpiece for public lectures on astronomy. Instrument makers and lecturers, including Benjamin Martin (ca. 1705-1782), published books describing the use of planetary models. Some instrument makers offered smaller versions for home use, including portable models that could be carried by itinerant lecturers. The availability of relatively inexpensive versions is indicative of the interest of the public in such instruments.
Planetaria enjoyed popularity, from the seventeenth century onward, as devices to demonstrate Sun-centered cosmology. Many models only show the Earth, Sun, and Moon, indicating that the phenomena associated with these bodies – day and night, the seasons, eclipses, and lunar phases – were considered of particular import. In general, those models that included the planets were intended to provide only approximate representations of astronomical motions. The relative sizes of and distances between planets were not accurately represented, nor were the post-Keplerian elliptical orbits of the planets; the scale of most planetaria requires that the orbits resemble circles. Further, even in the age of Newton, the planetary machines show mean motions and fixed orbits, without attempting to illustrate perturbations or deviations due to the gravitational effects of bodies other than the Sun. Planetaria were not intended to teach mathematical theories of astronomy. Generally speaking, a planetarium demonstrates the relative motions and positions of the astronomical bodies and is primarily designed for teaching. From the first half of the 20th century, the term “planetarium” has often described optical systems used with a projection instrument inside a domed theatre. However, the term is also routinely used to describe mechanical, non-optical demonstrations of astronomical motions.
The Device known as the “orrery”
The historian of scientific instruments, John Millburn, has warned of the confusion surrounding the terms “orrery” and “planetarium,” and the instability of their usage. The term “orrery,” which is often used in English-speaking countries instead of the word “planetarium,” derives from the name of Charles Boyle, the fourth Earl of Orrery (1676-1731), for whom such an instrument was made in 1712-13 by a London instrument maker, John Rowley (working by 1697, died 1728). This orrery is now in the collection of the Science Museum, London (inventory number 1952-73). The Rowley orrery depicted only the Sun, Earth and Moon.
Our knowledge of the origin of the orrery is, to some extent, based on the report of John Desaguliers, who explained that his contemporary Rowley had been sent an astronomical model made by the London clockmakers George Graham (1673/4-1751) and Thomas Tompion (1639-1713). Rowley copied the instrument “and made the first for the late Earl of Orrery, and then several others, with Additions of his own.”
The Graham/Tompion “proto-orreries” were designed to demonstrate the annual motion of the Earth around the Sun, the diurnal rotation of the Earth on its axis, and the revolution of the Moon around the Earth. An entry in the Minutes of the Spalding Gentlemen’s Society describes such an instrument:
Monday, March 2nd, 1713. Mr. Johnston gave the Soc. an Acct. of Mr. Tompion’s Curious Machine for explaining the Motion of the Sun, Moon & Earth according to the Copernic system.
The link to Copernican heliocentric cosmology is emphasized; there is no mention in this context of Isaac Newton. (A Graham/Tompion instrument is now in the collection of the Museum of the History of Science, Oxford (inventory number 97810); a similar example, signed by Graham, is in Chicago, at the Adler Planetarium, accession number A-156.)
The term “Grand Orrery” was used by 18th-century English instrument makers to describe a model which had been extended to include the motions of the planets (and their satellites), as well as the Earth and Moon; the astronomical bodies included varied. An orrery, then, has certain English associations which other foreign-made planetaria may not have, but it is not immediately clear that this includes any particular link to Newton or “Newtonianism.” Few Grand Orreries survive, and fewer still are on display in museums. A Grand Orrery (Wh.1275), signed Made by GEO ADAMS at TYCHO BRAHE’S HEAD, in Fleet Street LONDON, occupies pride of place in the main gallery of the Whipple Museum of the History of Science, in the Department of History and Philosophy of Science at the University of Cambridge. “Grand Orreries” are certainly grand—not only large, but expensively and richly decorated pieces of furniture.
Image 2: Grand Orrery by George Adams; circa 1750. Photographed circa 1970, without the orrery’s glass cover. Image © the Whipple Museum (Wh.1275).
Thomas Wright (who worked 1718-1747) further increased the visual appeal by adding an armillary hemisphere over the orrery itself. This is just the sort of Grand Orrery depicted in the Wright image, and on display in the Whipple. These grand orreries surmounted by an armillary hemisphere are visually striking, given their added height and overall impressiveness. But, as both 18th- and 20th-century commentators have noted, the addition of the armillary hemisphere served no useful purpose, and may only have confused people trying to understand the heliocentric motions conveyed by the orrery, because the overarching framework of the armillary sphere was associated with a geocentric perspective.
In his A compendious system of natural philosophy (1743), John Rowning (1701?-1771), a natural philosopher and mathematician who was a Fellow of Magdalene College, Cambridge, complained that
Artificers generally erect upon the Ecliptic some Semi-circles to represent some of the principal Circles of the Heavens. But this is wrong, and tends to Confusion; because these Circles being only imaginary, and arising from the apparent Motions of the heavenly Bodies, ought to have no Place in the Orrery:
Others found fault with this hybrid device as well. Benjamin Martin, in 1771, complained that such constructions were a waste of money, claiming that the orrery “stands in Need of none of the useless, expensive, and cumbersome Embellishments of Art.”
For Martin, the orrery was a valuable educational tool; in The Description and Use of both the Globes, the Armillary Sphere, and Orrery exemplified (1762, reprinted 1773) he pointed to its usefulness in arguing against the Ptolemaic conception of the universe. A plate from Martin’s The Description and Use of both the Globes [1773] even carries a banner proclaiming the Copernican character of the orrery. (However, it could be argued that orreries and planetaria do not give a true impression of Copernican cosmology either, for example, in terms of the relative size of the universe.)
Plate from Benjamin Martin, Description and Use of both the Globes . . . (1773), facing p. 197. Reproduced by permission of the Syndics of Cambridge University Library.
Viewed against the backdrop of contemporary accounts of the orrery, Wright’s depiction of A Philosopher giving that lecture on the Orrery, in which a lamp is put in place of the Sun gives the impression that those gathered around the illuminated model were not listening to a lecture related to Newton or “Newtonianism.” As these accounts indicate, in the 18th century the orrery was often described as Copernican, and was seldom (if ever) labelled as Newtonian. Furthermore, the impression that the Copernican hypothesis was not universally understood and accepted in the period is reinforced by the consideration of planetary models, some of which – especially the orrery surmounted by the hemispherical armillary – were seen by their contemporary critics to be confusing rather than enlightening. The character of orreries as astronomical models and the title of Wright’s painting suggest that the philosopher depicted would have been demonstrating phenomena such as day and night and eclipses, and not expounding a theory of attraction or gravitation.
In Wright’s powerful image, the demonstration of the place of the Sun in the universe and the phenomena associated with the Sun (for example, night and day, the phases of the Moon, and eclipses) are especially important. The artistic language of the painter, implementing strong contrasts between darkness and light, underscores the significance of such solar phenomena. Even in 18th-century “Newtonian” England, the heliocentric “Copernican” cosmology afforded Wright an outstanding opportunity to demonstrate the painterly effects of his chiaroscuro, through his depiction of a candlelit Grand Orrery.
Liba Taub is Director and Curator of the Whipple Museum of the History of Science, and Reader in History and Philosophy of Science, at the University of Cambridge.