Fine example of this celestial chart illustrating the Sun's orbit around the Earth, from Andreas Cellarius' Harmonia Macrocosmica.
Cellarius's chart illustrates the Ptolemaic theory of the Sun's orbit around the Earth. The chart is designed to explain the differences between the observed interval between the length of time from the Autumnal to the Vernal equinox (187 days) and the length of time from the Vernal equinox to the Autumnal equinox (178 days). This is, of course, due to the eccentricity of the earth's orbit and the varying speed at which the earth circles the sun.
The classical Greek explanation for this phenomenon was that the sun's geocentric orbit was off-centered from the earth, a feature which is shown here at five times in exaggeration. This allows for the earth to spend more time orbiting the sun during the northern hemisphere winter, when the earth both has further to travel and has a slower velocity (as it is further from the sun, therefore has more potential energy).
The map helpfully provides a number of reference lines, two of which are particularly important. The horizontal Aequinoctialis runs through the center of the earth, and shows the (supposed) location of the equinoxes, and the vertical Linea Apsidum, which shows the location of the solstices. It should be noted that while this theory is correct for explaining the differing lengths of the orbit, the exact position of the equinoxes and solstices is not necessarily correct, as this is also influenced by the earth's axial tilt.
The Greek geometer Apollonius of Solga showed that there are actually two mathematically equivalent solutions (under a coordinate change) for this issue. The first, as presented in the main figure, is repeated in the lower left and only requires an off-centered and elliptical orbit. The second solution, shown in the lower right, is that the sun orbits a secondary, fictional point that itself orbits the earth in a perfectly circular fashion; this is termed an epicycle.
There are 3 states of the charts:
- 1660: No page numbers. Some maps include the name of Johannes Van Loon as the engraver.
- 1661: Page numbers added in the bottom right corner. Some maps include the name of Johannes Van Loon as the engraver.
- 1708: Valk & Schenk imprint added.
The most sought after of all celestial atlases, this is the only one to be produced during the Dutch cartographic golden age. This work, Cellarius's magnum opus, was produced as a means to illustrate competing theories of celestial mechanics, during an era in which these issues were very much still up for debate. With scholarly precision, but in a manner accessible to the contemporary reader, Cellarius describes, contrasts, and analyzes the hypotheses and observations made by the great thinkers of classical antiquity in addition to those made by his contemporaries.
Of particular interest are the volume's finely engraved images designed to illustrate the concepts introduced. Plates in the work depict the Sun, the Earth, and the stars in a way they had not been seen before. These magnificent depictions take all the strengths of Dutch 17th-century engraving and apply it to the sky: information is simply presented and any critical eye will immediately start to understand the points that Cellarius conveys.
The plates themselves would have been engraved by several Dutch master engravers, but only two have signed their names: Frederik van den Hove, who made the frontispiece, and Johannes van Loon, a noted creator of nautical charts. By 1660, the work was complete.
In the text, Cellarius states his intention to publish a second volume that would adjust for this first volume's overreliance on the Ptolemaic model. This overreliance is present in several ways. In plates that pick a certain model of the Solar System, approximately ten show a pre-Copernican concept of the universe, while only two deal with a Copernican viewpoint and six with a Tychonic system. Further, the plates show little in the way of telescopic discoveries, such as the moons of Saturn. We note but two plates (23 and 28) in which a telescope is in active use among the many representations of astronomical tools in the other plates. It is likely that this intended second volume would have focused more heavily on modern astronomical discoveries.
The plates of the Harmonia can be divided into two sections: the first twenty-one deal with varying hypotheses on how the Solar System functions, citing Claudius Ptolemy, Tycho Brahe, Nicolaus Copernicus, as well as lesser-known figures such as Aratus of Soli and Aristarchus. The plates convey, with two-dimensional in plano and three-dimensional scenographia depictions, how the planetary motions within each model account for contemporary observations. Some plates focus on other themes, these include the influence of the Earth's tilt on climatic effects and how we observe the stars, or the explanation for the phases of the Moon.
The final eight plates look past the Solar System and instead focus on the constellations. While later scientific texts eschew discussions of these human constructions, in Cellarius's time they were still considered of critical scholarly importance. The most important recent innovations, which are displayed in various plates, are the discoveries and naming of Southern Hemisphere stars as well as the attempted renaming of the pagan constellations to fit Christian ideals. Some of these plates show the world as seen from outside the celestial realm, that is, we are looking from beyond the stars into our own existence, and these are truly remarkable in their perspective.
Andreas Cellarius was born in 1596 in Neuhausen and educated in Heidelberg. He emigrated to Holland in the early 17th century, and in 1637 moved to Hoorn, where he became the rector of the Latin School. Cellarius' best-known work is his Harmonia Macrocosmica, first issued in 1660 by Jan Jansson, as a supplement to Jansson's Atlas Novus. The work consists of a series of Celestial Charts begun by Cellarius in 1647 and intended as part of a two-volume treatise on cosmography, which was never issued.