Random Walk
A map of the world—or rather the parts the Romans knew or had heard about in 150 CE—from Claudius Ptolemy’s Geographia.
On the Map
From Neolithic cave painting to Google Earth, humans have used maps to depict, understand, and navigate their environment. Now some of the Caltech Archives’ finest treasures on the subject of mapping the earth, the skies, and longitude have gone on display, many for the first time, on the second floor of Parsons-Gates Hall of Administration. The On the Map exhibit includes Claudius Ptolemy’s 2nd-century map of the known world; Georg Braun and Frans Hogenberg’s beautifully illustrated Civitates Orbis Terrarum, from the latter part of the 16th century; a 1570 map of Russia by Abraham Ortelius; Johannes Bayer’s 1603 Uranometria; Johannes Kepler’s world map of 1627; a 17th-century planispheric celestial map by Andries van Luchtenberg; prints from Joan Blaeu’s 1662 Atlas Maior; and first editions of books by Tycho Brahe, Johannes Hevelius, Giovanni Domenico Cassini, and Christiaan Huygens.
Ptolemy’s map is an early 16th-century version reconstituted from his cartography and geography book, the Geographia, published in 150 CE. Ptolemy, a Roman citizen of Alexandria, knew that the earth was a globe—the ancient Greeks had worked it out centuries earlier—but his view of the world extends only from the zero-degree line of longitude off the west coast of Africa (beyond which no sailor had returned to tell the tale) to the 180-degree line through China, and from 60 degrees north latitude to 30 degrees south. He omitted the three-quarters of the globe that was still uncharted, a technique that humans still employ today when mapping unknown terrain such as Saturn’s moon Titan, currently under surveillance by JPL’s Cassini spacecraft. Cassini’s radar views a narrow swath of Saturn’s lunar companion with each flyby, and the resulting maps, in which Titan’s topographical features are interspersed with black regions for which no data exists, are in some sense Ptolemy’s intellectual descendants—JPL’s cartographers don’t fill the empty space with creations of their own fancy.
Cassini made this radar mosaic of Saturn’s moon Titan. The surface is covered in seas, tinted blue and black.
Cassini will, in all likelihood, map Titan more rapidly than humans mapped the earth: the Americas, after all, were not discovered by Europe until the late 15th century. But once the Age of Exploration got under way, the exciting accounts of new lands brought back by sailors sparked a renewed interest in geography among prosperous and literate Europeans. Printing presses, invented a few decades earlier, found a lucrative market in catering to the demand for information.
In 1513, the German cartographer Martin Waldseemüller, whose large map of the world (and the first map to use the name “America”) had sold well a few years earlier, decided to bring out Ptolemy’s Geographia. For centuries the Christian world had regarded the ancient geometer as a heretic, and the work was hidden away and forgotten until its rediscovery in the 14th century. Waldseemüller borrowed a manuscript copy, in Greek, from an Italian monastery. The maps were missing, but he reconstituted them, including the world map in the Caltech display, from Ptolemy’s extensive topographical list—a compendium of place names and geographical features along with their latitudes and longitudes. (The list was compiled from travelers’ reports, and many of the longitudes were wrong—or, at best, very bad guesses—which is why the landforms get increasingly distorted the farther one gets from the Mediterranean.)
In the decades that followed, decorative maps and atlases found ready buyers. Some of the finest were produced by the Flemish cartographer Abraham Ortelius, who pioneered the change from the woodcut printing of maps to copperplate engraving, with italic lettering and rich hand-coloring that greatly enhanced the definition and beauty of the prints. When his Theatrum Orbis Terrarum (“Theater of the World”), the first true atlas, sold well, he encouraged Georg Braun and Frans Hogenberg of Cologne to produce a companion book of town views and history, the Civitates Orbis Terrarum (“Towns of the World”).
With its first volume published in 1572, Braun and Hogenberg’s ambitious project took an additional 45 years to complete, and Caltech is fortunate to own four volumes from the six-volume first edition. Their scrupulously detailed town plans generally depict buildings and houses from a bird’s-eye perspective and are brought to life with drawings of people in local costume carrying out their trades, of animals, and of scenes from history, all accompanied by an account in Latin of the town’s situation, population, history, government, commerce, and traditions.
Anyone comparing a current map of Basel with this 1575 view from Braun and Hogenberg’s Civitates Orbis Terrarum (“Towns of the World”) might think that the Rhine has changed its course over the years. But what’s really changed is our notion that maps always have north at the top. In the 16th century, there was no convention for map orientation, and this view is from the north looking south. A compass rose to guide the viewer was also considered unimportant.
Today the “armchair traveler” has morphed into the “Google Earther,” as more and more people turn to cyberspace to swoop in on houses or the world’s cities. Interestingly, Wikipedia’s city pages provide almost the same information that Braun and Hogenberg did.
Humans were likely curious about the heavens even before they explored the world: following the daily course of the sun, moon, stars, and planets doesn’t involve any traveling. Early astronomers and geographers both used the same surveying instruments, such as quadrants and astrolabes; and both earth and sky maps have equators and poles, latitude and longitude. (The longitude of a star or planet is given by its right ascension, while the latitude is given by its declination.) For millennia, star tables—celestial topographical lists—played an indispensible role in predicting important events in the calendar such as equinoxes, solstices, phases of the moon, and eclipses (not to mention their use in casting horoscopes!), but they were so imprecise that, according to the young Tycho Brahe, “There are just as many measurements and methods as there are astronomers, and all of them disagree.”
Accordingly, Tycho (as he is commonly known), a Danish nobleman, made it his life’s work to take accurate, systematic observations from a single spot over many years. He persuaded King Frederick II of Denmark to give him the small island of Hven (modern Ven), in the straits between Denmark and Sweden, and to build him an observatory there and provide him with a generous income to fund it. Today’s astronomers should be so fortunate!
Tycho named his palatial astronomical research center Uraniborg, the Castle of the Heavens. With accommodations for up to a hundred observers, assistants, and visiting scholars, it was not unlike a modern astronomical research center, save for the alchemy workshop in the basement and the utter lack of telescopes (Tycho was the last major astronomer to survey the skies entirely by naked eye.) He later added Stjerneborg, the Castle of the Stars, an underground observatory with a rotating dome that sheltered his instruments from the buffeting winds that swirled around Uraniborg’s towers. A series of lakes provided waterpower for both instrument workshops and a mill that produced paper for publications. Unfortunately, after Frederick’s death, Tycho argued with his heir and had to abandon the island in 1597.
Uraniborg, Stjerneborg, and the lakes can be seen on the map of Hven in the Archive’s display—a reproduction of a colored engraving by Willem Blaeu from Joan Blaeu’s Atlas Maior, 1662. The young Willem, Joan’s father, had studied astronomy and globe-making with Tycho, and he went on to run a successful map-publishing business in Amsterdam. Uraniborg was demolished shortly after Tycho’s sudden death in 1601, but today we can zoom in on Ven via Google Earth and view Uraniborg’s partially restored gardens, the remains of Stjerneborg, and even, faintly, the remains of the lakes.
A map of Tycho Brahe’s island of Hven (now Ven) from Joan Blaeu’s Atlas Maior of 1662, showing the observatories Uraniborg and Stjerneborg and the lakes that provided waterpower.
Tycho’s assistant, Johannes Kepler, who would go on to attain some fame in his own right, finished the work by preparing a new set of star tables based on the Hven observations. These he published in 1627 as the Tabulae Rudolphinae, or “Rudolphine Tables,” in honor of Rudolf II of Austria, Holy Roman emperor and Tycho’s royal patron at the end of his life, and Kepler’s patron as well. The exhibit includes a photograph of a large world map folded inside Caltech’s copy of the Tables. The map’s unusual projection, comprising one whole hemisphere centered on Europe and Africa, flanked by two half hemispheres, was Kepler’s own design. It was probably intended to make it easier for navigators to plot their position by keeping the most-traveled seaways of the Known World contiguous. Kepler’s line of zero longitude is centered on Hven. Caltech is fortunate to have this map, as it is rare: the engraver had not finished it when the book was published, and after the astronomer’s death three years later, it lay forgotten until rediscovered in 1658.
Kepler also tackled the problem of accurately measuring one’s longitude, a necessity for any maritime power attempting to become a global presence. But although his method gave useful results on dry land, despite his best efforts, it proved impractical on a tossing deck. Among those who tried to find a better way were Giovanni Domenico Cassini, Christiaan Huygens, and England’s first Astronomer Royal, John Flamsteed; books and prints reflecting their work are also on display.
Nowadays, ships, planes, and even cars navigate with the help of satellites, and travelers (almost) always know exactly where they are. Life is safer and easier—but our curiosity about the world around us is as strong as ever. —BE
Barbara Ellis is a writer and researcher for On the Map, which is curated by Shelley Erwin, head of Archives and Special Collections. The majority of the books, prints, and artifacts on display were collected and later donated to Caltech by Earnest C. Watson, founder of the Watson Lecture Series and professor of physics and dean of the faculty at Caltech for many years. The Tabulae Rudolphinae are from the Rocco Collection, purchased by trustee Harry Bauer for Caltech in 1955.
Below: A rare and unusual map of the world designed by Kepler for his 1627 book of star tables, the Tabulae Rudolphinae.
