Cosmos #6: Travelers' Tales

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

The Role of Exploration in History

Prologue: The Voyager 2 Jupiter flyby

Comparisons to Early Sail Voyages

The "Passion to explore"

Sagan claims "The passion to explore is at the heart of being human". Is this really true? Sagan lists the following examples:

In addition, we can perhaps list a few others:

Of the thousands of cultures that have ever existed, only a handful ever made deliberate long-distance voyages of exploration. And there are some spectacular examples of complete lack of curiosity:

The motivation for exploration plays an important role in determining whether it happens.

The 17th Century Dutch Republic

Sagan draws parallels between our modern space exploration and the Dutch Republic. The Dutch Republic was newly independent from Spain after the ruinous Thirty Years War (1618-1648), which is also mentioned in Episode 3, Harmony of the Worlds.

How did Holland come to be ruled by Spain in the first place? Spain was ruled by one branch of the powerful Hapsburg family, whose other branch controlled large parts of central Europe. Through royal marriage and inheritance, not by military conquest, Holland ended up being ruled by one of the Spanish Hapsburgs. The Spanish Inquisition was particularly brutal in trying to stamp out Protestantism in Holland, and the Dutch retaliated in kind. The Holy Martyrs of Gorcum church east of Green Bay commemorates a group of 19 Catholic priests who were hanged by Dutch Protestants. It is believed to be the only church of that name in the U.S.

A single human lifetime encompasses the events of Episode 3, Harmony of the Worlds and the Holland portrayed in this episode, but what a difference in outlook! Sagan uses the old Amsterdam Town Hall as a symbol of the new world-view. One admirer claimed the hall dispelled the "Gothic squint and squalor of the Middle Ages". Sagan says "the Middle Ages had ended; the Enlightenment had begun"

Despite the fact that a lot of features of our culture can be traced to roots in the Middle Ages, and that the Middle Ages are often inaccurately stereotyped, it's hard to deny the differences we see between the Holland of this episode and the Germany of Kepler. One might see a similar contrast between the U.S. and the former Soviet Union as well. It's not entirely a matter of time so much as ideology and individual liberty.

Avarice and envy under feet of Justice

The Inland world map on the Town Hall floor is a more practical symbol of Holland's achievements. Holland became briefly a world power, but it was small and forced to live by its wits. It tended to be pacifist, but ended up in numerous small wars with other trading rivals, notably England. It was heavily taxed and simply had insufficient resources to endure lengthy competition with larger powers.

In terms of respect for liberty and human rights, Holland has been a world power far out of proportion to its size. The tolerance of Holland made it a place of refuge for intellectuals from less open parts of Europe (just about everyplace else). Among those who found refuge there were the Jewish philosopher Spinoza, and philosophers Rene Descartes and John Locke, whose ideas in turn influenced the leaders of the American Revolution.

(Holland's long tradition of enlightenment, alas, did not stop its soldiers from being pretty brutal at times in their failed attempt to stop Indonesia's drive for independence after World War II. And this after Holland's own brutal occupation by the Nazis. Moral: no society - none whatsoever - is immune to lapses into barbarism.)

The Dutch university of Leyden offered a professorship to Galileo. This brings up an interesting question. Why didn't Galileo go? It wouldn't have been hard for him to elude his guards. There are a lot of reasons that come to mind. His house arrest really wasn't that burdensome, he didn't want to leave familiar surroundings, his mistress and daughter didn't want to leave, and so on.

Holland also provided asylum to the Pilgrims, but they decided the skeptical, liberal climate of Holland was not conducive to their own lifestyle, so they eventually left for America. Contrary to popular mythology, they didn't come to Amerca to find religious freedom but to escape it.

Several topics mentioned in this episode are covered in more detail on other pages:

Holland briefly had colonies in North America, notably New Amsterdam. At the upper end of Manhattan Island, separated by 20 kilometers of forest wilderness, was another settlement named after the Dutch city of Haarlem. It has since dropped one of the a's. In one of its numerous scuffles with England, Holland lost its colony, which was renamed New York. Dutch names like Yonkers and Schuylkill still dot the lower Hudson River. Although they were rivals with England, Dutch financial innovations were readily adapted by the English and formed the basis for England's growth into the world's leading maritime power.

Does exploration equal openness?

Consider the other seafaring exploring powers of the time: Spain, Portugal, France, England. Or Russia, whose sea voyages were few but which was pushing with astonishing ease and rapidity across Asia to the Pacific at this time. After Holland, England was by far the most open and tolerant of these societies, followed by France, while the others were positively repressive. Indeed, Spain's glory days as an exploring power were far behind by this time.

It appears that democracy, tolerance and moderation can encourage exploration, but it's not a simple equation. Exploration doesn't necessarily make a society open and tolerant. Indeed, some people from repressive societies may go abroad precisely to find more freedom. Also, travel broadens some people but narrows others, convincing them of their own inherent superiority. Recall that early British visitors to India were often admirers of Indian achievements, and were looked down upon as having "gone native" by a later, more repressive wave of colonizers. Finally, some highly democratic societies like Switzerland were not engaged in exploration at all.

Constantine and Christian Huygens

Rene Descartes said of Constantine Huygens: "I could not believe that a single mind could occupy itself with so many things, and equip itself so well in all of them." Considering the source, that's about as high an intellectual compliment as anyone has ever received.

"World is my country - science my religion"

Anton Leeuwenhoek, a contemporary and colleague of Huygens, was the first to use the microscope for scientific observations. The microscope was a tiny glass bead created by melting a thin filament of glass, and was inspired by similar lenses used by drapers for examining cloth. These microscopes worked much better than you might suppose. The drawings of microbes shown in the video are quite accurate and easily recognizable. Some historians have doubted that Leeuwenhoek really observed all he claimed to, but in the April 1998 issue of Scientific American, Brian Ford published photographs taken through some of these instruments. In some cases the images rival those from modern microscopes.

The Discoveries of Christian Huygens

"Stars are other suns"

Why the Long-tube Telescopes?

The video shows Huygens using a very cumbersome telescope with a very long tube. Such telescopes were widely used in the late 1600's; some had tubes fifty feet long. The reason has to do with the limitations of lenses.

  1. A prism refracts different wavelengths of light different amounts and spreads the colors into a spectrum.
  2. A thick, sharply curved lens does exactly the same thing. Different colors are focused at different points. An object viewed through such a lens will be fuzzy, with colored fringes. This problem is called chromatic aberration.
  3. Simple lenses have spherical surfaces, but that's not the exact shape a lens ought to have. Spherical lenses don't focus all incoming rays to the same point, even rays of the same color. This is called spherical aberration. It applies to any optical element, lens or mirror, that has the wrong curvature, and is the flaw that severely impaired the Hubble Space Telescope when it was first launched.
  4. Thin lenses with gentle curves are much less affected by aberrations of all kinds than thick, heavily curved lenses. On the other hand, such lenses also focus images very far away (they are said to have long focal length). To get away from aberrations, 17th century astronomers often resorted to almost imperceptibly curved lenses with focal lengths of many feet.
  5. Modern lenses usually employ several kinds of glass with different optical properties, and are ground to more complex shapes than early lens-makers could achieve. Thus a modern telescope or binocular lens is nearly free of chromatic and spherical aberration. These designs were not invented until the mid 19th century.

Ironically, by the early 1700's many of the telescopic discoveries by Huygens and others had almost been forgotten. There may well have been nobody in Europe at that time who had ever seen Titan. The clumsy long telescopes had discovered all they were capable of seeing. There are real parallels here to the decline of the space program in the 1970's and 1980's, a "been there, done that" attitude. Telescopic observation revived with the improvement of reflecting telescopes that used parabolic mirrors to form images. These telescopes, invented by Isaac Newton, can be made free of chromatic and spherical aberration, and can be made much more easily than large lenses.

Exploration of Jupiter

Pioneer 10 and 11, 1973

Voyager 1 and 2

Traveler's Tales - new knowledge "Solar System = Jupiter + debris" > 90% of mass of planets "Star that failed" (of 2010) July 9, 1979 - first views of Europa How images transmitted Io - volcanos Discovery by Linda Morabito

The video closes with an imaginary trip to Saturn, which was really visited by Voyager 2. The imaginary landing on Titan will actually (we hope) be accomplished by the Cassini/hugens mission in 2002

More Information on the Jupiter System

Essential Points


Brian J. Ford, 1998; The Earliest Views, Scientific American, vol. 278, no. 4 (April, 1998), p. 50-53.

Brian Ford's Web Site.

Pioneer 11 Jupiter Encounter.
Special issue of Science, vol. 188, No. 4187, , 1975.
Voyager 1 Jupiter Encounter.
Special issue of Science, vol. 204, No. 4396, June 1, 1979.
Voyager 2 Jupiter Encounter.
Special issue of Science, vol. 206, No. 4421, November 23, 1979.

NASA Publications:

More Information on the Jupiter System
Return to Exploration of the Universe Index
Return to Professor Dutch's Home Page

Created 13 January 1998, Last Update 20 January 2020