The Dutch East India Company, a joint governmental and private enterprise, sent ships to the far corners of the world to acquire rare commodities and resell them at a profit in Europe. Such voyages were the life blood of the Republic. Navigational charts and maps were classified as state secrets. Ships often embarked with sealed orders. Suddenly the Dutch were present all over the planet. The Barents Sea in the Arctic Ocean and Tasmania in Australia are named after Dutch sea captains. These expeditions were not merely commercial exploitations, although there was plenty of that. There were powerful elements of scientific adventure and the zest for discovery of new lands, new plants and animals, new people; the pursuit of knowledge for its own sake.
The Amsterdam Town Hall reflects the confident and secular self-image of seventeenth-century Holland. It took shiploads of marble to build. Constantijn Huygens, a poet and diplomat of the time, remarked that the Town Hall dispelled “the Gothic squint and squalor.” In the Town Hall to this day, there is a statue of Atlas supporting the heavens, festooned with constellations. Beneath is Justice, brandishing a golden sword and scales, standing between Death and Punishment, and treading underfoot Avarice and Envy, the gods of the merchants. The Dutch, whose economy was based on private profit, nevertheless understood that the unrestrained pursuit of profit posed a threat to the nation’s soul.
A less allegorical symbol may be found under Atlas and Justice, on the floor of the Town Hall. It is a great inlaid map, dating from the late seventeenth or early eighteenth centuries, reaching from West Africa to the Pacific Ocean. The whole world was Holland’s arena. And on this map, with disarming modesty the Dutch omitted themselves, using only the old Latin name Belgium for their part of Europe.
In a typical year many ships set sail halfway around the world. Down the west coast of Africa, through what they called the Ethiopian Sea, around the south coast of Africa, within the Straits of Madagascar, and on past the southern tip of India they sailed, to one major focus of their interests, the Spice Islands, present-day Indonesia. Some expeditions journeyed from there to a land named New Holland, and today called Australia. A few ventured through the Straits of Malacca, past the Philippines, to China. We know from a mid-seventeenth-century account of an “Embassy from the East India Company of the United Provinces of the Netherlands, to the Grand Tartar, Cham, Emperor of China.” The Dutch burgers, ambassadors and sea captains stood wide-eyed in amazement, face to face with another civilization in the Imperial City of Peking.*
Never before or since has Holland been the world power it was then. A small country, forced to live by its wits, its foreign policy contained a strong pacifist element. Because of its tolerance for unorthodox opinions, it was a haven for intellectuals who were refugees from censorship and thought control elsewhere in Europe—much as the United States benefitted enormously in the 1930’s by the exodus of intellectuals from the Nazi-dominated Europe. So seventeenth-century Holland was the home of the great Jewish philosopher Spinoza, whom Einstein admired; of Descartes, a pivotal figure in the history of mathematics and philosophy; and of John Locke, a political scientist who influenced a group of philosophically inclined revolutionaries named Paine, Hamilton, Adams, Franklin and Jefferson. Never before or since has Holland been graced by such a galaxy of artists and scientists, philosophers and mathematicians. This was the time of the master painters Rembrandt and Vermeer and Frans Halls; of Leeuwenhoek, the inventor of the microscope; of Grotius, the founder of international law, of Willebrord Snellius, who discovered the law of the refraction of light.
In the Dutch tradition of encouraging freedom of thought, the University of Leiden offered a professorship to an Italian scientist named Galileo, who had been forced by the Catholic Church under threat of torture to recant his heretical view that the Earth moved about the Sun and not vice versa.* Galileo had close ties with Holland, and his first astronomical telescope was an improvement of a spyglass of Dutch design. With it he discovered sunspots, the phases of Venus, the craters of the Moon, and the four large moons of Jupiter now called, after him, the Galilean satellites. Galileo’s own description of his ecclesiastical travails is contained in a letter he wrote in the year 1615 to the Grand Duchess Christina:
Some years ago as Your Serene Highness well knows, I discovered in the heavens many things that had not been seen before our own age. The novelty of these things, as well as some consequences which followed from them in contradiction to the physical notions commonly held among academic philosophers, stirred up against me no small number of professors [many of them ecclesiastics]—as if I had placed these things in the sky with my own hands in order to upset Nature and overturn the sciences. They seemed to forget that the increase of known truths stimulates the investigation, establishment, and growth of the arts.†
The connection between Holland as an exploratory power and Holland as an intellectual and cultural center was very strong. The improvement of sailing ships encouraged technology of all kinds. People enjoyed working with their hands. Inventions were prized. Technological advance required the freest possible pursuit of knowledge, so Holland became the leading publisher and bookseller in Europe, translating works written in other languages and permitting the publication of works proscribed elsewhere. Adventures into exotic lands and encounters with strange societies shook complacency, challenged thinkers to reconsider the prevailing wisdom and showed that ideas that had been accepted for thousands of years—for example, on geography—were fundamentally in error. In a time when kings and emperors ruled much of the world, the Dutch Republic was governed, more than any other nation, by the people. The openness of the society and its encouragement of the life of the mind, its material well-being and its commitment to the exploration and utilization of new worlds generated a joyful confidence in the human enterprise.*
In Italy, Galileo had announced other worlds, and Giordano Bruno had speculated on other lifeforms. For this they had been made to suffer brutally. But in Holland, the astronomer Christiaan Huygens, who believed in both, was showered with honors. His father was Constantijn Huygens, a master diplomat of the age, a litterateur, poet, composer, musician, close friend and translator of the English poet John Donne, and the head of an archetypical great family. Constantijn admired the painter Rubens, and “discovered” a young artist named Rembrandt van Rijn, in several of whose works he subsequently appears. After their first meeting, Descartes wrote of him: “I could not believe that a single mind could occupy itself with so many things, and equip itself so well in all of them.” The Huygens home was filled with goods from all over the world. Distinguished thinkers from other nations were frequent guests. Growing up in this environment, the young Christiaan Huygens became simultaneously adept in languages, drawing, law, science, engineering, mathematics and music. His interests and allegiances were broad. “The world is my country,” he said, “science my religion.”
Light was a motif of the age: the symbolic enlightenment of freedom of thought and religion, of geographical discovery; the light that permeated the paintings of the time, particularly the exquisite work of Vermeer; and light as an object of scientific inquiry, as in Snell’s study of refraction, Leeuwenhoek’s invention of the microscope and Huygens’ own wave theory of light.* These were all connected activities, and their practitioners mingled freely. Vermeer’s interiors are characteristically filled with nautical artifacts and wall maps. Microscopes were drawing-room curiosities. Leeuwenhoek was the executor of Vermeer’s estate and a frequent visitor at the Huygens home in Hofwijck.
Leeuwenhoek’s microscope evolved from the magnifying glasses employed by drapers to examine the quality of cloth. With it he discovered a universe in a drop of water: the microbes, which he described as “animalcules” and thought “cute.” Huygens had contributed to the design of the first microscopes and himself made many discoveries with them. Leeuwenhoek and Huygens were among the first people ever to see human sperm cells, a prerequisite for understanding human reproduction. To explain how microorganisms slowly
develop in water previously sterilized by boiling, Huygens proposed that they were small enough to float through the air and reproduced on alighting in water. Thus he established an alternative to spontaneous generation—the notion that life could rise, in fermenting grape juice or rotting meat, entirely independent of preexisting life. It was not until the time of Louis Pasteur, two centuries later, that Huygens’ speculation was proved correct. The Viking search for life on Mars can be traced in more ways than one back to Leeuwenhoek and Huygens. They are also the grandfathers of the germ theory of disease, and therefore of much of modern medicine. But they had no practical motives in mind. They were merely tinkering in a technological society.
The microscope and telescope, both developed in early seventeenth-century Holland, represent an extension of human vision to the realms of the very small and the very large. Our observations of atoms and galaxies were launched in this time and place. Christiaan Huygens loved to grind and polish lenses for astronomical telescopes and constructed one five meters long. His discoveries with the telescope would by themselves have ensured his place in the history of human accomplishment. In the footsteps of Eratosthenes, he was the first person to measure the size of another planet. He was also the first to speculate that Venus is completely covered with clouds; the first to draw a surface feature on the planet Mars (a vast dark windswept slope called Syrtis Major); and by observing the appearance and disappearance of such features as the planet rotated, the first to determine that the Martian day was, like ours, roughly twenty-four hours long. He was the first to recognize that Saturn was surrounded by a system of rings which nowhere touches the planet.* And he was the discoverer of Titan, the largest moon of Saturn and, as we now know, the largest moon in the solar system—a world of extraordinary interest and promise. Most of these discoveries he made in his twenties. He also thought astrology was nonsense.
Huygens did much more. A key problem for marine navigation in this age was the determination of a longitude. Latitude could easily be determined by the stars—the farther south you were, the more southern constellations you could see. But longitude required precise timekeeping. An accurate shipboard clock would tell the time in your home port; the rising and setting of the Sun and stars would specify the local shipboard time; and the difference between the two would yield your longitude. Huygens invented the pendulum clock (its principle had been discovered earlier by Galileo), which was then employed, although not fully successfully, to calculate position in the midst of the great ocean. His efforts introduced an unprecedented accuracy in astronomical and other nautical clocks. He invented the spiral balance spring still used in some watches today; made fundamental contributions to mechanics—e.g., the calculation of centrifugal force—and, from a study of the game of dice, to the theory of probability. He improved the air pump, which was later to revolutionize the mining industry, and the “magic lantern,” the ancestor of the slide projector. He also invented something called the “gunpowder engine,” which influenced the development of another machine, the steam engine.
A detail from Christiaan Huygens’ Systema Saturnium, published in 1659. Shown is his (correct) explanation of the changing appearance of the rings of Saturn over the years as the relative geometry of Earth and Saturn changes. In position B the comparatively paper-thin rings disappear as they are seen edge-on. In position A they display their maximum extent visible from Earth, the configuration that caused Galileo, with a significantly inferior telescope, considerable consternation.
Huygens was delighted that the Copernican view of the Earth as a planet in motion around the Sun was widely accepted even by the ordinary people in Holland. Indeed, he said, Copernicus was acknowledged by all astronomers except those who “were a bit slow-witted or under the superstitions imposed by merely human authority.” In the Middle Ages, Christian philosophers were fond of arguing that, since the heavens circle the Earth once every day, they can hardly be infinite in extent; and therefore an infinite number of worlds, or even a large number of them (or even one other of them), is impossible. The discovery that the Earth is turning rather than the sky moving had important implications for the uniqueness of the Earth and the possiblity of life elsewhere. Copernicus held that not just the solar system but the entire universe was heliocentric, and Kepler denied that the stars have planetary systems. The first person to make explicit the idea of a large—indeed, an infinite—number of other worlds in orbit about other suns seems to have been Giordano Bruno. But others thought that the plurality of worlds followed immediately from the ideas of Copernicus and Kepler and found themselves aghast. In the early seventeenth century, Robert Merton contended that the heliocentric hypothesis implied a multitude of other planetary systems, and that this was an argument of the sort called reductio ad absurdum (Appendix 1), demonstrating the error of the initial assumption. He wrote, in an argument which may once have seemed withering,
For if the firmament be of such an incomparable bigness, as these Copernical giants will have it …, so vast and full of innumerable stars, as being infinite in extent … why may we not suppose … those infinite stars visible in the firmament to be so many suns, with particular fixed centers; to have likewise their subordinate planets, as the sun hath his dancing still around him?… And so, in consequence, there are infinite habitable worlds; what hinders?… these and suchlike insolent and bold attempts, prodigious paradoxes, inferences must needs follow, if it once be granted which … Kepler … and others maintain of the Earth’s motion.
But the Earth does move. Merton, if he lived today, would be obliged to deduce “infinite, habitable worlds.” Huygens did not shrink from this conclusion; he embraced it gladly: Across the sea of space the stars are other suns. By analogy with our solar system, Huygens reasoned that those stars should have their own planetary systems and that many of these planets might be inhabited: “Should we allow the planets nothing but vast deserts … and deprive them of all those creatures that more plainly bespeak their divine architect, we should sink them below the Earth in beauty and dignity, a thing very unreasonable.”*
These ideas were set forth in an extraordinary book bearing the triumphant title The Celestial Worlds Discover’d: Conjectures Concerning the Inhabitants, Plants and Productions of the Worlds in the Planets. Composed shortly before Huygens died in 1690, the work was admired by many, including Czar Peter the Great, who made it the first product of Western science to be published in Russia. The book is in large part about the nature or environments of the planets. Among the figures in the finely rendered first edition is one in which we see, to scale, the Sun and the giant planets Jupiter and Saturn. They are, comparatively, rather small. There is also an etching of Saturn next to the Earth: Our planet is a tiny circle.
By and large Huygens imagined the environments and inhabitants of other planets to be rather like those of seventeenth-century Earth. He conceived of “planetarians” whose “whole Bodies, and every part of them, may be quite distinct and different from ours … ’tis a very ridiculous opinion … that it is impossible a rational Soul should dwell in any other shape than ours.” You could be smart, he was saying, even if you looked peculiar. But he then went on to argue that they would not look very peculiar—that they must have hands and feet and walk upright, that they would have writing and geometry, and that Jupiter has its four Galilean satellites to provide a navigational aid for the sailors in the Jovian oceans. Huygens was, of course, a citizen of his time. Who of us is not? He claimed science as his religion and then argued that the planets must be inhabited because otherwise God had made worlds for nothing. Because he lived before Darwin, his speculations about extraterrestrial life are innocent of the evolutionary perspective. But he was able to develop on observational grounds something akin to the modern cosmic perspective:
What a wonderful and Amazing scheme have we here of the magnificant vastness of the universe … So many Suns, so many Earths … and every one of them stock’d with so many Herbs, Trees, and Animals, adorn’d with so m
any Seas and Mountains!… And how must our Wonder and Admiration be increased when we consider the prodigious Distance and Multitude of the Stars.
The Voyager spacecraft are the lineal descendants of those sailing-ship voyages of exploration, and of the scientific and speculative tradition of Christiaan Huygens. The Voyagers are caravels bound for the stars, and on the way exploring those worlds that Huygens knew and loved so well.
One of the main commodities returned on those voyages of centuries ago were travelers’ tales,* stories of alien lands and exotic creatures that evoked our sense of wonder and stimulated future exploration. There had been accounts of mountains that reached the sky; of dragons and sea monsters; of everyday eating utensils made of gold; of a beast with an arm for a nose; of people who thought the doctrinal disputes among Protestants, Catholics, Jews and Muslims to be silly; of a black stone that burned; of headless humans with mouths in their chests; of sheep that grew on trees. Some of these stories were true, some were lies. Others had a kernel of truth, misunderstood or exaggerated by the explorers or their informants. In the hands of Voltaire, say, or Jonathan Swift, these accounts stimulated a new perspective on European society, forcing a reconsideration of that insular world.
Modern Voyagers also return travelers’ tales, tales of a world shattered like a crystal sphere; a globe where the ground is covered, pole to pole, with what looks like a network of cobwebs; tiny moons shaped like potatoes; a world with an underground ocean; a land that smells of rotten eggs and looks like a pizza pie, with lakes of molten sulfur and volcanic eruptions ejecting smoke directly into space; a planet called Jupiter that dwarfs our own—so large that 1,000 Earths would fit within it.