Millennia ago, if you wanted to look up at the sky or across a broad valley, you might have used a long sighting tube to focus your attention and reduce glare, as did Aristotle and probably his predecessors. But no empty tube, however long—and whether cast in gold by an ancient Assyrian metalworker, carved from jade by an ancient Chinese artisan, or fastened to an armillary sphere by a mathematically astute medieval pope1—would improve your physiological capacity to detect the planet Neptune or assess the size of a rival army or navy massing on a distant shore.
Put a couple of lenses in the tube, though, and you’ve got yourself an optical telescope.
A tool for augmenting the senses, the telescope enables you both to detect things too faint to see and to resolve detail where your eyes would otherwise fail you. First, it shows you that an object exists; then, by revealing the object’s shape, motion, and color, it hints at what the object might be. The telescope’s task is to collect at a distance as much visual information as it can, and feed it to your brain via your eyes.
Whether you’re scanning the enemy or scanning the skies, every bit of information delivered by your telescope rides a beam of light. Structurally, a telescope is little more than a bucket for catching photons. Whether your goal is detection or resolution, the bigger the diameter of your light bucket, the more photons you’ll catch. The collection area increases as the square of the diameter. So if you triple the diameter, you increase the telescope’s power of detection ninefold. Resolution depends on the diameter of your telescope divided by the wavelength of light you’re observing. To maximize resolution, you want a bucket that’s much, much wider than your chosen wavelength. For visible light, with its wavelengths measured in hundreds of nanometers, a several-meter-wide bucket does swimmingly. And just as the wine lover wants a wineglass to be so thin that it is nearly absent as a boundary between lips and wine, the astrophysicist wants the design limitations of the telescope, the susceptibilities of the human observer, and the distortions of Earth’s atmosphere to be as absent as possible from the data.
Assistance in seeing at a distance arrived just four centuries ago, in the form of a pair of cookie-sized lenses firmly fixed inside a tube and presented by a spectacle maker named Hans Lipperhey in September 1608—right in the middle of the Catholic–Protestant conflict known as the Eighty Years’ War—to Prince Maurice of Nassau, commander-in-chief of the armed forces of the United Provinces of the Netherlands. This tube was the first historically substantiated, honest-to-god telescope, although allusions to earlier ones abound. Within half a year Galileo had learned of Lipperhey’s indispensable instrument and had built a better one of his own design.
Early telescopes gathered little light, and their images of distant objects, whether celestial or terrestrial, were blurry, distorted, and faint. The lenses were small and thick, made of imperfect glass, imperfectly curved and polished. Back in the days when, despite the panegyrics of the early writers, a telescope delivered barely more data than would an ordinary pair of opera glasses, its achievements were usually described in terms of magnification rather than resolution. Galileo’s very first telescope—a lead tube with two store-bought spectacle lenses, assembled early in the summer of 1609—made objects appear three times closer. As with the arithmetic that applies to the collecting area of telescopes, when we square the factor of three we get objects that are nine times larger than they would appear with the unassisted eye. By late autumn, Galileo had built himself a telescope in which objects appeared sixty times larger.2
Of course, seventeenth-century astronomers didn’t know how bad their telescopes were. All they knew was how good their telescopes were compared with human vision. So they did manage to discover some marvelous things. In the summer of 1609 the English astronomer Thomas Harriot, scientific aide to Sir Walter Raleigh, saw the crescent Moon sufficiently well to sketch a few of its surface features: the earliest known portrayal of the Moon as seen through a spyglass.3 That fall, Galileo, with a much better telescope at his disposal, saw and drew our Moon’s mountains and craters, as well as other “very great and wonderful sights”: a quartet of moons circling Jupiter; extra stars in the Orion nebula and the Pleiades cluster; and a pair of intermittent companions close to Saturn. Half a century later, looking through an even bigger, better telescope, Christiaan Huygens observed that Saturn’s companions were actually two arcs of a ring. A mere twenty years later, through a still better telescope, Giovanni Cassini picked out two concentric rings, separated by a gap.
During the millennia before aerial bombing, the sky was the domain of air, light, rain, wind, and deities. There was no reason to imagine that military dangers could be circumvented by looking up. Armies advanced in waves on the ground. The notion that the sky is a place to be monitored for protection from human adversaries is a twentieth-century perversion. Monitoring the faraway terrestrial landscape, however, was a long-held dream of generals, opticians, navigators, and surveyors alike.
It so happens that when Hans Lipperhey arrived in The Hague in September 1608 to present what his letter of introduction called “a certain device by means of which all things at a very great distance can be seen as if they were nearby,” intense peace negotiations were taking place, and the city was swarming with delegations of diplomats. The French were mediating between the Dutch representatives and their Spanish/Belgian adversaries, and both sides were internally divided about the wisdom of continuing to fight. Into the middle of all this walked the nice man from Middelburg with his optical invention, seeking promises of a patent and a pension. Not only did he get what he wanted, but his invention seems to have played an astonishing bit part in the negotiations.
According to an insider’s account of the invention’s wondrous capabilities, written in early October, just days after the commander-in-chief of Spain’s armed forces left The Hague, “From the tower of The Hague, one clearly sees, with the said glasses, the clock of Delft and the windows of the church of Leiden, despite the fact that these cities are distant from The Hague one-and-a-half, and three-and-a-half hours by road, respectively.” So impressed was the Dutch parliament with Lipperhey’s device that they sent the instrument to Prince Maurice, saying that “with these glasses they would see the tricks of the enemy.” The Spanish commander-in-chief, equally impressed, told Maurice’s kinsman Prince Henry, “From now on I could no longer be safe, for you will see me from afar.” To which Henry replied, “We shall forbid our men to shoot at you.”
The writer then elaborates on the instrument’s potential:
The said glasses are very useful in sieges and similar occasions, for from a mile and more away one can detect all things as distinctly as if they were very close to us. And even the stars which ordinarily are invisible to our sight and our eyes, because of their smallness and the weakness of our sight, can be seen by means of this instrument.4
From birth, the telescope represented the convergence of war and astronomy. It was obviously a dual-use instrument. Any courtier could see that it would revolutionize both intelligence-gathering and skywatching. Which is why Lipperhey got his money, Prince Maurice got his “glasses,” and Spain signed the Twelve Years’ Truce with the young Dutch nation on April 9, 1609.
The Vatican, too, was made aware of the worldly implications of the invention. In a letter written to Cardinal Scipione Borghese just before the signing of the truce, the archbishop of Rhodes spends a full three paragraphs describing Maurice’s new possession and announcing that a similar item is on its way to His Holiness by the next post. The Spanish commander, writes the archbishop, thought that Maurice “had procured this instrument in order in time of war to reconnoitre from a distance, or observe places he might want to besiege, or sites of encampments, or enemy forces on the march, or similar situations that might be turned to his advantage.” Having himself tried out one such instrument and been quite impressed by what was visible ten miles away, the archbishop is certain it will “provide much diversion [and] pleasure” to his superiors.5
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Not five months later, in late August 1609, Galileo Galilei—who described himself as “Florentine patrician and public mathematician of the University of Padua”—ascended Saint Mark’s Campanile in the Republic of Venice, accompanied by the republic’s senators, to demonstrate his own significantly improved spyglass. Having fulfilled his mission, he donated the spyglass to the senate and (successfully) petitioned the doge, the republic’s chief magistrate, for his patronage. Other entrepreneur-inventors had been busy working up and demonstrating versions of this desirable new instrument, of which word had spread far and wide. One such inventor even seems to have petitioned the senators of Venice before Galileo did. But Galileo had a powerful Venetian connection who smoothed the way for him and conceivably even let him examine his competitor’s version.6
Accompanying Galileo’s donation was a written sales pitch to the doge:
Galileo Galilei, a most humble servant of Your Serene Highness, . . . appears now before You with a new contrivance of glasses, drawn from the most recondite speculations of perspective, which renders visible objects so close to the eye and represents them so distinctly that those that are distant, for example, 9 miles appear as though they were only 1 mile distant. This is a thing of inestimable benefit for all transactions and undertakings, maritime or terrestrial, allowing us at sea to discover at a much greater distance than usual the hulls and sails of the enemy, so that for 2 hours and more we can detect him before he detects us and, distinguishing the number and kind of the vessels, judge his force, in order to prepare for chase, combat, or flight; and likewise, allowing us on land to look inside the fortresses, billets, and defenses of the enemy from some prominence, although far away, or also in open campaign to see and to distinguish in detail, to our very great advantage, all his movements and preparations; besides many other benefits, clearly manifest to all judicious persons.7
What could be more militarily useful to a seventeenth-century seafaring republic than the capacity to monitor enemy vessels? Indeed, few things could be more useful to any sort of republic, in any century, than the capacity to monitor the enemy’s movements anywhere: land, sea, air, space, or online. Eventually, satellites—descendants of the spyglass—would enable them to do so.
In the year 1267, more than three centuries before Hans Lipperhey put two lenses in a tube and betook himself to the nearest general, a scholarly Franciscan friar named Roger Bacon sent Pope Clement IV a hefty scientific treatise. Some of his thoughts were ahead of their time:
[W]e can so shape transparent bodies, and arrange them in such a way with respect to our sight and objects of vision, that the rays will be refracted and bent in any direction we desire, and under any angle we wish we shall see the object near or at a distance. . . . Thus a small army might appear very large, and situated at a distance might appear close at hand, and the reverse. So also we might cause the sun, moon, and stars in appearance to descend here below, and similarly to appear above the heads of our enemies. . . .
No one, possibly including Bacon himself, followed through on his suggestion, whether because Bacon’s concept was too spooky for its day or because glassmakers were not yet up to the task or because learned gentlemen had little interest in practical matters. By the sixteenth century, though, his writings had been dusted off and his ideas revivified.
One revivifier was the learned Oxford mathematician, astronomer, and all-round science maven John Dee, who owned at least one of Bacon’s works. In his “very fruitfull praeface” to a 1570 English translation of Euclid’s Elements of Geometry, Dee told his readers that anyone wishing to “make true report . . . of the numbers and Summes, of footemen or horsemen, in the Enemyes ordring” would “wonderfully helpe him selfe, by perspective Glasses.” Less than a decade later, in a book titled Inventions or devices. Very necessary for all generalles and captaines, or leaders of men, as well by sea as by land, one William Bourne wrote that a pair of properly positioned lenses “is very necessary in diverse respects, as the viewing of an army of men, and such other like causes.” And in 1589, in his best seller Natural Magick, Giovanbattista Della Porta spoke of the ancient “Glass” of an Egyptian king, “whereby for six hundred miles he saw the enemies ships coming.”8
Earth’s actual horizon sits no farther away than a few dozen miles from any observer, but exaggerations of the distance to the enemy are surely forgivable, given the percolating anticipation of what glass lenses would one day do. Little wonder, then, that when Lipperhey demonstrated his optical aid in The Hague in the autumn of 1608 before a group of military men, ministers, and mediators, they instantly understood its military utility. The chief French negotiator lost no time in procuring two for the French court. By the following spring, not only had Galileo learned of the invention, but the archduke of Austria and the pope each owned a telescope, foot-long spyglasses were for sale on the streets of Paris and Milan, and peace had been declared between Catholic Spain and Protestant Netherlands.9
The truce lasted until 1621. With the resumption of war, the Spanish commander-in-chief Ambrogio Spinola resumed his command. The siege and surrender of the fortress city of Breda in 1624–25 brought death to Prince Maurice and transient victory to Spinola, who is depicted graciously receiving the key to the city in an imposing canvas by the Spanish court painter Diego Velázquez. Grasped in Spinola’s gloved left hand and positioned near the focal point of the painting, as if to emphasize its role in the victory, is a spyglass nearly two feet long.10
Few people in history have arrived at the end of life without witnessing war, and seventeenth-century Europeans were no exception. What distinguishes their chapter is the unprecedented level of commercialization and bureaucratization of the pursuit. European entrepreneurs, merchants, and rulers devoted huge amounts of money and effort to the improvement of weapons and the institutionalization of paid standing armies that numbered in the tens of thousands. Many of Europe’s best scientists and inventors—in addition to considering questions related to commerce, mining, and marine transport—addressed themselves to matters directly or indirectly related to military technology: explosives, ballistics, velocity, air resistance, impact, innovative armaments, new methods of timekeeping, new means of surveying, and, of course, a raft of new sighting instruments.11 In the words of the seventeenth-century Irish optics expert William Molyneux, to use a sighting instrument was, in effect, to arm oneself:
Tis manifest by Experiments, that the ordinary Power of Man’s Eye extends no farther than perceiving what subtends an Angle of about a Minute, or something less. But when an Eye is armed with a Telescope, it may discern an Angle less than a Second.12
Nor were bards and scriveners immune to war fever. In England, beset in the 1600s by fifty-five years of actual warfare and many additional years of almost warfare, writers invented a slew of military metaphors. While the Royal Navy prepared for war with the Dutch by ordering hundreds of cannons and thousands of hand grenades,13 the poet Samuel Butler composed a long satire on the astronomers of the Royal Society observing the full Moon, in which he depicts his subjects as hungry for cosmic conquest:
And now the lofty tube, the scale
With which they heav’n itself assail,
Was mounted full against the Moon;
And all stood ready to fall on,
Impatient who should have the honour
To plant an ensign first upon her.14
Think of the nascent telescope as an emblem of an entire society readying itself for expansion, not of the mind but of the wallet, the jewel box, the dinner table, and the wardrobe. Merchants were on the lookout for opportunities. Armies and navies were on the go. Getting a good view of not merely the heavens but also the hills, forests, ports, palaces, and sea lanes was becoming strategically necessary.
Within a century of its invention, the telescope came in many models: some with mirrors, some with two lenses, some with three lenses, some meant to be propped up on stands, some small enough to be carried in the pocket and certainly in the
hand, some whose tubes were as big as a building, some whose widely separated components were suspended in the air without benefit of a tube.15 Some of the earliest versions were binoculars, including three commissioned from Hans Lipperhey by the Dutch government and delivered in good working order by February 1609.
Although none of the seventeenth-century telescopes measured up to those of later centuries, and not everyone could master the knack of seeing through them, the telescope and its cousin the binocular nonetheless brimmed with potential, both astronomical and military. But the breadth of astronomical possibilities surfaced only gradually and incidentally. Passable wide-field astronomical telescopes barely existed until the second half of the century, by which time Isaac Newton’s nemesis, the talented British scientist Robert Hooke, would have good cause to speculate that “there may be yet invented several other helps for the eye, as much exceeding those already found, as those do the bare eye, such as by which we may perhaps be able to discover living Creatures in the Moon, or other Planets [italics in original].” At first, however, rather than gazing at an uncharted section of sky to see what they could see and thus make discoveries of their own, skywatchers generally aimed their telescopes upward just to look at some of Galileo’s discoveries: the four major satellites of Jupiter, the textured surface of the Moon, the two “servants” of Saturn “who help him walk and never leave his side” (Saturn’s barely resolved rings, extending to both sides of the planet itself, second largest in the solar system).16
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