The Science of Shakespeare (5 page)

THE WANDERERS

But there were certain objects in the night sky whose behavior wasn't quite so simple. From ancient times, skywatchers noticed that there were a handful of starlike objects that did not quite move in unison with the other stars; they changed their position against the constellations from night to night and from season to season. Today we call them planets; the word derives from the Greek term for “wanderer.” Five of these wandering stars were known in ancient times—Mercury, Venus, Mars, Jupiter, and Saturn.

Although the planets wandered, they did not run amok: One could always depend on finding them within a narrow band that circles the night sky, the belt defined by the twelve constellations of the zodiac. In this respect, they are like the sun and moon, which also keep within the zodiac, and so one sometimes spoke of seven (rather than five) wandering bodies. But there were some intriguing differences in the paths that these wandering stars seemed to take: Mercury, looking like a dim reddish star, moved swiftly—only the moon seemed to move faster—and yet it always appeared close to the sun. Brilliant white Venus moved a little slower, and strayed a little farther from the sun, but not too far (neither planet was ever seen
opposite
the sun). Mars, with its distinctive reddish color, moved more slowly than the sun; so, too, did Jupiter and Saturn, both creamy white in color. Their paths took them across the entire sky, so that sometimes they were near the sun, sometimes opposite the sun. Of these, Saturn was the slowest of all; it took weeks before its motion against the background stars was perceptible, and required almost thirty years to complete a full circle relative to the background stars.

To the title character in Christopher Marlowe's
Doctor Faustus
, such motions were elementary. The doctor distinguishes “the double motion of the planets”—referring to their daily rising and setting, and also to their more complicated motion against the stars of the zodiac. Saturn's motion, he says, is completed “in thirty years, Jupiter in twelve, Mars in four, the sun, Venus, and Mercury in a year, the moon in twenty-eight days. Tush, these are freshmen's suppositions” (7.51–56). Actually, the period for Mars is closer to two years than four, but close enough: For Marlowe, and for his learned doctor, this basic comprehension of the heavens—knowing which objects were visible, in which part of the sky, and for how long—was everyday knowledge.

The planets, however, were more than just points of light in the night sky: They were also associated with gods. Each had its own powers, its own domain of influence. For both the Greeks and the Romans, Venus was the goddess of love; Mars was the god of war. Saturn was a god of agriculture and of time, while Mercury was a kind of messenger, a god of travel—which makes sense, given Saturn's plodding pace and Mercury's swiftness. Jupiter, often the brightest of the planets, was the king of the gods.
*

The movement of the planets showed many regularities—but also some downright peculiar behavior. From night to night, the planets
usually
edged a little bit to the east; as the weeks passed, this was easily observed. Eventually, they completed a full circle against the backdrop of the stars. But for several weeks or months each year they would reverse their direction, moving westward from night to night, before resuming their usual eastward motion. Astronomers refer to this backtracking as “retrograde” motion, in contrast to the more usual “direct” motion. Again, these were familiar terms in Elizabethan times—as much for their use in astrology as in astronomy. In
All's Well That Ends Well
, Helena plays with this idea, poking fun at Parolles's skills on the battlefield:

HELENA

Monsieur Parolles, you were born under a charitable star.

PAROLLES

Under Mars, I.

HELENA

I especially think under Mars.

PAROLLES

Why under Mars?

HELENA

The wars have so kept you under that you must needs be born under Mars.

PAROLLES

When he was predominant.

HELENA

When he was retrograde, I think rather.

PAROLLES

Why think you so?

HELENA

You go so much backward when you fight.

(1.1.190–200)

Mars, aside from being the god of war, was also the most perplexing of the planets. The magnitude of its retrograde movement was greater than that of the other planets, making it the most readily visible example of backward motion in the heavens and, at the same time, the object whose movement was most urgently in need of explanation. As the French king points out early in
Henry VI, Part 1
, “Mars his true moving, even as in the heavens / So in the earth, to this day is not known” (1.2.191–92). As familiar as retrograde motion was, it proved baffling to astronomers, who struggled to tweak their models of the heavens to explain this odd feature of planetary motion.

THE SPHERES ABOVE

Imagining the sun, moon, and planets affixed to a giant, transparent sphere was a promising start, but it was not quite enough: At the very least, each planet had to have
its own
sphere, so that it could move independently of the other wanderers; these nested spheres—think of the layers of an onion—could then rotate at different speeds, with the Earth at rest in the center. The innermost sphere carried the moon, which moved a significant distance from night to night; next was Mercury, then Venus. After that came the sun itself. Beyond the sun lay the spheres of Mars, Jupiter, and Saturn; and finally the sphere containing the stars themselves, sometimes called the “firmament” (as Prince Hamlet referred to it in the passage quoted at the start of the chapter). And so one would not speak of a single giant sphere, but of a system of spheres—a system like that imagined in
figure 1.1
. Perhaps the spheres were composed of some kind of crystal; they needed to be rigid and yet perfectly transparent.

Although this model had evolved significantly by the sixteenth century, the ancient picture just described was more or less how ordinary people imagined the universe in the time of Shakespeare's youth. When Hamlet, after seeing his father's ghost, says the vision threatens to make his eyes “like stars, start from their spheres” (1.5.22), his audience would have had no trouble catching the metaphor. Similar turns of phrase can be found throughout the canon. In
A Midsummer Night's Dream
, Oberon describes a mermaid's song—music so lovely that “certain stars shot madly from their spheres” in order to hear it better (2.1.153). And if you've ever seen a Western in which one character says to another that “this town isn't big enough for the both of us,” remember that Shakespeare was there first—though entire planets, rather than towns, were at issue. In
Henry IV, Part 1
, Prince Henry says to his archenemy, Harry Percy, “Two stars keep not their motion in one sphere, / Nor can one England brook a double reign / Of Harry Percy and the Prince of Wales” (5.4.64–66).

Fig. 1.1
In ancient Greece, the universe was earth-centered, with a system of concentric spheres carrying the stars, sun, and planets— including the sun and moon—across the sky. Only in the terrestrial realm do we find the four elements: earth, water, air, and fire. (In this fanciful 1599 engraving, Atlas carries the whole affair on his back.) This ancient model—with various tweaks—remained the dominant view for nearly 2,000 years.
The Granger Collection, New York

What we've described here is, roughly, how ancient civilizations across the Near East imagined the heavens for thousands of years: The cosmos was pictured as an intricate system of nested, transparent spheres, carrying the sun, moon, planets, and stars across the sky in their daily and yearly cycles. It was also the way the great thinker Aristotle imagined the universe in the fourth century B.C. By Aristotle's time, it was accepted that the Earth itself was spherical; but it was thought to be immobile, fixed at the center of the universe, surrounded by this intricate array of translucent spheres, carrying the five planets—or seven, if we count the sun and moon among these “wanderers.”

Aristotle also noticed a profound difference between what happened down here on the Earth, and what transpired in the heavens. The terrestrial realm—the “sublunar” world—was marked by continuous change; it was subject to corruption and decay. This stood in stark contrast to the perfection of the sun, moon, and planets, whose movements were as predictable and regular as a well-oiled machine. (The metaphor is less of an anachronism if we think of the cosmic machine as a divine creation rather than something constructed in a blacksmith's workshop, but either way we have an artifact bearing witness to the talent of its creator.) Here on Earth, everything was thought to be composed of the four elements—earth, air, fire, and water—described by the Greeks even before Aristotle. All that we see around us, from mice to mountains, can be thought of as a particular arrangement of these elements, as they move and combine in different forms. As Christopher Marlowe's Tamburlaine observes, “Nature that framed us of four elements, / Warring within our breasts for regiment…” (
Tamburlaine the Great, Part 1
2.6.58–59). Even Sir Toby Belch, in
Twelfth Night
, asks: “Does not our life consist of the four elements?” (2.3.9).

In a world of hierarchies, it is not surprising that the elements themselves were ranked according to their presumed nobility. Fire was the most worthy; next was air. Water, being heavier, filled the oceans below. Earth, the basest of the elements, lay at the bottom. However quaint such a system may seem today, it basically worked: When flames were observed to rise, it could be seen as an attempt to reach the heavenly spheres, their natural home; the fall of rain to the sea, or a thrown rock to the ground, could be similarly accounted for.

These elements, confined to the sublunar world, were constantly in flux. But the “superlunar” world—the heavens—showed no such signs of change. To Aristotle, this heavenly realm, with its various spheres, was composed of a kind of quintessence—literally a “fifth element.” Sometimes an additional sphere was added beyond the sphere of the fixed stars; this was the
primum mobile
(“that which moves first”), which was believed to set the whole system in motion.

In considering the motion of the heavenly bodies, Aristotle was influenced by Plato, who had in turn been influenced by the followers of Pythagoras, an early Greek thinker who saw the universe as inherently mathematical, its creator a kind of divine geometer. Among the many shapes pondered by the geometers, one was seen as more perfect than any other. This was the circle (or, in three dimensions, the sphere). As a medieval astronomer named Sacrobosco noted, there were three reasons why the heavens must be spherical: First, a sphere has no beginning and no end, and is therefore “eternal.” Second, a sphere encloses a larger volume than any other shape having the same surface area. And third, any other shape would seem to leave “unused” space. The first of these reasons, in particular, permeated Greek mathematical thought. And so Aristotle imagined the planets as moving in perfect circles. This was a little bit tricky, since it was well known that the planets do, in fact, display irregularities in their motion, as seen from Earth. But surely, he reasoned, this was an illusion: Aristotle and his followers were confident that, from the correct perspective, all heavenly motion was indeed perfectly uniform and perfectly circular.

CIRCLES UPON CIRCLES

This system of nested crystalline spheres was immensely appealing—but anyone who followed the movements of the planets closely came to realize that it was not quite enough; the motion of the planets was too complex. For example, it was still unclear how the circular movement of those spheres could account for retrograde motion. The best guess was that each planet required two such spheres: a large one, to account for the basic eastward motion; and a smaller one, to account for the “loops” that the planet traces out when moving in retrograde. These smaller circles were known as
epicycles
(from a Greek term meaning “a cycle displaced from the center”).

The most detailed account of such a system comes from the Greek mathematician and astronomer Claudius Ptolemy (ca. A.D. 90–168).
*
Ptolemy's system was intricate and sophisticated, employing geometrical contrivances that today sound unfamiliar to anyone except for historians of astronomy. We will not wade into Ptolemaic astronomy any more than we have to, but it is worth looking at its main elements. As in Aristotle's system, the Earth lies at the center of the universe. Each planet, as mentioned, has two motions: it moves in a small epicycle, with the center of the epicycle revolving around the Earth in a larger circle called a
deferent
. The deferent, meanwhile, is not centered precisely on the Earth, but on a nearby point called the
eccentric
. One more aspect of Ptolemy's astronomy merits our attention: Ptolemy had imagined not only that the heavenly bodies moved in perfect circles, but that they did so at a constant speed. This was problematic, because, as measured from Earth, the speed would not be constant in the system as described. But the speed
would
be constant relative to an imaginary point on the “other side” of the eccentric, displaced from the center by the same amount as the Earth. That imaginary point was called an
equant
.