Isaac Newton (5 page)

From matter to motion, to light, and to the structure of the cosmos. The sun drove the vortex by its beams. The ubiquitous vortex could drive anything: Newton sketched some ideas for perpetual motion machines. But light itself played a delicate part in the Cartesian scheme, and Newton, attempting to take Descartes literally, already sensed contradictions. Pressure does not restrict itself to straight lines; vortices whirl around corners. “Light cannot be by pression,” Newton asserted, “for then wee should see in the night a[s] wel or better than in the day we should se[e] a bright light above us becaus we are pressed downewards.…” Eclipses should never darken the sky. “A man goeing or running would see in the night. When a fire or candle is extinguished we lookeing another way should see a light.”
¹⁸

Another elusive word,
gravity
, began to appear in the
Questiones
. Its meanings darted here and there. It served as half of a linked pair:
Gravity & Levity
. It represented the tendency of a body to descend, ever downward. But how could this happen? “The matter causing gravity must pass through all the pores of a body. It must ascend againe, for else the bowells of the earth must have had large cavitys & inanitys to containe it in.…”
¹⁹
It must be crowded in that unimaginable place, the center of the earth—all the world’s streams coming home. “When the streames meet on all sides in the midst of the Earth they must needs be coarcted into a narrow roome & closely press together.”

Then again, perhaps an object’s gravity was inherent, a quantity to be exactly measured, even if it varied from place
to place: “The gravity of a body in diverse places as at the top and bottom of a hill, in different latitudes &c. may be measured by an instrument”—he sketched a balance scale. He speculated about “rays of gravity.” Then,
gravity
could also refer to a body’s tendency to move, not downward, but in any direction; its tendency to remain in motion, once started. If such a tendency existed, no language yet had a word for it. Newton considered the problem of the cannonball, still rising, long after leaving the gun. “Violent motion is made”—he struck the word
made
—“continued either by the aire or by motion”—struck the word
motion
and replaced it with
force
:

Violent motion (Newton’s drawing)
.
(illustration credit 2.2)

Violent motion is
made
continued either by the aire or by
motion
force imprest or by the natural gravity in the body moved.

Yet how could the cannonball be helped along by the air? He noted that the air crowds more upon the front of a projectile than on the rear, “& must therefore rather hinder it.” So the continuing motion must come from some natural tendency in the object. But
—gravity
?

Some of his topics—for example,
Fluidity Stability Humidity Siccity
²⁰
—never progressed past a heading. No matter. He had set out his questions.
Of Heate & Cold. Atraction Magneticall. Colours. Sounds. Generation & Coruption. Memory
. They formed a program, girded with measurements, clocks and scales, experiments both practical and imaginary. Its ambition encompassed the whole of nature.

One more mystery:
the Flux & Reflux of the Sea
. He considered a way to test whether the moon’s “pressing the atmosphere” causes the tides. Fill a tube with mercury or water; seal the top; “the liquor will sink three or four inches below it leaving a vacuum (perhaps)”; then as the air is pressed by the moon, see if the water will rise or fall. He wondered whether the sea level rose by day and fell by night; whether it was higher in the morning or evening. Though fishermen and sailors around the globe had studied the tides for thousands of years, people had not amassed enough data to settle those questions.
²¹

3
 
To Resolve Problems by Motion

C
AMBRIDGE IN
1664
HAD
for the first time in its history a professor of mathematics, Isaac Barrow, another former Trinity College sizar, a decade older than Newton. Barrow had first studied Greek and theology; then left Cambridge, learned medicine, more theology, church history, and astronomy, and finally turned to geometry. Newton attended Barrow’s first lectures. He was standing for examinations that year, on his way to being elected a scholar, and it was Barrow who examined him, mainly on the
Elements
of Euclid. He had not studied it before. At Stourbridge Fair he found a book of astrology and was brought up short by a diagram that required an understanding of trigonometry
¹
—more than any Cambridge student was meant to know. He bought and borrowed more books. Before long, in a few texts, he had at hand a précis of the advanced mathematics available on the continent of Europe. He bought Franz van Schooten’s
Miscellanies
and his Latin translation of Descartes’s difficult masterpiece,
La Géométrie
; then William Oughtred’s
Clavis Mathematicæ
and John Wallis’s
Arithmetica Infinitorum
.
²
This reading remained far from comprehensive. He was inventing more than absorbing.

At the end of that year, just before the winter solstice, a comet appeared low in the sky, its mysterious tail blazing toward the west. Newton stayed outdoors night after night, noting a path against the background of the fixed stars, watching till it vanished in the light of each dawn, and only then returned to his room, sleepless and disordered. A comet was a frightening portent, a mutable and irregular traveler through the firmament. Nor was that all: rumors were reaching England of a new pestilence in Holland—perhaps from Italy or the Levant, perhaps from Crete or Cyprus.

Hard behind the rumors came the epidemic. Three men in London succumbed in a single house; by January the plague, this disease of population density, was spreading from parish to parish, hundreds dying each week, then thousands. Before the outbreak ran its course, in little more than a year, it killed one of every six Londoners.
³
Newton’s mother wrote from Woolsthorpe:

Isack

received your leter and I perceive you
           letter from me with your cloth but
none to you your sisters present thai
love to you with my motherly lov
you and prayers to god for you I
your loving mother
     hanah
     wollstrup may the 6. 1665
⁴

The colleges of Cambridge began shutting down. Fellows and students dispersed into the countryside.

Newton returned home. He built bookshelves and made a small study for himself. He opened the nearly blank thousand-page commonplace book he had inherited from his stepfather and named it his Waste Book.
⁵
He began filling it with reading notes. These mutated seamlessly into original research. He set himself problems; considered them obsessively; calculated answers, and asked new questions. He pushed past the frontier of knowledge (though he did not know this). The plague year was his transfiguration.
⁶
Solitary and almost incommunicado, he became the world’s paramount mathematician.

Most of the numerical truths and methods that people had discovered, they had forgotten and rediscovered, again and again, in cultures far removed from one another. Mathematics was evergreen. One scion of
Homo sapiens
could still comprehend virtually all that the species knew collectively. Only recently had this form of knowledge begun to build upon itself.
⁷
Greek mathematics had almost vanished; for centuries, only Islamic mathematicians had kept it alive, meanwhile inventing abstract methods of problem solving called algebra. Now Europe became a special case: a region where people were using books and mail and a single language, Latin, to span tribal divisions across hundreds of miles; and where they were, self-consciously, receiving communications from a culture that had flourished and then disintegrated more than a thousand years before. The idea of knowledge as cumulative—a ladder, or a tower of stones, rising higher and higher—existed only as one possibility among many. For several hundred years, scholars of scholarship had considered that they might be like dwarves seeing farther by standing on the shoulders of giants, but
they tended to believe more in rediscovery than in progress. Even now, when for the first time Western mathematics surpassed what had been known in Greece, many philosophers presumed they were merely uncovering ancient secrets, found in sunnier times and then lost or hidden.

With printed books had come a new metaphor for the world’s organization. The book was a container for information, designed in orderly patterns, encoding the real in symbols; so, perhaps, was nature itself.
The book of nature
became a favorite conceit of philosophers and poets: God had written; now we must read.
⁸
“Philosophy is written in this grand book—I mean the universe—which stands continually open to our gaze,” said Galileo. “But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics.…”
⁹

But by mathematics he did not mean numbers: “Its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth.”

The study of different languages created an awareness of language: its arbitrariness, its changeability. As Newton learned Latin and Greek, he experimented with shorthand alphabets and phonetic writing, and when he entered Trinity College he wrote down a scheme for a “universal” language, based on philosophical principles, to unite the nations of humanity. “The Dialects of each Language being soe divers & arbitrary,” he declared, “a generall Language cannot bee so fitly deduced from them as from the natures of things themselves.”
¹⁰
He understood language as a process,
an act of transposition or translation—the conversion of reality into symbolic form. So was mathematics, symbolic translation at its purest.

For a lonely scholar seeking his own path through tangled thickets, mathematics had a particular virtue. When Newton got answers, he could usually judge whether they were right or wrong, no public disputation necessary. He read Euclid carefully now. The
Elements
—transmitted from ancient Alexandria via imperfect Greek copies, translated into medieval Arabic, and translated again into Latin—taught him the fundamental program of deducing the properties of triangles, circles, lines, and spheres from a few given axioms.
¹¹
He absorbed Euclid’s theorems for later use, but he was inspired by the leap of Descartes’s
Géométrie
, a small and rambling text, the third and last appendix to his
Discours de la Méthode
.
¹²
This forever joined two great realms of thought, geometry and algebra. Algebra (a “barbarous” art, Descartes said,
¹³
but it was his subject nonetheless) manipulated unknown quantities as if they were known, by assigning them symbols. Symbols recorded information, spared the memory, just as the printed book did.
¹⁴
Indeed, before texts could spread by printing, the development of symbolism had little point.