In August 1684 a handsome young astronomer named Edmond Halley boarded the London coach for Cambridge and sat back to ponder the events that had set him on an important mission. Earlier in the year, he had entered into a lively conversation with scientist Robert Hooke and Sir Christopher Wren, the noted architect of the new St. Paul's Cathedral in London. Halley suggested that the force of attraction between the planets and the sun decreases in inverse proportion to the square of the distance between them. If this were true, then each planet's orbit should take the form of Kepler's ellipse, a shape like a football, though somewhat more rounded.
Halley recalled that Hooke immediately "affirmed that upon that principle all the Laws of the celestial motions were to be demonstrated." Wren, who was also deeply interested in the new science, claimed that he, too, had reached the same conclusion. The problem, as all three admitted, was to find the mathematical means of proving it.
Anxious for a solution, Sir Christopher offered to give a valuable book to the friend who could deliver solid proof within the next two months. Hooke, to whom modesty was a stranger, claimed that he already possessed the required proof. However, he would keep it a secret for the time being so that his friends "might know how to value it, when he should make it public."
The deadline came and went without a word from Hooke, and spring soon turned to summer. Finally, after seven months of silence, Halley decided to act. He cast an anxious eye in the direction of Cambridge and made a fateful decision. He would visit Trinity College to see if the secretive Isaac Newton could shed some light on the matter.
Newton was living an even more isolated existence than before. Some years earlier his mother, Hannah, had caught what was described as a "malignant fever," a catchall term for any number of serious illnesses. Newton hurried to Woolsthorpe and took charge of Hannah's care, dressing her blisters and sitting up all night at her bedside. Unfortunately, she was beyond saving and died some days later. As her first child, Isaac inherited most of her property, making him an independently wealthy man.
A more recent blow was the departure from Cambridge of John Wickins, Newton's roommate of 20 years. Wickins became minister of the parish church at Stoke Edith, married, and fathered a son named Nicholas. Though they had been through much together, the two friends would never meet again and exchanged no more than a letter or two in the coming years.
Newton's prescription for loneliness was work, work, and more work. Humphrey Newton, Isaac's assistant and distant relative, observed: "I never saw him take any Recreation or Pastime, either in Riding out to take the Air, Walking, Bowling, or any other Exercise whatever, Thinking all Hours lost that was not spent in his Studies, to which he kept so close that he seldom left his Chamber." The reclusive professor had even more time to himself because Cambridge students were little interested in natural philosophy. Humphrey noted that his employer often lectured to the classroom walls. Finally, he stopped going to the lecture hall altogether.
The absent-minded professor
Over the years, Newton became the very model of the absent-minded professor. He ate little and often had to be reminded by Humphrey that the dinner delivered to his room had gone untouched. He would express surprise, walk over to the table, and eat a bite or two standing up. "I cannot say," Humphrey noted, that "I ever saw Him sit at [the] Table by himself."
Newton rarely went to bed until two or three in the morning and often slept in his clothes. He rose at five or six, fully refreshed. His long, silver hair was seldom combed, his stockings hung loose, and his shoes were down at the heels. On those rare occasions when he went out, it was usually to take a meal in the dining hall, overlooked by the giant portrait of Henry VIII.
“There goes the man that writt a book that neither he nor anybody else understands.”
But instead of crossing the Great Court, as he should have, Humphrey noted that Newton would turn into Trinity Street, stop after realizing his mistake, turn back, and then "sometimes without going into the Hall return to his Chamber again."
In good weather Newton was occasionally seen taking a stroll in his garden. Picking up a stick, he drew figures on the graveled walks, which the other Fellows sidestepped for fear of ruining a work of genius. According to Humphrey, "When he has some Times taken a turn or two he has made a sudden stand, turn'd himself about, run up the Stairs like another Archimedes, and with a eureka fallen to write on his Desk standing, without giving himself the Leisure to draw a chair to sit down on." So absorbed was Newton that he lost track of time and place. The days and dates on many of the papers recording his experiments do not match those of the calendar.
"I have calculated it"
As he stepped down from his coach on reaching Cambridge, Halley hardly knew what to expect. He had exchanged no letters with Newton and had met him only once before, in London. Furthermore, Hooke's name was bound to come up. Despite their mutual pledge not to kindle any more coal, Newton and Hooke were still feuding over scientific matters both great and small.
To Halley's surprise, and great relief, Newton was flattered by his visit. They talked of many things before the astronomer revealed his reason for seeking Newton out. What kind of curve, Halley finally asked, "would be described by the planets supposing the force of attraction towards the sun to be reciprocal to the square of their distance from it?"
Without hesitation, Newton responded that it would be an ellipse! Taken aback, Halley asked him how he knew it.
"I have calculated it," Newton replied.
When Halley asked to see the calculations, Newton began rummaging through stacks of papers while his excited visitor held his breath. As luck would have it, he was unable to find the critical documents, forcing Halley to depart without the written proof he required. However, all was not lost. Before they parted company, Newton promised to redo his calculations and send them on to Halley in London.
Seeds of a new science
Once again Halley's patience was sorely tested. Three months passed without a single word from Cambridge. What Halley did not know was that Newton had solved the problem of the elliptical orbit by employing a different mathematical method than before, but he was not satisfied. He spent much of those three months working on a nine-page manuscript titled De Motu Corporum in Gyrum (On the Motion of Revolving Bodies). Finally, in November 1684, nearly 11 months after Halley, Hooke, and Wren had taken part in the discussion that had started it all, a copy of De Motu was delivered to London.
Halley was astounded, for he held in his hands the mathematical seeds of a general science of dynamics—the study of the relationship between motion and the forces that affect it. Not wasting a moment, he headed north to Cambridge a second time. He must find out whether Newton would agree to have his paper set before the Royal Society and published for all the scientific world to see.
On December 10, Halley rose to address his fellow members of the Royal Society and its new president, Samuel Pepys. He gave an account of his most recent visit with Newton and of a "curious treatise," De Motu. Halley's report was duly recorded in the minutes, and he was urged to push Newton to publish his little work as soon as possible.
At first Newton may have thought of De Motu as an end in itself. But once his creative powers were loosed, there was no checking their momentum. "Now that I am upon this subject," he wrote Halley in January 1685, "I would gladly know the bottom of it before I publish my papers." In his mind's eye De Motu would serve as the germ of his masterpiece, the greatest book of science ever written. Thus began 18 months of the most intense labor in the history of science. In April 1686 Newton presented and dedicated to the Royal Society the first third of his illustrious work. He titled it Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), commonly referred to as the Principia.
The book that nobody understands
The Principia was not an easy book to read in Newton's day, nor is it now. After it was published, Newton was passed on the street by a student who is said to have remarked, "There goes the man that writt a book that neither he nor anybody else understands." The same would be said of Einstein when his papers on the theory of relativity were published some 250 years later.
By flinging gravity across the void, Isaac Newton united physics and astronomy in a single science of matter in motion.
When we step back and look at Newton's universe from afar, what is it, exactly, that we see? According to the Principia, we peer into a seemingly endless void of which only a tiny part is occupied by material bodies moving through the boundless and bottomless abyss. Newton's followers would liken it to a colossal machine, much like the clocks located on the faces of medieval buildings. All motions are reduced to mechanical laws, a universe where human beings and their world of the senses have no effect. Yet for all its lack of feeling, it is a realm of precise, harmonious, and rational principles. Mathematical laws bind each particle of matter to every other particle, barring the gate to disorder and chaos.
By flinging gravity across the void, Isaac Newton united physics and astronomy in a single science of matter in motion, fulfilling the dreams of Pythagoras, Copernicus, Kepler, Galileo, and countless others in between. And while Newton was unable to discover the true cause of gravity itself, a giant riddle still, the laws he formulated provided convincing proof that we inhabit an orderly and knowable universe.
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