Nicolaus Copernicus

Professional Life

However, not everyone at the Royal Academy was enthusiastic about Newton's discoveries in optics. Among the dissenters was Robert Hooke, one of the original members of the Royal Academy and a scientist who was accomplished in a number of areas, including mechanics and optics. In his paper, Newton theorized that white light was a composite of all colors of the spectrum, and that light was composed of particles. Hooke believed that light was composed of waves. Hooke quickly condemned Newton's paper in condescending terms, and attacked Newton's methodology and conclusions.

Hooke was not the only one to question Newton's work in optics. Renowned Dutch scientist Christiaan Huygens and a number of French Jesuits also raised objections. But because of Hooke's association with the Royal Society and his own work in optics, his criticism stung Newton the worst. Unable to handle the critique, he went into a rage—a reaction to criticism that was to continue throughout his life.

Newton denied Hooke's charge that his theories had any shortcomings, and argued the importance of his discoveries to all of science. In the ensuing months, the exchange between the two men grew more acrimonious, and soon Newton threatened to quit the society altogether. He remained only when several other members assured him that the Fellows held him in high esteem.

However, the rivalry between Newton and Hooke would continue for several years thereafter. Then, in 1678, Newton suffered a complete nervous breakdown and the correspondence abruptly ended. The death of his mother the following year caused him to become even more isolated, and for six years he withdrew from intellectual exchange except when others initiated correspondence, which he always kept short.

During his hiatus from public life, Newton returned to his study of gravitation and its effects on the orbits of planets. Ironically, the impetus that put Newton on the right direction in this study came from Robert Hooke. In a 1679 letter of general correspondence to Royal Society members for contributions, Hooke wrote to Newton and brought up the question of planetary motion, suggesting that a formula involving the inverse squares might explain the attraction between planets and the shape of their orbits.

Subsequent exchanges transpired before Newton quickly broke off the correspondence once again. But Hooke's idea was soon incorporated into Newton's work on planetary motion, and from his notes it appears he had quickly drawn his own conclusions by 1680, though he kept his discoveries to himself.

In early 1684, in a conversation with fellow Royal Society members Christopher Wren and Edmond Halley, Hooke made his case on the proof for planetary motion. Both Wren and Halley thought he was on to something, but pointed out that a mathematical demonstration was needed. In August 1684, Halley traveled to Cambridge to visit with Newton, who was coming out of his seclusion. Halley idly asked him what shape the orbit of a planet would take if its attraction to the sun followed the inverse square of the distance between them (Hooke's theory).

Newton knew the answer, due to his concentrated work for the past six years, and replied, "An ellipse." Newton claimed to have solved the problem some 18 years prior, during his hiatus from Cambridge and the plague, but he was unable to find his notes. Halley persuaded him to work out the problem mathematically and offered to pay all costs so that the ideas might be published.

Publishing 'Principia'

The work offers an exact quantitative description of bodies in motion in three basic laws: 1) A stationary body will stay stationary unless an external force is applied to it; 2) Force is equal to mass times acceleration, and a change in motion is proportional to the force applied; and 3) For every action, there is an equal and opposite reaction. These three laws helped explain not only elliptical planetary orbits but nearly every other motion in the universe: how the planets are kept in orbit by the pull of the sun’s gravity; how the moon revolves around Earth and the moons of Jupiter revolve around it; and how comets revolve in elliptical orbits around the sun.

The laws also allowed Newton to calculate the mass of each planet, calculate the flattening of the Earth at the poles and the bulge at the equator, and how the gravitational pull of the sun and moon create the Earth’s tides. In Newton's account, gravity kept the universe balanced, made it work, and brought heaven and earth together in one great equation.

Upon the publication of the first edition of Principia, Robert Hooke immediately accused Newton of plagiarism, claiming that he had discovered the theory of inverse squares and that Newton had stolen his work. The charge was unfounded, as most scientists knew, for Hooke had only theorized on the idea and had never brought it to any level of proof. However, Newton was furious and strongly defended his discoveries.

He withdrew all references to Hooke in his notes and threatened to withdraw from publishing the subsequent edition of Principia altogether. Halley, who had invested much of himself in Newton's work, tried to make peace between the two men. While Newton begrudgingly agreed to insert a joint acknowledgement of Hooke's work (shared with Wren and Halley) in his discussion of the law of inverse squares, it did nothing to placate Hooke.

As the years went on, Hooke's life began to unravel. His beloved niece and companion died the same year that Principia was published, in 1687. As Newton's reputation and fame grew, Hooke's declined, causing him to become even more bitter and loathsome toward his rival. To the bitter end, Hooke took every opportunity he could to offend Newton. Knowing that his rival would soon be elected president of the Royal Society, Hooke refused to retire until the year of his death, in 1703.