Robert Hooke - Scientist and Inventor
Robert Hooke can be described as one of the most inventive, versatile, and prolific scientists of the eighteenth century; however, his pedigree has been overshadowed by his contemporary, Isaac Newton. Newton and Hooke were rivals in the hotbed of London’s seventeenth century scientific community. Though every school child has heard the name of Isaac Newton, few are aware of Robert Hooke, a man who stood side-by-side with the intellectual giant Newton to help unravel the mysterious forces of the universe. Yet Hooke was much more than a scientist; he was a man who got things done. When London nearly burnt to the ground in early September 1666, Hooke was there helping to design and rebuild the city. He overcame many obstacles to achieve his many accomplishments, including his misshapen body and fragile health, which only seemed to add energy to this man of robust drive and success.
Robert Hooke was born on July 18, 1635, on the Isle of Wight off the southern coast of England, in the village of Freshwater. His father was a priest in the Anglican Church. Hooke came from a large family and was expected to continue the path of his father. His brothers became ministers, like their father, but Robert chose a different path. He was a sickly child and often suffered from painful headaches that would interrupt his studies. From an early age he was interested in things that were not typical for a young child. He loved to build mechanical contraptions and see how things worked, studied nature, flora, and fauna, and watched the stars. He enjoyed drawing and from an early age he showed great talent for art. He was enrolled in Westminster School in London under the Headmaster of the school Richard Busby; they would become lifelong friends. There, he quickly mastered the classical languages of Greek and Latin, and studied Hebrew as well as philosophy, and theology. During the time spent at school he continued his study of art and delved into his own study of natural sciences. When exposed to mathematics he quickly devoured the first six books of Euclid’s Elements in a week. After completing his education at Westminster, he went to Oxford University in 1653.
Robert Boyle and the Air Pump
At Oxford, he met the wealthy scientist and philosopher, Robert Boyle, who hired Hooke as his assistant to help him with his scientific experiments. Boyle learned of a new invention by the German inventor Otto von Guericke that could remove air from a chamber to create a partial vacuum. Boyle put Hooke to work on improving Guericke’s crude pump to produce the forerunner of the modern air pump. With the pump and Hooke’s help, Boyle discovered in 1662 that air was not only compressible but that this compressibility varied with pressure according to a single inverse relationship. This relationship is fundamental to the study of gases and has become known as Boyle’s Law.
When a ship set sail on a long voyage, it was imperative that the mariners knew their exact location, which required a latitude and a longitude. The latitude could be readily determined with great accuracy by measuring the position of the stars with a sextant. The measurement of the longitude was different matter, however; it required that the exact time be known. The rolling motion of the ship and the wide temperature variations made construction of an accurate ship-board chronometer in the seventeenth century very challenging. On land, a pendulum clock can be made to be quite accurate, whereas at sea, this type of clock didn’t work well. Hooke reasoned that an accurate clock might be constructed by the “use of springs instead of gravity for the making of a body to vibrate in any posture.” By attaching a spring to the arbor of the balance wheel, he would replace the pendulum with a vibrating wheel that could be moved because it oscillated around its own center of gravity. Thus, the idea behind the modern watch was conceived.
Hooke sought wealthy backers for his chronometer and enlisted financial support from Robert Moray, Robert Boyle, and Viscount William Brouncker. A patent was prepared for the chronometer, but before the deal could be completed, Hooke backed out. Apparently, his demands were greater than the three backers could afford.
In 1674, the Dutch scientist and inventor Christiaan Huygens constructed a watch controlled by a spiral spring attached to the balance. Hooke suspected that Huygens had stolen his design and cried foul. To prove his point, Hooke worked with the clock maker Thomas Tompion to make a similar watch as a present to the king. The watch bore the inscription “Robert Hooke invent. 1658. T Tompion fecit 1675.” Regardless of Hooke’s assertion, that the watch of 1658 employed a spiral spring or indeed worked is unclear. Neither Hooke’s nor Huygens’s watches worked sufficiently well enough to be used as a marine chronometer for determination of longitude. Regardless of whose watch worked or didn’t work or when, Hooke’s inventiveness was significant to the advancement of the chronometer.
Around 1660, a prominent group of scientists and natural philosophers, including Hooke, founded the Royal Society. The association itself gathered “naturalists” who did not look at doctrine through the eyes of the official church, but their approach was justified by the methodology as well as the philosophy of Francis Bacon.
Shortly after the founding of the Royal Society in 1662, Hooke was involved in the work of the association because of his skills and creativity, as well as a long-standing cooperation with Boyle. By the recommendation of one of the members, Robert Hooke became the Curator of Experiments, making him responsible for preparing and demonstrating “three or four considerable experiments” each week. This position placed on Hooke a large responsibility that few people could accomplish; researching, designing, building, and demonstrating more than one interesting experiment per week with limited resources and little help was indeed a tall order. Hooke seemed to thrive in this environment, performing at his intellectual and mental peak during the first fifteen years as curator.
Hooke was known by his colleagues as an extraordinary scientist but with not a very pleasing personality. He was quite suspicious of other inventors and scientists and would often accuse them of stealing his ideas. Sometimes the professional rivalries grew into serious long-standing conflicts. The ones who knew him say that it was difficult for him to open up to anyone and sometimes he would show signs of jealousy and envy with colleagues.
One of Hooke’s most important discoveries is related to the field of gravity and gravitational ratios. The generally accepted standpoint in science up to that time was that there was an invisible and undetectable fluid that permeated the universe, called “aether,” and it was responsible for the transmission of energy between the celestial bodies. Thus, the aether was viewed as a transferor of energy that has attracted or repulsed the celestial bodies. Robert Hooke introduced quite a revolutionary theory, which argued that “attraction is a characteristic of gravity.” He later elaborated on his theory and stated that gravity is valid for all the celestial bodies as well as that it was stronger as the bodies were closer, and that it weakened as the bodies were further from each other. Gravity, he said, is “such a power, as to cause bodies of a similar or homogeneous nature to be moved on toward another until they are united.” He entered into a series of correspondences regarding gravity with Isaac Newton, who published his master work Philosophiae Naturalis Principia Mathematica in 1687. In the Principia, Newton defined his three laws of motion and described the mechanics of elliptical orbits and gravitational attraction. Hooke cried foul once again–claiming Newton had stolen his work.
Though Hooke had written as early as 1664 on his ideas of the gravitational attraction between celestial bodies, he lacked the mathematical rigor developed by Newton. Newton himself acknowledged in 1686 that the correspondence with Hooke stimulated him to show that an elliptical orbit around a central attracting body placed at one focus of an elliptical orbit entails an inverse square force. Hooke did not discover the law of universal gravitation; rather, he set Newton on the correct approach to orbital dynamics and for this he deserves much credit.
The work of Robert Hooke that is most remembered is the book he published in 1665, Micrographia. This was the first major publication of the Royal Society, covering Hooke’s observations through a microscope and telescope. The book contained profuse illustrations of microscopic views of minerals, plants, animals, snowflakes, and even his own dried urine. The detail in the drawings spoke to his artistic and scientific abilities. The exquisite eighteen-inch-long close-up drawing of a flea is hardly less startling today than it would have been over three hundred years ago. Hooke is credited with coining the term “cell” for describing biological organisms, for the resemblance of the cells of a honeycomb to plant cells.
In addition to his microscopic observations, the book also contained Hooke’s theories on the science of light. At that time, very little was known about the nature of light and color, but it was a hot topic of research and debate within scientific circles, including among Hooke, Newton, and Christiaan Huygens. Hooke viewed nature with a mechanical philosophy, believing light consisted of pulses of motion transmitted through a medium in a wavelike manner. Hooke examined phenomena of colors of thin transparent films and noticed that colors are periodic, with the spectrum repeating itself as the thickness of the film increased. Newton’s experiments in optics had their origin in this reading of Micrographia, which became the foundation of Book Two of Opticks. Newton and Hooke engaged in an exchange of letters on the subject, sometimes heated, defending their position on the nature of light and color.
One of nature’s curiosities that perplexed seventeenth century science was the presence of fossils in a variety of locations, and their origin. These small, or sometimes large, stony remnants of the past, that were similar to shells or small organisms, had perplexed people since ancient times. The prevailing theory was that fossils were not remnants of past life forms, but rather made by the Earth to resemble, but were not previously living organisms. Hooke’s examination of petrified wood and fossils in Micrographia lead him to believe that fossils were ancient life forms that had been preserved by an exchange of mud or clay with the dead organism. In a later lecture on the subject of geology and fossils he concluded, “That there may have been divers species of things wholly destroyed and annihilated, and divers others changed and varied, for since we find that there are some kind of animals and vegetables peculiar to certain places, and not found elsewhere…” Hooke’s work on fossils and geology thrust a modern light on beliefs that were long held by ancient philosophers and theologians.
Robert Hooke. Micrographia
During the years following the publishing of the Micrographia, Hooke found time to conduct experiments before the Royal Society and deliver a series of lectures while continuing his work as a surveyor. During the 1670s he published a series of six short works that were combined into a single volume, the Lectiones Cathlerianae. One of the important discoveries revealed in the lectures was the law of elasticity, to which his name is still associated. The law of elasticity states that within the elastic limits of a material, the fractional change in size of an elastic material is directly proportional to the force per unit area. This result is very important to modern engineers as they design buildings, bridges, and just about every type of mechanical device.
The Great London Fire
What started as a simple fire in a bakery on Pudding Lane on Sunday September 2, 1766, turned into a fire storm fanned by wind that spread the fire throughout the city of London. By Monday the fire had pushed north into the city and by Tuesday much of the city was engulfed, including St. Paul’s Cathedral. The fire was finally put out when the strong east wind subsided, and the Tower of London garrison used gunpowder to create a backfire to halt the advance of the fierce flames. By the time the fire was under control, it had destroyed over 13,000 homes, nearly one hundred churches, and most of the public buildings. Lack of decisive action and trained firefighters has been credited with allowing the fire to spread so rapidly. The city had to be rebuilt and Robert Hooke wanted to help.
Hooke reacted rapidly to the destruction and developed a master plan to rebuild the city in a rectangular grid. The plan won approval by the city fathers but was never completely implemented. The city appointed Hooke as one of the three surveyors to reestablish property lines and supervise the rebuilding. Hooke worked alongside another technical expert, Sir Christopher Wren, who was a fellow member of the Royal Society. The position of surveyor turned out to be a financial windfall for Hooke as well as providing an outlet for his artistic talents. Hooke was credited with designing and supervising the construction of a number of prominent buildings, such as the Royal College of Physicians, Bedlam Hospital, and the Monument. His work in the reconstruction of London would take over a decade and added to his prestige as a leading scientific and technical expert.
In 1696, Hooke’s health began to fail. Richard Waller, secretary of the Royal Society, described Hooke’s decline, “He had for several years been often taken with giddiness in his head, and sometimes in great pain, little appetite, and great faintness, that he was soon very much tired from walking, or any exercise…” Robert Hooke died on March 3, 1703, in his room at Gresham College, where he had lived for the past forty years. Waller reported on Hooke’s passing, “His corps was decently and handsomely interred in the church of St Hellen in London, all the members of the Royal Society then in town, attending his body to the grave, paying the respect due to his extraordinary merit.”
Robert Hooke will long be remembered for his numerous contributions to science, architecture, and technology. Many of the modern conveniences we have grown accustomed to have their origins directly or indirectly in the pioneering work of this unsung hero of science.
Chronology of Robert Hooke
July 18, 1635 – Born in Freshwater, Isle of Wight, Great Britain.
1649 to 1653 – Attends Westminster School, under the headship of Dr. Richard Busby.
1657 or 1658 – Begins to study the pendulum and clock making.
1653 – Attends Christ Church, Oxford.
1657 to 1662 – Works for Robert Boyle as a paid assistant.
1658 – Makes a working air pump for Boyle.
1660 – Royal Society is founded.
1662 – Becomes curator of experiments for the Royal Society.
1663 – Graduates with Master of Arts from Oxford.
May 1664 – Observes a spot on the planet Jupiter and with continued observations proves the planet rotates.
September 1664 – Moves to Gresham College.
January 1665 – Elected Curator to the Royal Society at a salary of £30 per year.
January 1665 – Micrographia is published.
March 1665 – Becomes Gresham Professor of Geometry.
September 1666 – Great fire of London.
October 1666 – Nominated as one of London’s three representatives on the Commission to survey the ruined city.
December 1671 – Most of the destroyed homes in London have been rebuilt and the city is returning to normal.
February to June 1672 – Hooke and Newton are in a dispute over the nature of light and color.
1674 – Publishes his ideas about the “systems of the world.”
July 1675 – Helps design the Greenwich Observatory.
January to February 1676 – Hooke and Newton exchange conciliatory letters to resolve their differences.
June 1676 – Begins romantic relationship with Grace Hooke.
November 1679 to January 1780 – Hooke and Newton correspond on planetary motion and the inverse square law of gravitation.
January 1684 – Christopher Wren challenges Hooke to explain the motion of planetary bodies using the inverse square law. Hooke fails.
March 3, 1703 – Dies in London.
Note: All dates are per the new style calendar.
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