Robert Hooke, Natural Philosopher

Hooke and his contemporaries

Most who have studied some science will have come across Hooke's Law, that the extension of a spring is proportional to the applied force, but few will know of his theory of combustion or that his Micrographia was the first book on microscopy; that his astronomical observations were some of the best seen at the time and that there is a Hooke crater on the moon, named in his honour; that he contributed to knowledge of respiration, insect flight and the properties of gases; that his work on gravitation preceded Newton's; that he invented the universal joint and the anchor escapement in clocks and numerous other mechanical devices; and that he was an architect of distinction and a Surveyor for the City of London after the Great Fire. Everyone knows the names of Newton and Wren, but Hooke was as distinguished and deserves similar recognition. That he lacks such recognition stems from a mixture of temperament and bad luck.

In 1648 Hooke entered Westminster School under Dr Richard Busby, going on to Christ Church Oxford in 1653. It was here that he met some of those who would be lifelong companions in science and in the Royal Society. Many have become legendary: among his contemporaries were Robert Boyle, aristocrat and experimentalist; the mathematician John Wilkins; William Petty, economist and inventor; the astronomers Jeremiah Horrocks of Liverpool, John Flamsteed and Edmond Halley (the first two Astronomers Royal) and Christopher Wren, who was Savilian Professor of Astronomy at Oxford (1661) before he became more famous as an architect. Add to this Newton, the French astronomer Cassini, Christiaan Huygens, the patronage of King Charles II - and the legacy of Kepler, Galileo and Tycho Brahe, all of who had died in the first half of the 17th century - and Hooke's scientific environment can be seen to be rich indeed.

Science and technology

Hooke's Cometa illustrations show that he was an accomplished draftsman © Hooke's approach heavily influenced the change from Aristotelian medieval natural philosophy to scientific endeavour in a modern sense. His experiments represent the first examples of a carefully planned series of investigations, using purposely designed apparatus. Hooke understood very well that although technology can progress without science, science needs technology; measuring instruments were required to extend human perception, and these instruments had to be accurately made. Much of his effort was directed towards the improvement of measuring devices, effort that capitalised on mechanical skills he had practiced as a child.

Hooke held three appointments of considerable significance. From 1662 he was appointed Curator of Experiments at the newly formed Royal Society; his task was '..to furnish the Society [once a week] with three or four considerable experiments...', so it is as well that ideas came to him very quickly. As a result he seldom worked out his researches to their fullest extent before moving on, and indeed for some of them did not have the mathematical expertise. Other people, more focused, often developed the work to a point where they would justifiably receive credit for it. This frequently affronted Hooke since the indebtedness to his work was not always acknowledged, and he was often acerbically critical of the work of others. In this trait lay the origins of his major disagreements, with Newton and with Huygens, the latter over the invention of the spring balance escapement in clocks.

In 1664 Sir John Cutler founded a lectureship in mechanics for Hooke, though never actually paid him for these; and Hooke was appointed Gresham Professor of Geometry with rooms in Gresham College, in Bishopsgate Street, where he lived for the rest of his life.

Hooke the astronomer

Hooke's drawing illustrating his observation of comets © Astronomy was the science that Hooke pursued for longer than any other - he had a telescope permanently installed in his rooms at Gresham College, and the time when he was most active as an architect was also the time where he made great progress in astronomical observations.

The key to these was, as ever, the instrument. Hooke did much work on the development of the telescope, in particular recognising that the diameter of the object lens was crucial in capturing the maximum amount of light. In experiments to find the effect of lens diameter he invented the familiar iris diaphragm. He devised numerous ways of reducing the physical size of telescopes of long focal length, and machinery with which to move them. From this came his invention of the universal joint, found now in all motor vehicles.

The surface of planets particularly interested him; in 1664 and 1666 he reported spots as surface features on Jupiter; he claimed in later years to have measured the rotation of the planet, though the published credit belongs to Cassini. Micrographia (1665) contains detailed images of the lunar surface, observations which led to experiments in which Hooke attempted to explain how the craters could have been formed.

Late 1664 saw the arrival of a prominent comet, observed thoroughly by Hooke. The measurement of angles is critical in astronomy since reliable theory or explanation relies on the measurement of the size of remote objects by the angle they subtend at the observer's eye. Hooke gave much thought and exercised much ingenuity in solving this problem, but his designs were sometimes beyond the manufacturing capabilities of the day. Flamsteed, the Astronomer Royal, was particularly frustrated by the failure of some of Hooke's instruments to live up to their promise. In 1677 a second comet appeared, at which time Hooke published his work and his speculations on their nature. In particular he showed that comets have a solid nucleus, and that they generate their own light.

The title page of Hooke's Cometa © The planets cannot be observed for long without wondering about the nature of gravity, work that was to result in Hooke's infamous disagreement with Newton - an unwise enmity. Hooke needed to know the reasons for the shape of planetary orbits and wanted a mechanical explanation of gravity's effects. He started experiments in 1662 designed to measure gravity, but results were indecisive; however his observations of comets and planets enabled him by 1674 to propose that gravity affected all material bodies, that gravitational attraction can cause bodies to move in orbits, and that the closer the bodies the greater the attraction. By 1680 he had essentially refined the latter into the inverse square law.

Hooke and Newton

Hooke corresponded with Newton regularly, but was not enough of a mathematician to formulate gravitation in the Newtonian sense. When Newton published his work on gravity in Principia, Hooke felt that he had not been given enough credit for his earlier work, a view that Newton never forgave. Newton wrote to Halley (who was paying for the publication of Principia) in strong terms over the argument. The relationship became more and more acrimonious, such that Hooke became secretive in his work and Newton is said to have delayed the publication of Opticks until after Hooke's death. It has even been suggested that Newton destroyed Hooke's portrait.

Hooke's arguments with Newton, too powerful a man to be trifled with, and with Huygens has tended to overshadow his achievements and the general respect shown to his work, as well as his energy that was appreciated by those familiar with his company. There were also major disagreements with Oldenburg, President of the Royal Society, but even Wren, mild-mannered, found Oldenburg difficult.

Hooke the architect

At the same time as his astronomical observations were generating such interest, Hooke was immensely active as an architect. He was involved in the building of the Royal Observatory at Greenwich, but his role as Surveyor to the City of London after the Great Fire of 1666 is poorly appreciated. This is partly due to the fame of his partner Wren; partly because the works in which Hooke was largely involved were things such as boundary disputes and other planning matters, culverts, bridges - not major architectural works.

His radical plan for the rebuilding of the City was not adopted (possibly because of difficulties with boundaries) and does not survive. Of his major architecture only three examples remain: the Monument, usually attributed to Wren but certainly Hooke's; Ragley Hall in Warwickshire; and Willen Church in Buckinghamshire, built for Dr Busby. Neither of the latter two is in original condition. His building for the Royal College of Physicians and his magnificent Bethlehem Hospital (the 'Bedlam') were both demolished in the 19th century. Two statues from the Bedlam are in the Victoria and Albert Museum.

In the last year of his life Robert Hooke became blind and bedridden with swollen legs, suggestive of diabetes. His mind remained active. He died in his rooms at Gresham College, in Bishopsgate Street, on 3rd March 1703.

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Robert Hooke and the Royal Society by Richard Nichols (Book Guild, 1999)

About the author

Rod Beavon was born and educated in Birmingham. After a time as a technician at the University of Birmingham Medical School and also in the Department of Physics, he spent three years as a school technician. He gained Grad.RIC and PhD from the University of Aston in Birmingham, and is now Head of Science at Westminster School in London. Has been involved in examining Chemistry at O, GCSE and A level since 1974, and is now Chief Examiner for Edexcel (London) Examinations in Chemistry.