Robert Hooke (18.07.1635-3.03.1703) was an English physicist, a Fellow of the Royal Society (1663) and its secretary in 1677 — 83. He was born on the Isle of Wight. He studied at the University of Oxford, where he became an assistant to R. Boyle. From 1665 he was professor at the University of London.
His work was in the field of heat, elasticity, optics and celestial mechanics. About 1660, together with R. Boyle, he improved Guericke's air pump, and with C. Huygens he established (1665) the fixed points of the thermometer — the melting point of ice and the boiling point of water. In 1668 he showed that the boiling and melting points of all bodies are constant. He put forward (1665) the hypothesis that heat is a kind of motion of the particles of a body. In 1660 he discovered the law of elasticity for solids (Hooke's law).
He improved the microscope (1665), which enabled him to carry out a number of microscopic investigations, in particular to observe thin films (soap bubbles, oil films and the like) in beams of light and to study the structure of plants. The latter led him to the discovery of the cellular structure of organisms. In his work “Micrographia” (1665), drawing on his own microscopic investigations, he was the first to describe the cells of elder, dill, carrot and other plants, and he himself introduced the term “cell”. In “Micrographia” Hooke also gives his own theory of colours; he explains the colouring of thin films by the addition of light pulses reflected from the upper and the lower surfaces, and compares the propagation of light from a source with the spread of waves on water from a stone that has been thrown into it. He laid the foundations of physical optics. He was an active opponent of Newton's corpuscular theory of light, and he objected too to the view that white light is the sum of simple colours. In 1672 he carried out experiments on the diffraction of light similar to those of F. Grimaldi; he held to the wave theory of light and put forward the hypothesis that light waves are transverse.
In “A Treatise on the Motion of the Earth” (1674) he put forward the idea of gravitation and gave his own system of the universe. In 1680 he concluded that the force of gravitation is inversely proportional to the square of the distance. So, after I. Newton presented the manuscript of his “Principia” to the Royal Society in 1686, Hooke insisted on his own priority in the discovery of the law of universal gravitation. Newton, however, declared that this relationship had long been known to him and that he had in due course communicated it in a letter to C. Huygens.
He was the author of numerous inventions, in particular the barometer (1665), the maximum thermometer (1691) and others.