Robert Hooke
born July 18, 1635, Freshwater, Isle of
Wight, Eng.
died March 3, 1703, London
English physicist who discovered the law of
elasticity, known as Hooke’s law, and who did
research in a remarkable variety of fields.
In 1655 Hooke was employed by Robert Boyle to
construct the Boylean air pump. Five years
later, Hooke discovered his law of elasticity,
which states that the stretching of a solid body
(e.g., metal, wood) is proportional to the force
applied to it. The law laid the basis for
studies of stress and strain and for
understanding of elastic materials. He applied
these studies in his designs for the balance
springs of watches. In 1662 he was appointed
curator of experiments to the Royal Society of
London and was elected a fellow the following
year.
One of the first men to build a Gregorian
reflecting telescope, Hooke discovered the fifth
star in the Trapezium, an asterism in the
constellation Orion, in 1664 and first suggested
that Jupiter rotates on its axis. His detailed
sketches of Mars were used in the 19th century
to determine that planet’s rate of rotation. In
1665 he was appointed professor of geometry in
Gresham College. In Micrographia (1665; “Small
Drawings”) he included his studies and
illustrations of the crystal structure of
snowflakes, discussed the possibility of
manufacturing artificial fibres by a process
similar to the spinning of the silkworm, and
first used the word cell to name the microscopic
honeycomb cavities in cork. His studies of
microscopic fossils led him to become one of the
first proponents of a theory of evolution.
He suggested that the force of gravity could
be measured by utilizing the motion of a
pendulum (1666) and attempted to show that the
Earth and Moon follow an elliptical path around
the Sun. In 1672 he discovered the phenomenon of
diffraction (the bending of light rays around
corners); to explain it, he offered the wave
theory of light. He stated the inverse square
law to describe planetary motions in 1678, a law
that Newton later used in modified form. Hooke
complained that he was not given sufficient
credit for the law and became involved in bitter
controversy with Newton. Hooke was the first man
to state in general that all matter expands when
heated and that air is made up of particles
separated from each other by relatively large
distances.
