Giovanni Alfonso Borelli (28.1.1608 — 31.12.1679) was an Italian scientist and a member of the Accademia del Cimento in Florence. A pupil of Galileo. He was born in Naples. He was educated in Florence and Rome. In 1649 — 56 he was professor at the University of Messina, and in 1656 — 67 at the University of Pisa.
His research concerned physics, astronomy and physiology. He held that the motions of the heavenly bodies are caused by the interaction of two forces (centrifugal and centripetal) and that the planets gravitate towards the Sun for the same reason as heavy bodies do towards the Earth (1666). Together with V. Viviani he measured in 1656 the speed of sound in air and obtained a more accurate value than his predecessors. In 1667 he established the laws of the impact of inelastic bodies. He studied capillary phenomena, atmospheric pressure and the surface tension of water. In 1670 he discovered that the height to which a liquid rises in a capillary is inversely proportional to its diameter. He invented the heliostat, improved the thermometer and built a siphon barometer.
In his work “On the motion of animals”, published in 1680 — 81 (posthumously), he laid the foundations of iatromechanics.