Pieter van Musschenbroek (14.03.1692 — 19.09.1761) was a Dutch physicist. He was born in Leiden. He graduated from the University of Leiden (1715). He was professor at the universities of Duisburg (1719—23) and Utrecht (1723-40), and from 1740 at Leiden.
His research concerned electricity, heat and optics. In 1745, independently of E. Kleist, he invented the first capacitor, the Leyden jar, and carried out a number of experiments with it. He was the first to draw attention to the physiological action of an electric discharge. He carried out the first experimental studies of the thermal expansion of solids, which he recorded with the pyrometer he invented (1731); in 1747 he used it as a thermometer to measure the melting temperature of some metals. He studied the selective absorption of different colours in air and the strength of building materials. He gave tables of the specific gravities of many bodies (1751). He was the author of the first systematic course of physics, and his two-volume “Introduction to Natural Philosophy”, published in 1762, was an encyclopedia of the physical knowledge of its time.
A Fellow of the Royal Society, a member of the St Petersburg Academy of Sciences (1754) and a corresponding member of the Paris Academy of Sciences.