Philipp Johann von Jolly (26.09.1809-24.12.1884) was a German experimental physicist. He was born in Mannheim. He studied at the universities of Heidelberg and Vienna. From 1834 he was professor at the University of Heidelberg and from 1846 at the University of Munich (in 1846 he set up in Heidelberg the first university physics laboratory in Germany).
His work was in the field of mechanics, molecular physics and photometry. In 1874 he improved the air thermometer and determined the coefficient of expansion of air (0.36695 deg). He built a sensitive spring balance, a eudiometer and an air pump. He determined the mass and the density of the Earth, obtaining the value 5.692 g/cm3 for the mean density of the Earth (1878). He studied osmosis.