Bridgman entered Harvard University in 1900, and studied physics through to his Ph.D.. From 1910 until his retirement, he taught at Harvard, becoming a professor in 1919. In 1905, he began investigating the properties of matter under high pressure. A machinery malfunction led him to modify his pressure apparatus; the result was a new device enabling him to create pressures eventually exceeding 100,000 kgf/cm² (10 GPa). This was a huge improvement over previous machinery, which could achieve pressures of only 3000 kgf/cm² (0.3 GPa). This new apparatus led to a plethora of new findings, including on the effect of pressure on electrical resistance, and on the liquid and solid states. Bridgman is also known for his studies of electrical conduction in metals and properties of crystals. He developed the Bridgman seal and is the eponym for Bridgman's thermodynamic equations. Bridgman made many improvements to his high pressure apparatus over the years, and attempted the synthesis of diamond many times. He never succeeded. His writings on the philosophy of science advocated operationalism. He was also one of the 11 signatories to the Russell-Einstein Manifesto.