Johann Lambert. Historical portrait of the Swiss- German physicist Johann Heinrich Lambert (1728- 1777). Lambert contributed to many branches of science. He was the first person to measure the intensity of light in a scientific manner and so founded the science of photometry. The unit of light intensity, the lambert, is named after him. In mathematics, he constructed proofs that the numbers pi and e are irrational, and so cannot be expressed as the ratio of two whole numbers. He also did early work on what came to be known as non-Euclidean geometry. In astronomy, Lambert showed the Milky Way to be shaped like a disc and suggested that there might be other galaxies.