A scientific method including experimentation was first used by the Iraqi physicist and polymath Ibn al-Haytham (Alhazen), circa 1000 AD, in his Book of Optics, and he has been described as the “first scientist” for this reason.
There are notable examples of people who have moved back and forth among disciplines. A number of early scientists were priests, including the astronomer and physician Copernicus; and Gregor Mendel, whose discoveries on inheritance founded modern genetics, which provides a mechanism to explain Charles Darwin’s observations about evolution.
Descartes not only invented analytic geometry but formulated a theory of mechanics and advanced ideas about the origins of animal movement and perception. Vision interested the physicists Young and Helmholtz, who also studied optics, hearing and music. Newton extended Descartes’ mathematics by inventing calculus (contemporaneously with Leibniz). He provided a comprehensive formulation of classical mechanics and investigated light and optics. Fourier founded a new branch of mathematics – infinite, periodic series – studied heat flow and infrared radiation, and discovered the greenhouse effect. Von Neumann, Turing, Khinchin, Markov and Wiener, all mathematicians, made major contributions to science and probability theory, including the ideas behind computers, and some of the foundations of statistical mechanics and quantum mechanics. Many mathematically inclined scientists, including Galileo, were also musicians.
In the late 19th century, Louis Pasteur, an organic chemist, discovered that microorganisms can cause disease. A few years earlier, Oliver Wendell Holmes, Sr., the American physician, poet and essayist, noted that sepsis in women following childbirth was spread by the hands of doctors and nurses, four years before Semmelweis in Europe. There are many compelling stories in medicine and biology, such as the development of ideas about the circulation of blood from Galen to Harvey. The flowering of genetics and molecular biology in the 20th century is replete with famous names. Ramon y Cajal won the Nobel Prize in 1906 for his remarkable observations in neuroanatomy.
