World of Scientific Discovery on Edward Mills Purcell
Born in Taylorville, Illinois, Edward Purcell attended public schools near his hometown before enrolling at Purdue University in 1929; he received his B.A. in electrical engineering from the university in 1933. After spending a year in Germany as an exchange student, Purcell continued graduate studies in physics at Harvard University, earning his M.A. in 1936 and his Ph.D. in 1938. During World War II, Purcell and other scientists worked at the Massachusetts Institute of Technology Radiation Laboratory, developing microwave-based radar systems. This project was headed by Isidor Isaac Rabi who, several years earlier, had discovered a method for studying the magnetic properties of atoms. After the war, Purcell returned to Harvard as an instructor and began research on designing a new process for recording the magnetic strengths of nuclei.
Rabi's process was based upon the knowledge that an atomic nucleus will spin at a fixed rate, and that, by observing the behavior of the nucleus while placed within a magnetic field, much information could be derived about the nature of the atom. The problem with Rabi's process was that, in order to measure its nucleus's spin, a substance had to be vaporized--in other words, destroyed. By applying the radar technology he had studied during the war, Purcell discovered a method by which magnetic strengths could be recorded more accurately, and without harming the sample. His method used radio signals to determine the nuclear magnetic resonance (NMR) of an atom. This effect was easily measured since the radio frequency causing the resonance was indicative of the atom's magnetic strength.
Purcell was not the only scientist to apply radar theory to Rabi's process: the American Felix Bloch--who had also experimented with radar during World War II--designed a method nearly identical to that of Purcell. For their independent, simultaneous achievements, Bloch and Purcell shared the 1952 Nobel Prize for physics.
Although NMR scanning would eventually find tremendous usefulness in chemistry and medicine, Purcell was the first to employ it outside the realm of nuclear physics. In 1951, investigations using NMR helped determine the radio frequency of interstellar hydrogen. Using this frequency as a radio "fingerprint," Purcell and astronomer Harold Ewen (1922-) searched the heavens for dark patches of hydrogen that were invisible to telescopes. Their efforts resulted in the construction of the first radio telescope--a device which has since facilitated the mapping of the cosmos. Purcell's research marked the birth of radio astronomy.
NMR technology is also used by chemists to identify samples of elements, as well as to observe the structure of atoms. In medicine, NMR is used as a more delicate and more sensitive form of X-ray, and it is often used in cancer research.
Purcell continued to teach at Harvard until his retirement in 1980. He has received numerous honors from scientific academies, including the National Medal of Science. He has also served as an advisor to the President's Scientific Advisory Committee under Presidents Eisenhower and Johnson.
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