Ernest Courant (born March 26, 1920) is an American accelerator physicist and a fundamental contributor to modern large-scale particle accelerator concepts. His most notable discovery is his 1952 work with Milton S. Livingston and Hartland Snyder on the Strong focusing principle, a critical step in the development of modern particle accelerators like the synchrotron.
Currently, Ernest Courant is a member the National Academy of Sciences, and remains active as a distinguished scientist emeritus at Brookhaven National Laboratory. He has played a part in the work of Brookhaven for sixty years and has also been mentor to several generations of students. In this kind of generative academic influence, he can be compared to his father, the mathematician Richard Courant.
Early life 
He has written that he "came by science naturally". His mother's father, Carl Runge, is credited with the Runge-Kutta method for numerical solutions of differential equations. A maternal great-grandfather (Runge's father-in-law ) was Emil DuBois-Reymond, a pioneer in electrophysiology. Affinity for science and mathematics extended further than his biological family. Ernest Courant's childhood neighbors included the mathematician David Hilbert (his father's thesis director, in whose honor Ernest received the middle name of David) and the physicists Max Born and James Franck. Further, his father's students and colleagues became friends of the family, and often visited.
Ernest's early interests centered on chemistry. "I had a lab at home full of test tubes, Bunsen burners, and chemicals. Once there was a small fire (easily put out), but I got a sense of how things were put together."
Adolf Hitler came to power in 1933, and the neighborhood and its intellectual society were disrupted—along with the mathematics department at the University. Ernest's father had been born to a Jewish family of small businessmen, and he was now identified as a Jew, and an undesirable, by the new regime. Expelled from his position at the University of Göttingen, Richard Courant took a temporary teaching position in England, and the family abandoned Göttingen in favor of Cambridge for a few months. Forewarned by a Nazi acquaintance that the anti-Semitic storm would not settle but intensify, the family made plans to emigrate permanently. They returned only briefly to Germany before embarking to New York City, where his father had secured a post at New York University—and immigration visas to the USA.
Fluent in English from both early lessons and the recent period enrolled at the Perse School in Cambridge, Ernest was accepted at the Fieldston School of the School for Ethical Culture, with a scholarship, thanks to intervention by family friend (and Fieldston alumnus), J. Robert Oppenheimer.
Courant has worked at Brookhaven National Laboratory from 1948 to the present, first as an associate scientist in the Proton Synchrotron Division. He received tenure in 1955, and was promoted to senior scientist in 1960. In addition, he taught as an Adjunct Professor at SUNY Stony Brook from 1966 to 1986.
- 2007 University of Rochester distinguished scholar award
- 1987 First Annual Robert R. Wilson Prize of the American Physical Society
- 1986 Enrico Fermi Award from the Department of Energy, USA
- Boris Pregal Prize of the New York Academy of Sciences
References and further reading 
- Array of Contemporary American Physicists
- Courant, E. D.; Livingston, M. S.; Snyder, H. S. (1952). "The Strong-Focusing Synchrotron—A New High Energy Accelerator". Physical Review 88 (5): 1190–1196. Bibcode:1952PhRv...88.1190C. doi:10.1103/PhysRev.88.1190.
- Courant, E. D.; Snyder, H. S. (Jan 1958). "Theory of the alternating-gradient synchrotron". Annals of Physics 3 (1): 1–48. doi:10.1006/aphy.2000.6012.
- Distinguished Scientist Emeritus Ernest Courant Honored by University of Rochester (BNL Bulletin)
- "Richard Courant." World of Mathematics. Online. Thomson Gale, 2006. Reproduced in Biography Resource Center. Farmington Hills, Mich.: Gale, 2008.
- Courant, E. D. (December 2003). "Accelerators, Colliders, and Snakes". Annual Review of Nuclear and Particle Science 53: 1–37. doi:10.1146/annurev.nucl.53.041002.110450.
- "Richard Courant" biography at the University of St. Andrews.
- Former Faculty Homepage.
- Courant, E. D. (December 1968). "Accelerators for High Intensities and High Energies". Annual Review of Nuclear Science 18: 435–464. doi:10.1146/annurev.ns.18.120168.002251.
- Chao, A.; Courant, E. (2007). "Spin echo in synchrotrons". Physical Review Special Topics - Accelerators and Beams 10. doi:10.1103/PhysRevSTAB.10.014001.