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, though this work was preceded by that of Nicholas Christofilos.
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.