He played a part in the work of Brookhaven for sixty years and had 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.

[8] His mother's father, Carl Runge, is credited with the Runge-Kutta method for numerical solutions of differential equations.

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.

Forewarned by a Nazi acquaintance that the anti-Semitic storm would not settle but intensify, the family made plans to emigrate permanently.

Fluent in English from both early lessons and the recent months enrolled at the Perse School in Cambridge, Ernest was accepted at the Fieldston School in the Bronx, with a scholarship, thanks to intervention by family friend (and Fieldston alumnus), J. Robert Oppenheimer.

Courant worked at Brookhaven National Laboratory from 1948, first as an associate scientist in the Proton Synchrotron Division.

[10] Together with Hartland Snyder, he developed the Courant–Snyder parameters, a method for analyzing the distribution of particles in an accelerator or beam line.