Book excerpt: John W. Moffat was a poor student of math and science. That is, until he read Einstein’s famous paper on general relativity. Realizing instantly that he had an unusual and unexplained aptitude for understanding the complex physics described in the paper, Moffat wrote a letter to Einstein that would change the course of his life. Einstein Wrote Back tells the story of Moffat’s unusual entry into the world of academia and documents his career at the frontlines of twentieth-century physics as he worked and associated with some of the greatest minds in scientific history, including Niels Bohr, Fred Hoyle, Wolfgang Pauli, Paul Dirac, Erwin Schrödinger, J. Robert Oppenheimer, Abdus Salam, among others. Taking readers inside the classrooms and minds of these giants of modern science, Moffat affectionately exposes the foibles and eccentricities of these great men, as they worked on the revolutionary ideas that, today, are the very foundation of modern physics and cosmology.