During and after World War II, he held several positions in the United States government, including Chief Intelligence Officer at the US Embassy in London, Special Assistant to the Undersecretary of War, and Counsel to the US Senate Committee on Atomic Energy.
In 1940 Newman and Edward Kasner wrote Mathematics and the Imagination, in which they reported the mathematical idea of a very large but finite number, called a "googol", consisting of 1 followed by 100 zeroes, and a larger number called a "googolplex".
The four volumes cover many branches of mathematics and represent a 15-year effort by Newman to collect what he felt were the most important essays in the field.
With essays ranging from a biography of Srinivasa Ramanujan by Newman to Bertrand Russell's "Definition of Number", the series is often praised as suitable for any level of mathematical maturity.
[1] Newman also wrote Gödel's Proof (1958) with Ernest Nagel, presenting the main results of Gödel's incompleteness theorem and the mathematical work and philosophies leading up to its discovery in a more accessible manner.