Stanislav Ulam is an incredible man. Mathematician (Ulam Spiral, Monte Carlo Method), Manhattan Project participant, and part-time astronomer who devised a method for nuclear-explosive-powered space travel [0].
This result holds in spaces of considerable generality, but I'd have to look up the details now. Details are in P. Billingsley, 'Convergence of Probability Measures', 1999.
I used the result in a paper once. It's nice result and gets used occasionally in advanced work in probability.
http://en.wikipedia.org/wiki/Thermonuclear_weapon
There is a great autobiography by him called "Adventures of Mathematician".
A terrific book, still available but pricey (ca. $30 for a paperback). I have a dog-eared copy acquired 40 years ago in my library.
The closest Ulam comes to revealing atomic secrets in his book is to say the method he and Teller chose to produce a thermonuclear reaction requires the "repetition of certain arrangements." I always thought that was the perfection of obscurity.
Edit: sure not, it's Urey. Four letters, starts with U. Mental index hash fail :)