27 Interested Science readers can find a discussion of Schnirelmann’s proof in W. Dunham’s Journey Through Genius: The Great Theorems of Mathematics (Wiley, 1990) but will probably have to don a miner’s helmet and go all the way back to Proceedings of the London Mathematical Society Series vol. 2 no. 44, 1938 for T. Estermann’s “On Goldbach’s Problem: Proof That Almost All Even Positive Integers Are Sums of Two Primes.”