Longest mathematical proof

The most extensive "proof" in mathematics – essentially, a series of mathematical steps, leading to a result – was completed in 2004. The proof, which concerns the classification of mathematical symmetry groups – a concept aptly known as the "Enormous Theorem" – took 100 mathematicians three decades and some 15,000 pages of workings to pin down. In 2011, Michael Aschbacher, a mathematician at the California Institute of Technology – who undertook the bulk of the work – was awarded the $75,000 Rolf Schock prize in mathematics by the Royal Swedish Academy of Sciences.