Andrey Markov

Andrey Markov (1856–1922) was a Russian mathematician with a fierce temper and an even fiercer sense of principle. He gave us a beautifully simple idea about chance — and he also once tried to get himself excommunicated on purpose, just to make a point.

The headline achievement

Markov studied random processes with a memory-free twist: the Markov property says the future depends only on where you are now, not on the whole story of how you got there. That single assumption turns messy randomness into something you can actually compute. Markov chains now describe everything from shuffling cards and weather to the algorithm behind Google's page ranking and the text prediction on your phone.

To show his idea worked on real data, Markov famously went through the text of Pushkin's novel-in-verse Eugene Onegin and counted, by hand, how often vowels followed consonants and vice versa — thousands of letters, tallied one by one. It was one of the first times anyone treated language as a chain of probabilities. He was also gloriously combative: nicknamed "Andrey the Furious," he feuded with colleagues and, in protest at the Church excommunicating Tolstoy, wrote to ask that he be excommunicated too.