Today is the 200th birthday of Evariste Galois, who did not live to celebrate his 21st, but found time in his short 20 years to develop a circle of ideas that permeate modern mathematics. We know of these ideas because Galois spent the night of May 30, 1832 scribbling them furiously in a letter to a friend, in advance of the fatal duel he would fight the following morning. According to the great mathematician Hermann Weyl, “This letter, if judged by the novelty and profundity of ideas it contains, is perhaps the most substantial piece of writing in the whole literature of mankind.”
(If this were a less serious post, I might suggest that this famous letter was the first example of a Galois Correspondence.)
Now, two centuries later, every first year graduate student in mathematics spends a semester studying Galois Theory, and many devote their subsequent careers to its extensions and applications. Many of the greatest achievements of modern mathematics (for example, the solution to Fermat’s Last Theorem) are, at their core, elucidations of Galois’s 200-year-old insight.


A month ago, I posted a 
One hundred years ago today, 