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Hank introduces us to that great mathematical mind, Alan Turing, who, as an openly gay man in the early 20th century faced brutal prejudice that eventually led to his suicide, despite being a genius war hero who helped the Allies defeat the Nazis.

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[intro music]

Hank Green: There's a man that we have to thank for things like a world free of Nazis and full of computers, and we did not treat him particularly well as a society. Yes, I'm talking about Alan Turing.

Turing was born in England in 1912, and as he made his way through school, his teachers realized that he was not a normal brilliant kid -- he was an ultra mega super math genius. He could do things like solve complicated calculus problems in his head before his teachers taught him calculus.

But Turing differed from most of the other boys in his fancy boarding school in another way -- he was openly gay, and mind you, this was in a place and time when homosexuality was literally illegal.

But Turing's oppression didn't prevent him from kicking math's ass during the 1930s. He was interested in artificial intelligence, and in college, he postulated the Turing machine. He just thought... he didn't make it, he thought it up: a machine that could calculate anything calculable. In his head, he created the idea of a computer, and of computer programs, without any computers having ever existed. He just made the idea up.

Turing wasn't just a math prodigy; he was also an amazing engineer. When Britain joined in World War 2, its government hired Turing to help break the codes generated by Enigma, the German's crazy complicated encryption device. No one thought that these codes could be broken. So, Turing in short order designed a machine, an electromechanical machine that succeeded in breaking this unbreakable code, likely saving more British lives than any other person during World War 2.

So, Alan Turing was a genius and he was a war hero, no doubt about it. And then, after the war was over, in the 1950s, he was working on actually building computers that operated by the rules set by his Turing machine. One day in 1952, Turing came home to find that some of his stuff was missing, and so he called the cops, because he'd been robbed, and the cops came over and they were like, "Do you have any idea who might have robbed you?"

And Turing said, "Well, it might have been my boyfriend."

And they said, "Your boyfriend?"

And he said, "My boyfriend."

And then they arrested Alan Turing and charged him with gross indecency. He was given a choice between prison or probation providing he agree to undergo chemical castration, a hormone treatment that at the time was thought to "cure" homosexuality.

He chose this bizarre form of probation and was given routine estrogen injections over the course of two years, which not only, yes, indeed reduced his libido but made him very very depressed. A big fan of Snow White, so in 1984 he laced an apple with cyanide and ate it.

So not only was Alan Turing a super genius war hero and responsible for, you know, my iPhone, he was also a victim of some really brutal prejudice. Alan Turing, I know you can't hear me, but thank you for this wonderful world free of Nazis and full of computers that you helped create, and I'm sorry that the world was so screwed up back then.

Thank you for watching this episode of SciShow Great Minds. If you have other people that you think we should cover, questions or comments or ideas, you can get in touch with us on Facebook or Twitter or of course in the comments below. And if you want to keep learning more with us, go to and subscribe.

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