David L. Goodstein, in his book Feynman’s Lost Lecture:

Feynman was a truly great teacher. He prided himself on being able to devise ways to explain even the most profound ideas to beginning students. Once, I said to him, “Dick, explain to me, so that I can understand it, why spin one-half particles obey Fermi-Dirac statistics.” Sizing up his audience perfectly, Feynman said, “I’ll prepare a freshman lecture on it.” But he came back a few days later to say, “I couldn’t do it. I couldn’t reduce it to the fr

Source: Daring Fireball: Richard Feynman’s ‘Prepare a Freshman Lecture’ Test

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Eine Milliarde Euro, 100 Millionen Grad: Nach zehn Jahren Bauzeit soll Wendelstein 7-X jetzt Plasma erhitzen. Die Vision hinter dem Mega-Experiment: harmloser Atomstrom

Source: Wendelstein 7-X: Heiß, heißer, Greifswald!