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In a German interview some physicists were asked, what they would ask Einstein, if he were alive today. One of them wanted to know how Einstein came up with the idea of the equivalence principle, that inertial mass is the same as gravitational mass. Correct me if I'm wrong, but I always believed that was known way before Einstein. And I have an experiment in mind where one famous guy standing on a leaning tower and letting two things fall with different mass to test if gravity acts on every object the same.
My question is, does somebody know the name of this famous person, who conducted the experiment? I can't remember it.