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The Theoretical Minimum: What You Need to Know to Start Doing Physics by George Hrabovsky, Leonard Susskind

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Lecture 8: Hamiltonian Mechanics and Time-Translation Invariance

Doc was sitting at the bar drinking his usual—a beer milk shake—and reading the paper, when Lenny and George walked in. “What are you reading about, Doc?”

Doc looked up at Lenny over his glasses. “I see where this guy Einstein says, ‘Insanity is doing the same thing over and over and expecting different results.’ What do you think about that?”

Lenny thought for a minute. “You mean like every time I eat here I order chili, and then I get a stomachache?”

Doc chuckled, “Yeah, that’s the idea. I see you’re beginning to understand Einstein.”

Time-Translation Symmetry

You may wonder what happened to energy conservation and whether it fits the pattern relating symmetries to conservation ...

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