《星际迷航》里的物理学

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• A famous paradox is to be found in both science fiction and physics: What happens if you go back in time and kill your mother before you were born? You must then cease to exist. But if you cease to exist, you could not have gone back and killed your mother. But if you didn't kill your mother, then you have not ceased to exist Put another way: if you exist, then you cannot exist, while if you don't exist, you must exist. (查看原文)

  [已注销] 2013-05-18 20:34:56

• Jet pilots and NASA have a name for the force exerted on your body while you undergo high accelerations (as in a plane or during a space launch): G-forces. I can describe these by recourse to my aching back: As I am sitting at my computer terminal busily typing, I feel the ever-present pressure of my office chair on my buttocks -- a pressure that I have learned to live with (yet, I might add, that my buttocks are slowly reacting to in a very noncosmetic way). The force on my buttocks results from the pull of gravity, which if given free rein would accelerate me downward into Earth. What stops me from accelerating -- indeed, from moving beyond my seat -- is the ground exerting an opposite upward force on my house's concrete and steel frame, which exerts an upward force on the wood floor of ... (查看原文)

  [已注销] 2013-05-18 20:42:59

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