来自《耶鲁大学开放课程：基础物理 第3集 第3集》

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  Your reaction may be that you've seen Newton's laws,
  你们的反应可能是 我已经见过牛顿定律了
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  you applied them in school.
  以前在学校就学过
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  I've got to tell you that I realized fairly late in life
  我得告诉你们 我是很晚的时候才意识到
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  they are more subtle than I imagined the first time.
  它其实比我之前想象的要精妙得多
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  It's one thing to plug in all the numbers and say,
  我们平时只是把数字代进公式 然后说
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  "I know Newton's laws and I know how they work."
  "我懂牛顿定律 也知道怎么使用"
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  But as you get older and you have a lot of spare time,
  但随着你们年龄的增长 有更多空闲时间之后
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  you think about what you are doing,
  你就会思考你做的事情
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  which is something I have the luxury of doing right now,
  我现在就有很多闲暇思考这些问题
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  and I realized this is more tricky.
  我意识到这东西其实很精妙
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  I want to share some of that with you
  我想和你们分享一下心得
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  so you can fast forward
  这样你们就能更快地进步