Most of you, no doubt, know the story of Newton and the falling apple and how it led to his discovery of the law of
  gravity.
毫无疑问，你们大多数人都知道牛顿和掉落的苹果的故事，以及掉落的苹果如何导致他发现万有引力定律。
But how much do you know beyond that?
但除此之外，你们还知道多少呢？
Do you know what kind of man this great scientist was? Or where he stands in the history of science?
你们知道这位科学家是怎样的人吗？或他在科学史上占有什么地位？
If you don't, or even if you do, read the following lesson.
如果你不知道，或即使知道，都请读下面的课文。
Isaac Newton was born on Christmas Day, 1642. He grew up in the English countryside.
牛顿生于一六四二年的圣诞节。他在英国的乡下长大。
From the very first Newton was very much interested in the mysteries of nature.
从一开始牛顿就对大自然的奥秘很感兴趣。
One of the most difficult scientific problems of Newton's day was about the question of motion.
牛顿时代科学上最大的难题之一，就是关于运动问题。
Why did objects move? Scientists could see that stones rolled down hills, that wind blew leaves along the ground, and
  heavy objects fell to the earth when dropped.
物体为什么会移动，科学家可以看到石头滚下山来，风吹落叶满地跑，以及重物被拋下，就落向地球。
After Copernicus, they began to admit that the earth itself moved. "Were there laws that govern these various kinds of
  motion?" they asked themselves.
哥白尼之后，他们开始承认地球本身会转动。科学家们自问“是否有一些法则在支配各种运动呢？”
The Greeks had believed there were different rules for motion on earth and in space, and that there were unnatural
  movements on the surface of the earth.
希腊人曾经相信地球和太空有不同的运动法则，而且地球表面有一种异常的运动。
Galileo was the first person to challenge this Greek view of motion.
伽利略是第一位对希腊人的运动观提出质疑的人。
This Italian scientist was a follower of Copernicus.
这位义大利的科学家是哥白尼的信徒。
It didn't make much sense to Galileo to have different rules for motion on earth and in space.
对伽利略来说，地球上和太空中有不同的运动法则是没有多大意义的。
He made two important discoveries.
他做了两个重大发现。
First, he showed that motion was not unnatural.
第一，他表示运动并不是异常的。
On the contrary, an object once in motion would tend to continue in motion.
相反地，一个物体一旦在运动中，就会倾向于继续运动。
Second, Galileo worked out a mathematical formula for the motion of all objects that fell to the earth.
第二，伽利略对所有落向地球的物体的运动，发展出一个数学公式。
Galileo, however, did not explain how all motion in the universe worked.
然而，伽利略并没解说宇宙中的运动是如何产生的。
Much work had been done since Copernicus to observe and record the movements in the solar system.
自从哥白尼以后，观察并记录太阳系的运动的工作已经做得很多。