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Newton believed that gravity is a force that acts throughout the entire universe.
牛頓認為引力是作用遍布整個宇宙的力。
In 1686, he finally managed to break it down into one single mathematical equation.
1686年，他終于設法將它分解到了一個簡單的數學等式里了。
Newton's understanding of gravity is actually incredibly simple
牛頓對引力的認識實際上簡單的出乎意料，
that the force between two objects depends on only two things, the mass of the objects and the distance they are apart.
兩個物體之間的引力只不過依賴兩個情況，物體的質量以及他們之間的距離。
So, the more massive the objects, the stronger the force,
所以，物體的質量越大，引力就越強，
and, the further the objects are apart, the weaker the force.
同樣，物體之間的距離越大，引力就越小。
See, it's easy to show actually.
瞧 其實看起來很簡單。
Got a pen? So this is Newton's law of gravitation.
有筆嗎？這就是牛頓萬有引力定律。
The force is equal to the masses of the two objects, divided by the square of the distance apart of the objects.
引力等于兩個物體的質量除以物體之間的距離的平方。
And then there's Newton's gravitational constant,
然后是牛頓的萬有引力常數，
that just sets the scale -- it tells you the overall strength of gravity.
那只是放如一個比例，它表示綜合的引力強度。
With one beautiful bit of maths, Newton had figured out gravity, but not just here on Earth.
對于一個漂亮的數學公式，牛頓已經解決了引力，不光是地球上的引力。
The Moon seemed to orbit the Earth exactly as he predicted, as did the planets orbiting around the sun.
月球似乎確實如他預言的那樣圍繞地球運轉，行星圍繞著太陽運轉同樣如此。
Newton believed we live in a universe in which ultimately the movement of everything can be predicted.
牛頓認為，我們生活的宇宙中的一切物體的運動都能夠得到預測。
Newton's universal law of gravitation is one of the most important turning points in physics,
牛頓的萬有引力普遍規律是物理學里一個最重要的轉折點，
and that's because it really is universal.
那是因為它確實很普遍。
It allows you to predict not only how things move under the influence of gravity here on Earth
它使你不僅能預測在地球這里的引力影響下的物體如何運動，
but how the stars and planets and even galaxies move, all the way across the universe.
同時還能預測恒星、行星、生殖星系的運動，一直到囊括整個宇宙。
