Universal Gravitation
What is Universal Gravitation?
It is heard, "Newton saw the falling apple, and discovered gravitation".
However, this is not true.
It is only a creation that plainly expressed the achievement of Newton.
The apple falls. The moon advances in the sky on the other hand.
Therefore, people at that time believed that the principle that ruled the heavenly body and the movement law of the object of the ground were complete different things.
The person who had doubted this was Newton.
Newton thought, "The object of the heavenly body and the ground might follow the same law".
And, he assumed "Universal gravitation" as "A common principle to the fall of the apple and
the rotation of the moon", and proved it.
Newton thought, "All objects were mutually pulled against each other", and named this "Universal gravitation".
We have not seen the appearance that the object pulls mutually against each other, and it comes in contact.
Universal gravitation is very slight force.
However, universal gravitation comes to stand out in the earth and the moon because mass is large, too.
Therefore, the object in the vicinity of the ground is pulled to the earth by universal gravitation and falls.
The moon keeps rotating because universal gravitation to which the earth pulls the moon becomes a centripetal force on the other hand.
When mass is large, universal gravitation grows, too. When the distance is long, universal gravitation becomes small.
This is a law of universal gravitation.
This law is expressed by the following expressions.
"All objects are mutually pulled against each other. The magnitude of the force is in inverse proportion to the second power of the distance, and in proportion to the product of the mass of the object pulled against each other. "
This is a meaning of the expression.
G is a proportion constant, and it is especially said the universal gravitation constant.
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