Sir Isaac Newton's Law Of Universal Gravitation

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Gravity if one of the four fundamental forces in the universe. Though

the fundamental principles of it eluded scientists until Sir Isaac Newton was

able to mathematically describe it in 1687 (Eddington 93). Gravity plays a

serious part in everyday actions as it keeps everything on the ground; without

gravity everything would be immobile unless a force was applied (then it would

move infinitely because there would be no force to stop it).

Perhaps, the best place to start then would be with such a simple item

as an apple (after all it is what "sparked" Newton's creativity). The apple is

one of the two curiosities (the other being the moon) that led Newton to

discover The Law of Universal Gravitation in 1666 (Eddington 93). As Newton

later wrote, it is the story of the sight of an apple falling to the ground (he

was resting at Woolsthorpe because of the plague at Cambridge) that caused

Newton to wonder if this same force was what held the moon in place (Gamow 41).

Newton knew that an object fell to the earth at a rate of about 9.8

meters (32 feet) per second second as pointed out by Galileo. Thus "the apple

that fell from the tree" fell to Earth at about this rate. For the first basic

explanation of this we will assume a linear plane, one in which all forces act

in only one direction. Therefore when the apple fell it went straight towards

the center of the earth (accelerating at about 9.8 meters per second second).

Newton then figured that the same force that pulled the apple to Earth also

pulls the moon to the earth. But what force keeps the moon from flying into the

earth or the earth flying into the sun (Edwards 493)?

To better understand this, one other aspect must first be understood.

Galileo showed that all objects fall to the earth at the same rate (the classic

cannonball and feather proved this). But why? If a piano and a saxophone were

both dropped from the top of the Empire State Building then they would both slam

into the ground at the same rate. Newton realized then that the moon and the

apple were both being pulled towards Earth at the same rate but yet the moon was

the only one who resisted the force and stayed in its elliptical orbit

(Eddington 94). Newton's Third Law of Motion says that every force exerted by...

... middle of paper ...

... proposed the origin of gravity.

Newton's law always proved to be true in the common world but did not explain

the source of the force (Eddington 95). Albert Einstein proposed his Theory of

Gravity in his General Theory of Relativity. In this he said that space was a

three dimensional plane and that masses curved this plane in one way or another

(Eddington 95). Thus a massive object would cause a large "hole" and smaller

objects would "orbit" it. It is interesting to note that in either case,

Newton's or Einstein's law, both prove to be true in the common world. Massive

universal objects, such as black holes, are an exception but that's another

story in itself (Edwards 498).

Works Cited

Zitzewitz, Paul W., Robert F. Neff, and Mark Davids. (1992). Physics:

Principles and Problems. Peoria, Illinois: Glencoe.

Gamow, George. (1962). Gravity: Classic and Modern Views. Garden City, New

York: Anchor Books.

Eddington, Sir Arthur. (1987). Space, Time, & Gravitation: An Outline of the

General Relativity Theory. Cambridge: Cambridge University Press.

Edwards, Paul. (Ed.) (1967). The Encyclopedia of Philosophy. New York, New

York: MacMillan.

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