In the field of science the work of Sir Isaac Newton was one of the greatest contributions ever made by an individual. Although his career was long and littered with success, there were four discoveries that were considered to be his most important. These were his work on the nature of gravity, his famous Laws of Motion, his extensive work on light and color, and his creation of the reflecting telescope. Few people have ever come close to being as important as Newton to science. With all of the great works and discoveries he has made it is easy to see why this is so.
One of Isaac Newton's earliest and most recognized works was his contribution to the scientific study of the then little understood force of gravity. This contribution was his Universal Law of Gravitation. Thoughts of gravitation entered Newton's head as result of a certain apple tree and the tree's falling fruit. "In 1666, while Newton was sitting in the manor house garden at Woolsthorpe, he saw an apple fall from a tree. This triggered certain thoughts that he had been having about gravitation." (Knight vol. 2 41) Despite popular belief, the apple did not fall on his head. What actually happened was that he saw an apple fall from an apple tree and he began to wonder why it fell. From there his thoughts broadened to the rotation of the moon. It was already common knowledge that the moon revolved around the Earth and the planets revolved around the sun. This was caused by gravity. What Newton wanted to know was why the moon revolved around the earth instead of simply being pulled into the earth like the apple was. His thoughts gradually brought him to a conclusion, the Universal Law of Gravitation. According to Encarta Encyclopedia, the Universal Law of Gravitation was, "All bodies attract each other with a force proportional to the product of their masses, and inversely proportionate to the square of the distance between them." David C. Knight explains:
Practically, this law says that large, heavy objects pull each other harder than small, light ones. And the pull is greater between objects near each other than objects that are far apart. Further, Newton was to suggest that this law operated not only on objects on the earth, but for those in space as well. That was what Newton meant by the word universal in his great law--it worked everywhere in the universe. (vol. 1 46)
The reason the moon did not just fall right into the earth like the apple did was because it was too large, had its own motion, and was too far away. This law also explained why the planets revolve around the sun. Newton's work with gravity naturally led to his work with the Laws of Motion.
Newton developed three Laws of Motion. The first law was "A body at rest will remain a rest and a body in motion will continue in motion at a constant speed in a straight line unless acted upon by some outside force." (qtd. in Knight vol. 1 115) In simpler terms this means that if something is moving it will continue moving straight forward unless an outside force does something to it. One example of this would be if you were driving a car at forty miles per hour and suddenly hit a wall. The car would stop, becoming a body at rest. You, however, would not have been acted on by an outside force yet and would therefore continue moving straight forward at forty miles per hour until you were acted on by an outside force such as an air bag, the steering wheel, the dashboard, the wind shield, or the wall. The Second Law of Motion stated that "Any change in motion of a body is in proportion to the force pressing on it, and takes place in the direction of the straight line in which the pressing force acts." (qtd. in Knight vol. 2 116) This law means that the amount of change in the movement of an object depends on the amount of force acting on it. The Third Law of Motion states that "To every action there is always opposed an equal reaction" (qtd. in Christianson 293) This third law can be restated to say, "Whenever one body exerts a force on another, the second body exerts an equal and opposite force on the first body." (Knight 117) An example of this is the backward movement of the hand and arm after firing a gun. These laws are always true and have been very important to scientific progress because of their value to the study of outer space.
Isaac Newton became stuck while trying to figure out what the radius of the earth was in order to help him prove his Universal Law of Gravitation. Rather than guess and take a chance that he might be wrong, he decided to put the project on hold and study something else. That something else optics, or the study of color and light. Optics was a popular subject among scientists at the time because little was known about it. Newton was keenly interested. In his first published paper Newton himself described when and how he got started:
in the beginning of the year 1666 (at which time I applied myself to the grinding of optic glasses of other figures than spherical), I procured a triangular prism to try therewith the celebrated phenomena of colours . . . (qtd. in Andrade 50)
He soon began experimenting with the prism that he had just bought.
having darkened my chamber and made a small hole in my window shutters, to let in a convenient quantity of the sun's light, I placed my prism that it might thereby be refracted to the opposite wall. It was at first a very pleasant divertissement. (qtd. in Knight 50)
However the young scientist soon found that what had been done for hundreds of years for entertainment was a very serious scientific matter. The prism used a process called refraction to produce a color spectrum on the wall. The colors of the spectrum were, and still are, red, orange, yellow, green, blue, indigo and violet, in that order. That was not so surprising as the fact that the prism had turned a circular beam of white light into a patch of colors in which each individual color had become a strip five times as long as it was broad. This caused him to start thinking about the telescope that was being used at the time, the refracting telescope. The refracting telescope worked on the same light bending principal as the prism. Knight explains:
One thing was at once clear to the young thinker, who had already had some experience with the refracting telescopes of his day. Refracting telescopes depended on the use of lenses that bent light as prisms did. But if circular beams of light could be lengthened into wide colored strips, then how could an instrument, which depended upon this basic principle help but give images that were colored and blurred?
The way young Newton was to solve this problem in the next two years was to bring his name to the lips of the most advanced scientists of his day. (vol. 2 52)
The way Newton solved that problem was to invent his own telescope, a telescope that would revolutionize the way we would look at the heavens forever, the reflecting telescope.
Newton first set out to find a way to fix the refracting telescope. He soon found that this was impossible, and had to give up on the idea of refraction altogether. In the year 1667 Newton began work on his great invention, the reflecting telescope. However, Newton was not the first person to think of the reflecting telescope. A Scottish mathematician named James Gregory had suggested a plan for a reflecting telescope a few years earlier, but he never actually built it. After the creation of Newton's telescope, he and James Gregory became good friends. This was well illustrated by More, "Gregory became a warm friend and admirer of Newton, and there was no break in their friendship." (155) Gregory was also unaware of the main benefit of the reflecting telescope, namely the elimination of blurred and unwanted colors. Alone in his room Newton began to shape the first mirror for his reflecting telescope with his own hands. He spent days polishing its inwardly curved surface. It was formed from an alloy Newton himself had created--a mixture of tin, arsenic, and copper. He slaved for weeks building that thing. Knight notes:
Isaac worked with intense enthusiasm. The telescope he finally produced was ridiculously small. It was only six inches long, with a diameter of one inch! Yet it could magnify an object forty times--and this, as Newton himself pointed out, was as much as could be expected of a refracting telescope fully six feet long! (vol. 1 58)
Needless to say this was an amazing feat. Newton was also the first person to put the eyepiece on the side of any telescope. Reflecting telescopes are still predominantly used by most of the scientific community.
In conclusion, Sir Isaac Newton made many important contributions to the field of science. The most important of which were his work on gravity, his Laws of Motion, his work on light and color, and his reflecting telescope. These four works made a lasting impression in the field of science. If Newton had not figured out his Laws of Motion and his Universal Law of Gravitation the human race would probably not be capable of space travel. And if he had not invented the reflecting telescope we would probably still be using blurry refracting telescopes. In short, Isaac Newton was a genius of immeasurable depth who helped usher in a new era of scientific enlightenment and knowledge.
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on 3/30/99 for HTWM, Rich East High School, Park Forest, IL.
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