Doctrines of Newton
...d the planets avoid crashing into the sun? During this time period, Newton mind brought forth the theories that explain gravity and force. Most people are familiar with Newton and the apple tree stated here by Anderson: Newton did not really figure out gravity in the time it takes an apple to fall from a tree, though he himself gave us the apple legend. When he was an old man, he told the story to William Stukeley. They were drinking tea together under an apple tree in his garden. He said that he was sitting under a similar tree when the theory of gravity came to his mind. “It was occasion’d by the fall of an apple . . .” (p.44) Whether this incident really happened or not, it is a fact that Newton set his mind to the principles of gravity and the mathematics of motion. Using algebra, Newton solved equations to find the value of an unknown number, x. He eventually took this concept one step further to solve for the value of an unknown number that was constantly changing. He called this new branch of mathematics fluxions, which comes from the word flux, which means “constant changing or flowing.” It is what we now what we refer to as calculus. In 1667, Newton returned to Cambridge where he is elected Fellow of Trinity College. It was during this time that Newton kept remembering a childhood game he and others had played while in the schoolyard. Each child would take turns holding a pail of water, which was suspended by a rope that was tied to its handle and would spin around while twirling the pail. The fact that the water would not spill out of the pail had intrigued Newton and he relayed this same principle into an explanation for why the planets do not crash into the sun while in orbit. By applying this principle, Newton had discovered the concept of centrifugal force where a spinning body tends to move outward from the middle of its axis of rotation. Newton’s finding were touted, and in October of 1667 he was appointed Lucasian Professor of Mathematics at the age of twenty-six. He was the youngest person ever to hold that title. It was while he was at Trinity that he devised a formula that demonstrated how gravity force weakens over distance as in the case of the planets revolving around the sun. Thus, Newton’s Law of Gravitation as stated by Shipman, Wilson, & Todd: “Every particle in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them” (p. 54). An example of Newton’s law according to this inverse square principle is that if the distance between two objects were doubled, the force of attraction between them would be one-fourth of the attraction at the original distance. If the distance were tripled, the force of attraction between them would be one-ninth of the attraction at the original distance, and so on. Some important components in Newton’s Law of Gravitation are mass and weight. The weight of an object is the gravitational force exerted on an object. The mass of the object refers to the amount of material it is made up of. Whereas mass tends to be a constant of an object, its weight depends on the position of the object. Although the gravitational acceleration would change if an object were to be transported to different locations in space, the weight and mass would remain proportional to each other. In 1670, Newton invented a reflecting telescope that consisted of a concave mirror placed on the end of a cylinder. This innovative invention overshadowed the refracting telescope of Galileo Galilei. When the light from a distant object reached the mirror it would bounce back to a particular point of distance in front. He placed an eyepiece on the side of the cylinder, which created a magnified image of the object. Although Galileo’s previously telescope had been in wide use, it did not take long for astronomers to embrace Newton’s superior instrument. The popularity of his reflecting telescope attracted the attention of the Royal Society who inevitably invited Newton to join their ranks. In June of 1679, Newton’s mother passed away and she left most of her worldly possessions in his name including Woolsthorpe Manor. It was during this time that Newton became somewhat of a hermit and continued his experiments and discoveries in private. In 1684, Edmund Halley pondered Newton’s theory of the inverse-square law and how it could be applied to his study of astronomy. Halley left London to visit the reclusive Newton in Cambridge and asked what shape the path of a planet would be according to his findings. Newton stated that the path would be in the form of an ellipse and further explained the calculations behind this assertion. It was evident that Newton had been continuing to make breakthroughs in the field of science, even without an audience. Fame was never the intention of Newton; they were merely a consequence of his advancements. Newton published Philosophiae Naturalis Principia Mathematica, better known as Principia on July 5, 1687 as a Royal Society publication. Written in only eighteen months, this publication was the pinnacle of Newton’s achievements and provided a revelation in science. In it, Newton stated his theories and illustrated how they applied to moons, planets, and comets. It was through this information that Halley researched comet observations and successfully predicted that a bright comet that had been observed in 1682 would again make an appearance in 1758. Although Halley did not live to see his prediction unfold, the comet was appropriately named after him. In Principia, Newton stated three laws of motion, which remain the basis for the science of mechanics. Newton’s First Law of Motion as stated by Shipman, Wilson, & Todd: “An object will remain at rest or in uniform motion in a straight line unless acted on by an external, unbalanced force” (p. 47). This idea deals with the concept of inertia, which is the inclination for objects to resist change or movement. This purports that a force has to ...