Newton's laws - Essay Example

Sir Isaac Newton was an English physicist, mathematician, astronomer, inventor, philosopher and alchemist. A man of profound genius, he is widely regarded as one of the most influential scientists in history. Among his scientific accomplishments, Newton wrote the Philosophiae Naturalis Principia Mathematica, wherein he described universal gravitation and, via his laws of motion, laid the groundwork for classical mechanics. With Gottfried Wilhelm Leibniz he shares credit for the development of differential calculus. Newton was the first to promulgate a set of natural laws that could govern both terrestrial motion and celestial motion, and is credited with providing mathematical substantiation for Keplers laws of planetary motion, which he expanded by arguing that orbits (such as those of comets) could be elliptic, hyperbolic, or parabolic (Bell, 1937). In 1679, Newton started to work on mechanics, i.e., gravitation and its effect on the orbits of planets, with reference to Keplers laws of motion, and consulting with Hooke and Flamsteed on the subject. He published his results in De Motu Corporum (1684). This contained the beginnings of the laws of motion that would inform the Principia. Philosophiae Naturalis Principia Mathematica (now known as the Principia) was published 5 July 1687) with encouragement and financial help from Edmond Halley. In this work Newton stated the three universal laws of motion that were not to be improved upon for more than two hundred years. He used the Latin word gravitas (weight) for the force that would become known as gravity, and defined the law of universal gravitation. In the same work he presented the first analytical determination, based on Boyles Law, of the speed of sound in air. It was perhaps the force of the Principia, which explained so many different things about the natural world with such economy, that caused this method to become synonymous with physics, even as it is practised almost three and a half centuries after his beginning. Today the two aspects that Newton outlined would be called analysis and synthesis (Simmons, 1996). The Principia consists of three books 1. De motu corporum (On the motion of bodies) is a mathematical exposition of calculus followed by statements of basic dynamical definitions and the primary deductions based on these. It also contains propositions and proofs that have little to do with dynamics but demonstrate the kinds of problems which can be solved using calculus. 2. The second book was broken off from the first, since it would have otherwise become too long. It contains sundry applications such as motion through a resistive medium, a derivation of the shape of least resistance, a derivation of the speed of sound and accounts of experimental tests of the result. 3. De mundi systemate (On the system of the world) is an essay on universal gravitation that builds upon the propositions of the previous books and applies them to the motions observed in the solar system — the regularities and the irregularities of the orbit of the moon, the derivations of Keplers laws, applications to the motion of Jupiters moons, to comets and tides (much of the data came from John Flamsteed). It also considers the harmonic oscillator in three dimensions, and motion in arbitrary force laws. Newtons laws of motion (law of inertia, fundamental law of dynamics, law of reciprocal actions) were verified by experiment and observation for over 200 years, and they are excellent approximations at the scales and speeds of everyday life. At the atomic scale, they become a poorer approximation to quantum mechanics, and at speeds comparable to the speed of light, they become a poorer approximation to relativity. Just as they fail for material objects moving at speeds close to the speed of light, they fail for light itself. Newtons first law appeared to be in the past just a special case of the second law, and it was thought Newton stated the first law separately simply in order to throw down the gauntlet to the Aristotelians. However, modern physicists think that the First Law defines the reference frames in which the other two laws are valid. These reference frames are called inertial reference frames or Galilean reference frames, and are moving at constant velocity, that is to say, without acceleration. (Note that an object may have a constant speed through its motion path and yet have a non-zero acceleration, as in the case of uniform circular motion. This means that the surface of the Earth is not an inertial reference frame, since the Earth is rotating on its axis and orbits around the Sun. However, for many experiments, the Earths surface can safely be assumed to be inertial. The law of gravity became Sir Isaac Newtons best-known discovery. Newton warned against using it to view the universe as a mere machine, like a great clock. He said, "Gravity explains the motions of the planets, but it cannot explain who set the planets in motion. God governs all things and knows all that is or can be done." (Bell, 1937) His scientific fame notwithstanding, the Bible was Sir Isaac Newtons greatest passion. He devoted more time to the study of Scripture than to science, and said, "I have a fundamental belief in the Bible as the Word of God, written by those who were inspired. I study the Bible daily." Newton himself wrote works on textual criticism, most notably An Historical Account of Two Notable Corruptions of Scripture. He also attempted, unsuccessfully, to find hidden messages within the Bible. In his own lifetime, Newton wrote more on religion than he did on natural science. He believed in a rationally emanent world, but he rejected the hylozoism implicit in Leibniz and Baruch Spinoza. Thus, the ordered and dynamically informed universe could be understood, and must be understood, by an active reason, but this universe, to be perfect and ordained, had to be regular. Newton and Robert Boyle’s mechanical philosophy was promoted by rationalist pamphleteers as a viable alternative to the pantheists and enthusiasts, and was accepted hesitantly by orthodox preachers as well as dissident preachers like the latitudinarians. Thus, the clarity and simplicity of science was seen as a way to combat the emotional and metaphysical superlatives of both superstitious enthusiasm and the threat of atheism, and, at the same time, the second wave of English deists used Newtons discoveries to demonstrate the possibility of a "Natural Religion." The attacks made against pre-Enlightenment "magical thinking," and the mystical elements of Christianity, were given their foundation with Boyle’s mechanical conception of the universe. Newton gave Boyle’s ideas their completion through mathematical proofs, and more importantly was very successful in popularizing them. Newton refashioned the world governed by an interventionist God into a world crafted by a God that designs along rational and universal principles. These principles were available for all people to discover, allowed man to pursue his own aims fruitfully in this life, not the next, and to perfect himself with his own rational powers. The perceived ability of Newtonians to explain the world, both physical and social, through logical calculations alone is the crucial idea in the disenchantment of Christianity (Berlinski, 2000). Newtons laws of motion and gravity provided a basis for predicting a wide variety of different scientific or engineering situations, especially the motion of celestial bodies. His calculus proved vitally important to the development of further scientific theories. Finally, he unified many of the isolated physics facts that had been discovered earlier into a satisfying system of laws. Newtons conceptions of gravity and mechanics, though not entirely correct in light of Einsteins Theory of Relativity, still represent an enormous step in the evolution of human understanding of the universe. For this reason, he is generally considered one of historys greatest scientists, ranking alongside such figures as Einstein and Gauss. Works Cited: 1. Bell, E.T.. Men of Mathematics, New York: Simon and Schuster, 1937. 2. Berlinski, David, Newtons Gift:How Sir Isaac Newton Unlocked the System of our World, Simon & Schuster, 2000. 3. Simmons, J, The giant book of scientists -- The 100 greatest minds of all time, Sydney: The Book Company, 1996. Read More