I.

Introduction

Isaac Newton (1642-1727), English physicist, mathematician, and natural philosopher, considered one of the most important scientists of all time. Newton formulated laws of universal gravitation and motion—laws that explain how objects move on Earth as well as through the heavens (see Mechanics). He established the modern study of optics—or the behavior of light—and built the first reflecting telescope. His mathematical insights led him to invent the area of mathematics called calculus (which German mathematician Gottfried Wilhelm Leibniz also developed independently). Newton stated his ideas in several published works, two of which, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy, 1687) and Opticks (1704), are considered among the greatest scientific works ever produced. Newton’s revolutionary contributions explained the workings of a large part of the physical world in mathematical terms, and they suggested that science may provide explanations for other phenomena as well.

Newton took known facts and formed mathematical theories to explain them. He used his mathematical theories to predict the behavior of objects in different circumstances and then compared his predictions with what he observed in experiments. Finally, Newton used his results to check—and if need be, modify—his theories (see Deduction). He was able to unite the explanation of physical properties with the means of prediction. Newton began with the laws of motion and gravitation he observed in nature, then used these laws to convert physics from a mere science of explanation into a general mathematical system with rules and laws. His experiments explained the phenomena of light and color and anticipated modern developments in light theory. In addition, his invention of calculus gave science one of its most versatile and powerful tools.