Scientists who changed our beliefs

Isaac Newton and the Law of Gravity

Our second important scientific advance stems from the first. Isaac Newton’s (1543-1727) Universal Law of Gravitation helps support Copernicus’ observation that the earth and other planets revolve around the sun. Newton argued that the idea came to him when he saw an apple fall from a tree straight down to the earth. From there he made the important leap that, in a sense, the apple was like the moon in that each body was draw toward the earth. Newton’s (1543-1727) Universal Law of Gravitation was published in his Principia (Philosophiae Naturalis Principia Matematica) in 1687. Newton’s Law of Gravitation states that each body of mass attracts all other bodies of mass through a force along the line that intersects both masses. That force is gravity and it is directly proportional to the product of the two bodies of mass, and inversely proportional to the square of the distances between the two bodies of mass. Although others had posited similar ideas earlier than Newton, most notably Robert Hooke who published his System of the World in the 1660s, Newton was the first to not only present the idea of gravity but also offer scientific proof to support his claim in the form of a mathematical equation describing the Law of Gravitation. It wasn´t until 1798 that the calculation of a value for g, the gravitational constant, was possible thanks to the work of Henry Cavendish who was able to conduct a laboratory experiment to calculate the gravitational pull between two bodies of mass. Thus, Isaac Newton’s contribution to scientific advances lies both in his Universal Law of Gravity and also in his demonstration of that law. In this way, Newton moved beyond the traditional emphasis on describing natural phenomena to explaining such phenomena and providing a deeper understanding of the world around us. While Newton’s law is accurate enough for practical use, there are certain aspects of Newton’s Universal Law of Gravitation that are cause for concern. For example, Newton’s law cannot be used to accurately predict light deflection due to gravity. The result predicted by Newton’s Universal Law of Gravitation is just half the amount of deflection actually observed. A more accurate calculation is provided by the next important scientific advance, the Theory of General Relativity presented by Albert Einstein.