Terme de Glossaire

An English philosopher, mathematician, physicist, alchemist and astronomer. An emblematic figure in the sciences, Isaac Newton is above all known for his universal theory of gravitation. Gravitation is the force of attraction one body exerts over another. When it is exerted by the Earth this force is called ‘gravity’ or ‘weight’. According to Newton’s law of gravitation, the force of attraction grows when mass increases. Legend has it that Newton came to understand the principle when he saw an apple falling from a tree. Isaac Newton is also behind the three universal laws of motion. The first takes note of the principle of inertia: ‘A body on which no force is acting does not change its quality of motion.’ The second evokes the basic principle of dynamics: ‘The variation in the quantity of motion is proportional to the forces exercised on it,’ and the last one, the principle of action and reaction: ‘Two bodies exert on each other forces of equal intensity and in the opposite direction,’ takes into account the fact that to a force (F) which is exerted on a body there corresponds a second force (F') of the same intensity but working in the opposite direction. His work Philosophiæ Naturalis Principia Mathematica, written in 1686, is considered as a major work in the history of science. It is in this book that he describes universal gravitation, formulates the three laws of motion and lays the foundations of classical mechanics.