| Philosophiae naturalis principia mathematica | |
| 1687 |  |
| Isaac Newton(1642-1727) | |
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Newton was an influx where into streamed the main trends of achievements in natural science which had been achieved before him, and also a fountainhead wherefrom flowed trends of research that followed him. In this remarkable book, Newton organized and unified achievements made in mechanics initiated by Tartaglia and later developed by Stevin, Galileo and Huygens, and also achievements in astronomy, accomplished by Copernicus, Brahe, Kepler, Galileo and Huygens. As an influential book that completely changed the foundation of science, one can hardly overestimates the decisive value of this work as revolutionary not only in the history of science, but also in the history of human civilization as well. If one can say that science is a way of grasping the world, then Newton established a new world system, a new “paradigm” for the world. Newton’s “Principia” consisted of three books. In the first book, Newton began with several definitions in the fashion of Euclid’s “Stoicheia”. He defined mass, momentum, inertia as the force of inactivity, applied force and centripetal force with superb abstract, logical clarity. After that Newton presented three famous axioms, the so-called Newtonian laws, which were based on these fundamental concepts. The first law is that of inertia, which affirms that everybody maintains a state of rest or a state of uniform motion in a straight line, except when the state is forced to be altered by applied force. The second law asserts that the change of motion is proportional to applied force, and arises in the direction of the straight line in which force is applied. The third law maintains that action and reaction are equal and their opposite is the mutual action between two bodies. The third law was his most original contribution to mechanics. In the first two laws Newton owed his definitions to the contributions of his predecessors, but he was the first to strictly formulate and logically organize them. The second book dealt with hydrodynamics, decisively rejecting Descartes’s vertical cosmos theory. It was in the third, however, that Newton’s greatest achievement the theory of universal gravitation appeared. In it, Newton asserted that everybody obeys a principle of mutual gravitation in which two bodies attract each other with a force that is in proportion to their mass and in inverse proportion to the square root of the distance between them. Newton along with Robert Hook and other scientists knew that force must be in inverse proportion to the distance between two bodies from facts they had derived from Kepler’s third law and Huygens’s formula of centripetal force in uniform circular motion described in Huygens’s’ “Horologium” in 1673. This law could only be applied to bodies or planets in uniform circular motion and could not be applied to those in elliptical motion in compliance with Kepler’s first and second laws. Newton was the only one to synthesize all of them and assure the application of dynamics to the general cosmology based on the theory of gravitation. Newton established a simple, clarified theory which applied to all things in the universe from the smallest particle to huge heavenly bodies, that is, his theory of universal gravitation. With this Newton created and indisputable position for the mechanistic view of the universe which is still prevalent among us. |
