Prof. Muni Mahendra Kumar
Newton adopted the laws of Euclidean geometry. He assumed the space to be flat, and on the basis of this assumption he asserted that the geometry of space was Euclidean. The laws of optics, such as the rays of light always travel in a straight line and never meet each other as they travel parallel to each other, were based on the Euclidean geometry of space. In the field of mechanics, the motion of bodies was considered to take place with respect to the absolute space. Newton used the empty space as a system of reference within which it was possible to distinguish absolute motion. For, when any body moves, its motion is ordinarily considered as relative to other bodies. But if there is no object which is absolutely at rest, the motion of all bodies become relative. For instance, a ship is moving in a sea; then the motion of the ship is said to take place relative to water. But water itself is not at rest; it also undergoes motion on account of the motion of the earth which moves relative to the sun. Thus it means that the ship as well as water move. Further, the sun too, together with its whole solar system, goes on moving in space and so on. Thus in absence of any body being absolutely at rest, the question as to what is the frame of reference, arises at once. To solve this puzzle, Newton first of all suggested[1] that it was possible that in the remote regions of the fixed stars or perhaps far beyond them, there might be some body absolutely at rest, and that making it a frame of reference, the absolute motion of the bodies might be distinguished. But at the same time he felt that it was not possible to obtain knowledge about that fixed frame of reference through observation. He, therefore, concluded that the absolute space, which is always at rest, should be used as a frame of reference.
He established his hypothesis of motionless absolute space on the basis of the laws of dynamics. Dynamics concerns with the relation of force with acceleration, motion, speed, etc. In relative motion, the value of acceleration also should be relative. But Newton, on the basis of mathematical calculations, showed that acceleration of a moving body depended upon the force producing the motion, and hence, was not relative. In Newton's Second Law of Motion, this fact was stated thus-
Force = Mass x Acceleration
Newton used this equation to explain the centrifugal forces and the motion of the rotating system. His explanation was generally accepted by the scientists, and hence, his theory of absolute space was also unanimously adopted as the foundation of classical physics. Thus Newton's concept of space had remained unshaken in the realm of physics till the announcement of theory of relativity by Dr. Einstein.
Newton's theory of absolute time was also accepted by the scientists unanimously. It was the characteristic of Newton's concept that according to it, time was regarded as an independent entity. Also, the absolute time and the absolute space were independent of each other. In Newton's mechanics, the motion of the bodies was not thought to effect the flow of time. Newton held that time flowed equally without regard to anything external from the infinite past into the infinite future.
