Question #6fd31

1 Answer
Dec 2, 2017

Discovery of the limitations of Newtonian Laws led to two revolutionary ideas in physics at the beginning of the last century -
(1) The Relativity Theory (1905), and
(2) The Quantum Theory (1900)

Limitation 1: Newtonian Mechanics come with built-in assumptions about space and time. The assumptions being - space is absolute (distance between two points is space is the same for all inertial observers) and time is absolute (time interval between two events is the same for all inertial observers).

These assumptions were found to be not true later. But the discrepancy between prediction and observation because of these erroneous assumption show up only when the speed of the inertial frames approach the speed of light. Modifying Mechanics by relaxing these assumptions is the Relativity Revolution and the new physics is called Relativistic Mechanics.

Limitation 2: Newtonian Mechanics also come with many other assumptions which were found to be not true. It assumes that particles (localized) and waves (non-localized) are two separate phenomena. But in the microscopic world it became evident that particle nature and wave nature are two different aspects of the same phenomena (wave-particle duality).

Phenomena such as photoelectric effect and Compton effect show that light behave like particles (which were established to be waves by Young & Fresnel). If light shows both wave and particle properties, it is possible that particles such as electrons may show wave properties. This was the deBroglie hypothesis . This was confirmed by Davisson-Germer Experiment.

A consequence of this wave-particle duality of nature, is the loss of determinism. Also the classical ideas of continuous nature of physical quantities such as Energy, Momentum etc. have to be given up. Physical quantities such as energy, charge etc. are quantized. The new mechanics that embodies all these revolutionary ideas is called Quantum Mechanics.