Quantum Mechanics

Newtonian mechanics must be replaced by Einstein’s special theory of relativity when dealing with particle
speeds comparable to the speed of light. As the 20th century progressed, many experimental and theoretical
problems were resolved by the special theory of relativity. For many other problems, however, neither
relativity nor classical physics could provide a theoretical answer. Attempts to apply the laws of classical
physics to explain the behavior of matter on the atomic scale were consistently unsuccessful. For example,
the emission of discrete wavelengths of light from atoms in a high temperature gas could not be explained
within the framework of classical physics. As physicists sought new ways to overcome these issues, another
revolution took place in physics between 1900 and 1930. A new theory called quantum mechanics was highly
successful in explaining the behavior of particles of microscopic size. The first explanation of a phenomenon
using quantum theory was introduced by Max Planck. Many subsequent mathematical developments and
interpretations were made by a number of distinguished physicists, including Einstein, Bohr, de Broglie,
Schrödinger, and Heisenberg.