Why statistical mechanics was introduced?

When we consider bodies at macroscopic level they consist of uncountable atoms or molecules i.e about 10^23 atoms/gm mole. In such cases we cannot predict the result of interactions between atoms with the help of ordinary classical laws of motion. In order to solve such a situation, a new branch of science called statistical mechanics is introduced.

Statistical mechanics is the branch of science which establishes the interpretation of macroscopic behavior of system in terms of its microscopic properties. It doesn't deal with motion of each particle but it takes into account the average or most probable properties of system with out going into interior details of characteristics of its constituents.

The larger the number of particles in the physical system considered, the more nearly correct are statistical predictions.

Before the advent of quantum theory, Maxwell, Boltzmann, Gibbs etc applied statistical methods making the use of classical physics. These statistical methods are known as "classical statistics" or "maxwell boltzmann statistics".

These statistics explained successfully many observed physical phenomenon like temperature, pressure, energy etc; but couldn't explain adequately several other experimentally observed phenomenon like black body radiation, specific heat at low temperature etc.

In order to explain such phenomenon "quantum statistics" was introduced and developed by Fermi, Dirac, Bose, Einstein with new approach by using new quantum idea of discrete exchange of energy between system.


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