Maxwell-Boltzmann statistics, Bose-Einstein statistics and Fermi-Dirac statistics all describe how energy is distributed in different physical systems at a given temperature.
For example, Maxwell-Boltzmann statistics describes how the speeds of particles are distributed in an ideal gas.
The temperature of a gas is only a statistical average of the total energy of the gas. But at a given temperature, not all particles have the exact same speed as the average: some are higher and others lower than the average.
For a large number of particles however, the fraction of particles that will have a given speed at a given temperature is highly deterministic, and it is this that the distributions determine.
One of the main interest of learning those statistics is determining the probability, and therefore average speed, at which some event that requires a minimum energy to happen happens. For example, for a chemical reaction to happen, both input molecules need a certain speed to overcome the potential barrier of the reaction. Therefore, if we know how many particles have energy above some threshold, then we can estimate the speed of the reaction at a given temperature.
The three distributions can be summarized as:
Figure 1.
Maxwell-Boltzmann vs Bose-Einstein vs Fermi-Dirac statistics
. Source.
A good conceptual starting point is to like the example that is mentioned at The Harvest of a Century by Siegmund Brandt (2008).
Consider a system with 2 particles and 3 states. Remember that:
Therefore, all the possible way to put those two particles in three states are for:
  • Maxwell-Boltzmann distribution: both A and B can go anywhere:
    State 1State 2State 3
    AB
    AB
    AB
    AB
    BA
    AB
    BA
    AB
    BA
  • Bose-Einstein statistics: because A and B are indistinguishable, there is now only 1 possibility for the states where A and B would be in different states.
    State 1State 2State 3
    AA
    AA
    AA
    AA
    AA
    AA
  • Fermi-Dirac statistics: now states with two particles in the same state are not possible anymore:
    State 1State 2State 3
    AA
    AA
    AA
Figure 1.
Maxwell-Boltzmann distribution for three different temperatures
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Most applications of the Maxwell-Boltzmann distribution confirm the theory, but don't give a very direct proof of its curve.
Here we will try to gather some that do.

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