This document provides a brief history of statistical physics from the 17th century to present day. It outlines the development of kinetic theory of gases, caloric theory, and statistical mechanics. Key figures discussed include Daniel Bernoulli, Rudolf Clausius, James Clerk Maxwell, Ludwig Boltzmann, and J. Willard Gibbs. The document concludes that statistical physics remains an active area that can provide insights into nonlinear systems and irreversible processes.

1. History of Statistical Physics
By
Aqeel A. Al-Taie
May, 2016

2. Outline:
• Introduction
• Historical development:
• - Kinetic theory of gases
• - Caloric theory
• - Statistical mechanics
• Conclusions

3. Introduction
Statistical Physics: Unfinished & High
active part of physics.
We do not have the theoretical framework
to describe highly irreversible processes
such as fracture.
Properties of nonlinear systems that lead to
complicated pattern formation processes
is beyond our study of statisical physics.

4. Historical Development
In 17th century, the gas laws was formulated
when the physical nature of the air surrounding
the earth established .
The invention of the mercuri barometer by
Evangelista Torricelli (1608–47) and the fact
that Robert Boyle (1627–91) introduced the
pressure P as a new physical variable where
important steps. Then Boyle–Mariotte’s law PV
= const. for constant temperature, where V is
the volume, was formulated.

5. Kinetic Theory of Gases
The Swiss physicist and mathematician
Daniel Bernoulli published in 1738, the
Hydrodynamics which laid the basis for
the kinetic theory of gases. In this work,
Bernoulli posited the argument, still used
to this day, that gases consist of great
numbers of molecules moving in all Daniel Bernoulli
directions, that their impact on a (1700-82)
surface causes the gas pressure that
we feel, and that what we experience
as heat is simply the kinetic energy of
their motion.

6. Caloric Theoty
Bernoulli’s kinetic theory received so little
attention because most of scientists at that
time believed in the so–called caloric theory
of heat.
In this theory heat was a substance called
”caloric”. Caloric was considered to
be a fluid composed of particles which repel
each other.Each matter particle was thought to
be surrounded by an atmosphere of caloric
whose density increases with temperature.the
attractive forces between matter particles are of
gravitational origin just as the forces
between the sun and the planets.

7. At a certain distance between matter particles
there would be equilibrium between the caloric
repulsion and the gravitational attraction.
Reputed scientists as Pierre Simon de Laplace
(1749–1827) gave a very sophisticated
derivation of the gas laws within the caloric
theory.
In 1847, James Joule published a
paper in which he stated the
principle of conservation of energy.
From his experiments he concluded
that heat is not a substance but a form
of energy, this thing defeated the caloric theory.

8. In 1857 The german physicist Rudolf
Clausius published a paper on the
diffusion of molecules which
contributes in the kinetic theory; and
coins the term"entropy" from the Rudolf Clausius
Greek word for transformation,τροπη. (1822-88)
He proposes the amount of energy in
the universe is constant and that
the entropy of the universe is
constantly increasing.

9. In 1859, Scottish physicist
James Clerk Maxwell
formulated the Maxwell
distribution of molecular
velocities, which gave the
proportion of molecules James Clerk Maxwell
having a certain velocity in (1831-79)
a specific range. then in 1864, Ludwig
Boltzmann (1844-1906) extends Maxwell's
distribution law to include external forces.
In the case of gravity, he worked through the
distribution of densities and pressures and
that thermal equilibrium was maintained.

10. In 1884, the term "statistical
mechanics" was coined by the
American mathematical physicist
J. Willard Gibbs, he publishes
Graphical Methods in the
Thermodynimcs of Fluids and a Method of
Geometrical Representation of the
Thermodynamic Properties of Substances by
Means of Surfaces, introducing many new
graphical techniques.
Statistical Mechanics

11. In this century, Lars Onsager (1903–1976)
made several outstanding contributions. By
his exact solution of the Ising model, in two-
spatial dimensions, he proved that the
framework of statistical physics could
indeed tackle the problem of phase
transitions.

12. Conclusions
The motivation for studying the statistical
physics because the properties of non-
linear system granular media, earthquakes,
friction and many systems underlying to the
scope of statistical physics.
The field of statistical physics is in a phase of
rapid change. New ideas and concepts
permit a fresh approach to old problems.