Ludwig Boltzmann

The energy of the universe is constant; the entropy of the universe tends toward a maximum.

The atomists have won a complete victory.

All our ideas and concepts are only internal pictures.

The second law can never be proved mathematically by means of the equations of dynamics alone.

The theory of heat is essentially a mechanical theory.

The most probable state is the one with the highest entropy.

My theories are not for the present, but for a time when the current opposition will have died down.

The problem of explaining the irreversible approach to equilibrium on the basis of reversible laws of motion is the fundamental problem of statistical mechanics.

We do not need to assume any special force to explain the pressure of a gas; it is simply the result of molecular impacts.

The concept of entropy is the most subtle and profound in all of physics.

If one considers heat as motion, then the entire theory of heat becomes a part of mechanics.

The universe, considered as a mechanical system, began in a very improbable state.

The laws of probability apply to the world of atoms just as they do to games of chance.

I have devoted my life to the service of science, and I have not been understood.

The H-theorem provides a mechanical interpretation of the second law.

The detailed motion of every single molecule is far too complicated for us to follow, but the average behavior of many molecules is simple and law-like.

The task of the theoretical physicist is to construct mental pictures of the processes of nature.