# What is kinetic theory?

What is kinetic theory? I am taking a course on fluid dynamics right now, and I have been wondering about one thing for some time now. We have three ways to look at a gas ($N$ particles):

1) Microscopic: The state (position and velocity) of each particle is known at every point of time. Evolution of the state is determined by Newton.

2) Kinetic: We have a distribution function f (as the solution of the Boltzmann-equation) of the particles. We have derived the Boltzmann equation by using Heuristic arguments and Newton.

3) Macroscopic: Looking at macroscopic quantities.

Is this correct? And is the essence of the kinetic view the fact that we have a distribution function and an evolution equation for that? Especially in contrast to the microscopic view? In addition, I wrote down the word "continuum" next to kinetic in my lecture notes but can't make sense of that.

And another question: We derived the macroscopic view from the kinetic view, but i am not so sure about the relation between the microscopic view and the kinetic view.

• Continuum mechanics: There are an infinite number of infinitesimally small particles, making it impossible to know the state of each and every one of them. Instead one describes state in terms of thermodynamic variables (pressure, temperature, density, ...) as functions of position and time. Aug 17 '18 at 15:13
• Please refine this question so (a) you are asking just one question, and (b) the question isn't so broad that we need to write a textbook, or even a chapter of a textbook to answer it. As is, this question will almost certainly be closed. Aug 17 '18 at 15:14