I am no expert on phase space, I'll just spout back what little I can remember about it to try and give you an idea how complex and profound these kind of questions are, and how little resemblance the world of particle physics hass compared to our everyday world of levers, pulleys, ping-pong balls and ordinary objects.

Phase space isn't a real physical thing. Its a mathematical construct of six dimensions, three space dimensions, x, y, z; and three momentum dimensions Px, Py and Pz. Certain particle interactions can be mapped into phase space where they exhibit certain properties and follow certain laws which can be used to predict their behavior.

At any moment, a particle in phase space will have a position vector mappable into three orthogonal components, and a momentum vector mappable into three orthogonal components. According to the Pauli Exclusion Principle only two particles (of opposite spin) can simultaneously exist in a hypervolume of phase space. This limits the amount of particles which can exist in dense, hot gases. This quantum process overwhelms the classical Gas Laws in places like stellar interiors, preventing gases from being compressed any further. These so-called degenerate gases are why stars blow up. The back pressures expected from the Gas Laws are no longer sufficient to prevent gravitational collapse, and the star's core implodes in on itself, faster than the outer layers can fall it to catch up with them. Boom.

I didn't look this up, its just something I remember from a long time ago because I thought it was very, very interesting. I repeat it only to try and communicate to you how you simply cannot do particle physics with high school algebra and the common concepts and objects of our ordinary, everyday experience.

This is what makes science so frustrating (and one reason I got out of it). You simply cannot work at this level of abstraction without lots of preparation and training. Its like playing Bach when you've been deaf from birth. You need conceptual tools that the ordinary individual, no matter how intelligent he may be, does not have at his disposal. It is sad, our sense of fairness and intellect leads us to believe that by simple hard work and common sense (and a little research on the internet) we should be able to figure anything out.

The truth is we cannot.