3-dimensional 1-particle gas:
One hard sphere is moving in a cubic box with semicircular
scatterers mounted on some walls.
Velocity space is now 3-dimensional, with a 2-dimensional
spherical energy surface.
To demonstrate the equal a priory density on the
energy surface we project the spherical surface onto a rectangle,
using Lambert's area preserving (and therefore density preserving)
Interestingly, the velocity density p(vx) is now a
And yet another dimension ...