The Ideal 2D Gas with Gravity simulation shows the motion of a 2-dimensional ideal gas with N particles confined in an vertical strip of the 2-d Euclidean space, under the action of a constant gravitational field. At t=0 the the gas is far from its equilibrium state: the initial position distribution is uniform in a certain orthogonal region of the strip. The velocities of the particles have random directions and their magnitudes are identical. Because of the particle-particle (p-p) interactions(8,9) and under the action of the gravitational field, the system is moving towards its state of equilibrium.

A supplemental pdf document describes the theoretical model of the 2-dimensional gas and derives the probability distribution in the phase space, which determines its equilibrium state. The time sequence of the position distributions converge to the "exponential atmosphere" and that of the velocities to the Maxwell-Boltzmann distribution. The gas converges to its equilibrium state which is well-defined and independent of the initial state of the gas. In the simulation, we can watch the evolution of the gas towards its equilibrium state. Uses can observe the dependence of the equilibrium position-distribution on the strength of the gravitational field. They can also carry out measurements in the virtual environment, and compare the achieved results with their theoretical predictions.