This model demonstrates the effect of a gravity on gas molecules. It is one in a series of GasLab models that use the same basic rules for what happens when molecules run into each other. In this model, a gaseous "atmosphere" is placed above the surface of a "planet", which exerts a gravitational pull on each molecule. The molecules "escape" if they reach the top of the screen. The initially uniform energy and density of the gas becomes nonuniform as the model runs.

For detailed instructions on using the program, take a look at the info window from the Atmosphere model.

Download the StarLogoT source code for the Atmosphere model:
Download atmosphere

To run this file you need StarLogoT2002 for the Macintosh.
(download StarLogoT)

Click on one of the pictures to see a quicktime movie of the model:
The movie shows the evolution of molecules with initially uniform speeds and density. One molecule's path is traced in yellow. The graphs show histograms of a) average energy and b) density as a function of height after the model has run for a while.