The gravitational simulation used in the following is constructed from the model given here and here.
It draws the paths followed by a collection of n interacting gravitating bodies. The paths may be displayed in all colors or monochromatically. The interacting object may also be displayed as simple points. When "trails" are displayed, and when one path crosses another, the wavelength of the point of crossing is incremented by one color value. This gives you a sense of areas of relatively high activity. Also, the "rainbow" trail feature can be used to give you a sense of particle velocity. A rapid change of color along a trail indicates a slow particle whereas a slow change of color along a path indicates a rapidly moving particle.
The units used are all abstract.
This tool will also synthesize the sound you might hear if you could listen to the gravitational waves of a single isolated body within an n-body system.
This tool is provided to you free of charge (under the GNU license) and is given partially in source form as well as the active-X component. The source code is given in an hypertext application - an .hta file. Because the language is simple JavaScript you may modify it to define placement, velocity & mass of each individual particle. There are a few other paramters you may modify as well ... the code is fairly obvious.
The following pages display sample images that have been generated by this tool. On some pages you'll find a matching sound file.
Besides being useful as a simulation of gravity, its just fun to watch, and listen to. I have even used used it to create the graphics, (textures) for computer games.