This is a little toy that simulates the effect of gravity. You can specify the mass, location and velocity of any number of objects, and also give a name and colour to each. The programme will then run a simulation of their interaction with each other.
The time increment between successive iterations can be specified, and so can the Universal Gravitational Constant. But both of these parameters have default values that work fairly well.
Be warned, however, that the programme is incomplete. There is no help file (so this page is all the documentation you get), and some of the other features in the menus do not work. In particular, the "tracking" feature has no effect. The purpose of this feature is to keep any object, or the system's centre of mass, in the middle of the screen at all times.
Another feature I never got around to implementing is Coalescence: you will find that when two objects get really close together, they will fly apart at an improbable speed - often this will result in the effective end of your simulation. So I decided to make a more realistic effect by merging two objects into one if their separation became less than some threshold. But this feature never quite came to be. Sorry.
When you launch the programme, you will be greeted by a little message suggesting how to proceed. Click OK, and you'll get the main window. You can change the Gravitational Constant or the Time Increment values from the Configuration menu, or add an object from the Object menu. An existing object can be edited from there. Or you can load one of the sample data files using the File menu. The File menu also has a "Save As..." item that you can use to save your own simulation data. The data files are plain text, so you could edit or create one with an ordinary text editor, if you want.
Once a few objects have ben loaded or created, the Simulation menu is enabled. Use it to start the simulation. If you want to stop the simulation, to exit the programme, re-load the data file or whatever, the Simulation menu is the way to do it.
Gravity is free to anyone who wants it. Simply download the Zip file (44,452 bytes) and install it on your PC. You do need to be running Windows, but that's the only requirement. Should you ever wish to uninstall Gravity, all you need to do is delete the zip file and the files it contains. It is recommended that you create a new folder on your system and install Gravity into it. Then uninstalling is simply a matter of deleting the folder. Gravity does not do anything to your registry or store any information of any kind anywhere on your system, except when you choose to save a simulation.