So what? Well, if you're a sad git (mea culpa) it can be fun - remember Newton's Balls? The two images above were both obtained using screenshots. The left hand one was derived from the a simulation that ships with Gravity 6 where the Earth, Moon and Mars are all in orbit around Saturn (now you know how sad I am). The right hand image is an animated image made using a few frames from another simulation - the jerkiness you see is due to keeping down the size of the image your browser has just downloaded and is not (usually) a feature of the program.
You don't but it's free and maybe even educational. It ships with a number of pre-built "universes" including some pretty bitmaps to wrap around your balls (e.g. Saturn above) and the Help file includes some tutorials to help you to learn the program.
I believe there is a certain elegance to the fact that, in a Newtonian worldview, you can describe the gravitationally induced motion of planets, moons and stars simply by noting that:
As you may see if you decide to play with the program, the way three or more bodies can interact and change each other's orbits is remarkable and sometimes even beautiful.
Gravity 6 was inspired by a program called Gravity written in 1991 by George Moromisato. His program ran simulations in two dimensions and I wanted to see what difference running in three dimensions would make. The Gravity 6 source code was developed totally independently but by way of tribute to George I am releasing Gravity 6 as freeware. I hope he approves.
Gravity 6 runs under Windows 9x, NT4, 2000, XP and Vista. If installing under a Vista standard user account select "All Users" when prompted or no Start Menu shortcuts will be created for that account.
It needs OpenGL which does not ship with Windows 95 but can be obtained as an add-on from Microsoft at ftp://ftp.microsoft.com/softlib/MSLFILES/OPENGL95.EXE if it has not already been installed by your graphics card driver and/or a computer game.
Critically, how well Gravity 6 will run depends on how well your graphics card accelerates OpenGL. If you want to run the simulation used to derive the left hand image above then you will need a fast graphics card with good OpenGL support - a fast processor alone won't be enough!
Gravity 6 doesn't need a sound card!
The Download page provides instructions on downloading and installing Gravity 6.
Gravity 6 may not be right for you. There are other programs available and while I can neither make no recommendations as to fitness for purpose nor have I tested them the following links may be helpful:-
|Author (if known)|
|Gravitator 2||Mac||Dan Reed|
|Gravity||Windows||Uranisoft Co. (This is not the original Gravity written by George Moromisato)|