If Spheres Really Made Music...

What if you used the equations of gravitational motion to make music? What would that sound like? See for yourself with Kepler's Orrery, "a generative music system that uses gravity equations to compose and play ambient music."

I was actually searching for a web site on building an orrery out of Legos (to simulate the detection of exoplanets as done by the Kepler spacecraft, as I saw the other night at Starfest) when I found this application created by artist Simran Gleason. It runs as a Java applet and is also available for the iPhone and iPod Touch (I just downloaded and installed it, 99 cents). The Java version actually gives you more controls such as choosing which MIDI sounds will be used, though the iPhone version is more interactive (you can play god and toss massive gravitational objects anywhere you like with your fingertip).

It isn't strictly Newtonian (and it's not General Relativity either). The author injects elements of randomness, anti-gravity, and friction to avoid overly repetitive music that might take 365 days to play. You can read about how he does it here - it's pretty much doing the same thing that Orbiter is doing when it runs a space simulation, figuring out all the forces acting on each object in the "world" at each time step, calculating the accelerations and collisions, moving the bodies, and repeating. It's just that instead of Apollo 11 landing on the Moon, you get music! The video above is one example of the kind of sounds it can produce (more here). I've only played for a few minutes and now I need to get to bed, but I really like this little gravitational music toy.