planets and such

Urmas Sisask is an Estonian composer. He derived a "planetary scale" from the number of seconds it takes each planet to complete one revolution around the sun. Each planet had its own pitch (at that time there was nine of them), but four of them were repeated in different octaves, ultimately reducing the scale to five pitches. The final scale is C#, D, F#, G#, A. Although originally each of the pitches have their own specific octaves, they are at least 20 octaves below middle C, and are hence used in the reduced pentatonic scale in the habitual octaves.
This piece, "Voices of the Universe", is so far my favorite by him. I believe he used his planetary scale, but don't know for sure (though it certainly sounds like it, doesn't it?).

You can read more about Sisask and see his calculations here.