When you connect an odd number of digital logic inverters in a ring, you’ll get a Ring Oscillator – one of the simplest types. This configuration has no stable state, so the 1s and 0s chase each other around the ring, creating oscillations. Normally this isn’t easy to visualize, but Make Flickr Pool contributor ellindsey000 made a pendant that illustrates the principle beautifully:
This actually looks much better in person — I’m at the 26C3 conference, where someone (sorry, I’ll try to get your name!) built a replica based on ellindsey000’s photos. The LEDs are ultraviolet, causing different spots in the center marble (which contains uranium) to glow. What the video above doesn’t show is that the UV LEDs are barely visible and the glow inside the marble seems to move almost as if it was a liquid.
The schematic matches the construction in circular symmetry – both are beautiful:
More pictures: complete gallery, including how it looks in daylight.