a rainbow in my hand

I don't know if you've ever held the underside of a compact disc up to white light, but if you do and play with the angles, the light splits into wonderful hues, like a prism. It's the diffraction grating effect Feynman talks about in QED. I'd been without one for a while, but got an old CD from my host, so I can enjoy pure hues at will again. It actually seems better in room light than in bright sunlight, maybe because solar glare can get too blinding. The easy mode is just a line of color from hub to edge, but with the right angle you can get various effects, including a halo around the whole rim.