In a dark room, I put a camera on a tripod, facing straight up, but as low to the ground as possible. Suspended above the camera on a ceiling was a single source of light (such as a laserpen, a mini-flashlight, or a single Christmas tree light bulb). Swing the object of light and take an exposure for as long as you want, or until it stops moving altogether. Have fun experimenting with different ways of pushing the light source, and different exposure times and different light sources.
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