Walking home in the evening, on a snowy sidewalk by a busy street: I look down and see brief flashes of light in front of my feet as I stride along. What's up? A quick experiment shows that headlights of approaching cars are reflecting from the white snow-coated soles of my shoes. Every time I lift a foot to take a step, the light bounces: car to shoe to ground to eyes. It's just like the way sunlight hits the earth, ricochets to the moon, and comes back as "Earthshine", a glow on the dark side of a few-days-old moon. Wow!

^z - 2010-12-20