Lumpy lunar illusion
Are you folks aware of a phenomenon based on the universal expectation that objects are illuminated by light coming from above? Several startling optical illusions are based on this quirk of the mind. For example, the sharp moon map in “Orbiter delivers sharp moon map” (SN: 7/30/11, p. 12) makes the moon look like it is covered with big bumps! Turn the page upside down, and voila — the bumps turn into craters.
Jeff Brewer, Newton, Mass.
Count on crows to know
Regarding “When birds go to town” (SN: 8/27/11, p. 26), I have observed other corvids that recognize a specific animal that has proven to be a threat. We had a cat that successfully caught a Steller’s jay chick. For the remaining five years of the cat’s life, she was a marked assassin! She could not leave the house without invok