Using millimeter wave technology, which the TSA says emits 10, 000 times less radio frequency than a cell phone, the machine scans a traveler and a robotic image is generated that allows security personnel to detect potential threats -- and, some fear, more -- beneath a person's clothes.

CNN: Airport security bares all, or does it?

At sunset, the sun appears red (the blue light has been scattered out of that image, too), so the cells of the eye that detect red are overloaded and incapable of registering weaker red signals.

ECONOMIST: In a flash