Time-Lapse: Refraction

Air bends light. Well, OK, not exactly. A beam of light could pass through air all day long (as long as you have a layer of air 26 billion km long) and not deviate a whit. But if the density of that air changes, the light will bend. This is called Snell's Law, and you're already familiar with it: It's why a spoon in a glass looks bent or broken; the light from the spoon bends as it passes from water to air, distorting what you see. The Earth's atmosphere has layers to it, thin blankets of air of...