Three ancient optical illusions explained by modern science
Optical illusions remind us that things are never exactly as they seem. (Lena Vargas/)Illusions have fascinated humans for centuries. Before we fully understood the science of sensation and perception, philosophers like Aristotle simply observed the world—and picked up on some weird stuff. According to Vincent Hayward, who studies such phenomena at the Institute for Intelligent Systems and Robotics in Paris, these tricks occur when experience and context make you expect one feeling but perceive another due to abnormal circumstances. Here are three of Aristotle’s earliest observed illusions, explained by modern science.Waterfall illusionWhile watching a moving river, Aristotle noticed that when he shifted his attention to stationary rocks, they wiggled upstream. Neurons that process motion tire after focusing on the same activity. When struck with a still object, cells that track movement in the opposite direction have a stronger impact in comparison, and send it swimming away.AfterimagesAfter staring directly at...