Lucy in the sky
Benjamin Franklin once said, “Never confuse motion with action.” But if motion is not action, then what exactly is motion? Let’s break it down.
Imagine you are pointing your video camera at your favorite ball game. Inside your camera is a lens that focuses the image onto a CCD chip, which is a matrix of light detectors. How can a matrix of light detectors possibly see a ball rolling? The answer is, it can’t. The camera doesn’t see motion whatsoever, because the only thing light detectors can detect is changes in light magnitude, not light position. If the edge of the ball passes over a single light detector, the detector will react, but that’s trivially due to fact that the light level on the detector changed as the ball changed position. The same detector would react identically to a stationary edge that increased its brightness without having moved. To track the change in position of an object, you need to add something, such as a brain, that can interpret the output of all the detectors in concert. Read more…
Illusions: Motion from Brightness,
