The Bell Jar

A famous experiment in high school physics involves putting an electric buzzer in a bell jar, a glass container from which the air can be removed by a pump. When the air is removed, the sound of the buzzer disappears. As early as the seventeenth century, it was recognized that sound needed some medium to travel in. In a vacuum, such as exists inside the bell jar, there is nothing to carry the sound waves, so you don't hear the buzzer inside. To be more specific, sound is a pressure wave, or d...

 What Makes Something a Distinct Object?

Let me look at the envelope from a very basic point of view, that of the neurophysiology of raw perception itself. Forgive me if it’s a bit oversimple. Take me-on the back of your retina I’m upside down, focused at the center but fuzzy at the edges, two-dimensional, a barrage of photons releasing rhodopsin and triggering neural impulses along the visual nerve. At the same time, the pressure wave I’m setting up right now with all this talk is causing little hairs inside the cochlea, in y...