Bat

every flap is a call. the rock answers.

fly a bat through a pitch-black cave: every tap is a wingbeat and a call, and the rock lights up only when its echo comes home -- the nearest first -- so you see ahead only if you called in time

A bat hunting in the dark finds its way by echolocation: it calls, and listens for what comes back. How long an echo takes is set by distance alone, because the sound has to get there and back at 343 metres a second, so rock one metre away answers in about six thousandths of a second and rock ten metres away in sixty. Near rock is always heard before far rock, which is how a bat builds a picture out of time. Many small bats call once per wingbeat, because the same muscles that drive the wings push the air out of the lungs, and so calling costs a flying bat almost nothing. Here the sound is slowed about twelve times so the order can be seen. The cave is drawn after Prometheus Cave near Kutaisi in Georgia, whose halls are lit in colour and whose passages are not.

Concepts: sound, perception, biology.

An interactive you play with one thumb, on Wundr.