Our five senses give us some astonishing capabilities. We can see a candles flame 30 miles away on a dark, clear night, and smell a single drop of perfume diffused in a three-room apartment. We can taste .04 ounce of table salt in 530 quarts of water. Our sense of touch can detect a pressure that depresses the skin .00004 inch on the face or fingertips. And we can tell where a sound is coming from even when it arrives at one ear just .0003 second before its arrival at the other ear.