the physical world is basically vibration. Whether we think of this vibration in terms of waves or of particles, or perhaps wavicles, we never find the crest of a wave without a trough or a particle without an interval, or space, between itself and others. In other words, there is no such thing as a half wave, or a particle all by itself without any space around it. There is no on without off, no up without down. Although sounds of high vibration seem to be continuous, to be pure sound, they are not. Every sound is actually sound/silence, only the ear does not register this consciously when the alternation is too rapid. It appears only in, say, the lowest audible notes of an organ. Light, too, is not pure light, but light/darkness. Light pulsates in waves, with their essential up/down motion, and in some conditions the speed of light vibrations can be synchronized with other moving objects so that the latter appear to be still. This is why arc lights are not used in sawmills, for they emit light at a pulse which easily synchronizes with the speed of a buzz saw in such a way that its teeth seem to be still.