The dark crowd cannot be seen directly, the dark crowd does not interact with the light, but the dark crowd can be detected by measuring its gravitational effects on visible crowds. The visible crowd moves toward the dark crowd, as insects toward a black-light trap, in the tropism we call *history*. Riot guns with rubber bullets, tear gas, water cannons, flying wedges of heavily armored police, are not only incapable of dispersing the dark crowd, but, by inciting a phase change in the visible crowd, expand its ranks.