History rushes forward, and we like to point at the boulders that seem to cause the most turbulence. We call these disturbers Martin Luther, Albert Einstein, Stalin, or any other famous person from history who left a mark big enough that most of us still know them. These big boulders cause turbulence, but the riverbed, all the little stones, cause the real diversion by being swept up by rushing water and the turbulence, thus changing the direction of what flows forward.  A great boulder lying in a dry lake will move nothing, let alone disturb history, and a river without strong currents and disturbing boulders will flow forever with little change.