Continuing the train of thought from last episode, the atom bomb brings us back to the Norman Conquest, when the Saxons got undone by a new technology in warfare--the stirrup--which leads to additional advances, first in warfare, then in agriculture and society. The improved plow, the horsecollar and the horseshoe bring an expansion in cultivation of land that eventually elevates the standards of living for common people in the late Middle Ages. An economic revolution follows in the cities, leading to trade with the Far East, new industries, and further advancements in science. A problem in a mine in Germany leads to a discovery in atmosphere. An accidental encounter with static electricity leads to a whole new field of experimentation. We end up with the telephone--and the radio telescope.