The laying of the first transatlantic telegraph, to pluck an idea out of the air. Or, the rise of Freud's ideas in society in the latter half of the 20th centu

The laying of the first transatlantic telegraph, to pluck an idea out of the air. Or, the rise of Freud's ideas in society in the latter half of the 20th century. Or, the change from hunter-gatherer societies to agrarianism. Or, The Terror in france and the various other european uprisings of that time. Or, lest we forget, WORLD WAR FUCKING TWO. EDIT: I'm defining 'great' here as 'greatest change' because 'greatest progress' is ill-defined to the point of meaninglessness. EDIT2: Here's another one: the invention of the 2" ABS plastic pipe and it's employment in sanitation and irrigation. Although it obviously depends on how old you are as to whether or not that falls within "our lifetimes."