1. The Qin and the Han were the first and the second imperial dynasties of China. They helped to expand the territory, created a centralized government and also established its own bureaucracy method thanks to their emperors. China was located in a difficult area and many world civilizations were not able to have access to it during that period of history; for that reason, emperors and scholars had the obligation to create and found their own civilization and make it blossom.
2. The geography of ancient China allowed the civilization to develop itself in an isolated area since it was a big land which flourished away from the rest of the world. It had arid deserts (the Gobi Desert and the Taklamakan Desert) to the north and west, the Pacific Ocean to the east, and impenetrable mountains (the Himalaya Mountains) to the south; additionally, they had two major rivers, the Yellow River and the Yangtze River, a great source of fresh water, food, fertile soil, and transportation. All this helped China to progress independently from other world civilizations.
In addition to giving retirees money, Social Security was "<span>requiring retirees to spend their money in the US." which of course spurred the economy. </span>
I'd say the combustion engine, even though it was toyed with in the mid-west during the cowboy era, it wasn't until after the Civil War in which it was a fully effective gasoline powered engine.
