In 1491 the Inka ruled the greatest empire on earth. Bigger than Ming Dynasty China, bigger than Ivan the Great’s expanding Russia, bigger than Songhay in the Sahel or powerful Great Zimbabwe in the West Africa tablelands, bigger than the cresting Ottoman Empire, bigger than the Triple Alliance (as the Aztec empire is more precisely known), bigger by far than any European state, the Inka dominion extended over a staggering thirty-two degrees of latitude—as if a single power held sway from St. Petersburg to Cairo.

Compared with U.S. cities, Japanese cities bend over backward to help foreigners. The countryside is another matter.

The embrace of a new technology by ordinary people leads inevitably to its embrace by people of malign intent.

A smartphone links patients' bodies and doctors' computers, which in turn are connected to the Internet, which in turn is connected to any smartphone anywhere. The new devices could put the management of an individual's internal organs in the hands of every hacker, online scammer, and digital vandal on Earth.

Historically, large-scale global trade has served two functions: 1) the exchange of goods between willing sellers and buyers described in Econ 101 textbooks; 2) as a tool of state aggrandizement, in which the private parties are stand-ins for governmental interests.

A whole bunch of big technological shocks occurred when Asian innovations - paper, gunpowder, the stirrup, the moldboard plow and so on - came to Europe via the Silk Road.

Smartphones can relay patients' data to hospital computers in a continuous stream. Doctors can alter treatment regimens remotely, instead of making patients come in for a visit.