The Western mind seems sometimes to forget how impoverished many parts of the world still are. Electricity, a ubiquitous source of energy in the developed world, remains a luxury for billions of people who weren't lucky enough to be born in the U.S. or Germany in the 21st century. Energy use per person would have to grow by a factor of 10 in Africa to reach the levels it was at in Germany in 1965, which is why billions of people cook for their families by burning animal dung. That practice causes extremely unhealthy air pollution and CO2 emissions, but...