Light pollution
During a family holiday (a California road trip) we have been enjoying the stunning beauty of starry nights above the Grand Canyon and elsewhere. (Not my photo, I hasten to admit.) This wonderful sight was available to everyone since the dawn of human history up until very recently. In the late eighteenth century, the industrial revolution began to place an umbrella of smog above the minority of humans who lived in cities. Then, between the world wars, the great blessing of electric light brought light pollution, and now hides the stars from most of us. It is an extraordinary irony...