Anglo-Saxon period: The pre-electrical world was a world of darkness. People got up and went to bed with the sun. Artificial lighting consisted of firelight and candles or small lamps burning whale or olive oil, or rushes dipped in animal fat. On a clear night in Anglo-Saxon England the sky would have been powdered with stars.

Late twentieth century: Today earth's great urban centers can light up the night. Airplane travelers can see the lights of towns, cities, and interstates. Relatively few stars can be seen

Anglo-Saxon period: The population of Britain in the early Middle Ages was probably under three million people. Land was still being reclaimed for farming, difficult in a country where most of the native trees will readily regrow from stumps. In Anglo-Saxon England wolves still roamed the countryside. The edges of forests were important for game, wood, and food for...