Primary pollutants come directly from fossil fuel burning and agricultural activities. Secondary pollutants form when primary pollutants react with atmosphere. Air pollution causes breathing problems and damages ozone layer
John E. Bortle developed a nine-level scale for measuring night sky brightness. Published in Sky & Telescope magazine in February 2001. Aims to help skywatchers evaluate observing site darkness
One-third of human population cannot see Milky Way due to artificial lighting. 99% of US and EU citizens experience light pollution 10% brighter than natural. Light pollution in North America and Europe increases 6% yearly. Project led by Fabio Falchi started in 2001 with US Air Force satellite data
Environmental pollution is the release of harmful substances damaging the environment. Pollution occurs when environment cannot process toxic substances naturally. Problems are greatest in developing world due to poor technologies
Nocturnal animals are active at night and sleep during the day. They have highly developed senses of hearing, smell, and eyesight. Many nocturnal creatures have larger eyes relative to body size
Electric lighting replaced candles and gas lights in early 20th century. Volta created first electric battery in 1799-1800. Warren de la Rue invented first electric light bulb in 1840. Edison and Swan independently developed functional incandescent lamps in 1870s. Coolidge introduced tungsten filament in 1912