Free Astronomy Magazine March-April 2023

MARCH-APRIL 2023 L ess than 100 years ago, everyone could look up and see a spectacular starry night sky. Now, millions of children around the world will never experience the Milky Way where they live. The increase and pervasive use of artificial light at night not only impairs our view of the universe, but negatively affects our environment, our safety, our energy consumption and our health. [The Interna- tional Dark Sky Association] M ap of light sources detected by the VIIRS instrument, onboard the Suomi satellite, in 2021. On the website www.lightpollutionmap.info it is possible to interact with this map, selecting different options that provide different interesting views. [C. Kyba et al.] The view of the starry sky, a unifying human legacy over thousands of years, has been all but lost to most people now living in urban and sub- urban settings. It is estimated that over 80% of the world’s population lives in an urban environment that is so illuminated by artificial light as to have negative effects their health: sleep disturbances, obesity, diabetes and some types of cancer. The lights we have installed in our homes and along the streets have altered the circadian rhythm of many people, who sleep for less time and less deeply. Even short periods of expo- sure to very dim light can reduce melatonin concentrations in our bodies by half; a non-negligible fact given that melatonin not only plays a vital role in maintaining our sleep- wake cycles, but it is also a power- ful antioxidant. As melatonin levels drop, our deep sleep is disrupted and our ability to fight off disease is re- duced. And it’s not just humans who suffer from light pollution. Noctur- nal animals, in particular, find them- selves forced to change their habits or territories. Light pollution con- tributes to the deaths of millions of birds every year. Particularly exposed to increased light pollution are many migratory birds, especially those that fly at night. Skyglow can also affect the timing of migrations and other seasonal behaviors by disrupting biological clocks. Birds exposed to light pollution at their wintering sites can begin migration earlier than species that are not exposed to artificial light, a major problem if