Light pollution is an effect of inefficient and ineffective lighting and is harmful to human and animal health and completely erases the ancient tradition of amateur astronomy. Exposure to light pollution can cause a variety of health problems in humans. The main problem is that it alters the circadian clock, the 24-hour day/night cycle, causing mental and physiological problems. Physiological problems include brain wave patterns, hormone production, cellular regulation, and other biological activities. Mental health includes, but is not limited to, depression, insomnia, cardiovascular disease, and cancer. “Studies show that the circadian cycle controls ten to fifteen percent of our genes,” explains Paolo Sassone-Corsi, chair of the Department of Pharmacology at the University of California, Irvine, who has conducted extensive research on the circadian clock. “So disruption of the circadian cycle can cause a lot of health problems.” Premature babies have also been found to suffer due to exposure to artificial light in hospitals. An association has been made between breast cancer and shift work that was limited to women who had worked rotating night shifts for 30 or more years. Having artificial light always on has also affected astronomy. “A large number of children today, especially those living in urban areas, have never seen a truly starry sky,” Bennett told UPI from Boulder. “Given that the sky has been the inspiration for much of human culture and science throughout history, losing our connection to the sky is not only tragic but could also be detrimental to the future of our civilization.” More than two-thirds of the population of the United States and about half of the European Union p...... half of paper ...... light has enabled people to work long hours and engage in recreational activities. The earth appears strikingly illuminated by all the streetlights when viewed from a plane, satellite or spaceship at night. Works Cited Price, Sean. "Light pollution". National geographic world. August 2001: 19-24. GENTLEMEN Discoverer. Network. February 05, 2014.Martin, Mike. “Light pollution hinders astronomers.” UPI. August 14, 2001: np SIRS Discoverer. Network. 05 February 2014.Perspective. Environmental Health Outlook and Web. February 7, 2014. "Two Positives of Light Pollution." 2002JRASC..96...24P. Journal of the Royal Astronomical Society of Canada, nd Web. 20 February 2014. .Kelley, Beth. "Light pollution". spies.org. SPIE Professional and Web. March 1 2014. .