The Mystery of Sleep~ Rest for the body, Activity for the brain ~Everyone sleeps. While humans sleep, they do not procreate, protect and feed their young, gather food, earn money, write papers, etc. Surely, at least once, most people have wondered why they sleep despite these inconveniences. According to Greier (48), it is difficult for scientists to answer the seemingly simple question of what exactly sleep is for. Sleep takes up a third of humans' lives, which seems like a waste of precious time; However, no one can survive without sleep. According to Shelton (5), drowsy drivers in the United States cause approximately 56,000 car accidents each year. Additionally, Wolfson and Carskadon (875) interestingly report that students who get good grades sleep longer than those who struggle or fail in school. Additionally, the Chernobyl nuclear accident, the Three Mile Island near-meltdown, the environmentally disastrous Exxon Valdez oil spill, and the loss of the Challenger space shuttle were all caused by people who made mistakes due to lack of sleep (Coren 1). Sleep deprivation appears to have detrimental effects on humans' daily lives. Sleep is a state marked by reduced consciousness, diminished skeletal muscle activity, and depressed metabolism. Humans normally sleep in patterns that follow five observable progressive stages (stages 0–4) of non-rapid eye movement (NREM) sleep and a distinct pattern of rapid eye movement (REM) sleep (Coren 31). An electrical encephalogram (EEG), designed by Hans Berger in 1919, is used to measure the electrical activities of neurons during stages: Stage 0 is not true sleep, but lying down and preparing for sleep. During stage 1, the...... middle of paper...... (1997): 48-50.Hobson, Allan J. {Sleep}. New York: American Science Library, 1995. Meddis, Ray. {The sleep instinct}. Boston: Routledge and Kegan Paul, 1977. Moreno, Anne. "Why do we sleep? A good night's sleep is important for your health and also for your success in life." {Current Health 2} 25.2 (1998): 6-13. Rechtschaffen, Allan. “Current Perspectives on Sleep Function.” {Perspectives in Biology and Medicine} 41.3 (1998): 359-90. Shelton, Deborah L. "Sleep-deprived drivers linked to highway 'carnage'" {American Medical News} 38.26 (1995): 5-6. Stampi, Claudio, ed. {Why We Nap: Evolution, chronobiology and functions of polyphasic and ultrashort sleep} By Jurgan Arnoff. Boston: Birkhauser, 1992. Wolfson, Amy R. and Mary A. Carskadon.} 69.4 (1998): 875-89.