Van Winkle", first published in 1819 in his collection of short stories The Sketch Book of Geoffrey Crayon, Gent., is about a man in colonial America named Rip Van Winkle who falls asleep on one of the Catskill Mountains and wakes up twenty years later after the American Revolution. The story is now considered one of the greatest classics of American literature. In studies on consciousness and philosophy As an altered state of consciousness, dreamless deep sleep has been used as a way to investigate animal/human consciousness and qualia. Insights about differences of the living sleeping brain to its wakeful state and the transition period may have implications for potential explanations of human subjective experience, the so-called hard problem of consciousness, often delegated to the realm of philosophy, including neurophilosophy (or in some cases to religion and similar approaches). In art Of the thematic representations of sleep in art, physician and sleep researcher Meir Kryger wrote, "[Artists] have intense fascination with mythology, dreams, religious themes, the parallel between sleep and death, reward, abandonment of conscious control, healing, a depiction of innocence and serenity, and the erotic." See also Co-sleeping Hypnogram Microsleep Morvan's syndrome Oleamide Power nap Rheum Sleep epidemiology Sleep in space Sleep-learning Sleep medicine Sleep paralysis Sleeping positions Somnology Somnophilia Start school later movement Sudden infant death syndrome Sudden arrhythmic death syndrome Unconsciousness Yawn Yoga-nidra References Further reading External links Rethinking Sleep, David K. Randall, New York Times, September 2012 How to Sleep, James Hamblin, The Atlantic, January 2017 Mental states Unsolved problems in neuroscience