Sleep

　　It'sclearthateveryoneneedstosleep.Mostpeoplerarelythinkabouthowandwhytheysleep,however.Weknowthatifwesleepwell,wefeelrested.Ifwedon'tsleepenough,weoftenfeeltiredandirritable.

　　Itseemstherearetwopurposesofsleep:physicalrestandemotionalandpsychologicalrest.Weneedtorestourbodiesandminds.Bothareimportantinorderforustobehealthy.Eachnightwealternatebetweentwokindsofsleep:activesleepandpassivesleep.Thepassivesleepgivesourbodytherestthat'sneededandpreparesusforactivesleep,inwhichdreamingoccurs.

　　Throughoutthenight,peoplealternatebetweenpassiveandactivesleep.Thebrainrests,thenitbecomesactive,thendreamingoccurs.Thecycleisrepeated:thebrainrests,thenitbecomesactive,thendreamingoccurs.Thiscycleisrepeatedseveraltimesthroughoutthenight.Duringeighthoursofsleep,peopledreamforatotalofoneandhalfhoursontheaverage.