NOVA:MysteriesofSleepLikevirtuallyeveryotheranimal,humansneedsleeptosurvive.Butwhy?Whatdowegainfromspendingnearlyathirdofourlivesinsuchadefenselessstate?Andwhat'satstakeifwesleeppoorly?Thefunctionsofsleephavelongbeensomethingofamystery.Butnowscien