▁o zone . ▁Since ▁the ▁term ▁is ▁col lo qu ial , ▁it ▁la cks ▁an ▁official ▁definition ▁similar ▁to ▁dawn , ▁d usk , ▁and ▁the ▁three ▁stages ▁of ▁tw il ight . ▁R ather , ▁it ▁refers ▁to ▁a ▁state ▁of ▁natural ▁light ing ▁that ▁usually ▁occurs ▁around ▁the ▁na ut ical ▁stage ▁of ▁the ▁tw il ight ▁period ▁( at ▁dawn ▁or ▁d usk ). ▁ ▁How ▁and ▁when ▁it ▁happens ▁The ▁still ▁commonly ▁presented ▁incorrect ▁explanation ▁claims ▁that ▁the ▁Earth ' s ▁post - sun set ▁and ▁pre - sun r ise ▁atmosphere ▁sole ly ▁receives ▁and ▁dispers es ▁the ▁sun ' s ▁shorter ▁blue ▁w avel ength s ▁and ▁sc at ters ▁the ▁longer , ▁re dd ish ▁w avel ength s ▁to ▁explain ▁why ▁the ▁h ue ▁of ▁this ▁hour ▁is ▁so ▁blue . ▁In ▁fact , ▁the ▁blue ▁hour ▁occurs ▁when ▁the ▁Sun ▁is ▁far ▁enough ▁below ▁the ▁horizon ▁so ▁that ▁the ▁sun light ' s ▁blue ▁w avel ength s ▁domin ate ▁due ▁to ▁the ▁Ch app uis ▁absor ption ▁caused ▁by ▁o zone . ▁Even ▁some ▁websites ▁dedicated ▁to ▁information ▁about ▁o zone ▁still ▁propag ate ▁the ▁incorrect ▁claim ▁that ▁o zone ▁does ▁not ▁contribute ▁to ▁the ▁blue ▁color ▁of ▁the ▁sky , ▁though ▁this ▁effect ▁is ▁much ▁we aker ▁during ▁the ▁rest ▁of ▁the ▁day , ▁between ▁morning ▁and ▁evening ▁tw il ight . ▁ ▁When ▁the ▁sky ▁is ▁clear , ▁the ▁blue ▁hour ▁can ▁be ▁a ▁color ful ▁spect acle , ▁with