. ▁The ▁photo ▁of ▁the ▁forest ▁fire ▁in ▁Canada ▁is ▁an ▁excellent ▁example ▁of ▁this ▁variation . ▁Near ▁the ▁ground , ▁where ▁most ▁burning ▁is ▁occurr ing , ▁the ▁fire ▁is ▁white , ▁the ▁h ott est ▁color ▁possible ▁for ▁organ ic ▁material ▁in ▁general , ▁or ▁yellow . ▁A bove ▁the ▁yellow ▁region , ▁the ▁color ▁changes ▁to ▁orange , ▁which ▁is ▁cool er , ▁then ▁red , ▁which ▁is ▁cool er ▁still . ▁A bove ▁the ▁red ▁region , ▁comb ust ion ▁no ▁longer ▁occurs , ▁and ▁the ▁un comb usted ▁carbon ▁particles ▁are ▁visible ▁as ▁black ▁smoke . ▁ ▁The ▁common ▁distribution ▁of ▁a ▁fl ame ▁under ▁normal ▁gravity ▁conditions ▁depends ▁on ▁con ve ction , ▁as ▁so ot ▁tends ▁to ▁rise ▁to ▁the ▁top ▁of ▁a ▁general ▁fl ame , ▁as ▁in ▁a ▁cand le ▁in ▁normal ▁gravity ▁conditions , ▁making ▁it ▁yellow . ▁In ▁micro ▁gravity ▁or ▁zero ▁gravity , ▁such ▁as ▁an ▁environment ▁in ▁outer ▁space , ▁con ve ction ▁no ▁longer ▁occurs , ▁and ▁the ▁fl ame ▁becomes ▁spher ical , ▁with ▁a ▁t endency ▁to ▁become ▁more ▁blue ▁and ▁more ▁efficient ▁( although ▁it ▁may ▁go ▁out ▁if ▁not ▁moved ▁stead ily , ▁as ▁the ▁CO 2 ▁from ▁comb ust ion ▁does ▁not ▁dis per se ▁as ▁readily ▁in ▁micro ▁gravity , ▁and ▁tends ▁to ▁sm other ▁the ▁fl ame ). ▁There ▁are ▁several ▁possible ▁explan ations ▁for ▁this ▁difference , ▁of ▁which ▁the ▁most ▁likely ▁is ▁that ▁the ▁temperature ▁is ▁sufficiently ▁even ly ▁distributed