https://www.wtamu.edu/~cbaird/sq/2015/12/01/can-a-fire-have-a-shadow/
https://www.wtamu.edu/~cbaird/sq/2013/06/21/how-does-plasma-make-a-campfire-flame-orange/
https://www.wtamu.edu/~cbaird/sq/2013/06/21/how-does-plasma-make-a-campfire-flame-orange/