From July 23, 1916
Will ‘Cold Light’ Soon Be a Scientific Fact?: M. Dussaud, French Engineer, Has Just Reported Definite Progress in Solving Problem That Will Be Revolutionary (PDF)
The problem in 1916: nobody had yet invented a “moving picture projector on which the film may be stopped without danger of ignition.” If you’ve ever pressed pause on a YouTube video without your computer blowing up, you know that this problem was solved.
Basically, most of the light through man-made sources a century ago was wasted as heat. Less than 10 percent made it through as energy. By contrast, for a firefly about 96.5 percent of their light made it through as energy. In 2011 a team of scientists at Tokyo Metropolitan University invented a 100 percent efficient artificial light source.