Valk: Imaginary illustration of the surface of the sun, circa 1725
The quest for power and energy begins with an imaginative conception that answers the question, “What is energy?” A related question is, “What is the sun?” One of the first people to offer a scientific or philosophical explanation for the sun was the ancient Greek philosopher Anaxagoras, who reasoned that it was a giant flaming ball of metal. Some 2,000 years later human understanding of the sun has advanced to the knowledge that the sun is not on fire, but is a continuous nuclear explosion converting hydrogen to helium plus energy for a small amount of converted mass. This 1725 volume includes a speculative image of the surface of the sun as a ball of fire, much like any other fire that an observer might see on Earth. Scientists did not figure out that nuclear fusion powered the sun until 200 years later in 1920.