Brilliant_ The Evolution of Artificial Light - Jane Brox [85]
14. Cold Light
Practically every illuminant in use to-day is patterned after the sun and stars.... No artificial lamp is known but that gives off ample heat to be felt by the hand. It is all "hot light."
—E. NEWTON HARVEY, 1931
OVER DECADES, INCANDESCENT BULBS had grown far stronger and more dependable than those first assembled in Edison's factories. The quality and strength of the glass had improved, as had the efficiency of the vacuum. Most important, the filament had evolved from carbon to tungsten and finally ductile tungsten (tungsten alone is quite brittle and therefore fragile). By 1922 renowned General Electric scientist Charles Steinmetz could claim, "Today we are producing ... sixty-eight times as much light as we could produce with the lights in use fifteen years ago." The greater brilliance required greater heat, of course, and ductile tungsten filaments are hot: "A 60-watt bulb operates at a temperature twice as high as that of molten steel in a blast furnace. Asbestos or fire brick would melt like wax at such a heat. Yet the tiny filament wire in the lamp measures less than 2/1,000 inch in diameter—finer than a human hair." While such heat had its practical uses—to incubate chicks and keep piglets warm—in homes, offices, and factories, it largely went to waste. This was acknowledged even by Tesla, Edison, and others in the incipient years of incandescence. As early as 1894, one New York Times reporter exclaimed, "What a preposterous dissipation there must be of the energy stored in a lump of coal between its first liberation by combustion and its final emergence in the form of electric light!"
By the 1930s, coal powered much of the growing electric grid, and government officials had become concerned about the stress the ever-increasing use of electricity was exerting on known coal reserves. Additionally, labor strife in the mines sometimes affected the supply of fuel to power stations, so the development of a less wasteful illuminant—a practical "cold light"—had great appeal. Toward such an end, physicist E. Newton Harvey undertook extensive studies of bioluminescence in the natural world—glowworms, the gills of mushrooms, jellyfish, foxfire, beetles, fireflies—in an attempt to reproduce its effects for practical human light. Harvey had great hopes for bioluminescence because the reaction between the chemical compound luciferin and the enzyme luciferase, which produces bioluminescence, is extremely efficient: virtually all the energy generated goes toward creating light; almost none is lost as heat. Additionally, the reaction is reversible. As Harvey noted, "Here you have an animal that makes its fuel and burns it and produces light ... and then it takes the combustion product and reconverts it into fuel again, and the fuel is ready to be burned a second time. The firefly is able to un-burn its candle."
Humans have historically used bioluminescence to see in the dark, and not only as a last resort, the way pitmen used glowing, rotting fish to work in the fiery Tyne mines. For centuries throughout Southeast Asia, people gathered fireflies and released them into tight wooden cages or perforated, hollowed-out gourds so as to have light in the evening. Sometimes they let them loose into the trees to illuminate tea gardens and pathways. In nineteenth-century Japan, capturing fireflies was a gainful means of employment:
At sunset the firefly hunter starts forth with a long bamboo pole and a bag of mosquito netting. On reaching a suitable growth of willows near water he makes ready his net and strikes the branches twinkling with the insects with his pole.