You can trace 4,000 years of economic growth through the history of light. Our journey from the candle, made from of animal fat, to the LED lights we have today tells a lot about our modern economy.                                                                                                                                                                                           Throughout most of human history, if you wanted light at night you had to make a fire or make and use a candle. Both took a lot of time, a lot of effort, and were really expensive. In Babylonian times, 4,000 years ago, you would have worked a whole day to afford ten-minutes of light. Ten minutes! Up until modern times, when the sun went down it was extremely dark. And the dark was something that was dangerous. Making candles was very labor-intensive. It involved heating up animal fat and dipping and re-dipping wicks into the molten lard. Tallow candles are stinking, smoking sticks of animal fat.       

Productivity and the Price of Light                                                                                                                                                                                                                                               Productivity is the amount a person can produce with a day’s labor. For thousands of years work was not very productive. Growing food was hard. You worked all day and you could buy almost nothing with what you earned. From Babylonian times to around 1800, even though there were improvements in making light, they were very modest. In the 1800s, people started using whale oil to make light. Sperm whales have a lot of fat, and that became the modern source of illumination.

The Near Extinction of Sperm Whales                                                                                                                                                                                                                                        Sperm whales were hunted mercilessly in the mid 1700s and early 1800s. It was the intense demand for this sperm whale oil that nearly drove the whales into extinction. These whales became the first animal to be commercially mass marketed. Whalers, after depleting the Atlantic, Pacific, and Indian Oceans, were having to chase smaller whales in colder and more extreme waters. 

Fossil Fuels Make an Appearance                                                                                                                                                                                                                                                  Then around 1850, overfishing drove the the price of whale oil up dramatically. At this point there was this big breakthrough with kerosene. When the first kerosene lamps came out, it was the kind of oil people had dreamed about for centuries. Kerosene burned brighter. It was cleaner. And it was a lot cheaper.  With kerosene, you got about five hours of light for a day’s labor as opposed to the 10 minutes of light in earlier times. Kerosene is a petroleum product and its innovation sparked the rise of the American petroleum industry in the 1850s. With kerosene people didn't have to huddle in the dark at night anymore. Streetlights become more common. People start going out more at night. Kerosene lit the world and saved the whales. But kerosene was not without its problems -  Kerosene lamps dripped, smelt and set fire to things.

The Modern Era Shines                                                                                                                                                                                                                                                                          Then along came the light bulb - and changed everything.   By 1900, one of Thomas Edison's carbon filament bulbs would provide you with continuous illumination, 100 times as bright as a candle. For your day’s labor, you could now get 10 days of bright, clean light. By 1990, it was 10 years of glorious light for one  day's labor. A couple of years after that, thanks to compact fluorescent bulbs, it was more than five times longer — 50 years of light for a day’s work. From our earliest civilizations, the price of light today has reduced by a factor of 500,000.

 A Perverse Paradox                                                                                                                                                                                                                                                                               That brings us to the most efficient and cost effective lighting yet, LED. Light Emitting Diodes are on track to cut power consumption for lighting by over 40%. That would also reduce U.S. CO2 emissions by some 100 million metric tons a year. A good thing, right?  It would have been great if the story of light ended there. A phenomenal reduction in the cost of artificial light makes it more available and affordable for billions of us. But the drop in cost from LED and other technologies has lead to an increase in consumption. This is because of a quirk in human thinking known as the Jevons paradox. This theory suggests that as things become more efficient, we use more. An economist, William Jevons noticed, back in 1865, that when stoves became more efficient, people used more coal. Thus, the paradox. 

 Another Example of the Jevon's Paradox                                                                                                                                                                                                                                For example, we drive bigger cars as the fuel economy improves. Another example - new refrigerators are around 17% more energy efficient. So, this incremental savings in energy allows us to increase the size of our refrigerators. I noticed it is popular to now get a fridge and a half, or two fridges. I know couples who have not only two refrigerators but a deep freezer where they stash a half a cow! In Europe and much of the world, most people have small fridges, because they shop every day for fresh food in their neighborhood. Having a smaller fridge not only makes you eat healthier, it improves cities by building community.

 The World is Ablaze with Light                                                                                                                                                                                                                                                       This is true with our new and efficient LED lights. We see lighted signs where we never saw them before: big LED monitors over urinals, or where the conventional menu boards at fast food restaurants have been replaced by a huge line of LED monitors. Giant LED billboards line our streets. Competing gas stations at highway intersections found that if they were brighter, they got more business. So of course, the competition became even more lit up. All the extra light was not necessary except to boost sales.                          

Essentially, lighting has become so cheap to run, thanks to the low cost of energy and the efficiency of lighting, that we are using far more of it, everywhere in the world, and particularly in developing countries with their dramatically improving standards of living. And often, in these parts of the world, electricity is being generated  with dirty coal.

 Illumination and the Impact on the Living Earth                                                                                                                                                                                                                  All of these extra lights at night are disrupting the world’s ecosystems Nocturnal animals sleep during the day and are active at night. Light pollution radically alters their night time environment by turning night into day. Artificial lights disrupt this nocturnal activity, interfering with reproduction and reducing populations. This is true of insects and plants also. Do you know why a moth flutters around your porch light? Moths have always used the moon for navigation. Your porch light is a poor substitute for the moon.