From Ancient Fire Pits to LEDs: Lighting in a nutshell

The story of light

With Christmas over three months gone, one's festive tree has ideally already been disposed of (the real ones) or stored away in the basement (the artificial ones). Still, how Christmas trees came to light over the past centuries pretty well reflects the history of lighting in general. While our grandparents used to jeopardize their homes gathering around a candle-lit Christmas tree, our parents had to put up with strings of tiny light bulbs that didn't work anymore if just a single one went out. Today, we can resort to candle imitations, which neither torch our home nor break when we stare a little too long, thanks to LED technology.

The discovery of electricity

The development of how civilization has brought light to its streets and homes basically benefited from two discoveries: fire and electricity. It goes without saying that the former was ages ago and served the purpose of being able to fillet saber-tooth tigers in the glow of crackling fire pits. Later, the open fire was poured into tighter (and therefore much safer) casts; into oil lamps. As the name suggests, another ingredient was necessary, namely oil or another flammable liquid. At first, it was animal fat that was poured into a container with a wick made of plant fibre sticking out. The oldest example of such an early lamp is a hollowed stone with burn marks that was used at least 40,000 years ago and was found in Edertal in northern Hesse, Germany. The oil lamps that we know from illustrations of the Aladdin tale were much prettier: bowls with a long neck from which the illuminating flame flickered. The candles that have been used since approximately the First Century AD work on a similar principle except that the fuel was solid, making the lamp vessel superfluous.

Then, after people had read, eaten and socialized over the flickering light of open fire (or at least covered by glass) for centuries, the discovery of electricity made for a nice change in the concept of light in the darkness. Mankind had suspected the existence of something like this for centuries – after all, lightning flashed through the sky and electric eels roamed the waters. But it has only been 350 years that science has been able to make use of electricity, even though it wasn't anything useful at first. In 1663, Otto von Guericke, the mayor of Magdeburg at the time, invented a machine made of a rotatable sulphur globe that was used a few years later by philosopher Gottfried Wilhelm von Leibniz to elicit the first electrically produced spark. When the Englishman Francis Hauksbee built a similar apparatus with a glass sphere in 1706, he was able to create light through the touch of his hand that was strong enough to be used for reading. But since it wasn't very convenient to rotate the globe and touch it with your hand at the same time, Hauksbee's machine merely served as entertainment during parties. But from this time on, the study of electricity took big steps forward: Milestones such as Benjamin Franklin's lightning rod, Luigi Galvani's frog legs conducting electricity, and Alessandro Volta's battery made such progress in so little time that the International Exposition of Electricity was held in Paris between August and November 1881. Apart from the first electric car and the first electric tram, it also displayed an invention for which the American scientist Thomas Alva Edison took out a patent just one year earlier: the "electric lamp," the light bulb.

Edison's invention was a small filament connected to two wires that was heated through electricity, which therefore started incandescing. A surrounding glass bulb kept oxygen away from the filament and prevented it from burning in a short time span. Other scientists had admittedly developed a similar concept earlier, but it was Edison who, after some years of experimenting, successfully built a light bulb that lasted for 1,000 hours, didn't smell or flicker, and that was able to be switched on and off. When Frenchman Marcel Depréz introduced a system with which electricity could be transmitted over a power line almost two kilometers in length, Oskar von Miller, co-founder of the German Museum in Munich, did things in style and planned a transmission of electricity over a much longer distance. In partnership with Depréz, he set up the world's first direct current transmission over a distance of 57 kilometers from Miesbach to Munich. This marked the kickoff for so-called electrification, the extensive electricity supply to households. It was the foundation for Edison's light bulb to conquer the world. Since 95 percent of the electricity that light bulbs use is converted into heat, and only the five remaining percent are actually needed to produce light, the search for a more economical alternative began. Only a few years after Edison's invention, American electrical engineer Peter Cooper Hewitt patented his mercury-vapor lamp, the predecessor to today's energy- saving light. Mercury was ionized in a bulb with electricity, which illuminated it. However, it wasn't until 1973 that Edward Hammer, an engineer at General Electric, developed today's common spiral-shaped compact fluorescent lamp – this is what energy-saving lights are actually called. Instead of mercury, he used a mix of the noble gases neon and argon. As it would have cost about $25 million to produce the light in series, however, Hammer's employers set his plan aside for now. This brought imitators to the scene, and eventually Philips introduced his SL* series as the first energy-saving lamps to the world market. But because they were much too long and too heavy for most lamps that were used in private homes, they were slow sellers. It was the invention of electronic ballast, reducing the dimensions of the lamps significantly, that made the energy-saving lamps suitable for large-scale use.

LED

In December 2008, the EU decided to ban the good, old light bulb with the purpose of saving energy and protecting the environment. They were gradually taken off the market within four years. Since September 2012, the 130-year old invention by Thomas Edison has been history. Not only did the energy-saving lamp take its place, but as did the light emitting diode – LED in short. How this technology works was already known before the light bulb's invention, but it was not until 1962 that it was developed. How come? Well, the world simply should have listened to German electrical engineer Ferdinand Braun. He gave a talk about how crystals conduct power as early as 1876. According to Braun's findings, electricity flows only in one direction. LEDs take advantage of this principle. Their core is made of two semiconductor crystals that don't touch each other. One is made of silicon, the other of gallium. Simply put, the electrons discharge from silicon to gallium when the LED is switched on, triggering flashes of light that are perceived as luminous power. The elements the semiconductor crystals are made of influence the colour of the light that the LED emits. This way, we can not only choose white light for our ceiling light, but also gimmicks of different colours – like our Christmas tree, for example.

Text: Alexander Kords | Illustration: Assa Ariyoshi