He just renovated a lighthouse, so why was he awarded the Nobel Prize this year?

In 1912, the Royal Swedish Academy of Sciences decided to award that year's Nobel Prize in Physics to Swedish engineer Nils Gustav Dahren. When the news came out, the academic community was in an uproar. Even today, a hundred years later, there are still some complaints about this year's award.

This is not surprising. Throughout the history of the Nobel Prize in Physics, the awards in most years have been more favorable to basic research and theoretical achievements. Only a few have won awards based on engineering applications, such as Lippmann (1908), who invented color photography, Marconi and Bryan (1909), who invented wireless telegraphy, and Kilby (2000), who invented the integrated circuit. Darren's award-winning achievements are not only more inclined to the engineering field, but also have narrower application scenarios - the gas storage and automatic valves he made are only for the automatic control of lighthouses, which does not seem to meet the Nobel Prize's standard of "making the greatest contribution to mankind". More importantly, more than a hundred years later, due to the popularization of global positioning systems, ship automatic identification systems and civilian radars, the practical functions of lighthouses themselves have been basically replaced. Does Darren, who only made technological innovations in lighthouses, really deserve the honor of the Nobel Prize in Physics?

In fact, if we have a deep insight into the evolution history and significance of lighthouses, it is not difficult to find the answer to the question.

A lighthouse is more than just a simple “light + tower”

Image source: Tuchong Creative

To those who are not familiar with the history of lighthouses, lighthouses around the world look the same - just a bright light on the top of a tower by the sea. Strictly speaking, this perception is not wrong. Since early human navigation activities were mainly carried out near the coast, most lighthouses at that time were set up on the coasts or islands of port cities. Take the Lighthouse of Alexandria, which is known as one of the Seven Wonders of the World, for example. It is a 100-meter square tower built on the island of Pharos in Alexandria. During the day, it uses the huge metal mirror on the top of the tower to reflect sunlight. When night falls, the brazier in front of the metal mirror will be ignited, and the light emitted by the vegetable oil will be reflected by the mirror to guide the ship.

In the more than a thousand years since then, the construction method and operating principle of lighthouses have not changed much, but people's development and utilization of the ocean have continued to deepen. Some ships began to enter the hinterland of the ocean far away from the coast, and the reefs hidden under the water became an indelible nightmare for sailors.

Building a lighthouse as a guide on an isolated reef in the ocean that is prone to shipwrecks seems to be a good solution to the problem, but it is not easy to realize this vision. In 1698, the British built a pure wooden lighthouse on the vortex reef off the coast of Plymouth, but it was destroyed by huge waves just five years later. In 1708, another lighthouse made of wood and steel was rebuilt on the original site, but it was also destroyed by fire in 1755. It was not until 1759 that British engineer John Smith used stones and concrete as building materials to increase the strength of the lighthouse, and adopted an appearance structure similar to the small waist tower in Guangzhou, my country to reduce the impact of huge waves. At this point, the world's first truly offshore lighthouse, the Smith Lighthouse, was finally completed.

Brighter, lighter, more stable, the light on the lighthouse is the soul

Smith's innovation solved the problem of building a tower on an isolated reef in the ocean, but compared to the tower body, the light on the lighthouse is the most important. When the Smithton Lighthouse was built, the light-emitting part of the lighthouse was not fundamentally different from the Lighthouse of Alexandria. Although people used whale blubber instead of vegetable oil to increase the brightness, and floated the brazier on the mercury liquid surface to achieve stability, and the reflector used to reflect the light was upgraded to a spring drive to ensure uniform rotation, the lighthouse still had the defects of insufficient light source brightness and insufficient projection distance. Especially in the deep ocean with bad weather conditions, the raging sea breeze would not only blow the flames back and forth and affect the brightness, but also often blow out the lights and cause reef accidents.

Fortunately, the invention wave of the Industrial Revolution, which was gradually reaching its peak, provided the possibility to improve these shortcomings. In 1782, inventor Amy Argon discovered that using a tubular glass to cover the flame could not only eliminate the influence of wind, but also make the flame burn higher and more fully. The lamp using Argon's tubular wick can increase the brightness by six or seven times compared to directly burning grease! And if the reflector behind the flame is replaced with a convex lens in front of the flame, the distance the light can travel can also be greatly increased.

But new problems followed. The huge convex lens was not only expensive, but also heavy. Coupled with the mechanical parts that rotated with it, the total weight of the entire lighthouse light source components became increasingly bloated. Some small lighthouses simply could not carry such a light source system. This problem was not solved until 1823 by French engineer Augustin Jean Nephiel. He used a thinner threaded lens to maintain the performance of the convex lens in refracting parallel light, and greatly reduced the weight and cost of the lens. After trying this lens at the Godouen Lighthouse at the mouth of the Gironde River, he found that the lighthouse light was clearly visible 32 kilometers away. This lens is still widely used today, and we can see it on car lights and mobile phone flashlights.

The technological innovation of lighthouses is changing with each passing day, but the number of lighthouses at that time was too small. Guarding a lighthouse requires human participation. Those lighthouses that are isolated in the ocean must be built large enough to sustain the long-term lives of the lightkeepers. Coupled with the huge fuel consumption, the cost of building and maintaining lighthouses is very staggering. Throughout the 19th century, even the most developed maritime powers could only set up a small number of lighthouses in key sea areas. For sailors, sailing is still full of risks. If they want to travel safely and smoothly around the world, sailors still need to wait for the decisive innovation led by Darren.

Sailors’ benefactor and guiding light

Darren's homeland, Sweden, has a long coastline and many islands, and has always been in urgent need of cheaper and more reliable lighthouse technology. It was in this era that Darren, who was working at a Swedish gas tank company, came into contact with lighthouses. At this time, Darren was obsessed with technical research in the field of acetylene storage and transportation. Before this, people had discovered that acetylene can emit bright white light and has a much higher combustion efficiency than oil, but acetylene storage and transportation is very difficult, especially when the container is bumped, it is very easy to explode. To solve this problem, Darren first dissolved acetylene in acetone, and then poured it into a gas tank with microporous interior at 10 times the atmospheric pressure. This practical technology was soon applied to lighthouses. In order to further reduce the consumption of acetylene, Darren once again developed an automatic gas valve based on the actual needs of lighthouses. He found that lighthouses did not need to be lit all the time. The acetylene lamp only needed to burn for 1/10 to 1/30 seconds. The instantaneous flash was enough for ships in the distance to spot them. By flashing once every few seconds, 1 liter of acetylene could emit thousands of flashes. If the frequency of flashes from each lighthouse was different, sailors only needed to observe the difference in the frequency of the flashes to know which lighthouse they were observing.

In order to further improve the automation of the lighthouse, Darren invented the daylight switch in 1907. This device consists of four metal rods sealed in a vacuum glass tube, three of which are polished to the original metal color with high precision, and the bottom one is painted black. When exposed to sunlight, the black metal rod absorbs heat and expands faster than the other three, thereby blocking the gas valve switch and the light goes out. When the sunlight weakens, the black metal rod shrinks to the same length as the other metal rods, the gas valve is connected, and the light is reignited.

With these three inventions, the lighthouse's lighting device can operate automatically without human intervention, and the overall fuel consumption has been sharply reduced by 97%! After being put into use in 1907, this device reduced the cost of a lighthouse that originally cost 200,000 kronor to 9,000 kronor, and the annual operating cost also dropped from 25,000 kronor to 60 kronor! In the following years, a wave of lighthouse innovation swept the world. Countless unmanned lighthouses and automatic beacons appeared in the originally remote and dangerous sea areas. Daylight switches are also widely used in the field of automated control of urban lighting, and the application of acetylene storage technology in the field of metal cutting and welding continues to this day.

With the development of new technologies, lighthouses and the many technological innovations made by Darren and other researchers for lighthouses have gradually fallen into silence. However, in the context of the times, these engineering innovations did create extraordinary social and economic benefits. The beams of light swept across the sea, saving countless ships from distress and giving countless seafarers hope to return home. This is why sailors affectionately called Darren "the benefactor and the beacon." Even looking back today, this story is still very meaningful - scientific exploration allows us to understand the world from a new perspective, and the application of technology based on science helps us constantly reshape the world. From this perspective, isn't the story that happened on the lighthouse itself a beacon of scientific spirit that guides the way forward?

The article is produced by Science Popularization China-Starry Sky Project (Creation and Cultivation). Please indicate the source when reprinting.
Author: Wandering science writer

Reviewer: Wang Yangzong, Director of the Research Center for the History of the Chinese Academy of Sciences