Jizhou Wang
Professor Meyer
Matter, Energy, Space, and Time
December 4, 2018
Technological Advancements that Enabled a Physical Explanation of Light
Since the ancient times, scientists have been working tirelessly to uncover the mystery of light, but they made little meaningful progress for thousands of years. It was in the 19th century that several scientific breakthroughs made a physical explanation of light possible. During that time, there was a general passion toward electricity and magnetism within the scientific community, and many talented scientists devoted their lifetime into the research of electromagnetism. Now, looking back, it is evident that the 19th century was a “golden age” for science. Not only did the discoveries of modern science inspire various technological inventions, but the technological advancements also enabled further breakthroughs in science, especially in the field of electromagnetism. This paper will trace and connect the technological inventions in the 19th century that facilitated the research on electromagnetism, which eventually led to a widely-accepted physical explanation of light.
Batteries and galvanometers are probably the two most “fundamental” inventions that established the foundation for further research on electromagnetism. Prior to the invention of batteries and galvanometers, there was not a convenient source of electricity, nor was there a reliable means of measuring electric current. As a result, the experiments that could be done to investigate the nature of electricity and magnetism were rather primitive, and they did not produce many useful results. Things greatly changed after batteries and galvanometers became common experimental apparatus.
Alessandro Volta was the one who was credited with the invention of batteries. Born in a wealthy family, Volta did not attend college, but he started conducting scientific experiments in a physics laboratory since his young adulthood. By the end of 18th century, he had already become a well-known scientist. However, Volta is remembered by people today due to his invention of battery. Unlike his colleague, Galvani, who proposed the existence of the so-called “animal electricity” as demonstrated by the twitch of dissected frogs’ legs, Volta believed that the generation of electricity does not require animal parts (Tretkoff). To prove his point, Volta managed to create a battery which consisted of alternating silver or zinc disks separated by paper soaked in salt water or sodium hydroxide (“Alessandro Volta”). It was the year of 1800, and Volta’s battery turned out to be a huge success. Nowadays, most people do not know that Volta’s battery was originally designed to settle the scientific dispute between Galvani and Volta, but no one in the modern society could imagine life without battery.
In fact, the scientific community was deeply amazed by this new source of electricity, and Volta’s battery was soon used in various chemistry and physics experiments. For example, in 1800, William Nicholson and Anthony Carlisle observed the decomposition of water into hydrogen and oxygen with the help of Volta’s battery. The phenomenon is now called “electrolysis” (“Alessandro Volta”). Also, batteries were utilized in Faraday’s research on electromagnetism, which resulted in the groundbreaking discovery of electromagnetic induction. (Tretkoff).
Volta’s battery, though it was an absolutely amazing invention, was not without any deficiencies. Over the years, improvements have been made to enhance the performance of batteries. In 1839, William Grove invented the first fuel cell; In 1859, Gaston Plante developed the first rechargeable lead-acid battery; and by the end of the 19th century, the rechargeable nickel-cadmium battery was invented by Waldmar Jungner, which is still widely-used today (“History and Timeline”).
After the invention of batteries, scientists were able to conduct a series of experiments investigating the property of electricity. As the experiments became more and more sophisticated, the need for a meter that can accurately measure electric current became urgent. In 1824, Andre-Marie Ampere announced the invention of galvanometer. Interestingly, the instrument was named after Galvani, the great Italian scientist whose dispute with Volta was discussed above. The early galvanometer had very simple design. It consisted of a compass surrounded by a coil of wire. The deflation of the compass needle served as an indicator of the presence, direction, and strength of an electric current. The scientific community happily embraced this brilliant invention (“Galvanometers & Meters”).
Unfortunately, just like the early batteries, the early galvanometers were imperfect in many ways. For example, the deflation of the magnetic compass needle on the early galvanometers was not linearly proportional to the current, which made reading the measurements a troublesome task (“Galvanometer”). Moreover, the readings of the early galvanometers were inaccurate and even at times inconsistent, which made it not ideal for physics experiments that demanded both accuracy and consistency in data acquisition (“Galvanometers & Meters”). In response to the demand for a kind of galvanometer with better performance, Jacques-Arsene d’Arsonval and Marcel Deprez developed in 1882 a galvanometer with permanent stationary magnet and a moving coil of wire. This new type of galvanometer provided more accurate and consistent measurements. Later, Edward Weston further improved the design of the galvanometer. The technical details of Weston’s galvanometer are too sophisticated to be discussed in this paper, but it must be recognized that his design was one of ingenuity. Even today, people continue to use Weston’s galvanometer, which is quite amazing considering that his galvanometer was developed over a century ago (“Galvanometer”).
(A Voltaic Pile) (Struers Tangent Galvanometer)
The invention of batteries and galvanometers is truly one of the most remarkable moments in the history of technological development. Without batteries and galvanometers, humans would never get to uncover the mystery of electromagnetism and light. However, it must be noted that, although batteries and galvanometers are brilliant inventions, little scientific progress could be made if they were scientists’ only tools. Fortunately, the invention of batteries and galvanometers inspired numerous technological innovations in the 19th century, two of which were electromagnets and generators. With the invention of electromagnets and generators, scientists further revealed the complex relationship between electricity and magnetism, which eventually led to Maxwell’s famous equations. Only then did a physical explanation of light became possible.
The British electrical engineer William Sturgeon is generally considered the inventor of electromagnets. Though he was in military service for a few years, he started his scientific career in his mid-thirties. In 1825, he successfully created the first electromagnet, which was basically a piece of horseshoe-shaped iron wrapped with copper wire (“William Sturgeon”). Back in the 19th century, it was the first time that humans were able to make a magnet different from permanent magnets. Moreover, the magnitude of the electromagnet’s magnetic attraction could be controlled by changing the strength of the electric current, and the electromagnet itself could be turned on or off easily. Not surprisingly, the electromagnets soon drew people’s attention and became extensively used in both research and industry (“What Are the Uses”).
The invention of electromagnets demonstrated the Danish scientist Oersted’s discovery that electricity emitted magnetic waves, and it also inspired numerous other technological innovations later in the century. For example, the electric telegraph was made possible by a strong electromagnet ((“William Sturgeon”). The invention of electromagnet was probably the first time the complex interaction between electricity and magnetism was utilized by humans for scientific and industrial purposes, but it was certainly not the last. Just a few years after Sturgeon’s invention of electromagnet, Michael Faraday introduced the first electric generator in 1831 (“History of Generators”).
Michael Faraday was a talented scientist and inventor, who made productive contributions to various scientific fields during his lifetime. In 1831, he observed that when a magnet was passed back and forth through a coil of wire, a flow of electric current was generated, as indicated by the reading in the galvanometer. Through this experiment, Faraday discovered the Law of Electromagnetic Induction, and he invented what was called “the Faraday Disk,” which was in essence an electric generator (“History of Generators”).
Faraday’s generator was a great invention, but scientists were not satisfied by the amount of power it could generate. In 1832, a French instrument maker, Hippolyte Pixii, inspired by the Faraday Disk, introduced the first magneto electric generator (“History of Generators”). Nowadays, virtually all electric power around the world is produced by applying Faraday’s Law of Electromagnetic Induction (“Michael Faraday’s Generator”). Truly, Faraday’s generator has had profound influence not only on the history of science, but also on the entire modern civilization. It is inconceivable to someone living in the 21st century what a world without electric generators would look like.
(Illustration of Sturgeon’s Electromagnets) (A Faraday Disk)
As the paper has shown, electromagnets and generators, as well as batteries and galvanometers, are all the amazing products of human intelligence. Those technological advancements not only forever changed the lives of ordinary people, but also deeply influenced the worldview of physicists. They gave Maxwell the inspiration for his equations that beautifully unified the theory of electricity and magnetism. Those equations, which unexpectedly led to a physical explanation of light, is simply referred to as “Maxwell’s equations” today.
Before Maxwell’s work, the studies of electricity, magnetism, and light are largely considered separate fields. By the mid-1800s, the decades of investigation gave people a rather deep understanding of electricity and magnetism. Naturally, scientists started their search for a common theory with the capability of accounting for all the phenomenon of electromagnetism. Maxwell, then Professor of Natural Philosophy at King’s College London, proposed four equations that could explain everything known about electromagnetism. The derivation of the four equations are beyond the scope of this paper, but it should be mentioned that the four equations possessed an indescribable mathematical beauty. Noticeably, Maxwell’s equations had profound impacts well beyond the narrow field of electromagnetism. They played a crucial role in the theory of relativity, and later, in the field of quantum mechanics, leaving an indelible mark on the history of modern physics (“Maxwell’s Equations”).
Now it is finally the time to ask why Maxwell’s equations gave a plausible physical explanation of light. Maxwell’s equations showed that the electromagnetic fields propagate at the speed of 300000000 meters per second, which is exactly the speed of light. This was quite an astounding discovery since Maxwell’s equations were proposed to explain not light phenomenon but electromagnetic phenomenon. That implies that there must be some connections between light and electromagnetism. In fact, it was not long before scientists came to the realization that visible light is just a special type of electromagnetic waves (“What Are Maxwell’s Equations”). Of course, that light is a form of electromagnetic waves is not the most perfect answer to the question “what is light,” but it is the first successful attempt at revealing the nature of light. To a great extent, Maxwell’s equations are the foundations upon which further scientific research could be conducted to investigate the nature of light.
Without the invention of batteries, galvanometers, electromagnets, and generators, people would never be able to explain what light truly is. Those technological innovations were the products of many theoretical studies on the subject of electricity and magnetism, and they in turn served as tools and inspirations for further inquiry into the nature of electromagnetism and light. People today will always remember those great inventions, for they not only brought much convenience into the lives of ordinary people but also paved the way for a physical explanation of light.
Works Cited
“Illustration of Sturgeon’s Electromagnets.” Universe Today. Scientific American. n.d.
“A Faraday Disk.” Generatormag. 21 June 2017. https://www.generatormag.com/history-of-
generators/
“A Voltaic Pile.” American Physical Society. vol. 15, no. 3, 2006.
https://www.aps.org/publications/apsnews/200603/history.cfm
“Struers Tangent Galvanometer.” Sparkmuseum. n.d.
http://www.sparkmuseum.com/GALV.HTM