Hitting the Books: Without glass, we'd have never discovered the electron

MIT Press

Excerpted from The Alchemy of Us - How Humans and Matter Transformed One Another by Ainissa Ramirez. Reprinted with permission from The MIT PRESS. Copyright 2020.

Long before the Great War, in 1895, science and magic were hard to separate. That year, Wilhelm Roentgen took a ghostly picture of his wife’s hand using mysterious rays that showed her bones. These invisible rays, later called X-rays, shot out of a contraption made of metal and glass that looked like something out of Dr. Frankenstein’s laboratory. Newspapers packed their pages with depictions of a person’s insides on the outside, and readers snatched up copies. Scientists were also enchanted by X-rays. Some of them wanted to know what else they could do. Others wondered where they came from. All these scientists understood that a battery attached to a stretched glass globe spawned a glowing stream called a cathode ray, and when this cathode ray collided with a piece of metal inside the globe, out came X-rays. Their thinking was that there must be more to these cathode rays. So while the whole world was wowed with X-rays, a few scientists were hoping to find the next great thing in cathode rays. Little did they know that this bright stream would explain how the world worked.

Cathode rays had been known for decades, but there was little consensus about their origin, and eventually the case went cold. With the renewed interest in them, scientists obsessed over every move of cathode rays, writing articles with reports of their behavior, though not yet knowing that cathode rays held a key to their science understanding. Locked in those cathode rays was the currency of all chemical reactions. Locked in those cathode rays was the answer to science questions from how toasters work to how planets were born. Locked in those cathode rays were the droplets that powered a river of modern technologies from televisions to computers to cellphones. Unbeknownst to these early scientists was that inside the cathode ray was a part of the atom that they didn’t know existed—the electron. But deciphering the puzzle of cathode rays required uncovering clues. Just as the popular character Sherlock Holmes used his intellect and his magnifying glass to solve mysteries, scientists too had to observe cathode rays under glass. For some scientists, this puzzle was too delicious to turn down, and Joseph John Thomson was one of them. It was this short man from the nineteenth century who would make the giant leap that made the technologies of the twentieth and twenty-first centuries possible.

Thomson’s potential in answering one of the biggest questions of his day seemed doubtful when he was fourteen years old in 1870. All he wanted to be was a botanist. As a small boy growing up near the city of Manchester, England, he spent all his pocket money on weekly gardening magazines. His father, a modest bookseller, wanted him to have a stable trade as an engineer. Being an engineer was good work, as Manchester’s textile mills turned American cotton into goods. To please his father, J. J., as Joseph John Thomson was nicknamed, attended Owen’s College in Manchester in 1870. But when his father died, J. J. scrambled to stay in school by winning scholarships. He entered Trinity College in Cambridge to study mathematics, choosing the beauty of numbers, instead of their utility, as in engineering. Walking on the hallowed grounds that Sir Isaac Newton strolled was an achievement for any son of a bookseller. But J. J. never fit in.

J. J. may not have felt at home at this old university, but his genius certainly was at home there. By 1895, Thomson was the thirty-nine-year-old head of the Cavendish Laboratory at Cambridge University, blossoming into an absentminded mathematics professor. His eyeglasses had two positions—one on his nose, which meant he was thinking, and the other on his forehead, which meant he was thinking more. He did not trouble his brain with worry about his appearance so his hair was long, his mustache overgrown, and his chin badly shaven. His brain was congested with abstract ideas, so his new research on cathode rays meant there’d be even less space to worry about ordinary things.

Uncovering the origin of the cathode rays was a perfect puzzle for J. J. because it challenged him by linking abstract ideas with observable events. Cathode rays shot from one electrical connection to another inside of a glass tube without air, and there were two dueling beliefs among scientists about how cathode rays moved in the world. One group thought that cathode rays were a wave that was a wrinkle in the ether. Others concluded that the beam was made up of small bits of particles acting together, like a migrating flock of birds. “Neither side was wholly right nor wholly wrong,” said J. J. There was evidence to support both ideas, but the cathode ray could not be both.

One definitive way to see if a cathode ray was a wave or a particle was to observe its dance with magnets. There was an old theory that said that if cathode rays fly undisturbed by a magnet, they are a wave; and if a magnet deflects the ray, they are made up of particles. J. J. wanted to test this theory and learned that fourteen years earlier, in 1883, another scientist performed this very same experiment. Cathode rays did not move when a magnet was nearby, supporting the wave argument. But J. J. thought there was something wrong with that earlier attempt. Scientific tools had advanced since then, and could draw more air out of a glass tube to better create a vacuum. A vacuum with less air was the habitat where cathode rays thrived best. So J. J., who believed that cathode rays were full of particles, wanted to repeat this old experiment using a glass tube with less air in it, made possible with an improved vacuum. J. J.’s mathematical genius, unfortunately, did not translate into manual dexterity. For such a small man, he was a Victorian bull in a china shop. When he visited his students in the laboratory, they’d wince when he offered help, and quickly tried to move fragile things out of his way. They took deep breaths when he sat on a lab stool to speak. Life was no better at home. J. J.’s wife did not permit him to use a hammer in the house.

J. J. needed help with his experiments and that help came from a former chemistry assistant, Ebeneezer Everett. While the name Ebeneezer conjures a miserly image, Everett was a dashing, mustached man, with cowboy good looks, who leaned a bit to seem less tall. Little is known of this Everett, except that he was a patient soul and a virtuoso for making laboratory glassware out of common soda lime glass into works of art that would have pleased a Murano glass master. Lab benches were full of Everett’s glass constructions, braced in place with wood brackets, with wires on every surface and sticking up into the air. Everett was the scientific brawn to J. J.’s brain. Starting in late 1896, J. J. wanted to make a cathode-ray Obstacle course to settle this wave/particle debate. Everett made a sophisticated glass bulb with pieces inside, reminiscent of a model ship in a bottle. On one end of the glass two metal pins stuck out that were attached to the ends of a battery to produce the cathode ray. Inside the glass, the cathode rays sprayed out in many directions like water out of a hose and were focused into a narrow stream, with two slits that acted like a nozzle. That beam then hit the interior surface of a round bulb, creating a green glow.

Cathode rays required that there be very little air inside the glass tube. “This was more easily said than done,” said J. J. To remove the air, Everett poured liquid mercury into a tower, which he connected to his glass bulb with a glass bridge. As the heavy liquid fell, it sucked air across the bridge from the glass bulb, creating a vacuum. Removing the air sometimes took most of the day, so Everett started in the morning before the hurricane in the form of J. J. Thomson arrived in the laboratory in the afternoon.

Only glass worked for these experiments. Copper would not do, nor any metal for that matter, for metals would bury the cathode ray. Wood or clay would not work either, for they could not hold a vacuum. Clear plastics hadn’t been invented yet. Glass was the best keeper of a vacuum; transparent, uninterested in conducting electricity, and malleable to an inventor’s imagination. But, mostly, glass was vital in science because it allowed scientists to do what they do best, which is to use their power of observation—and this was what J. J. excelled at.

Sometimes J. J. complained to his colleagues about his glassware. “I believed all the glass in the place is bewitched,” he said. Standard recipes did not yet exist for glass. Some parts of a glass tube were richer in key ingredients than others. To build with glass required compositions that were uniform all over, so that they would melt at the same temperature. And a glass piece divulged how well the bond was made only after many hours of work had passed. Sometimes glass whispered with a small air leak that there was something wrong, other times it screamed with explosions. Glass was temperamental, and it was up to Everett to tend to it like a newborn baby. In the summer of 1897, Everett completed J. J. Thomson’s obstacle course for testing cathode rays. He inserted two additional metal plates and attached them to another battery, creating an electric field, as a way to nudge the rays. As Everett turned the contraption on, J. J. saw that the cathode ray moved downward to the metal plate connected to the positive end of the battery. This told J. J. that the cathode ray was negative. Everett then put a huge horseshoe magnet around the center of the glass tube, and when he turned it on, J. J. saw that the cathode ray moved up, like migrating birds swept up by a strong wind. From J. J.’s mathematical calculations, written on the backs of random scraps of paper, he was able to deduce that the cathode ray was made of small bits that were electrically charged and negative. He calculated they were smaller than an atom, and were thus the tiniest part of matter yet discovered.

And when he and Everett repeated these experiments with different metal plates and with different gases inside the tube, J. J. saw that these same small negative charges existed in all materials. He called these bits corpuscles, but they would later be known as electrons. J. J.’s discovery changed the world, but he could not predict that it would. This small and odd man found the small and odd electron, opening up a door in science and expanding the understanding of matter. The discovery of the electron gave us clues about how galaxies and planets formed, because the exchange of electrons, in chemical bonds, explained how hot gases from the Big Bang coalesced into us. This discovery also revealed the basic building block of technology. With the electron, scientists would come to understand the workings of circuits, static electricity, batteries, piezoelectricity, magnets, generators, and transistors. With the knowledge of electrons, technology—and society—blossomed.

When J. J. Thomson was growing up, many inventions that we now take for granted did not exist. There was “no car, no airplane, no electric light, no telephone, no radio.” But the electrons in his glass, which made up electricity, would power all these machines as well as later developments such as computers, cellphones, and the internet. As smart as J. J. was, he could never have predicted that this abstract science would have practical implications. But it did, and it had many. With his discovery, humanity was thrust into a new age—an electronic one. None of these technologies, however, would have happened if it weren’t for the ability to see electrons in action. Our modern world was made possible by the ancient and old material of glass.