Beat the books: we would never have discovered the electron without glass

admin 2020-05-02 15:05

MIT Press

Long before the First World War, 1

895, science and magic were difficult to separate. This year Wilhelm Roentgen made a ghostly picture of his wife’s hand with mysterious rays that showed her bones. These invisible rays, later called X-rays, shot out of a metal and glass device that looked like something from Dr. Frankenstein’s laboratory. Newspapers packed their pages with pictures of someone inside, and readers grabbed 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 of these scientists understood that a battery attached to a ball of stretched glass produced a glowing current called the cathode ray, and when that cathode ray collided with a piece of metal inside the globe, x-rays came out. They thought that these cathode rays had to contain more. While the whole world was overwhelmed by X-rays, some scientists hoped to find the next big thing in cathode rays. They didn’t know that this bright current would explain how the world works.

Cathode rays had been known for decades, but there was little agreement about their origin, and eventually the case got cold. With renewed interest in them, scientists became obsessed with every movement of cathode rays and wrote articles with reports of their behavior, although they did not yet know that cathode rays were a key to their scientific understanding. The currency of all chemical reactions was included in these cathode rays. These cathode rays included the answer to scientific questions from how toasters work to the birth of planets. The droplets that supplied a flow of modern technologies from televisions to computers to cell phones were enclosed in these cathode rays. These early scientists did not know that there was a part of the atom inside the cathode ray that they did not know existed – the electron. In order to decipher the riddle of the cathode rays, however, clues had to be uncovered. Just as the popular character Sherlock Holmes used his intellect and magnifying glass to solve puzzles, scientists also had to observe cathode rays under glass. For some scientists, this riddle was too tasty to reject, and Joseph John Thomson was one of them. It was this little nineteenth-century man who made the giant leap that made the twentieth and twenty-first century technologies possible.

Thomson’s potential to answer one of the greatest questions of his time seemed doubtful when he was fourteen in 1870. He just wanted to be a botanist. As a young boy who grew up near the city of Manchester in England, he spent all his pocket money on weekly gardening magazines. His father, a humble bookseller, wanted him to have a stable craft as an engineer. Being an engineer was a good job as the Manchester textile factories turned American cotton into goods. To please his father, J. J., as Joseph John Thomson was called, attended Owen’s College in Manchester in 1870. When his father died, J.J. endeavored to receive grants to stay in school. He entered Trinity College, Cambridge to study mathematics, and chose the beauty of numbers instead of their usefulness as in engineering. A walk on the sacred grounds on which Sir Isaac Newton walked was a feat for any bookseller’s son. But J.J. never suited it.

J. J. may not have felt at home at this old university, but his genius was certainly at home there. By 1895, Thomson was the thirty-nine-year-old director of the Cavendish Laboratory at Cambridge University and developed into an absent-minded math professor. His glasses 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 didn’t worry about his appearance to his brain, so his hair was long, his mustache was overgrown, and his chin was shaved badly. His brain was overflowing with abstract ideas, so his new research on cathode rays meant that there was even less space to do ordinary things.

The discovery of the origin of the cathode rays was a perfect puzzle for J.J. as it challenged him by combining abstract ideas with observable events. Cathode rays shot from one electrical connection to another within a glass tube without air, and there were two duels among scientists over how cathode rays moved in the world. One group believed that cathode rays were a wave that was a fold in the ether. Others concluded that the beam consisted of small particles that worked together like a flock of birds. “Neither side was right or wrong,” said J.J. There was evidence to support both ideas, but the cathode ray couldn’t be both.

A definite way to determine if a cathode ray was a wave or a particle was to observe its dance with magnets. There was an old theory that cathode rays that fly undisturbed by a magnet are a wave; and when a magnet deflects the beam, they are made up of particles. J. J. wanted to test this theory and learned that fourteen years earlier, in 1883, another scientist was doing this experiment. Cathode rays did not move when there was a magnet nearby, which supported the wave argument. But J. J. thought there was something wrong with this earlier attempt. The scientific tools had advanced since then and could draw more air from 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 with a glass tube with less air, which was possible with an improved vacuum. Unfortunately, J. J.’s mathematical genius did not lead to manual dexterity. For such a small man, he was a Victorian bull in a china shop. When he visited his students in the lab, they flinched when he offered help and quickly tried to get fragile things out of the way. They took a deep breath as he sat on a lab stool to speak. Life was no better at home. J. J.’s wife did not allow him to use a hammer in the house.

J. J. needed help with his experiments and this help came from a former chemistry assistant, Ebeneezer Everett. While the name Ebeneezer conjures up a stingy picture, Everett was a dashing man with a mustache and good cowboy look who bent a little to look less tall. Little is known about this Everett, except that he was a patient soul and a virtuoso who made laboratory glass from ordinary soda-lime glass into works of art that a Murano glass master would have liked. The lab benches were full of Everett’s glass structures, which were fastened with wooden clips, had wires on every surface, and protruded into the air. Everett was the scientific force for J. J’s brain. From the end of 1896, J. J. wanted to create an obstacle course for cathode rays to settle this wave / particle debate. Everett made a nifty glass pear with parts inside that resemble a model ship in a bottle. At one end of the glass protruded two metal pins attached to the ends of a battery to generate the cathode ray. Inside the glass, the cathode rays sprayed like water from a hose in many directions and were focused in a narrow stream with two slits that acted like a nozzle. This beam then hit the inside surface of a round light bulb and produced a green glow.

Cathode rays required very little air in the glass tube. “It was easier said than done,” said J.J. To remove the air, Everett poured liquid mercury into a tower, which he connected to his glass bulb via a glass bridge. When the heavy liquid fell, it sucked air out of the glass flask over the bridge and created a vacuum. Air removal sometimes took most of the day, so Everett started in the morning before the J. J. Thomson hurricane arrived in the laboratory in the afternoon.

Only glass worked for these experiments. Copper would not do metal or metal because metals would bury the cathode ray. Wood or clay wouldn’t work either because they couldn’t hold a vacuum. Clear plastics had not yet been invented. Glass was the best keeper of a vacuum; transparent, uninterested in the conduct of electricity and malleable for an inventor’s imagination. But most of the time, glass was critical in science because it allowed scientists to do what they do best, using their powers of observation – and that was what set J.J apart.

Sometimes J. J. complained to his colleagues about his glassware. “I thought the whole glass in the place was bewitched,” he said. There were no standard recipes for glass. Some parts of a glass tube were rich in important ingredients than others. Building with glass required compositions that were uniform everywhere so that they could melt at the same temperature. And a piece of glass showed how well the connection was made after many hours of work. Sometimes glass whispered with a little air leak that something was wrong, sometimes it screamed of explosions. Glass was spirited and it was up to Everett to take care of it like a newborn. In the summer of 1897, Everett completed J. J. Thomson’s obstacle course to test cathode rays. He inserted two additional metal plates and attached them to another battery, creating an electric field to drive the beams. When Everett turned on the device, J.J. saw the cathode beam move down to the metal plate that was connected to the positive end of the battery. This said to J.J. that the cathode ray was negative. Everett then placed a giant horseshoe magnet around the center of the glass tube, and when he turned it on, J.J. saw the cathode ray move upward like migratory birds caught in a strong wind. From J. J.’s mathematical calculations written on the back of random scraps of paper, he could conclude that the cathode ray consisted of small bits that were electrically charged and negative. He calculated that they were smaller than an atom and thus the smallest part of matter that has been discovered so far.

And when he and Everett repeated these experiments with different metal plates and with different gases in the tube, J.J. saw that the same small negative charges were present in all materials. He called these bits corpuscles, but they later became known as electrons. The discovery of J.J. changed the world, but he couldn’t predict that it would. This little and strange man found the little and strange electron, opened a door in science and broadened the understanding of matter. The discovery of the electron gave us clues as to how galaxies and planets formed, because the exchange of electrons in chemical bonds explained how hot gases from the Big Bang melted into us. This discovery also revealed the cornerstone of the technology. With the electron, scientists would understand the functioning of circuits, static electricity, batteries, piezoelectricity, magnets, generators and transistors. Technology – and society – flourished with knowledge of electrons.

When J. J. Thomson grew up, many inventions that we take for granted today didn’t exist. There was “no car, no plane, no electric light, no phone, no radio.” But the electrons in his glass that made up electricity would drive all of these machines, as well as later developments like computers, cell phones, and the Internet. As clever 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 taken to a new age – an electronic one. However, none of these technologies would have happened if it had not been possible to see electrons in action. Our modern world was made possible by the old and old glass material.

Original Source