Strange Glow

by Timothy J Jorgensen

  It all began with mathematical calculations performed in 1867 by physicist James Clerk Maxwell (1831–1879). Maxwell noticed some similarity between the wavelike characteristics of light and the properties of electrical and magnetic fields. From this observation, he formulated a set of equations that described waves of what is now called electromagnetism traveling through empty space. For the shorter wavelengths,20 his equations accurately described the known properties of light, so it was concluded that light was, in fact, a form of electromagnetism. Likewise, if you plugged values corresponding to longer wavelengths into Maxwell’s equations, they also described some physical properties. But of what? That wasn’t at all clear, because the existence of electromagnetic waves with wavelengths longer than light’s was unknown at the time. Did such electromagnetic waves really exist, or was it all just mathematics carried too far? The hunt was on, and it lasted for over 20 years. Finally, in 1888, Heinrich Hertz (1857–1894) was able to experimentally produce and detect long wavelength electromagnetic waves (radio waves) in his laboratory. Unfortunately, Hertz died young and was never able to carry his discovery to its next logical phase.

  When Hertz died, his scientific achievements were reviewed in the popular press, and caught the eye of Marconi, a young electricity enthusiast. Only 20 years old at the time, Marconi, like no other, fully appreciated the potential of Hertz’s work. Though he had minimal formal training in electricity, Marconi started with that little knowledge and jumped wholeheartedly into the field of radio waves.

  It was the chance discovery, in 1891, of an apparently unrelated phenomenon by French scientist Édouard Eugène Désiré Branly (1844–1940), that opened the door to radio communications. Branly found that an electric spark could increase the electrical conductivity of nearby metal filings enclosed within a glass tube. If the tube were then tapped with a finger, the filings would become disoriented again and conductivity would stop. Furthermore, the phenomenon could be demonstrated to occur even when the spark and the tube were on opposite sides of the room. It wasn’t long before an electric bell was hooked up to the tube, and public demonstrations were being made of sparks ringing bells from across the room through apparently empty space. Thus, a new scientific parlor trick was born.

  Lodge and his colleagues first made the speculation, which turned out to be correct, that the phenomenon was due to Hertz’s waves being emitted by the spark, but they failed to see the practical significance of this phenomenon for communications. (At least they failed to appreciate it initially.) Only Marconi saw it for what it was—a new means to transmit telegraphic signals without wires.21

  Working initially in his home attic in Italy with funding from his father—a financially successful businessman and farmer—Marconi was able to transmit wireless telegraphic signals short distances. He methodically improved the technology to lengthen the distance signals could travel, and subsequently solicited commercial backing. Eventually, on December 12, 1901, Marconi made the first transatlantic transmission (from Poldhu, England, to St. John’s, Newfoundland, Canada). With the success of that transmission, wireless telegraphy instantly became a contender to the undersea transatlantic cable as a communication medium between the United States and Europe.22 Marconi also made the technology portable and marketed it to shipowners through his business, the Marconi International Marine Communication Company. The Titanic was equipped with the latest of Marconi’s marine telegraphs when it hit an iceberg during its maiden voyage on April 14, 1912. Wireless distress signals in Morse code, transmitted from the sinking ship, brought rescue vessels. Unfortunately, they arrived too late for the many who froze to death in the frigid sea due to insufficient lifeboats; but they were a godsend to the rest.

  Although Marconi’s only interest in radio waves was for wireless telecommunications for the good of humanity (and profit for himself), others saw more sinister uses. He was once asked by a journalist: “Could you not from this room explode a box of gunpowder placed across the street in that house yonder?” Marconi answered that, as long as the gunpowder had been prewired for electrical ignition, it could easily be achieved.23 Still others saw the potential for radio communication use in warfare, and Marconi was soon visited by German spies seeking to obtain a telecommunication advantage in the looming hostilities that would become the First World War. No one, however, foresaw radar, one of the most powerful military uses for radio waves. Radar would become the radio wave technology of the Second World War.

  Marconi’s telegraphic radio technology was further developed by engineers to allow full audio transmission rather than simply the intermittent clicking of Morse code.24 This innovation allowed radio to become a major vehicle for the news and entertainment industries. By the 1930s, a console radio could be found in virtually every home in America.

  How is it that Marconi was able to transmit radio waves across the entire ocean? Marconi’s basic strategy for long-distance radio transmission was to build very high antennae and increase electrical power as much as possible. His transatlantic transmission of December 12, 1901, utilized up to 300,000 watts of power25—enough to power 5,000 sixty-watt light bulbs26—to propel his wireless telegraph message across the ocean. His approach worked, but all that power wasn’t necessary. He subsequently learned that if he had shortened the wavelength of the radio waves just a small amount, he could have greatly increased transmission distances without all that excess wattage.27 He later said that his fixation on wattage, rather than also attending to wavelength, was the biggest mistake of his career.28 He had underappreciated the great importance of wavelength in transmission distance. We will soon see that wavelength is the primary factor determining radiation’s health effects as well.

  Marconi and his coworkers realized that the electrical power levels they were dealing with were very dangerous, and they took extensive precautions to protect themselves from electrocution during their experiments.29 In contrast, they were never wary of radio waves and took no precautions at all to protect themselves from the possible health effects. Likewise, the public seemed equally unconcerned about the potential health consequences of radio waves … with one notable exception.

  Before his transatlantic attempt, Marconi first sought to demonstrate transmission across a humbler body of water; namely, the English Channel. In preparing for a transmission on the French side of the channel in the little town of Wimereux, Marconi’s work crew was interrupted one night by a man who barged into the transmission room wielding a handgun. The man claimed to be suffering from some sort of internal pain, which he attributed to the radio wave transmissions, because the symptoms apparently started when Marconi’s crew began their experiments. He demanded that all further transmission stop, and his gun proved to be very persuasive.

  Fortunately, one of Marconi’s engineers, W. W. Bradfield, thought quickly and told the man that all would be made right if he would just put down his gun and allow himself to be immunized against radio waves. Although skeptical, the gun-wielding man acquiesced to the treatment, and Bradfield gave him a slight electrical shock as an “immunization.” Bradfield told him the immunization would convey lifelong resistance to radio-wave illnesses. Satisfied, the man left. Apparently his symptoms abated, because the workers never heard from him again.30

  Marconi’s crew did suffer one transmission-related death, though. On Sunday, August 21, 1898, on an island off of Ireland, a young technician was preparing a transmission station in a house on the edge of a seaside cliff by stringing transmission wires outside one of the bedroom windows. No one knew the details of the mishap, as he was unwisely working alone. But the next day his body was found at the base of the 300-foot cliff. Presumably, he had somehow slipped and fallen to his death.31

  Marconi himself died in Rome on July 20, 1937, at the age of 63, after a brief illness. The exact cause of his death is unknown. He was given a state funeral by the Italian government, and, the next day, radio stations everywhere in the world participated in two minutes of silence in tribute to the m
an who had made it all possible.32

  A BULLET DODGED

  Unfortunately for hospital patient Toulson Cunning in Montreal, Canada, the standard of care was amputation. Cunning had the ill luck to have been shot in the leg on Christmas Day, 1895. Despite painful surgical explorations by his doctors, the bullet could not be located. Amputation appeared imminent. But, as fate would have it, Cunning would become the first beneficiary of the medical use of x-rays. His leg would be spared the knife.

  While Cunning writhed in his bed in pain, Professor Wilhelm Conrad Roentgen (1845–1923),33 in Würzburg, Germany, had his own worries that Christmas night. Just days earlier, he had made what would prove to be one of the most momentous discoveries of the century, but at the time he was concerned that he might have overlooked something and been badly mistaken. He confided to one of his colleagues at the University of Würzburg, “I have discovered something interesting, but I do not know whether or not my observations are correct.”34 They were.

  Roentgen had discovered invisible rays that could pass through solid objects. This was an outrageous claim at the time, and Roentgen likely wouldn’t have believed it himself if he hadn’t seen it with his own eyes. It seems that he and most everyone else were unaware that another scientist, Hermann von Helmholtz (1821–1894), had predicted in 1893 that rays with wavelengths shorter than visible light, if they existed, would be able to pass through matter.35 Had Roentgen known of von Helmholtz’s theoretical work, he might have been less worried about his own experimental findings, but not much less.

  FIGURE 2.1. WILHELM CONRAD ROENTGEN. Roentgen discovered x-rays in 1895, and won the first Nobel Prize in Physics for his efforts (1901). X-rays became an immediate sensation among scientists and lay people alike because of their mysterious ability to penetrate solid objects, and for their potential utility in diagnosing disease.

  Roentgen was not the type of scientist who put much stock in theorizing and grand hypotheses. He was an experimentalist. He believed in the existence of only those things that he could directly measure and test in his laboratory. Roentgen’s philosophy was that all knowledge was acquired empirically. To him, science advanced through many hours of hard trial-and-error work, coupled with a little luck. By putting in the laboratory time, the perceptive scientist afforded himself the chance to make an important discovery. A casual observer might have discounted the strange glow coming from the fluorescent screen hanging in his laboratory. But Roentgen realized that the glow on the screen coincided precisely with the electricity experiments he was performing on the other side of the room. But exactly what was it that caused this strange glow?

  Roentgen’s experiments involved running an electric current through a vacuum tube, commonly known as a Crookes tube after its inventor, William Crookes (1832–1919). Crookes was a self-styled chemist who never worked for a university. Rather, he supported himself by publishing scientific periodicals. He was primarily interested in chemical elements, and his seminal contributions to the chemistries of selenium and thallium won him admittance into the Royal Society—the United Kingdom’s most prestigious body of scientists—at the young age of 31.

  Crookes was also fond of making gadgets from glass. He spent a lot of time playing with a novelty item invented by the famous German glassblower Heinrich Geissler (1814–1879). Geissler found that neon and some other gasses confined within a tube glowed in different colors when electricity passed through them. By blowing the glass tubes into various shapes, brightly colored artwork could be produced. These tubes eventually developed into what we now know as neon lighting. Crookes decided to study the science underlying Geissler’s tubes, and ended up creating his own namesake tube that would provide him with worldwide fame even greater than Geissler’s.

  A Crookes tube can be thought of as a light bulb lacking a filament. It’s typically in the form of a clear glass tube in the shape of a pear with electrodes at each end, and is about the size of an American football. William Crookes found that by applying high voltages across the tube he could produce mysterious cathode rays, which could be seen if the Crookes tube were coated with fluorescent material, or if the cathode ray beam were pointed at a fluorescent screen (a sheet of glass or cardboard coated with some fluorescent chemical).

  FIGURE 2.2. CROOKES TUBE. Crookes tubes were widely used in physics laboratories in the late 1800s to study the rays emitted from the cathode (negative electrode) of the tube. Roentgen was studying the properties of cathode rays when he accidentally discovered that the anode (positive electrode) of the tube, typically shaped like a Maltese cross, emitted its own rays, but of an undetermined type. Since their identity was a mystery, Roentgen called them “x” rays. (Source: Fig. 244 in Lehrbook der Experimentalphysik 2nd ed., by E. von Lommel, Leipzig: Johann Ambrosius Barth, 1895)

  It turned out that cathode rays are really just electrons jumping through empty space. Crookes tubes are vacuum tubes. That is, they contain no air or any other gas, just empty space. Since there are no gas molecules or filament to conduct them, electron flow is not possible in a Crooke’s tube until very high voltages are applied across the electrodes, at which point electrons begin to jump from one electrode (i.e., the cathode) to the other (i.e., the anode) across the empty space. It was just these jumping electrons that were the explanation for what Crookes was calling cathode rays. The study of cathode rays was a hot topic among physicists in Roentgen’s day, and virtually all physicists had Crookes tubes in their laboratories. Roentgen was no different.

  Remarkably, whenever Roentgen experimented with his Crookes tube, he noticed a faint glow even on fluorescent screens that were not in the vicinity of the cathode ray beam. The glow persisted even when the Crookes tube was completely blocked from the fluorescent screen with objects handy in his laboratory, including cardboard, books, and rubber. It was as though some type of invisible rays were coming from the tube, penetrating these materials, and hitting the fluorescent screen. Thinking these mysterious rays were some new form of light, he tried to bend them with a prism just as Newton would have undoubtedly attempted, but to no avail. They could not be bent with a prism, so they weren’t rays of light. Thinking alternatively that perhaps they might just be stray electrons escaping from the tube, he tried to bend their path with a magnet.36 That didn’t work either, thus ruling out electrons as the source of the glow. All rays known at the time (i.e., light rays and cathode rays) were deflectable by either prisms or magnets, but these mysterious “rays” were affected by neither … and they penetrated solid objects! It was simply amazing. Whatever was going on was something new that had never been described before. What were these invisible rays, how were they being formed, and how did they penetrate the objects? He didn’t know. So Roentgen called them “x” rays.

  Roentgen continued to investigate the penetrating ability of x-rays and found that metal could block them, while they readily passed through wood. This allowed him to play a little game whereby he could “see” coins concealed in a wooden box by detecting their shadow on the fluorescent screen. These stunts raised the question: If wood was transparent to x-rays, what about human flesh? When he placed his hand in front of the screen, he could see, to his astonishment, the shadow of his own bones! His bones blocked the x-rays while his flesh did not. Thus, the medical potential of this new discovery was immediately apparent to Roentgen.

  An avid nature photographer and outdoor enthusiast, Roentgen lugged his cameras on annual hiking vacations throughout Switzerland. He stored a lot of photographic equipment in his laboratory. This was a convenient location, since he lived with his family in an apartment above his lab. Roentgen decided to see what x-rays would do to his photographic film. When he replaced the fluorescent screen with his film, he found after developing it that he could produce a permanent image similar to the shadowy ones he saw on the fluorescent screen.37

  FIGURE 2.3. X-RAY OF ROENTGEN’S WIFE’S RINGED HAND. This x-ray photograph was one of the very first ever taken. Such photographs, showing shadows of huma
n bones, both amazed and terrified people.

  On December 22, 1895, Roentgen took a trusted friend—his wife—into his confidence. He called her down from their apartment to his laboratory. He demonstrated his discovery with the glowing screen, and then he took a “photograph” of her hand. In a short while, he developed the film and showed it to her. She was both astounded and frightened by what she saw.

  It should be kept in mind that this was a time when skeletal bones were only seen after a person died and their flesh had decayed away; an image of a skeleton was then the universal depiction of death. In fact, when Roentgen showed his wife the image of the bones in her hand, she is said to have exclaimed, “I have seen my own death!”

  After producing the image of his wife’s hand, things moved very quickly. Roentgen knew he had to publish as soon as possible to establish the primacy of his discovery, and he thought the fastest route would be through a local scientific journal. He approached a friend who was the president of the Würzburg Physical Medical Society with a handwritten manuscript. Although the Society typically only published the proceedings of oral presentations delivered at their meetings, in this instance the editor decided to publish first and schedule the oral presentation for later. The manuscript was quickly sent for typesetting and just made the December 1895 issue of the society’s journal. The article was entitled “On a New Kind of Rays,” and it appeared on December 28, 1895.38