Karl Ferdinand Braun

German physicist

• Born: June 6, 1850
• Birthplace: Fulda, Hesse-Kassel (now in Germany)
• Died: April 20, 1918
• Place of death: Brooklyn, New York

Braun developed the oscilloscope, which enabled researchers to see electrical waveforms in real time and was an important stepping-stone in the development of modern radars and of all-electronic television.

Primary field: Electronics and electrical engineering

Primary inventions: Wireless telegraphy; cathode-ray oscilloscope

Early Life

Karl Ferdinand Braun (BROWN) was born in 1850 in Fulda, a city in the principality of Hesse-Kassel, which would soon be incorporated into the militarily aggressive German kingdom of Prussia, and ultimately into the German Empire. Braun’s father, Konrad Braun, was a civil servant working as a court clerk. His mother, Franziska Braun, née Gohring, was the daughter of the elder Braun’s supervisor in the civil service.

After successfully completing the course of study in the local Gymnasium, or high school, Braun went to the University of Marburg to pursue a higher education. That path ultimately led him to the University of Berlin, where he earned his doctorate in 1872, writing a dissertation on the vibrations of elastic rods and strings. His work was interesting in its implications for thermodynamics, which at the time was still in its infancy and still largely confined to studies of high-temperature machines such as steam engines.

Life’s Work

After completing his doctorate, Braun began to concentrate primarily on electrical phenomena. One of his earliest investigations was into the behavior of some metallic sulfide crystals, which conducted electricity only in one direction. His work would become the foundation for the development of the crystal detector, an early semiconductor device used in detecting and rectifying radio waves before the development of reliable vacuum tubes.

Over the next several years, he would move from one university to the next, always holding relatively prestigious positions in their departments of physics but never able to attain a stable appointment. That changed in 1895, when he finally returned to the University of Strassburg (modern Strasbourg), in Alsace, which at the time was part of the German Empire. He would continue to hold that position until his death and ultimately became so satisfied with it that he even turned down an offer of an endowed chair at the extremely prestigious University of Leipzig.

In the late 1890’s, Braun became increasingly interested in the Crookes tube, an early prototype of the cathode-ray tube (CRT), which was a development of the diode originally developed by Thomas Alva Edison as part of research into why incandescent light bulbs were developing stains on the inside. By hanging a second element, or plate, inside the bulb, he was able to detect a current, which he named the Edison effect, but he could see no practical use for it, setting that work aside to pursue other projects with more immediate monetary rewards.

The Crookes tube modified the plate into a set of deflectors that could cause the cathode to emit a stream of electrons toward the far end of the tube, which could be coated with a phosphorescent material. The earliest forms of the CRT were instrumental in the discovery of the electron, which proved that electricity was particulate in nature rather than a fluid as experimenters as early as Benjamin Franklin had simply assumed, an assumption enshrined in terms such as “current” that were too deeply embedded in the discipline to be uprooted.

However, Braun saw additional potentials for the CRT, and by modifying it so that a fluctuating current could be imposed upon the plate voltage, he created the first oscilloscope. At last, scientists and engineers had a device that could display electrical waveforms in real time, which was extremely useful in the diagnosis of faults in complex electronic equipment. Even the basic phase reversal of alternating current (AC) could be observed on an oscilloscope, allowing engineers at power plants to see when a generator was lagging or otherwise malfunctioning.

Braun’s first practical application of the oscilloscope was in radio transmission, when Guglielmo Marconi revealed that his transmitter would send signals only a few miles. By attaching an oscilloscope to the system, Braun was able to identify the upper limit on the Hertz oscillator, a key part of the antenna, by which further expansion of the spark gap actually decreased its output rather than increasing it. Braun then proceeded to design an entirely new type of antenna for Marconi’s transmitter, removing the spark from the system by taking the antenna out of the transmitter circuit and having the signal be conveyed to the antenna by means of condensers, huge wire coils that transformed electricity into magnetic fields that would induce electrical current in the antenna. As a result, he was able to increase power and gain increased transmission distance in a fairly linear fashion. He also applied this discovery to Marconi’s radio receiver, isolating the antenna from the detector circuits so it was less likely to pick up random static rather than the signal its user was seeking. As a reward for this breakthrough, Braun shared the 1909 Nobel Prize in Physics with Marconi.

His success with Marconi’s transmitter ignited an interest in all aspects of radio transmission and detection. Braun developed a new kind of antenna that would transmit only in a single plane, unlike the earlier antennas that sent radio waves in all directions, rather like a spherical version of the ripples radiating outward from a rock thrown into a still pond. The unidirectional radio antenna was useful in sending a signal that was intended only for recipients in one particular area, for instance a military unit such as a squadron of ships at sea.

Braun also recognized the utility of radio in navigation. Although the development of the marine chronometer had greatly improved the accuracy of open-ocean navigation, its margin of error could still become deadly as ships approached dry land. Particularly if storms had thrown them off course since their last opportunity to take sun sightings and compare the local time to the reference time carried by the chronometer, ships could easily be thrown onto rocks when their navigators had placed them a mile or two away. Although lighthouses built along the coast could provide some warning for the most treacherous approaches such as Cape Hatteras or the Isles of Scilly, heavy rain or fog could obscure their lights until a ship was dangerously close. By contrast, radio waves passed untroubled through even the heaviest rain and fog. If one could establish a system of radio beacons along the shoreline, particularly near dangerous approaches and important harbor, sailors would have a readily available navigation tool no matter the weather.

In 1914, Braun became entangled in patent litigation in a U.S. court and as a result came to the United States. While he was there, he was also able to look into the various voice transmissions being pioneered by Reginald Aubrey Fessenden, Lee De Forest, Edwin H. Armstrong, and others. However, his age and resultant ill health delayed his testimony repeatedly, until the United States entered World War I in 1917. As a result, Braun was regarded as an enemy alien and prevented from returning to his native land, although his age and standing as an eminent scientist prevented any formal accusations of spying or internment.

Being trapped on the far side of the Atlantic, unable to contact his family and friends or to speak on behalf of German scientists as a result of the hostilities, was a very wearing situation for the elderly Braun, who had already experienced episodes of ill health. The final blow was a fall that broke his hip. Although he was hurried to the hospital, the injury refused to heal, leaving him bedridden. As it sunk through to him that he would never again be able to live an independent life, the will to live seeped out of him and he died in his Brooklyn apartment during the spring of 1918, with the end of the war still months away. Because the war made it impossible for his remains to be returned to his homeland, they were instead cremated so the ashes could be held safely until such time it was possible to transport them to Germany.

Impact

With the oscilloscope, Braun became the “father of the video display.” The oscilloscope not only was immediately useful for physicists and electrical engineers studying the operation of circuits but also demonstrated the ability of the cathode-ray tube to display information in visual form. Thus, both Vladimir Zworykin and Philo T. Farnsworth turned to the CRT for their television receivers, and the developers of the minicomputer and microcomputer used the CRT to show data and operations. Although the CRT has been superseded by solid-state devices such as the liquid crystal display, those technologies became possible only because the CRT made television and personal computing profitable.

Bibliography

Davis, L. J. Fleet Fire: Thomas Edison and the Pioneers of the Electric Revolution. New York: Arcade, 2003. A history of the early days of electricity, culminating in the invention of radio.

Fisher, David E., and Marshall Jon Fisher. Tube: The Invention of Television. Washington, D.C.: Counterpoint, 1996. Includes information on Braun’s CRT work as part of the prehistory of electronic television.

Kurylo, Friedrich, and Charles Susskind. Ferdinand Braun: A Life of the Nobel Prizewinner and Inventor of the Cathode-Ray Oscilloscope. Cambridge, Mass.: MIT Press, 1981. Book-length biography with in-depth coverage of Braun’s life.

Lewis, Tom. Empire of the Air: The Men Who Made Radio. New York: Edward Burlingame Books, 1991. A history of the early days of radio. Places Braun in the larger context of the development of radio, from wireless telegraphy to commercial broadcasting.