Book Review: Probing the Sky with Radio Waves: From Wireless Technology to the Development of Atmospheric Science by Chen-Pang Yeang
Document ID: 225
The Pennsylvania State University, University Park, PA, U.S.A.
Probing the Sky with Radio Waves: From Wireless Technology to the Development of Atmospheric Science. Chen-Pang Yeang. 376 pp. University of Chicago Press, Chicago, IL, 2013. Price: $60.00 (hardcover). ISBN 13-978-0-226-01519-4. (Russell Philbrick, Reviewer.)
Book Review
This book focuses on the early steps in one of the remarkable advances of 20th century science, the discovery of the ionosphere, which led to mankind’s step into the Space Age. Yeang recounts the research and the struggles that led to this discovery during the first half of that century, and stimulated the curiosity that resulted in space exploration during the second half. The people and the events of those early days are chronicled in a fascinating way by the author. It is interesting to learn about the many steps, both experimental and theoretical, taken by researchers, thinkers, and tinkerers. Although some of the many theories and early experiments with radio waves were correct, many were not. But all contributed to a discovery that whetted appetites to learn more about “what is up there?”—leading rapidly to discoveries about the upper atmosphere and the space environment.
Wireless telegraphy originated in the 1890s, following soon after the dipole experiments of Hertz in Germany (1886–1889). In 1891, British scientist George Minchin conducted a transmission experiment over a distance greater than 100 ft, and that distance was quickly extended at laboratories in Europe. In Italy, Marconi transmitted a signal that reached 3 km in 1894. A neighbor of Marconi’s family in Bologna, Augusto Righi, who invented the induction electrometer and later wrote an early paper on wireless telegraphy, helped to inspire the work of Marconi. But Marconi found little interest and support for his experiments in Italy. A family friend at the U.S. Consulate in Bologna arranged a trip to England for him in 1896, at age 21. There he obtained support for his experiments on wireless telegraphy from the British Post Office. During the next few years, he conducted experiments that by 1899 extended the range over which wireless signals could be sent to almost 50 km. These longer distances caused scientists to become interested in the bending of waves around the Earth. In collaboration with British scientist John Fleming at University College London, Marconi prepared a high-power transmitter near Cornwall and embarked on an experiment to receive signals across the Atlantic. He first erected a receiving antenna at a station on Cape Cod, but a storm destroyed it so he relocated his station to Newfoundland. His laboratory assistants in England were instructed to send a series of three dots (SSS in Morse code) several times around noon. At the station in Newfoundland, Marconi and his assistant, George Kemp, heard a series of sharp clicks four times. The first signals were received on 12 December 1901, and the event was reported to the world two days later by the New York Times. These results attracted further international attention and confirmation, from signals Marconi received on the SS Philadelphia sailing from England to New York in February 1902. His efforts were recognized with the 1909 Nobel Prize.
We must admire the work of the scientists as they approached this new area of exploration, with its experimental and theoretical questions to test, eventually resulting in a new chapter in the book of knowledge. Ideas and experimental results were often communicated by letters between colleagues, or spread from teachers to students. Important contributions to theory were made by mathematical physicists from Cambridge University. Solutions to propagation problems required Bessel and Hankel functions and Legendre polynomials to formulate theories in spherical coordinates. British, French, and German theorists led most of the early physical modeling. Soon after Marconi’s 1901 experiment, the American Arthur Kennelly and the English scientist Oliver Heaviside independently postulated a high-altitude reflecting layer that became known as the Kennelly–Heaviside Layer. (Many people today, if they were able to make a connection, would associate the Heaviside Layer with Andrew Lloyd Webber’s musical “Cats,” based on a T. S. Eliot poem. When Old Deuteronomy takes Grizabella on a journey to the ethereal or heavenly place for her reincarnation, they travel to the Heaviside Layer; there is no indication that this was the ionosphere.) The first theory for bending of electromagnetic waves around the Earth was put forth by MacDonald at Cambridge University, near the turn of the century. This surface wave model followed in a manner similar to diffracting acoustic waves and it was the focus of the theorists in England, France, and Germany during the next decade. Experimental results came primarily from collaborations between U.S. and English scientists, who extended Marconi’s experiments. As experiments continued to provide more data, wave diffraction ideas gave way to electron scattering models. We can only imagine the efforts of scientists performing those experiments a century ago, when they had to make their own capacitors and wind their own inductors; experimental research proceeded a bit differently in the days before our ability to shop at a local Radio Shack or receive parts overnight from Newark or Allied Electronics. But it was not until the contributions of many scientists that it was possible for Edward Appleton to confirm the existence of and describe the ionosphere in 1927, for which he was awarded the 1947 Nobel Prize.
Yeang presents a scholarly and fascinating account of how early research with radio waves opened many pathways to advance electromagnetic wave communication, and resulted in steps to explore the space around our world. His extensive referencing provides the source materials, which describe the efforts of those early researchers, as they performed experiments and developed our theoretical understanding of electromagnetic wave propagation in the great out-door laboratory. The path of learning was not straight, as evidenced by the many false starts and incorrect paths described in this book. Students and scholars who study electromagnetic theory, and professors who teach it, would benefit from this historical review of the trials, successes, and failures during the first half of the 1900s. This history certainly drives home the fact that research means “trial” as the test of an idea, and the efforts to prove or disprove it. After my many years of ionospheric and upper atmosphere research, with experiments using rockets and satellites, as well as using ionosondes and incoherent scatter radar, and teaching a senior level course on space physics and a graduate course on the ionosphere and upper atmosphere, I still learned many interesting things about the early developments of the field from Yeang’s account. Many of the ideas tried by the early researchers, while making efforts to understand the mysteries of radio waves, were off the mark. However, their observations eventually led to the routine use of the radio, long distance communications, and the discovery of the ionosphere. Also, I think this book offers a useful account of the trials and tribulations that all researchers face as they enter new research areas. We too often lose sight of this part of scientific discovery because textbooks and papers describe, and students are taught, the successful experiments and theories. Yet understanding nature often requires bringing together experimental results and theoretical models on a subject several times to get it right. Young researchers often do not realize that not every experiment or theoretical idea considered along the way actually answers questions asked by researchers, but each step contributes a small correction to the path which finally results in the textbook descriptions of today. It would be useful for young researchers in the physical sciences to read this book, just to see how the small and sometimes larger steps lead to understanding of a subject. The reading of this book is doubly recommended for any researcher who considers topics related to open-path communications, radar, ionospheric sounding, space physics, GPS technology, and electromagnetic waves in general.
This excellent book provides an interesting and useful account of the subject. The only addition I would have appreciated is a short chronology listing the contributors to and locations of landmark events between 1890 and 1950. Descriptions are presented in the context of the sequence of activities at a particular location, and hence, it is easy to lose sight of events occurring at other places that influenced activities at the location being described.