Edward Victor Appleton

English physicist

• Born: September 6, 1892; Bradford, England
• Died: April 21, 1965; Edinburgh, Scotland

Nobel Prize–winning physicist Edward Victor Appleton is credited with confirming the existence of the ionosphere (a layer of Earth’s upper atmosphere) and the E layer within it, as well as with discovering the F layer, also known as the Appleton layer. Appleton’s findings directly led to the discovery of radar technology.

Primary field: Physics

Specialty: Atmospheric sciences

Early Life

Edward Victor Appleton was born in September 1892 in Bradford, Yorkshire, England, to Peter Appleton, a warehouse worker, and Mary Appleton. After elementary school, Appleton won a scholarship to Hanson Grammar School, which he attended from 1903 to 1911. Appleton’s parents, aware of his academic gifts, were supportive of his studies. He also enjoyed playing cricket and was active in music as both a singer and a pianist. Appleton earned a first-class grade in the London matriculation examination at the age of sixteen and passed the London intermediate examination the following year, both of which opened opportunities for higher learning. He was awarded the Isaac Holton Scholarship to St. John’s College, University of Cambridge, to study natural sciences. In 1913, Appleton graduated from Cambridge with a degree in natural sciences, then went on to pursue additional studies in physics. He briefly studied under W. L. Bragg, researching the structure of metallic crystals. In 1915, he married Jessie Longson, the daughter of a reverend.

When Appleton left Cambridge, Europe was in the midst of World War I. Appleton served his country by joining the Duke of Wellington’s Regiment, also known as the West Riding Regiment. He later served in the Royal Engineers, a branch of the British armed forces that provides engineering and related services to the military, such as the construction of buildings and other infrastructure. Appleton was also trained in early radio technology, which would later prove crucial to his atmospheric research.

After World War I, Appleton returned to Cambridge, where he began to research atmospheric physics and radio waves. In 1920, at age twenty-eight, he became an assistant demonstrator in experimental physics at the Cavendish Laboratory of the University of Cambridge. Only two years later, Appleton was appointed sub-lector at Trinity College. In 1924, he became a professor of physics at London University.

Life’s Work

In 1924, while at London University, Appleton began to research radio signals. Using a transmitter that belonged to the British Broadcasting Corporation (BBC), he conducted experiments to test earlier theories of a gaseous atmospheric layer that could reflect radio waves. Appleton noticed that although the strength of the radio signal was constant during the day, it fluctuated at night, and he was able to prove that radio waves that were transmitted into the atmosphere reflected back to Earth upon contact with an ionized layer. His experiments made a case for the existence of the atmospheric layer later called the ionosphere, previously theorized to exist, and the region within it known as the E layer. Appleton’s discovery made use of radiolocation methods that would prove highly useful in military efforts during World War II.

Shortly thereafter, in 1926, Appleton expanded on his research of the ionosphere, discovering within it an additional layer above the E layer that is unaffected by atmospheric conditions and reflects signals with greater strength; this layer, which contains stronger electrical properties, makes it possible to transmit short-wave radio communication around the world. In honor of the discovery, the layer, formally called the F layer, also became known as the Appleton layer. Around 1929, Appleton continued his radio research in Norway, where he studied the aurora borealis (the luminous phenomenon that occurs in the Northern Hemisphere and is commonly referred to as the northern lights). In 1931, having determined the heights of the ionospheric layers, Appleton published the results of his research. He was elected vice president of the American Institute of Radio Engineers the following year. Appleton returned to Cambridge in 1936 as a professor of natural philosophy. During the years that followed, he lectured on his radio transmission research, which used radio waves to measure the properties, relative density, and height and size of the atmosphere.

In 1939, at the beginning of World War II, Appleton was appointed secretary of the Department of Scientific and Industrial Research, an organization concerned with physical science. Appleton focused the department on issues of domestic infrastructure, such as protecting food supplies from insects, and structural engineering, such as roads and buildings. He served as the administrator of Great Britain’s nuclear fission project, overseeing the movement of equipment and materials. During the war, Appleton also served on the Scientific Advisory Committee of the War Cabinet.

Utilizing Appleton’s research on the ionosphere, Sir Robert Watson-Watt, a Scottish electronic engineer and inventor, led a team of scientists in developing advanced radiolocation technology that allowed the British military to detect enemy aircraft. The use of radar, which has since become commonplace, represented a major advantage for the Allies during World War II and famously played an important role in the Battle of Britain, when the British Army was able to detect and give early warning of German aircraft. The Battle of Britain is viewed as a turning point in the war, and Appleton’s contributions to the radar technology that strengthened wartime strategy cannot be overstated. In 1941, Appleton was knighted, one of the highest honors available to citizens of the United Kingdom.

Perhaps the crowning achievement of Appleton’s scientific career came in 1947, when he was awarded the Nobel Prize in Physics “for his investigations of the physics of the upper atmosphere, especially for the discovery of the so-called Appleton layer.” The honor was likely inspired by the research Appleton performed in the 1920s and his related publication in 1932.

In 1949, Appleton retired from the Department of Scientific and Industrial Research and became principal and vice-chancellor of the University of Edinburgh. He held several administrative positions late in his career but remained an active researcher and publisher, especially on the subject of the ionosphere. To that effect, he founded and served as editor in chief of the Journal of Atmospheric and Terrestrial Physics in 1950. Appleton delivered six broadcasts in 1956 called “Science and the Nation,” in which he explained different topics of current scientific interest.

Appleton’s wife, Jessie, passed away in 1964; the couple had raised two children. Shortly thereafter, Appleton married his former secretary Helen Shannon Allison. On April 21, 1965, Appleton died of heart failure in his home in Edinburgh.

Impact

A highly respected figure in the field of physics, Edward Victor Appleton made important contributions in atmospheric research, confirming the existence of the E layer and discovering the F layer. His discoveries on the composition and magnetic properties of the ionosphere continue to be relevant in the twenty-first century, when satellite signals can be impacted by the ionosphere. Appleton’s experimental methods made use of radio technology that would grow into more advanced tools of radar detection, and his 1932 publication outlining radio-wave propagation and the ionosphere is generally credited as laying the foundation for the radar technology that allowed Allied Forces to detect German aircraft during World War II. Appleton was recognized not only for his scientific findings but also for his military service in both World War I and World War II. In addition to winning the Nobel Prize in Physics in 1947, Appleton received the Medal of Merit from the US government—the highest award given to a civilian—for his work in the development of radar. In 1948, Appleton was appointed to the Pontifical Academy of Science by Pope Pius XII. He was elected president of the British Association for the Advancement of Science in 1953, and also served as chairman of the British National Committee for Radio-Telegraphy.

Bibliography

Clark, Ronald W. Sir Edward Appleton. New York: Pergamon, 1971. Print. Chronicles Appleton’s upbringing, military service, discovery of the ionosphere, and work after World War II. Index.

Henry, John. “The Physical Tourist.” Physics in Perspective 9.4 (2007): 468–501. Print. Contextualizes historically prominent physicists and related scientists within the history and geography of Edinburgh, Appleton’s home later in life.

Ratcliffe, J. A. Edward Victor Appleton: 1892–1965. Biographical Memoirs of Fellows of the Royal Society 12.1 (1966): 1–21. Print. A comprehensive biography of Appleton’s life, published by the Royal Society following his death. Chronicles his childhood, education, military service, and professional activities.

Sullivan, Woodruff T., III. Cosmic Noise: A History of Early Radio Astronomy. New York: Cambridge UP, 2009. Print. A detailed history of radio astronomy, including the pioneers of radar technology. References Appleton’s work and that of his contemporaries. Index, illustrations.