Biography:Edward Appleton

| module=Scientific careerFields

• Atmospheric physics
• Radio science

Institutions

• University of Cambridge (1920–1924, 1936–1939)
• King's College London
  (1924–1936)
• DSIR (1939–1949)

Academic advisorsJ. J. ThomsonNotable students

• Miles Barnett
• Edward Bowen
• Karl Emeléus
• W. M. H. Greaves
• Charles Oatley
• J. A. Ratcliffe
• James Sayers

}} Sir Edward Victor Appleton (6 September 1892 – 21 April 1965) was a British physicist who received the Nobel Prize in Physics in 1947 for his contributions to the knowledge of the ionosphere, which led to the development of radar and shortwave radio.

Biography

Edward Victor Appleton was born on 6 September 1892 in Bradford, England, the son of Peter and Mary Appleton.

Appleton attended Hanson Grammar School, before entering St John's College, Cambridge, where he obtained a B.A. in Natural Science in 1913 and an M.A. in Physics the following year. During the First World War, he joined the West Riding Regiment, later transferring to the Royal Engineers. After the end of the War, he returned to Cambridge to research radio waves.

In 1920, Appleton became Assistant Demonstrator in Experimental Physics in the Cavendish Laboratory. In 1922, he was initiated into Freemasonry. In 1924, he was appointed Wheatstone Professor of Physics at King's College London, returning to Cambridge in 1936 as Jacksonian Professor of Natural Philosophy. In 1939, on the outbreak of World War II, the British government appointed Appleton as Secretary of the Department of Scientific and Industrial Research.

From 1949 until his death in 1965, Appleton was Principal and Vice-Chancellor of the University of Edinburgh. From 1960, he was involved with the university's plans for a CDA (Comprehensive Development Area), which would have demolished 125 acres of Edinburgh's historic southside, resulting in the loss of many homes and businesses. This University-led project blighted the area for a decade before being abandoned in the mid 1970s. One recent study describes Appleton as a megalomaniac in his desire to carry out these plans.

In 1956, the BBC invited Appleton to deliver the annual Reith Lectures. Across a series of six radio broadcasts, titled Science and the Nation, he explored the many facets of scientific activity in Britain at the time.

Research

Appleton thought the best place to look for evidence of the ionosphere was in the variations he believed it was causing around sunset in radio signal receptions. It was sensible to suggest these variations were due to the interference of two waves but an extra step to show that the second wave causing the interference (the first being the ground wave) was coming down from the ionosphere. The experiment he designed had two methods to show ionospheric influence and both allowed the height of the lower boundary of reflection (thus the lower boundary of the reflecting layer) to be determined. The first method was called frequency modulation (FM) and the second was to calculate the angle of arrival of the reflected signal at the receiving aerial. The FM method exploits the fact that there is a path difference between the ground wave and the reflected wave, meaning they travel different distances from sender to receiver.

Let the distance AC travelled by the ground wave be h and the distance ABC travelled by the reflected wave h' . The path difference is:

$h^{\prime }-h=D$

The wavelength of the transmitted signal is λ. The number of wavelengths difference between the paths h and h' is:

$\frac{h-h^{\prime }}{\lambda }=\frac{D}{\lambda }=N$

If N is an integer number, then constructive interference will occur, this means a maximum signal will be achieved at the receiving end. If N is an odd integer number of half wavelengths, then destructive interference will occur and a minimum signal will be received. Let us assume we are receiving a maximum signal for a given wavelength λ. If we start to change λ, this is the process called frequency modulation, N will no longer be a whole number and destructive interference will start to occur, meaning the signal will start to fade. Now we keep changing λ until a maximum signal is once again received. The means that for our new value λ', our new value N' is also an integer number. If we have lengthened λ then we know that N' is one less than N. Thus:

$N-N^{\prime }=\frac{D}{\lambda }-\frac{D}{{\lambda }^{\prime }}=1$

Rearranging for D gives:

$D=h-h^{\prime }=\frac{1}{\frac{1}{\lambda }-\frac{1}{{\lambda }^{\prime }}}$

As we know λ and λ', we can calculate D. Using the approximation that ABC is an isosceles triangle, we can use our value of D to calculate the height of the reflecting layer. This method is a slightly simplified version of the method used by Appleton and his colleagues to work out a first value for the height of the ionosphere in 1924. In their experiment, they used the BBC broadcasting station in Bournemouth to vary the wavelengths of its emissions after the evening programmes had finished. They installed a receiving station in Oxford to monitor the interference effects. The receiving station had to be in Oxford as there was no suitable emitter at the right distance of about 62 miles (100 km) from Cambridge in those days.

This FM method revealed that the point from which waves were being reflected was approximately 56 miles (90 km). However, it did not establish that the waves were reflected from above, indeed they may have been coming from hills somewhere between Oxford and Bournemouth. The second method, which involved finding the angle of incidence of the reflected waves at the receiver, showed for sure that they were coming from above. Triangulations from this angle gave results for the height of reflection compatible with the frequency modulation method. We will not go into this method in detail because it involves fairly complex calculations using Maxwell's electromagnetic theory.

Far from being conclusive, the success of the Oxford–Bournemouth experiment revealed a vast new field of study to be explored. It showed that there was indeed a reflecting layer high above the Earth but it also posed many new questions: What was the constitution of this layer? How did it reflect the waves? Was it the same all over the Earth? Why did its effects change so dramatically between day and night? Did it change throughout the year? Appleton would spend the rest of his life answering these questions. He developed a magneto-ionic theory based on the previous work of Lorentz and Maxwell to model the workings of this part of the atmosphere. Using this theory and further experiments, he showed that the so-called Kennelly–Heaviside layer was heavily ionised and thus conducting. This led to the term ionosphere. He showed free electrons to be the ionising agents. He discovered that the layer could be penetrated by waves above a certain frequency and that this critical frequency could be used to calculate the electron density in the layer. However these penetrating waves would also be reflected back, but from a much higher layer. This showed the ionosphere had a much more complex structure than first anticipated. The lower level was labelled "E layer," which reflected longer wavelengths and was found to be at approximately 78 miles (125 km). The high level—which had much higher electron density—was labelled "F layer," and could reflect much shorter wavelengths that penetrated the lower layer. It is situated 186 – 248 miles (300 – 400 km) above the Earth's surface. It is this, which is often referred to as the Appleton layer, that is responsible for enabling most long range shortwave telecommunication.

Personal life

Appleton's grave in Morningside Cemetery, Edinburgh.

In 1915, Appleton married Jessie Longson, with whom he had two daughters.

In 1965, three years after his wife Jessie's death, Appleton married Helen Lennie. He died that year on 21 April in Edinburgh at the age of 72. He is buried in Edinburgh's Morningside Cemetery with Helen. The grave lies towards the extreme western side near the new housing to the north-west.

Recognition

Memberships

Year	Organisation	Type	Ref.
1927	Royal Society	Fellow
1936	American Academy of Arts and Sciences	International Honorary Member
1947	Royal Society of Edinburgh	Honorary Fellow
1948	Pontifical Academy of Sciences	Academician

Awards

Year	Organisation	Award	Citation	Ref.
1929	Institute of Radio Engineers	IRE Morris Liebmann Memorial Prize	"For his investigations in the field of wave propagation."
1933	Royal Society	Hughes Medal	"For his researches into the effect of the Heaviside layer upon the transmission of wireless signals."
1946	Institution of Electrical Engineers	Faraday Medal
1947	Royal Swedish Academy of Sciences	Nobel Prize in Physics	"For his investigations of the physics of the upper atmosphere especially for the discovery of the so-called Appleton layer."
1947	Institute of Physics	Chree Medal and Prize
1948	Danish Academy of Technical Sciences	Valdemar Poulsen Gold Medal	"For outstanding contributions to radio technics and particularly for remarkable achievement in research on the ionosphere."
1950	Royal Society	Royal Medal	"For his work on the ele [sic] transmission of electromagnetic waves round the earth and for his investigations of the ionic state of the upper atmosphere."
1950	Royal Society of Arts	Albert Medal
1962	Institute of Radio Engineers	IRE Medal of Honor	"For his distinguished pioneer work in investigating the ionosphere by means of radio waves."

Chivalric titles

Year	Head of state	Title	Ref.
1941	George VI	Knight Commander of the Order of the Bath
1946	George VI	Knight Grand Cross of the Order of the British Empire

Commemoration

In 1973, the Radio Research Station was renamed the Appleton Laboratory. In 1979, it merged with the Rutherford Laboratory to become the Rutherford Appleton Laboratory.

In 2008, the Institute of Physics' Chree Medal and Prize (of which Appleton was a recipient) was renamed the Edward Appleton Medal and Prize.

Appleton Tower in Edinburgh, Appleton crater on the Moon, and Appleton Academy in the City of Bradford are also named after him.

See also

• Journal of Atmospheric and Terrestrial Physics, founded by Appleton
• Appleton–Hartree equation

Further reading

• Appleton, EV; Ratcliffe, JA (1929). The Physical Principles of Wireless. Methuen. 
• IET Appleton lectures
• Miss nobel-id as parameter with the Nobel Lecture, 12 December 1947 The Ionosphere (Citation: Nobel Prize in Physics: 1947, "for his investigations of the physics of the upper atmosphere especially for the discovery of the so-called Appleton layer."
• "Sir Edward Victor Appleton (1892–1965): Appleton was an English physicist and Nobel prize winner who discovered the ionosphere." Historic Figures, bbc.co.uk. Accessed 21 October 2007. (Photograph of Appleton c. 1935 ©). [Provides link to Nobel Foundation account, listed above.]
• Science and the Nation The BBC Reith Lectures, 1956, by Edward Appleton
• Davis, Chris. "Treasure in the Basement". Backstage Science. Brady Haran. http://www.backstagescience.com/videos/basement_treasures.html. 

External links

• Memoirs of Sir Edward Victor Appleton, 1920 – 1966
• Sir Edward Appleton; The Discovery of the Properties of the Ionosphere

Academic offices
Preceded by C. T. R. Wilson	Jacksonian Professor of Natural Philosophy 1936–1939	Succeeded by John Cockcroft
Preceded by Sir John Fraser	Principal of the University of Edinburgh 1948–1965	Succeeded by Michael Swann