Biography:Edward Appleton

| module=EducationHanson Grammar SchoolAlma materSt John's College, Cambridge (BA, MSc)Known forProving the existence of the ionosphereSpouse(s)

• Jessie Longson
  (m. 1915; died 1962)
• Helen Lennie (m. 1965)

Children2Awards

• FRS (1927)
• Hughes Medal (1933)
• Order of the Bath (Knight Commander, 1941)
• Faraday Medal (1946)
• Nobel Prize in Physics (1947)
• Chree Medal and Prize (1947)
• Royal Medal (1950)
• RSA Albert Medal (1950)
• IRE Medal of Honor (1962)

TitleJacksonian Professor of Natural Philosophy (1936–39)Scientific careerFieldsAtmospheric physicsInstitutions

• Cavendish Laboratory (1920–24)
• King's College London (1924–36)
• University of Cambridge (1936–39)
• DSIR (secretary, 1939–49)

Academic advisors

• Ernest Rutherford
• J. J. Thomson

Notable students

• Edward George Bowen
• Karl George 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 experimental physicist who received the Nobel Prize in Physics in 1947 "for his investigations of the physics of the upper atmosphere especially for the discovery of the so-called Appleton layer".

Biography

Early years

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

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.Sc. in Physics the following year. He was also a member of Isaac Newton University Lodge.

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

During the First World War, Appleton joined the West Riding Regiment, and later transferred to the Royal Engineers.

Middle years

In 1920, Appleton became Assistant Demonstrator in Experimental Physics in the Cavendish Laboratory at Cambridge. In 1922, he was initiated into Freemasonry. He was Professor of Physics at King's College London (1924–1936) and Jacksonian Professor of Natural Philosophy at the University of Cambridge (1936–1939). From 1939 to 1949, he was Secretary of the Department of Scientific and Industrial Research.

Appleton was knighted in 1941, and was awarded the Nobel Prize in Physics in 1947 for his contributions to the knowledge of the ionosphere, which led to the development of radar.

Later years

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.

The grave of Sir Edward Victor Appleton, Morningside Cemetery, Edinburgh

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.

Research

The frequency modulation 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 frequency modulation 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, 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 as is responsible for enabling most long range short wave telecommunication.

Recognition

Awards

• 1927: elected a Fellow of the Royal Society
• 1933: Hughes Medal of the Royal Society
• 1936: elected a Foreign Honorary Member of the American Academy of Arts and Sciences
• 1046: Faraday Medal of the Institution of Electrical Engineers
• 1947: Nobel Prize in Physics of the Royal Swedish Academy of Sciences
• 1947: Chree Medal and Prize of the Institute of Physics
• 1950: Royal Medal of the Royal Society
• 1950: Albert Medal of the Royal Society of Arts
• 1962: Medal of Honor of the Institute of Radio Engineers

Honours

• Rutherford Appleton Laboratory
• Appleton Medal and Prize
• Appleton Suite at Bradford Register Offices
• Appleton Tower at the University of Edinburgh
• Appleton Science Building at Bradford College
• Appleton Academy, a school in the Wyke area of the City of Bradford
• Appleton crater on the Moon
• Appleton layer, the higher atmospheric ionised layer above the E-layer
• Annual Appleton Lecture at the Institution of Engineering and Technology

See also

• Journal of Atmospheric and Terrestrial Physics, founded by Appleton

References

• 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