John William Strutt, 3rd Baron Rayleigh

In 1871, Rayleigh published the first theoretical treatment of the elastic scattering of light by particles much smaller than the light's wavelength, a phenomenon now known as Rayleigh scattering, which notably explains why the sky is blue. He studied and described transverse surface waves in solids, now known as Rayleigh waves. He contributed extensively to fluid dynamics, with concepts such as the Rayleigh number (a dimensionless number associated with natural convection), Rayleigh flow, the Rayleigh–Taylor instability, and Rayleigh's criterion for the stability of Taylor–Couette flow.

Rayleigh also formulated the circulation theory of aerodynamic lift. In optics, he proposed a well-known criterion for angular resolution. His derivation of the Rayleigh–Jeans law for classical black-body radiation later played an important role in the birth of quantum mechanics (see ultraviolet catastrophe). His textbook, The Theory of Sound (1877), is still used today by acousticians and engineers. He introduced the Rayleigh test for circular non-uniformity, which the Rayleigh plot visualises.

Rayleigh served as President of the Royal Society from 1905 to 1908, and as Chancellor of the University of Cambridge from 1908 until his death in 1919.

Biography

John William Strutt was born on 12 November 1842 at Langford Grove, Maypole Road in Maldon, England, the son of Clara Elizabeth (née La Touche) and John James Strutt, 2nd Baron Rayleigh. In his early years, he suffered from frailty and poor health. Strutt attended Eton College and Harrow School (each for only a short period), before entering Trinity College, Cambridge, in 1861, where he studied mathematics. In 1865, he received a Bachelor of Arts (Senior Wrangler and Smith's Prizeman), and was elected a Fellow of Trinity College the following year. He obtained a Master of Arts in 1868.

In 1871, Strutt resigned from his fellowship to marry Evelyn Balfour, the daughter of James Maitland Balfour, with whom he had three sons. In 1873, on the death of his father, he inherited the Barony of Rayleigh.

Rayleigh died on 30 June 1919 in Witham at the age of 76, and was buried in the graveyard of All Saints' Church in Terling. His son Robert, a physicist, succeeded him as Baron Rayleigh.

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Career and research

In 1879, Rayleigh was appointed Cavendish Professor of Physics at the University of Cambridge. In 1883, Rayleigh first described dynamic soaring by seabirds in Nature. The following year, he resigned as Cavendish Professor to continue his experimental work at Terling Place. In 1887, he succeeded John Tyndall as Professor of Natural Philosophy at the Royal Institution.

Rayleigh carefully and precisely measured atomic mass of oxygen and hydrogen, and by 1892 he moved on to nitrogen. By isolating nitrogen in different ways he discovered a small but significant difference, which indicated a heavier inert gas present in the air besides nitrogen. William Ramsay joined this research topic, and in August 1894 they discovered argon. For research related to this discovery, Rayleigh and Ramsay were awarded the 1904 Nobel Prizes in Physics and Chemistry, respectively.

Around 1900, Rayleigh developed the duplex (combination of two) theory of human sound localisation using two binaural cues, interaural phase difference (IPD) and interaural level difference (ILD) (based on analysis of a spherical head with no external pinnae). The theory posits that we use two primary cues for sound lateralisation, using the difference in the phases of sinusoidal components of the sound and the difference in amplitude (level) between the two ears.

Rayleigh received the degree of Doctor mathematicae (honoris causa) from the Royal Frederick University on 6 September 1902, when they celebrated the centennial of the birth of mathematician Niels Abel.

From 1905 to 1908, Rayleigh served as President of the Royal Society. From time to time, he participated in the House of Lords; however, he spoke up only if politics attempted to become involved in science. During the First World War, he was President of the Advisory Committee for Aeronautics, which was located at the National Physical Laboratory and chaired by Richard Glazebrook. In 1919, Rayleigh served as President of the Society for Psychical Research. As an advocate that simplicity and theory be part of the scientific method, he argued for the principle of similitude.

Religious views

Rayleigh was an Anglican. Though he did not write about the relationship between science and religion, he retained a personal interest in spiritual matters. When his scientific papers were to be published in a collection by the Cambridge University Press, Strutt wanted to include a quotation from the Bible, but he was discouraged from doing so, as he later reported:

When I was bringing out my Scientific Papers I proposed a motto from the Psalms, "The Works of the Lord are great, sought out of all them that have pleasure therein." The Secretary to the Press suggested with many apologies that the reader might suppose that I was the Lord.

Still, he had his wish and the quotation was printed in the five-volume collection of scientific papers. In a letter to a family member, he wrote about his rejection of materialism and spoke of Jesus Christ as a moral teacher:

I have never thought the materialist view possible, and I look to a power beyond what we see, and to a life in which we may at least hope to take part. What is more, I think that Christ and indeed other spiritually gifted men see further and truer than I do, and I wish to follow them as far as I can.

— Rayleigh (1910)

Rayleigh held an interest in parapsychology and was an early member of the Society for Psychical Research (SPR). He was not convinced of spiritualism but remained open to the possibility of supernatural phenomena. Rayleigh was the president of the SPR in 1919. He gave a presidential address in the year of his death but did not come to any definite conclusions.

Recognition

Memberships

Awards

Honours

Commemoration

A lunar crater, as well as a Martian crater, are named in his honour. The asteroid 22740 Rayleigh was named after him on 1 June 2007. The rayl, a unit of specific acoustic impedance, is also named for him.

Sir William Ramsay, his co-worker in the investigation to discover argon, described Rayleigh as "the greatest man alive" while speaking to Lady Ramsay during his last illness.

H. M. Hyndman said of Rayleigh that "no man ever showed less consciousness of great genius".

In honour of Lord Rayleigh, the Institute of Acoustics sponsors the Rayleigh Medal (established in 1970) and the Institute of Physics sponsors the John William Strutt, Lord Rayleigh Medal and Prize (established in 2008).

Many of the papers that he wrote on lubrication are now recognized as early classical contributions to the field of tribology. For these contributions, he was named as one of the 23 "Men of Tribology" by Duncan Dowson.

There is a memorial to him by Derwent Wood in St Andrew's Chapel at Westminster Abbey.

The National Physical Laboratory (NPL) bestows the Rayleigh Award annually to "the authors of the most outstanding NPL paper published in the previous calendar year."