Science Saturday-John William Strutt.
John William Strutt, 3rd Baron Rayleigh: Noblest Essex County Genius
In this Science Saturday series Charlie Keeble discovers that only one Essex scientist has ever won a Noble prize and has a peerage title that is still held onto by the current Baron of Rayleigh. Here is the story of the third Baron of Rayleigh, John William Strutt and his remarkable achievements in thephysical sciences.
John William Strutt was born in Maldon, Essex in November 1842 to the Rayleigh estate of Terling Place. The peerage he inherited was created in 1821 for Charlotte Mary Gertrude Strutt the wife of Joseph Strutt, Member of Parliament for Maldon from 1727 to 1816. It passed into John William Struttupon the death of his father, John James Strutt in 1873. The current owner of the Barony of Rayleigh is John Gerald Strutt.
The 3rd Baron of Rayleigh John William Strutt was educated at Eton College. He then went onto study mathematics at Trinity College, Cambridge in 1861. After graduating with a Masters in 1868 he then went onto undertake an academic career at the university working his way up to become a professor of physics. Throughout his career as a scientist he explored and analysed many phenomena in fluid mechanics and acoustics.
Strutt’s first breakthrough as a physicist came in 1871 when he published a paper on a study he made on the effect of the scattering of light by atmospheric particles. This was used to explain how the sky is blue. When the blue end of the electromagnetic spectrum of light from the Sun passed through the atmosphere, the blue end of the spectrum is scattered by the oxygen-nitrogen particles of the air. Thus it caused the sky to appear blue. This is now known as Rayleigh scattering and it explains how all gasses get their colours depending on what colour of the light rays they scatter according to their wavelength in the electromagnetic spectrum.
Wave movements are very much the principle of what Lord Rayleigh mastered in his research on the physical world. He already has his name tied to Rayleigh scattering and he would soon have several other physics related effects attached to his name. In 1885 he predicted the presence of waves on the surfaces of solid objects that were caused by earthquakes. These became known as Rayleigh waves and they travel in longitudinal and transverse motions and they decrease exponentially as the wave travels far from it’s source.
The effect of Rayleigh waves can be seen when objects withinthe ground are moved in an elliptical direction with the direction of the wave, and travel with the wave as the earthquake occurs. These Rayleigh waves are now used to help seismologists understand the way structural damage happens to buildings during an earthquake. This led them to help engineers develop methods of construction to make buildings withstand violent shaking so they can reduce the amount of damage to cities.
The Rayleigh name is very much widely used in physics and can also be found in fluid dynamics. There is the Rayleigh number (Ra) which is a dimensionless number associated with buoyancy-driven flow, known as natural convection. The Rayleigh number is a measure of the behaviour of fluids due to differences of temperature and density at the top and bottom of the liquid. It’s practical applications in fluids can tells us the time it takes a parcel of warm water to transport itself in a hot body of water like a cup of tea at a certain speed.
There is also other physical behaviours in matter that use the Rayleigh name. There is Rayleigh flow and the Rayleigh-Taylor instability, both of which are used in fluid dynamics.Then there is the Rayleigh-Jeans law, which is used to measure the light and other forms of radiation being emitted by black bodies at a given temperature. A black body is a scientific name for a body that absorbs radiation like the way the planets absorb light from the Sun. The Rayleigh-Jeans law later played a role in the development of quantum mechanics. I am not that well versed in physics subjects like quanta and radiation so I will avoid attempting to explain things in this article I don’t understand very well.
Among other things in physics that John Strutt, who by now was Lord Rayleigh, became known for was in formulating the circulation theory in aerodynamic lift. This explains the way aeroplanes catch the air to generate lift under their wings. In optics Rayleigh proposed the criteria for angular resolution that describes the ability for a camera or telescope to determine small details of an object, thereby making it a major determinant of image resolution. What this means to the average person is that with angular resolution you can sharpen the image by focusing it on one particular object that is important to the subject of your shot.
John Strutt’s legacy in physics made a very good impression on the academic elite of the world of science. In 1904 he was awarded the Nobel Prize for Physics for investigation into the densities of gases, which included his discovery of the inert gas argon in 1894. He also committed to his lordly duties in the House of Lords when called upon to get involved in political matters affecting science. Throughout his life he had written hundreds of research papers and books, which included a textbook called The Theory of Sound and it’s still used by sound engineers since it was published in 1877. When he died in June 1919 he was succeeded as Lord Rayleigh by his son Robert John Strutt as the 4th Baron of Rayleigh.
Robert Strutt was also a successful physicist like his father. He followed in his father’s footsteps to Cambridge where he became a research student to the legendary discoverer of the electron, Sir Joseph Thompson. Robert would later write his biography as well as that of his father John. In 1910 he discovered that when an electrical discharge in nitrogen gas occurs it produces “active nitrogen”. Active nitrogen is an alternative form of nitrogen in the same physical state but the major difference is that the atoms of this gas don’t bond together.
Later in 1916 while working with a colleague called Alfred Fowler, Robert Strutt proved the existence of ozone in the Earth’s upper atmosphere. This is now called the ozone layer and it was discovered when they observed the ultraviolet spectrum of the setting sun. They did this using a device called a spectroscope. I used one of these at the Open University and it reveals the constituent parts of gases by a spectra of colours.
After his father passed away Robert carried on working at the family house called Terling Place where the Rayleigh family still live to this day. He conducted experiments in a private laboratory there where he went onto make another groundbreaking discovery in atmospheric physics, which was a continuation of John Strutt’s Rayleigh scattering observations.
Robert differentiated two types of light in the night sky. One was the aurora known as the northern lights and the other was the airglow that explained how the night sky never went completely dark at night. Airglow occurs from the faint emission of light by the atmosphere caused by self-illuminated gasses. By discovering this property of our planet’s atmosphere he showed how gases in the atmosphere became illuminated with light producing these effects of the sky dancing with light.
