This post is in celebration of two men linked to my home town of Kendal, who have had some little level of influence over science. The first one is more of a stepchild of Kendal, John Dalton, whose atomic theory revolutionised chemistry. The second is an errant child of Kendal, Sir Arthur Eddington, who was born in the town, but who soon left for pastures new. The place where Dalton lived was coincidentally also the place where Eddington was born – Stramongate School. On the site of that former school (abandoned in 1932), there is a green plaque from the Kendal Civic Society.
John Dalton was born in Eaglesfield, a village not far from Cockermouth on the 6th of September, 1766. He was the son of a weaver who began running his own school at the age of twelve. Not unnaturally for someone in this area, he took up an interest in meteorology. At the age of fifteen, he and his brother Jonathon moved to Stramongate school in Kendal, then owned by his cousin, to help run it. They took over the school in 1786. Whilst in Kendal, Daltan became acquainted with John Gough, a blind polymath Kendalian. Gough was a man of many talents who taught Dalton languages and started him off making a meteorological journal that Dalton would keep up until he died. Gough acted as a maths tutor for many influential people in that time, included William Whewell, who would later be the man to coin the term ‘scientist’.
Dalton left Kendal in 1793 to head off to Manchester, his first work Meteorological Observations and essays already on Kendal’s printing presses. His work on the weather and wondering about the motions of the atmosphere lead Dalton to explore the concept of the atom. Could gases be thought of as collections of atoms? If we understood their composition, could we then not work out how they acted? Dalton realised that gases under constant pressure expanded linearly under heating and would reduce to liquids under cooling. Dalton also derived Dalton’s Law, which states that the pressure of a mixture of gases is equal to the sum of the partial pressure of each of the constituent gases. He also derived a table of atomic weights of six elements and brought about the idea of compounds – molecules – where atoms of different elements were combined. His atomic theory can be spelt out as:
- Elements are made of tiny particles called Atoms
- All atoms of a given element are identical
- The atoms of different elements differ and can be distinguished by their relative weights
- Atoms of different elements can combine to form compounds. A given compound will always have the same relative numbers of different types of atoms.
- Atoms can’t be created, divided or destroyed chemically, chemistry only alters the grouping.
In 1844 after a series of strokes, Dalton recorded his final entry in his meteorological journal on July 26th. The following day, he was found dead. He is remembered in a number of ways – statues, busts and roads in Manchester, Dalton schools for Quakers, a lunar crater and of course Dalton House one of the four houses of my own Kirkbie Kendal School.
Of course, for my own research, his most important studies were the partial pressure laws, later incorporated in the ideal gas laws and hydrostatics, which govern the atmospheric models used today.
Sir Arthur Stanley Eddington
Eddington was another Quaker from the north-west of England. He was born in 1881 in Stramongate School, where his father was the headmaster and therefore successor to Dalton. His father died of Typhus three years later and Eddington’s family moved to Weston-super-Mare. Eddington proved a prodigious child and at the age of sixteen followed Dalton to Manchester, where he lived in Dalton Hall. His success there lead to a scholarship to Cambridge in 1902, where he excelled greatly. In 1905, he began research in thermionic emission, but did not do so well. The following year he became the assistant to the Astronomer Royal at Greenwhich. Put to work on measurements of parallax, he showed the skill that was to place him as the best measuring man in England. This earned him a scholarship to do research at Trinity college Cambridge and in 1914 he took over as head of Cambridge Observatory.
Eddington worked on the Internal Constitution of Stars, both his area of research and a great work. He used thermodynamics and the concept of radiation pressure to develop the first true understanding of stellar processes. Eddington further went on to speculate about the energy source of stars, deducing that gravitational collapse couldn’t keep a star shining for the lengths of time geology suggested the world had been around for. He supported an idea of slow annihilation of matter and found its expression in nuclear fusion. He also came up with the mass-luminosity relationship, which determined that stars of greater mass shone brighter.
Although the above works give him the most enduring legacy amongst working scientists, who still use his equations to this day, publically, he is best remembered for his work with relativity. This began with correspondence between him and the relatively unknown German scientist Albert Einstein. As they didn’t speak each other’s language, the correspondence was carried out in the language of mathematics – Eddington requesting Einstein use his new theory of gravitation to explain the orbit of Mercury, whose dynamics had evaded explanation with Newton’s or Kepler’s laws. This was done during a most unsettled time – the countries of the two scientists were at war and both scientists were pacifists and vilified for being so. The result of the correspondence was that Eddington became convinced of the veracity of General Relativity and so determined to prove observationally a theory that had until then been treated as an intellectual curiosity, but not much more.
In 1919, Eddington set out to Principe in Africa to take photographs during a total solar eclipse. He sent another team to Brazil, but they were clouded out. Eddington’s team too found cloud, but the photographs were taken nonetheless, some of which were found to be acceptable. Einstein’s theory contended that space and time were warped by gravity and that close to a large source of gravity – such as the Sun, the warping would be enough to act a bit like a lens, distorting the stars behind the Sun. Eddington had a photograph of the area of the sky the Sun was to be in front of during the eclipse, he had photographs of the same area of sky with the eclipsed sun in it. He made the final measurements to see if the background stars near the Sun had been shifted in public, and in doing so found for Einstein. It was the first observational proof of the predictive power of General Relativity and confirmed Einstein’s fame. It was also the first Gravitational Lensing observation to be made – a hot astronomical topic to this day.
Eddington was knighted in 1930 and also made an Honorary Freeman of Kendal in the same year. He, as well as Dalton, has a crater named for him as well as a medal of the Royal Astronomical Society. He also has the astronomical society of Kendal – the Eddington Society and a house of Kirkbie Kendal School named for him.
During the International Year of Astronomy, 2009, an expedition is to be made to Principe to honour Eddington’s own. A plaque will be revealed, lectures given in Principe, the UK and US and a gravitational lensing centre opened. The plaque will be laid down on May 29th, 90 years to the day of the eclipse.