Sir Arthur Stanley Eddington (1882 - 1944)
Arthur Eddington was a British astronomer, physicist and mathematician who made a number of breakthroughs in astrophysics. He was born in Cumbria in the north of England before moving to Weston-super-Mare as a child, where despite being from modest means he excelled at school and earned a scholarship to Owen's College, Manchester (now the University of Manchester). He graduated with a physics degree in 1902, which in turn led to an offer to join Trinity College, Cambridge where he completed his masters studies. His love of astronomy led him to work at the Royal Observatory in Greenwhich, London, where he excelled, before returning to Cambridge five years later.
He was the first person to hypothesise that stars were powered by the nuclear fusion of hydrogen into helium in the 1920s paper The Internal Constitution of Stars. The limit to how bright a star can be before it begins to collapse in on itself is named after him, the Eddington Limit, or Eddington Luminosity.
He is most famous, however, for his work on the Theory of Relativity, having explained Einstein's theory to the English-speaking world, and on the 29th May 1919 conducted observations of a solar eclipse to confirm the theory. His work on this expedition was considered so crucial that he was prevented from entering military service during the First World War. Arthur was fighting conscription anyway as a conscientious objector and pacifist, though he did offer to join an ambulance unit, or work as a harvest labourer on home soil.
The expedition to view the eclipse took Arthur to the island of Principe, off the west coast of Africa where the eclipse could be viewed in full, and with a good chance of clear skies. During the darkness of the eclipse Arthur then took photographs of stars close to the Sun, normally obscured by the light of the Sun during the day, these stars showed that their light was being shifted by the gravitational field of the Sun - and confirmed Einstein's theory of relativity. He later wrote this short poem about the discovery:
Oh leave the Wise our measures to collate
One thing at least is certain, LIGHT has WEIGHT,
One thing is certain, and the rest debate—
Light-rays, when near the Sun, DO NOT GO STRAIGHT.