It's hard to imagine that Albert Einstein's name was not recognized around the world.
But even after he had ended his theory of relativity in 1
Einstein's ideas were caught by the blockades of World War I, and even more by the vicious nationalism that made "hostile" science in the UK undesirable.
But Einstein, a socialist, and Eddington, a Quaker, both believed that science should overcome the divisions of war.
It was their partnership that enabled the Theory of Relativity to burst the trenches and make Einstein one of the most famous personalities in the world.
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Einstein and Eddington did not meet during the war or did not send direct messages. Instead, a mutual friend in the neutral Netherlands decided to spread the new theory of relativity in the UK.
Einstein was very fortunate that it was Eddington, the Plumian professor at Cambridge and officer of the Royal Astronomical Society, who received this letter.
Not only did he understand the complicated mathematics of theory, but as a pacifist he was one of the few British scientists who wanted to think of German science at all.
He campaigned for Einstein to revolutionize the foundations of science and return the scientists to internationalism.
Einstein was the perfect symbol for this – a brilliant, peaceful German who disproved any wartime stereotype while challenging Newton's deepest truths.
Desperate struggle to test Einstein's theory Eddington starved to death behind the blockade and lived under government supervision to defend his political views. He tried to convince a hostile English-speaking world that an enemy scientist was worthy of their attention.
He wrote the first books on relativity, held popular lectures on Einstein, and became one of the great science communicators of the 20th century.
His books remained on the bestseller lists for decades, he was constantly present on the BBC radio and was finally knighted for this work.
It was hard to convince the United Kingdom to worry about space-time and gravity as submarines sank food vans and thousands of young people died in Flanders, Belgium.
Only Einstein's ideas were not enough. The theory of relativity is strange: twins age differently and planets are trapped in space.
Eddington needed definitive proof that the theory of relativity is true and that Einstein is right and that only his international approach can revolutionize science.
His best option was to test a bizarre prediction of Einstein's general relativity theory.
When light passed near a massive body like the sun, gravity would bend the rays so easily, Einstein said.
This meant that the image of a distant star was slightly shifted – the star seemed to be in the wrong place.
Einstein predicted a certain number for this shift (1.7 arc seconds, or about 1/60 millimeter on a photo). An astronomer would find it difficult to measure this, but it could be done.
Unfortunately, it is usually not possible to see stars during the day, so you would have to wait until a total eclipse has occurred to make the observation.
Total solar eclipses are rare, short, and often located in uncomfortable locations that require extensive travel for European astronomers. Einstein had tried for years to test this prediction, without success.
Eddington, however, thought he could make it to an imminent solar eclipse in May 1919, visible in the southern hemisphere.
Even with the submarine threat, no country was better positioned than Britain to undertake an expedition to test Einstein's prediction.
Eddington needed a lot of support for that. Fortunately, he was a close friend of Frank W. Dyson, the astronomer Royal. Dyson secured the funding, though the war made it difficult despite the money to procure the required equipment.
Worse, it was possible that Eddington was unable to join the expedition – possibly because he was in prison.
A Quaker, Eddington was a conscientious objector to military service and refused to attend conscription. Many other Quakers were imprisoned or doing hard labor.
After many failed appeals, Eddington appeared to have been arrested, but at the last moment he received a waiver (no doubt from his politically savvy friend, the royal astronomer).
Surprisingly, it was given on the condition that he conducted the expedition to test Einstein's theory.
"Biggest moment in life"
The ceasefire in November 1918 meant that the expedition could continue.
Eddington wanted to make sure that the expedition's findings, whatever they were, drew Einstein's attention to the world.
So he and Dyson launched a public relations campaign to inspire the scientific community as well as ordinary people for the results.
The newspapers were ready to tell what Eddington was as an epic battle between British Newton and upstart Einstein.
Einstein, who was suffering from severe hunger during the war and was trying to navigate through revolutionary Berlin, knew little about it.
Instead, Eddington and his colleagues had to test Einstein's prediction almost completely himself.
Two teams were sent to observe the solar eclipse: one to Brazil and one – led by Eddington – to the island of Principe in West Africa.
After months of intensive measurement and math Eddington had a positive result.
He called this the greatest moment of his life: "I knew Einstein's theory had passed the test and the new view of scientific thinking had to prevail."
He presented the results in a Royal Society room filled with scientists and reporters eager to hear who had won, Einstein or Newton (even as Newton's portrait looked over the proceedings).
The announcement caused quite a stir. The President of the Royal Society declared this to be "one of the highest achievements of human thought".
The Times headline was "Revolution in Science" the next day.
Eddington had planned the event perfectly. Almost overnight, Einstein went from an obscure academician to a sage whom everyone wanted to know more about.
And Eddington gave the public what she wanted. As the chief apostle of the Theory of Relativity in the Anglophone world, he was the one every newspaper and magazine visited.
His lectures had to dismiss hundreds of people. Those who made it not only learned about the strange physics of relativity, but also about Einstein as a symbol of international science that could rise above the hatred and chaos of war.
Einstein himself could hardly rise from his sickbed. He heard about the results of a telegram about the Netherlands.
He was pleased that his theory had been confirmed, though he was confused by the media's firestorm that suddenly enveloped his life.
Never again would he be able to venture through his front door without being addressed by reporters.
Without Eddington, the theory of relativity would have been unproven, and Einstein would never have become an icon of genius.
Eddington was Einstein's most important ally, though they did not meet until after the end of the war.
Their collaboration was crucial not only for the birth of modern physics, but also for the survival of science as an international community in the darkest days of the First World War.
Matthew Stanley is the author of Einstein's War: How Relativity conquered nationalism and shook the world