AHEAD IN THE STARS: Arthur Eddington and the Great Eclipse of May 29, 1919

by Geoff Olson (May 2019)

“Wherever a way opens we are impelled to seek, conscious that in this activity of mind we are obeying the light that is in our nature.”
– Sir Arthur Stanley Eddington

A total solar eclipse is an extraordinary event. The air cools as the moon slowly nibbles into the disc of the sun, and for a few uncanny minutes the daytime world plunges into night. Stars appear and birds turn silent.

May 29 is the 100th anniversary of the most significant eclipse in the history of science. Essentially, it allowed confirmation of Albert Einstein’s theory of relativity through measurement of altered starlight.

In a legendary 1905 paper, Einstein collapsed Isaac Newton’s absolute space and absolute time into one flowing continuum, “space-time.” As a bonus, he presented matter and energy as two sides of the same cosmic coin. These extraordinary notions followed from one simple proposition: the speed of light is the same for all observers, regardless of their relative speeds. This was his paradigm-popping theory of “special relativity.”

Einstein had a thing for unification. In a 1915 paper, the frizzy-haired physicist spot-welded gravity and inertia into one geometrical field, warped by the presence of matter-energy. This equally revolutionary “general relativity” posited that light’s path in space could be bent by massive bodies like stars.

The cosmologist John Wheeler succinctly described the generalized version of relativity: “Matter tells space-time how to curve, and curved space tells matter how to move.”

Initially, Einstein’s radical ideas were entirely theoretical, and unsupported by scientific evidence. And this is where Arthur Stanley Eddington comes in. Four years after Einstein’s paper on general relativity, the mild-mannered British physicist traveled to Africa to perform an epochal scientific experiment. This historical moment signaled the transition from the Old World of science (populated with billiard-ball like atoms and eternally ticking clocks) to a chancy New World populated with bizarre, previously unknown entities: black holes, quasars, quarks, and things that go bump in the lab.

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Arthur Stanley Eddington was born in 1882 in Kendal, Cumbria, a modest-sounding English town. As I discovered on an eclipse-hunting road trip in 1999, a drive through the British countryside can be a Pythonesque experience. In just short distances from London you can encounter clerical skin conditions (Bishop’s Itchington), swamp apes (Marsh Gibbon), larval apocalypse (Maggot’s End), hits below the belt (Nether Wallop), and fashion suggestions (Matching Tye).

I once read somewhere that Brits consider it bad form to ask their place of birth, and now I think I understand. I’d be a bit taciturn myself if I spent my formative years in Mousehole or Ratney.

While I was in stitches with a road map, the British media was in a lather about the upcoming solar eclipse of August 11. Lacking a believable Apocalypse in the tribal, moon-eating-the-sun sense, reporters came up with one of their own. Supposedly every other Brit from Shellow Bowels to Puddletown were planning to squeeze themselves into their dinky vehicles and head for a little corner in southwest England, where complete darkness from the moon’s shadow was to fall: the “path of totality”. The chaos would unimaginable, reporters said, though they did their best to imagine it. (The previous eclipse in Britain took place in 1927. I noted with satisfaction that viewing was said to be best in Giggleswick.)

Luckily for Eddington, he didn’t have to anticipate a British land assault to witness an eclipse. He only had to sail to an island off the coast of Africa.

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Eddington was that rare breed of scientist, one capable of conveying difficult concepts accurately with literary flair. (“Shuffling is the only thing which Nature cannot undo,” he wrote of entropy.) By popularizing astronomy in a time of spectacular discoveries, the quiet, diffident scholar followed a grand British tradition of science popularization initiated by “Darwin’s Bulldog,” Thomas Henry Huxley.

His father, headmaster of a Quaker school, died of typhus in 1884 when Arthur was not yet three. The widowed mother managed to raise her son and daughter on a small income. Luckily, at the age of sixteen, young Eddington won a scholarship to the college that would become the University of Manchester.

In 1913 Eddington landed a professorship in astronomy at Cambridge. He continued his studies at Cambridge, followed by employment at the Royal Observatory at Greenwich. The Great War commenced in July of 1914, silencing communications between the scientific communities of England and Germany. The young astronomer only knew of relativity theory through a smuggled copy of Einstein’s paper.

It was Eddington’s colleague, Frank Watson Dyson, Astronomer Royal of Britain, who first conceived a test for Einstein’s theory. The theory predicts that light is bent in the presence of gravitational fields — twice as much as Newtonian physics predicts — but the amount either way is very small. Dyson had a brainstorm: the sun is an extremely massive body, and rays of light skirting the edge of the sun on the way to Earth would bend by a measurable amount. This bending would be observable during a solar eclipse, when the disc of the sun is blocked by the moon in transit.

The stars that are normally invisible would shine in the brief darkness of the eclipse, and those closest to the disc of the sun would have measurably altered positions in the sky, due to the predicted bending of starlight.

Astronomers can calculate eclipses many years in advance, and Dyson determined that on May 29, 1919, a total solar eclipse would be viewable throughout South America, across the Pacific, and into Africa. The area of totality — the region where the moon’s blockage of sunlight is complete — would travel across the remote island of Príncipe, in the Gulf of Guinea off the west coast of Africa.

Critically, it was the longest solar eclipse since May 27, 1416, and it would occur just as the sun was crossing the bright Hyades star cluster: perfect for measuring bent light. (It’s one of those happy accidents in science that as viewed from Earth’s surface, the moon’s disc precisely blocks the disc of the sun, no more and no less than 100 percent. This allows witnesses to see the solar corona, a hot gas of filaments rising from the sun’s surface.)

Like his father, Eddington was a lifelong Quaker. Representative beliefs of the faith, including pacifism and internationalism, worked their way into Eddington’s words and deeds. With Britain’s introduction of military conscription in March of 2016, the young astronomer followed his conscience and prepared to apply for an exemption as a conscientious objector.

Cambridge spared him confrontation with the state by requesting and receiving an exemption, on the grounds that Eddington’s work was in the national interest. The Ministry of National Service later appealed against the exemption, and Eddington claimed conscientious objector status before a tribunal in June of 1918. Frank Dyson intervened with a written statement insisting on Eddington’s importance for the astronomical expedition to Africa. The tribunal granted a further twelve months of exemption from military service under the condition Eddington pursue his astronomical work in preparation for the 1919 expedition. The war ended before Eddington’s time ran out.

Reading a smuggled paper from an enemy scientist? Objecting to military service? In some quarters in today’s world, Eddington would be pegged as a dupe, a terrorist sympathizer, or an agent for a hostile power. Or fodder for an HBO drama…

— — — — — — — — — — — — — — –

Let’s move forward in time by eighty years. On August 11, 1999, the moon’s shadow began it’s slow progress across the Atlantic Ocean and, before noon, was traversing the southern United Kingdom then on to northern France and parts of Western/Eastern Europe. I was in Southern England, where the predicted chaos from a mass migration of British eclipse-hunters failed to pan out. The broadcast Cassandras had the reverse effect: the anticipated lemming-like rush for the southwest coast resulted in mass avoidance.

The overcast skies helped greatly, nixing a last-minute exodus of Peugeots and Volvos. That was my cue. My brother-in-law and I hopped into a car and made from Cambridge to Cornwall on he morning of the 11th, hoping for a furtive glimpse of a sight last granted to the gobsmacked residents of Giggleswick.

— — — — —

With the onset of the Great War on July 28, 1914, wartime production tied up all the factories capable of producing the heavy-duty astronomical equipment necessary for any eclipse-viewing expedition to Africa. The end of hostilities on November 1918 left only a few months for things to get underway. Orders were placed, and an assortment of large telescopes, astronomical devices and motorized reflective mirrors were duly cranked out for the mission.

Cambridge made arrangements for Eddington and his team to travel to Principe. A second team, led by Andrew Crommelin and Charles Rundle Davidson of the Royal Greenwich Observatory, were sent to another target area on the path of totality, in Sobral, Brazil.

It turned out that view conditions were less than perfect in Principe, with the skies clearing only partly during the actual eclipse. The team in Sobral had a much better view. However, they later found to their disgust that all 19 images taken by their main telescope were out of focus. The instrument had been warped by tropical temperatures. Luckily, they had with them a smaller 10 inch telescope, which is said to have provided the best data from the joint expedition.

On the evening of November 6, 1919, Dyson, Eddington and Crommelin stood before a full house at the Royal Society in London, and revealed their findings: Einstein was right.

The news quickly went global. The New York Times offered this cheery headline: “LIGHTS ALL ASKEW IN THE HEAVENS / Men of Science More or Less Agog Over Results of Eclipse Observations / Einstein Theory Triumphs / Stars Not Where They Seemed or Were Calculated to be, but Nobody Need Worry.”

Some science historians later questioned the results. It’s known that Eddington discarded some photographic images as flawed, and it’s these that supplied data closer to the Newtonian estimate for bent starlight. This certainly sounds like “massaging the data,” if not rolfing it into scientific agreement.

Theoretical physicist professor Peter Coles dismissed such accusations after performing a reanalysis of Eddington’s values using modern statistical techniques. “I’ve done this and found no evidence that Eddington ‘cooked the books’,” he stated in an April edition of Nature. (This echoes a 1979 re-analysis of the data, which found no evidence of experimental bias.)

With the worldwide dissemination of the Eddington/Dyson news, a relatively obscure German physicist became a household name, and a British astronomer the most recognized explicator of his ideas. Einstein himself held that Eddington’s 1923 book, The Mathematical Theory of Relativity, was “the finest presentation of the subject in any language.”

— — — — — — — —

Fast forward to the eclipse of 1999. Just outside of Cornwall, My brother-in-law and I found a spot just inside the path of totality and parked the car. Making our way up a rise in Greater Buttocks (or wherever we were), we discovered a storybook setting of rolling hills and thatched cottages. Grey skies as predicted, but several times the disc of the sun poked through the cloud cover, with the moon gnawing into its side. Feeble sunlight from the crescent sun resulted in a surprising drop in temperature. We shivered in our t-shirts.

But disappointment was not in the cards. It turned out the clouds acted as a projection screen for the penumbra of the moon — the shadowy area that surrounds the umbra of total darkness. A huge dark shape, dozens of miles across, appeared on the western horizon. The disc slowly moved above us like an alien mothership, and in seconds everything went from twilight to night, as if on a dimmer switch. The lights in the hamlet below blinked on

After about a minute of not-quite total darkness, the process played in reverse, but to the opposite horizon. Seagulls screamed their morning cries, with a particularly crazed edge, it seemed. The cows looked stunned — pretty much unchanged, in other words. I felt a little stunned myself. It was one of the most uncanny, spectacular things I’ve ever witnessed, with a weird hint of menace. There were two teenage girls standing near us; one of them had burst into tears.

You can imagine the power wielded by priest-kings of ancient empires, had they astronomers capable of predicting solar eclipses. It would be like “take all our our women, anything! Just don’t let the lights go out again in Swineshead, that scared us silly!”

— — — — — — — — — — — — —

Following the successful mission in Principe, Eddington settled down at Cambridge to theoretically probe the makeup of distant stars. He used Karl Schwarzschild’s model of stars as hot gases held together by the opposing forces of gravity and heat, in dynamic equilibrium. Rather amazingly, the young astronomer succeeded in calculating the pressure and density of stellar cores. He concluded the temperature of stars’ interiors must be in the millions of degrees, rather than in the thousands, as previously thought.

The 1930 publication of Eddington’s Internal Constitution of the Stars birthed the modern theory of stellar evolution. “A star is drawing on some vast reservoir of energy by means unknown to us. This reservoir can scarcely be other than the sub-atomic energy which, it is known, exists abundantly in all matter; we sometimes dream that man will one day learn to release it and use it for his service. The store is well-nigh inexhaustible, if only it could be tapped,” he wrote, anticipating by two decades the Faustian discovery of nuclear fusion.

The astronomer predicted that stars the size of our sun would end their days as “white dwarves,” and predicted — accurately — we would find such a beast in the distant star Sirius B. He lyrically and amusingly described the physics of white dwarves in 1927:

“We learn about the stars by receiving and interpreting the messages which their light brings to us. The message of the Companion of Sirius when it was decoded ran: “I am composed of material 3,000 times denser than anything you have ever come across; a ton of my material would be a little nugget that you could put in a matchbox.” What reply can one make to such a message? The reply which most of us made in 1914 was — “Shut up. Don’t talk nonsense.””

Eddington’s books hold up surprisingly well to this day. His scientific depth weaves like a deep bass line through his writings, with humorous asides playing above the prose — as evidenced by some doggerel from New Pathways in Science in 1938:

“There once was a brainy baboon,
Who always breathed down a bassoon,
For he said, “It appears
That in billions of years
I shall certainly hit on a tune.”

On the less exalted side, Eddington’s bio is darkened by a famous dispute with the astronomer Subrahmanyan Chandrasekhar, who was then a student of astronomy at Cambridge. Chandrasekhar had performed calculations indicating that “degenerate” stars of sufficient mass would collapse into points of infinite density — what scientists decades later termed “black holes.” Eddington insisted the student from India had conjured a mathematical monstrosity with no bearing on the physical world. In Chandrasekhar’s telling of the tale, Eddington deliberately embarrassed and sabotaged him at a critical scientific meeting. The famed astronomer is rendered as blinkered, mean-spirited and racist. A man ahead in the stars, but perhaps not ahead of his time?

Ironically, it was the phenomenon that Eddington rejected as impossible that later proved Einstein’s theories in a cosmically dramatic form. In April of this year, the Event Horizon Telescope, a global network of radio telescopes, gave the world its first reconstructed view of the “accretion disc” around a black hole — the stellar material spiralling toward the object’s event horizon.

In his book Gravity’s Century: From Einstein’s Eclipse to Images of Black Holes, author Ron Cowen writes, “These two experiments — the eclipse expeditions of 1919 and the Event Horizon Telescope observations a century later — bookend an era unlike any other in the history of science…. The first provides the first tantalizing evidence about how gravity shapes spacetime. The latter shows how dramatic that effect can be.”

Decades after Eddington’s success at Principe, the detection of light bending around massive objects in space — “gravitational lensing” — has become a yardstick for measuring so-called dark matter and the expansion of the universe.

The degree of bent starlight during a solar eclipse is vanishingly small. But a solar eclipse certainly doesn’t require scientific equipment and charts to amaze; protective viewing glasses are all that’s required. In 1999, I was just inside the path of totality on a cloudy day, so I did not witness the event in its full power. But what I witnessed has stuck in memory to this day. When the blazing disc of the sun behaves so contrary to everyday experience, the resulting feeling can only be termed uncanny. And that’s even when an eclipse is predicted to occur, right down to the second.

I did not get a chance to witness the solar eclipse of August 21, 2017, which tracked across the continental US. Yet I and millions of others were witness to press photos of a US president squinting at the sun without protective eyewear — and that was astonishing enough.

— — — — — — — —

Eddington did not limit his investigations to the nature of the sun, the stars, and beams of light bent by the force of gravity. He also tentatively probed the subtle connections between mind and cosmos, in a manner adventurous for an academic of his time.

He noted how the “shadow-world” of mathematical symbols that physicists worked with had only a passing resemblance to the world reconstructed by the human mind. In his most popular book, The Nature of the Physical World, he suggested that “the stuff of the world is mind-stuff,” and then strained to narrow down his neologism. “It is difficult for the matter-of-fact physicist to accept the view that the substratum of everything is of mental character. But no one can deny that mind is the first and most direct thing in our experience, and all else is remote inference,” he wrote.

In most of academia, “mysticism” has mostly negative connotation, as a placeholder for superstitious or otherwise muddy thinking. It has more specific and respectable definition for today’s students of folklore and religion, and Eddington’s own interpretation of the mystic experience anticipates viewpoints expressed by 21st century transpersonal psychologists:

“If I were to try to put into words the essential truth revealed in the mystic experience, it would be that our minds are not apart from the world, and the feelings that we have of gladness and melancholy and our yet deeper feelings are not of ourselves alone, but are glimpses of a reality transcending the narrow limits of our particular consciousness — that the harmony and beauty of the face of Nature is, at root, one with the gladness that transfigures the face of man,” he wrote in The Nature of the Physical World.

These thoughts echoed the sentiments of his Quaker upbringing. The Quaker founder George Fox held that every individual had a piece of God within him or her in the form of an “Inner Light.” Eddington’s interest in Einsteinian light was mirrored in his belief of a light — figurative or literal — within. He also took the pursuit of truth as informing both science and spirituality. “You will understand the true spirit neither of science nor of religion unless seeking is placed in the forefront,” he observed in 1929.

However, Eddington was too sophisticated a thinker to accept the simplistic notion that human perceptions create physical reality, as this passage from The Nature of the Physical World makes plain:

“There is a doctrine well known to philosophers that the moon ceases to exist when no one is looking at it. I will not discuss the doctrine since I have not the least idea what is the meaning of the word existence when used in this connection. At any rate the science of astronomy has not been based on this spasmodic kind of moon. In the scientific world (which has to fulfill functions less vague than merely existing) there is a moon which appeared on the scene before the astronomer; it reflects sunlight when no one sees it; it has mass when no one is measuring the mass; it is distant 240,000 miles from the earth when no one is surveying the distance; and it will eclipse the sun in 1999 even if the human race has succeeded in killing itself off before that date.”

When an Archbishop asked Einstein what effect the theory of relativity would have on religion, the physicist responded, “None. Relativity is a purely scientific theory, and has nothing to do with religion.” In noting Einstein’s reply, Eddington added acidly, “In those days one had to become expert in dodging persons who were persuaded that the fourth dimension was the door to spiritualism.”

In spite of such sentiments, the influential British logician and atheist Bertrand Russell smelled a whiff of theism in Eddington’s writings, and publicly disparaged him. In 1928, the astronomer responded to such criticisms: “The religious reader may well be content that I have not offered him a God revealed by the quantum theory, and therefore liable to be swept away in the next scientific revolution.”

Knighted in 1930, Eddington maintained a lifelong position of awe toward the object of his study: a sublime universe of which humankind was a flawed expression. “We are bits of stellar matter that got cold by accident, bits of a star gone wrong,” he observed.

— — — — — — — — — — — —

As a Quaker, Eddington worked occasional references to seeking and inner light in his prose. “If our so-called facts are changing shadows, they are shadows cast by the light of constant truth. So too in religion we are repelled by that confident theological doctrine… but we need not turn aside from the measure of light that comes into our experience showing us a way through the unseen world,” he wrote in Science and the Unseen World in 1929.

The astronomer was correct in accepting a model for an expanding universe that Einstein himself rejected and later described as his “greatest blunder.” However, he also rejected the Big Bang model on aesthetic grounds, and dismissed black holes as physical impossibilities. Toward the end of his life he labored, as did Einstein, to weave a grand unified theory successfully uniting the subatomic realm with the expanding universe. It’s a target that both thinkers failed to reach. (That said, Eddington’s efforts to identify an algebraic basis for fundamental physics, incorporating space-time into a higher-dimensional structure, were precursors to similar efforts by today’s theoretical physicists.)

The quiet astronomer died, unmarried, in 1944. Almost four decades later, In a survey of his scientific work for the Royal Astronomical Society, the astronomer G.W. Whitrow predicted that Eddington’s theoretical work on universal constants and stellar structure will long remain “as reminders of one of the most original and penetrating intellects of the twentieth century.”

Geoff Olson is a Vancouver-based writer and political cartoonist. He is currently working on a book exploring the links between light, the cosmos and consciousness called Lightgeist.

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