In early September 1922, a group of astronomers sailed to a remote Kimberley beach, encamped behind a series of sand dunes, and soon made history.
On September 21, they proved Albert Einstein’s theory of relativity.
But for such a significant moment in science, surprisingly very few people know much about it.
So, as the event marks its centenary, it’s time to take a look back at the incredible story of the Wallal Expedition…
What was the Wallal Expedition?
The full name, Wallal: the 1922 Solar Eclipse Expedition to Test Einstein’s Theory, says it all.
In 1915, Albert Einstein had published his Theory of Relativity, arguing that gravitational objects subjected to a gravitational force distort space-time around them. Essentially he said space is curved.
Up to this point, Isaac Newton’s understanding of ‘absolute space and absolute time‘ was accepted as fact. Scientists believed that space was rigid.
But Einstein’s theory was just that – a theory. And a controversial one. Seven years later it was still unproven.
Top scientists from around the world had collaborated to suggest that the best way to prove the theory would be to observe and document the light from a distant star that curves as it enters the Sun’s gravitational field.
But even though there were cameras back then that could capture rays of light, the overwhelming light of the sun made it impossible to photograph them.
It was concluded that capturing these images during a total solar eclipse would be their best bet.
Several attempts have been made by various scientists – the most notable in 1919 when a British team led by Sir Arthur Eddington observed and recorded the curvature of starlight during a total solar eclipse just off the west coast of Africa. But still Eddington himself declared the expedition a success, but the results failed to convince the wider scientific community.
More distracting starlight had to be recorded from a larger number of stars to officially validate Einstein’s theory.
A solar eclipse was scheduled to begin on September 21, 1922, beginning in Somalia and sweeping across Christmas Island before becoming visible in the sky over Wallal from mainland Australia.
At first, Christmas Island was thought to be the best location, but the weather there was too unpredictable. In Wallal, however, it rained for two days every September – giving much better chances of clear skies on the day of the eclipse.
But while Wallal’s weather was ideal, the remote location presented other challenges.
Located behind a series of sand dunes at Eighty Mile Beach, 300km south of Broome, the only infrastructure there was an old telegraph station and there were no roads in or out.
How did all the people and all the big, heavy equipment it took to pull this off get to Wallal? And how could a sustainable camp be built there? The option was immediately dismissed by most of the world’s scientists.
“The British said Wallal was a completely hopeless place and there was no way they could send an expedition there,” he says David Blair, Professor Emeritus at the University of Western Australia (UWA).
But Professor Alexander Ross, then head of mathematics and physics at UWA, was determined to convince the international community of astronomers that he could make it work.
“Alexander Ross figured it all out,” says David, explaining that even though the tide at Eighty Mile Beach was a mighty 30 feet, Ross knew it was possible to get a ship in since pearl boats used to ply the area.
Ross also learned of a freshwater spring used by the local Indigenous people, and further investigation revealed that the state government had built a well at Wallal decades earlier to feed a cattle route through the area.
“So he published a rebuttal and sent it to the world’s most famous eclipse astronomers, including Canada’s Link Observatory director William Campbell and Clarence Chant, now referred to as the ‘Father of Canadian Astronomy’.”
Both agreed that they would come to Australia and join an expedition to Wallal.
With Campbell and Chanting on board, the idea soon gained momentum and Ross was able to secure the support of the Australian government.
“The then Prime Minister Bill Hughes was very enthusiastic about it. He agreed that the Navy would provide personnel to support the expedition and that the brand new Trans-Australian Railway should be used to bring all telescopes (coming from California first) from Sydney to Perth,” says David.
What was finally achieved is nothing short of extraordinary.
At the beginning of September, the 30-strong expeditionary group landed at Eighty Mile Beach with the support of the Royal Australian Navy.
The group included astronomers from America, Canada and India, as well as local teams from UWA and the Perth Observatory. Documentary filmmakers and photographers also hitchhiked, as did some of the astronomer’s family members.
“They couldn’t bring a steamer, so they got a steamer to tow a two-masted sailboat (The Gwendolin) as close to the coast as possible,” explains David. “Then when the tide receded the boat was stranded in the sand, but when the tide went up there were a lot of waves.”
35 tons of supplies and equipment had to be hauled off the boat, up the beach and across a few miles of sand dunes.
The group used rowboats to transport equipment from the boat to the mudflats. From there, the owners of a nearby cattle station provided donkey teams, four-wheel wooden carts, and labor to carry the huge load.
But while it was a massive feat in itself, getting everyone and everything to Wallal was only the first phase of the expedition.
After the camp was set up, all the equipment had to be assembled on site after being transported in parts.
Huge cameras and telescopes required equally huge mounts to hold them in place—they required towers so tall they needed their own concrete foundations.
But soon these massive structures were completed, wireless communications established, photographic darkrooms built, and all the tools and instruments needed to capture the evidence needed set up, tested, refined, and ready for the eclipse.
How was Einstein’s theory of relativity proven?
Photos taken during the total solar eclipse in Wallal showed the deflection of starlight.
David explains, “When space is curved, the concept of a straight line is different – straight is curved.”
Simply put, light always travels in a straight line, but when space around the sun is curved (due to the sun’s gravitational pull), then light emitted by stars also curves.
In all, the Wallal Expedition observed 140 stars during the eclipse, and the measured deflection of these stars was extremely accurate, with an error bar of less than one percent.
“Their results were so accurate that they sent a telegram to Astronomer Royal saying, ‘Prediction confirmed: no more eclipse expeditions needed!'” says David.
And Einstein was right about that. The Wallall expedition had successfully gathered solid evidence for his then-controversial theory of relativity.
contribution of the indigenous people
Wallall was not entirely uninhabited. Currently 100 Nyangumarta people lived in the area.
In fact, “wallal” means “sweet water” in the local language.
“There’s very little mention of these people in the scientific record,” says David.
“But if you look at the photos, you see Aboriginal people in almost every photo, especially at the tremendous unloading work.”
Other photos show tribal people helping to erect structures, sourcing and carrying stone for foundations, lighting bonfires, and helping out at camp.
The photographs document their contribution.
While many of the Aboriginal people photographed lived in Wallall, many others who joined the expedition were workers on the nearby cattle station.
A photographer at the camp also took a series of portraits of the Nyangumarta people you will see talking and children showing interest in the equipment.
“You also see them looking through the telescopes and stuff,” says David.
“In these photos, they look happy and enthusiastic and happy to be there.”
importance for science
Once Einstein’s theory of relativity was accepted as fact, everything scientists thought they knew about space was turned on its head.
The room was curved. It was four dimensional. It was a malleable medium.
This paved the way for future discoveries such as black holes, neutron stars, and most recently, gravitational waves.
“Gravitational waves are waves in the curvature of space. So when you have the fact that space can curve, it doesn’t seem at all surprising that if it can curve, it can curl,” says David.
“We couldn’t even have talked about it Gravitational waves, if only we still had the idea that space is rigid.”
The University of Western Australia is hosting a two week celebration of the Wallal Expedition centenary with a range of activities and events.
Uncovering Einstein’s New Universe, written by David Blair, Ron Burman and Paul Davies, will also be presented during the centenary celebrations.
Related: A Brief History of the Universe
