In early September 1922, a group of astronomers sailed to a secluded beach in the Kimberleys, set up camp behind a row of sand dunes, and soon made history.

On September 21, they proved Albert Einsteon’s theory of relativity.

But for such an important moment in science, it’s surprising that very few people know much about it.

So, on the occasion of the centenary of the event, it’s time to look back on the incredible story of the Wallal Expedition…

What is the Wallal Expedition?

The full name, Wallal: The 1922 Solar Eclipse Expedition to Test Einstein’s Theory, says it all.

In 1915, Albert Einstein published his theory of relativity, claiming that gravitational objects experiencing gravitational pull warp spacetime around them. Essentially he said space was 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.

However, Einstein’s theory was just that – a theory. And controversial. Seven years later, it was not yet proven.

The best scientific minds around the world had worked together to assume that the best way to prove the theory would be to observe and document light from a distant star bending as it entered the Sun’s gravitational field.

But although cameras existed at the time capable of capturing light beams, 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.

Multiple attempts by different scientists have been made – most notable in 1919 when a British team led by Sir Arthur Eddington observed and recorded the curvature of starlight just off the west coast of Africa. But good Eddington himself proclaimed the expedition a success, the results did not convince the wider scientific community.

More deviant starlight had to be recorded by more stars to officially declare Einstein’s theory correct.

An image of a total solar eclipse taken during Sir Arthur Eddington’s expedition, showing the curvature of light. image credit: Wikimedia commons

An eclipse was predicted for September 21, 1922 that would begin in Somalia and pass over Christmas Island, before being visible from the Australian mainland in the sky above Wallal.

At first, Christmas Island was considered the best place, but the weather there was too unpredictable. Wallal, however, averaged two rainy days each September, offering a much better chance of clear skies on the night of the eclipse.

But while Wallal’s weather was ideal, the remote location produced a different set of challenges.

Located behind a row of sand dunes on Eighty Mile Beach, 300 km south of Broome, the only infrastructure was an old telegraph station and there were no entry or exit roads.

How could all the people and all the big heavy equipment needed to pull this off get to Wallal? And how to build a sustainable camp there? The option was immediately rejected by most scientists around the world.

“The British said Wallal was a completely hopeless place and there was no possibility of an expedition going there,” says Emeritus Professor of the University of Western Australia (UWA), David Blair.

But Professor Alexander Ross, then director of mathematics and physics at UWA, was determined to convince the international community of astronomers that he could make it work.

Professor Alexander Ross in his officer’s suit at the University of Western Australia, 1935. Image credit: UWA Archives

“Alexander Ross has it all figured out,” says David, explaining that even though the tides at Eighty Mile Beach were up to nine meters high, Ross knew it was possible to get a ship in because pearl boats frequented the area.

Ross also discovered a source of fresh water used by the local indigenous population, and further investigation revealed that decades earlier the state government had built a well at Wallal to service a cattle route through the region.

“So he published a rebuttal and sent it to the world’s most famous eclipse astronomers, including the director of Canada’s Link Observatory, William Campbell and Clarence Chant, who is now described as “the father of Canadian astronomy”.

Both agreed that they would come to Australia and join an expedition to Wallal.

With Campbell and Sing on board, the idea quickly gained momentum and Ross was able to gain support from the Australian government.

“The Prime Minister at the time, Bill Hughes, was very enthusiastic about it. He approved that the Navy provide personnel to help the expedition and that the brand new Trans-Australian Railway be used to bring all the telescopes (coming from from California) from Sydney to Perth,” says David.

In the end, what has been achieved is simply extraordinary.

The Royal Australian Mint released a special domed commemorative coin to mark Wallal’s centenary. Image credit: Royal Australian Mint

In early September, the 30-person expedition party landed at Eighty Mile Beach, aided by the Royal Australian Navy.

Among the group were 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 members of the astronomer’s family.

“They couldn’t bring a steamer so they took a steamer to tow a two-masted sailboat (Gwendoline) as close to the coast as possible,” says David. “Then when the tide went out the boat ran aground on the sand, but as the tide came in there were a lot of waves.”

Thirty-five tons of supplies and equipment had to be moved from the boat, down to the beach and over a few miles of sand dunes.

The group used rowing boats to transport equipment from the boat to the mudflats. From there, the owners of a nearby cattle ranch provided teams of donkeys, four-wheeled wooden carts and labor to help haul the huge load.

A group of men and a team of donkeys carrying equipment and supplies from Gwendoline down to the beach. Image credit: State Library of Western Australia.

But while a massive achievement in itself, getting everyone and everything to Wallal was only the first phase of the expedition.

After setting up camp, all the equipment had to be assembled on site, after being transported in pieces.

Huge cameras and telescopes needed equally huge supports to hold them in place – requiring towers so tall they needed their own concrete foundations.

But soon these massive structures were completed, wireless communications were established, photographic darkrooms were built, and all the tools and instruments necessary to capture the evidence they needed had been installed, tested, fine-tuned, and ready for use. ‘eclipse.

How was Einstein’s theory of relativity proven?

Photographs taken at Wallal during the total eclipse showed the deflection of starlight.

David explains: “If space is curved, then the concept of a straight line is different – ​​the straight line is curved.

Simply put, light always travels in a straight line, but if space is bent around the Sun (due to the Sun’s gravitational pull), the light emitted by stars will also bend.

Illumination test during the solar eclipse in Wallal. Image credit: State Library of Western Australia

In total, the Wallal Expedition observed 140 stars during the eclipse, and the measured deviation of these stars was extremely accurate, with an error bar of less than one percent.

“Their results were so perfect that they sent a telegram to the Astronomer Royal saying ‘Prediction maintained: no more eclipse expeditions needed!'” says David.

And so, Einstein was right. The Walall expedition had managed to gather strong evidence for his then-controversial theory of relativity.

Astronomers examining the solar eclipse at Wallal. Image credit: State Library of Western Australia

Contribution of indigenous peoples

Walall was not completely uninhabited. At the time 100 The Nyangumarta lived in the area.

In fact, “Wallal” means “fresh water” in the local language.

“In the scientific records, there is hardly any mention of these people,” says David.

“But if you look at the photos, what you see are Aboriginal people in almost all of the photos, especially doing the massive unloading work.”

Other photographs show Aboriginal people helping to erect structures, procuring and transporting stones for foundations, lighting campfires and helping around the camp.

The photographs prove their contribution.

While many of the indigenous people pictured lived in Walall, many others who joined the expedition were workers from the nearby cattle ranch.

A camp photographer also produced a series of portraits of the Nyangumarta people you see them socializing in and kids looking at gear.

“You also see them looking through telescopes and things like that,” David explains.

“In these photos, they look bright, excited and happy to be there.”

Significance for science

Once Einstein’s theory of relativity was accepted as fact, everything scientists thought they knew about space was turned upside down.

Space was curved. It was in four dimensions. It was a deformable medium.

This paved the way for future discoveries like black holes, neutron stars and, more recently, gravitational waves.

“Gravitational waves are ripples in the curvature of space. So once you have the fact that space can bend, it doesn’t seem at all surprising that if it can bend, then it can bend,” David explains.

“We couldn’t even talk about gravitational waves if we still had the idea that space is rigid.

The University of Western Australia is hosting a two-week celebration, marking the centenary of the Wallal Expedition with a series of activities and events.

Uncovering Einstein’s New Universe, a book written by David Blair, Ron Burman and Paul Davies, will also be launched during the centenary celebrations.

Related: A little history of the universe