Hello from Sydney! Welcome to my blog that will cover physics and issues affecting physicists, with an Antipodean slant.
I’m a rare breed: a medical physicist turned science writer. In my clinical career I’ve done everything from plan complex radiation therapy treatments to decontaminate radioactive toilets. I arrived in the harbour city seven years ago after completing a PhD in ultrasound imaging in Edinburgh. For my first post I’ve been keeping my eyes peeled for something with a distinctly Australian flavour for you.
Living here, it would be hard not to have noticed the hive of activity that is the astronomy community. Interviewing Nobel Laureate Brian Schmidt last year for Physics Worldmagazine, he told me that now is “the best time it’s ever been for Australian astronomy”.
The current boom includes the Murchison Radio-astronomy Observatory in outback Western Australia that opened last October. The observatory is home to the Australian Square Kilometre Array Pathfinder (ASKAP) and the Murchison Widefield Array. Each of these Square Kilometre Array precursor telescopes have an ambitious array of projects and have already started acquiring data.
But during the opening of the ASKAP it was talk of much earlier astronomical observations that piqued my interest.
Godfrey Simpson, along with other members of the local Aboriginal Wajarri community, named each of the ASKAP antennas. Before they did, Simpson talked about the detailed knowledge that his people have of the night sky. This knowledge has enabled them to navigate at night and has provided a calendar, marking dates for ceremonies and the hunting and harvesting of different forms of bushtucker.
“Were we the first astronomers?” Simpson asked. It’s an exciting thought that the Wajarri people and other first Australians could have been practising a form of astronomy for the tens of thousands of years they’ve been in the country.
Ray Norris is a radio astronomer with the CSIRO – the Australian Government research organisation – and has been investigating the question since 2006, outside of his day job as principal investigator on the Evolutionary Map of the Universe – or EMU – survey project at ASKAP. The project name is a nod to his extracurricular research: the aboriginal emu-in-the-sky constellation is formed from the dark dust clouds (rather than the stars that form Western constellations) across the disc of the Milky Way. Norris admits to being sceptical at first but was “astounded” by what he subsequently found. “There’s very good evidence that [Aboriginal] people really were trying to understand how the sky works,” says Norris.
As a physicist, Norris’ approach has been to apply the scientific method to his investigations, using evidence that has included accounts from Aboriginal communities to test various hypotheses about the indigenous understanding of the sky. It’s an unusual approach as far as anthropology research goes, which Norris has found doesn’t commonly use impartial hypothesis testing, instead presenting evidence that supports a particular viewpoint. He laughs when he mentions the bemused responses he’s had from some of the humanities journals that he’s submitted papers to.
One of several investigations focused on the Yolngu people’s understanding of the tides. The Yolngu (pronounced Yoll-knew) live in Arnhem Land, a remote region east of Darwin in the Northern Territory. Over a series of meetings, elders told Norris how for some (unknown) time they’ve recognised that the moon was inextricably linked to the tides.
The Yolngu correctly observed that the heights of the tides vary over the month with the lunar cycle. They also recognise that the tide rises and falls on their coastline twice a day, in step with the position of the moon in the sky. Their explanation is quite different from the physical explanation, but consistent with their observations. They believe that the height of the tides varies in-step with the filling and emptying of the moon with seawater, where the full moon is full of water and the new moon is empty.
“In their cultural context it was a perfectly reasonable hypothesis that correctly predicted their observations,” says Ray.
Frustratingly, there’s no way of knowing how long since the Yolngu made this connection as such knowledge is not documented in Aboriginal culture. Norris and other researchers speculate that the explanation has been passed down for thousands of years, like many other oral traditions are thought to have been.
This could see the Yolngu matching or even preceding the Romans and the ancient Greeks in their thinking. It’s also possible that they had already made the connection when Galileo was dismissing the moon’s influence as mystical nonsense. Ultimately, though, researchers haven’t yet been able to date the knowledge.
Norris and his colleagues have investigated several other Aboriginal accounts of the sky, including similar cultural explanations of lunar and solar eclipses that demonstrate an understanding of the required alignment of the sun, Earth and moon for both. More studies are in the pipeline.
Back at the Murchison Observatory , it would be fair to ask why the local Wajarri community should accept the intrusion of a radio observatory on their lands, close to their sacred sites. In fact, the Wajurri community have welcomed the new observatory with open arms, in part as it continues a tradition of astronomy in the area. “It’s part of their culture to look at the sky and try to figure it out,” says Norris. And so a long tradition of astronomy in Australia continues…
Image: Emu in the Sky. Credit: Barnaby Norris