Teacher background information

For millennia Aboriginal and Torres Strait Islander Peoples have made continuous observations of the night sky, recording the repeated patterns and relationships between celestial bodies to build a wealth of astronomical data. Aboriginal and Torres Strait Islander Peoples’ astronomical knowledges contain useful scientific information that, through the longevity of data collected, connects phenomena in the sky with occurrences and events on Earth. The knowledge accumulated by astronomical observation has long facilitated the prediction of environmental events, and records are preserved and communicated in cultural stories, petroglyphs, stone arrangements and paintings. This elaboration provides students with the opportunity to research how Aboriginal and Torres Strait Islander Peoples’ astronomical knowledges are applied and used to predict events, including tides, weather and seasonal changes.

Aboriginal and Torres Strait Islander Peoples have observed the patterns of the motions of celestial bodies in the sky for many thousands of years. The recurring patterns were, and continue to be, used as a system for many purposes, such as to track time, signify important events and indicate seasonal changes. Aboriginal and Torres Strait Islander Peoples continuous surveillance observed relationships between celestial phenomena and events on Earth. Regular cyclical phenomena involving the sun, moon and Earth have informed many Aboriginal and Torres Strait Islander Peoples’ practices and technologies, such as systems of time keeping and the construction and utilisation of fish traps that are based on tidal events. Not all astronomical events occur in regular cyclical patterns; some can be unexpected and irregular. Unexpected phenomena observed in the sky, such as solar eclipses, moon halos and stellar scintillation, have long been understood by Aboriginal and Torres Strait Islander Peoples to be unique, irregular events. However, the continuous observations of such events over millennia have enabled Aboriginal and Torres Strait Islander Peoples to connect these celestial occurrences with particular events on Earth, such as weather patterns and seasonal changes.

Astronomy is the branch of science that studies celestial objects and phenomena, including the stars, moons, planets and comets, and the effort to understand and explain such objects and phenomena. Astronomy depends on the acquisition of data from observations of astronomical objects; data can be analysed and evaluated to explain celestial objects, events and phenomena, and the connection with, or influence on, events on Earth. For millennia Aboriginal and Torres Strait Islander Peoples’ vast knowledge of celestial objects and events has informed investigations to describe the patterns and relationships of these objects and make predictions about events on Earth.

Tides are the rise and fall of sea levels caused by the gravitational forces of the sun and moon, and Earth’s rotation on its axis. The gravitational force of the moon is strongest at the point of the earth that is directly facing the moon. The effect of this force is seen when the movement of ocean water pulls in the direction of the moon, causing a high tide. Due to Earth’s rotation on its axis and differential gravitational forces, the side of Earth that is farthest away from the moon also experiences a high tide. The two high tides draw water away from other oceans, resulting in two low tides between the high tides. When the sun and moon are directly in line with Earth, that is, at times of a full moon or new moon, the gravitational effects of the sun and moon combine to produce a larger high tide known as a spring tide. As there is a new or full moon approximately every two weeks, spring tides are also seen about every fortnight. When the line from the Earth to the moon is at right angles to the line from the Earth to the sun (known in astronomy as quadrature), the sun negates some of the effect of the gravitational force of the moon resulting in tides lower than usual, or neap tides.

The Yolŋu Peoples of north eastern Arnhem Land have long understood these patterns and have recorded the knowledge connecting tides with phases of the moon in cultural histories. The Dampier Peninsula region of Australia experiences immense tidal variation due to a unique combination of an unusually large continental shelf and a recessed coastline. These factors, combined with the gravitational forces of the moon and sun, amplify the tides and can cause tidal variation of up to 11 metres. The Bardi Peoples of the Dampier Peninsula region of Western Australia have long travelled between islands, using the knowledge of lunar phases and the connection with tides to time the travel with the occurrence of neap tides when passage between the Islands can be safely undertaken. For millennia Bardi Peoples have taken advantage of low tides to access vast intertidal reefs, rock shelves and mudflats. Rich sources of food, cultural and economic resources, such as fish, and pearl and trochus shells, can be found in these areas. Similarly, Torres Strait Islander Peoples use neap tides to access crayfish.

Aboriginal and Torres Strait Islander Peoples’ regular, continuous observations of the position and phase of the moon and the correlation with ocean tides, have long enabled predictions about the time and height of the next tide.  Cyclical patterns of celestial objects and the relationship with events on Earth informed the construction of tidal fish traps. Fish traps are human-made structures, generally constructed from stone, that are positioned in an inter-tidal area. Tasmanian Aboriginal Peoples of the north west coast used boulders to construct tidal fish traps for the regular harvest of fish. At high tide, the walls of the fish traps are submerged, allowing fish to move into the area to feed. As the tide recedes, the water flows out of the structure, leaving the fish trapped in shallow pools within the stone walls. The Tommeginer People understood the timing of low tides and they returned to the traps to harvest the fish at this time.

Tidal fish traps constructed by the Narungga Peoples of the Yorke Peninsula region of South Australia are positioned perpendicular to the shoreline and the direction of tides and currents. In the same area, the Burgiyana fish trap at Point Pearce in this area is constructed within the minimum and maximum tidal range, so that at high tide the walls of the trap are submerged and, as the tide recedes and the water flows out of the structure, fish are trapped and can be harvested. The fish traps on Erub Island in the Torres Strait are constructed from basalt boulders placed in an arc shape over a distance of approximately 200 metres. At high tide the boulders are completely covered by water and when the tide recedes the trapped fish, crabs and other marine animals can be easily harvested. The Erubam Le Peoples of Erub Island have familial responsibility for the fish traps and continue to use and maintain the fish traps today. The regular patterns of the appearance and phases of the moon have long enabled Aboriginal and Torres Strait Islander Peoples to accurately predict tidal stages. The relationship between Earth’s moon and tides has long been observed and the application of knowledge and understanding is evident in the construction of tidal fish traps that provide reliable access to marine resources.

While the relationship between the phase and position of the moon from Earth with ocean tides can be predicted with regularity, other astronomical events can be unexpected and appear only occasionally. Information about such events has long been monitored and recorded by Aboriginal and Torres Strait Islander Peoples, who have used this body of knowledge to correlate astronomical phenomena with incidences on Earth. When ice crystals are suspended in the upper atmosphere, light from the moon is refracted and reflected by the ice crystals. This can result in the appearance of a halo around the moon. Contemporary science recognises that moon halos often precede a low-pressure system that frequently brings rain and cooler temperatures within the next day. Aboriginal Peoples have long understood the relationship between moon halos and weather changes. The Euahlayi and Kamilaroi Peoples of New South Wales have cultural records that connect the appearance of moon halos with rain, and the moon halo signifies to the Peoples of the western desert region that the Moon-man is taking shelter from approaching bad weather.

Stellar scintillation is a term that describes variation in the brightness of stars caused by atmospheric disturbances. It is caused by the passing of light through atmospheric effects, such as changes in air density, temperature, humidity and turbulence. These changes affect the refractive index of incoming starlight resulting in the scintillation effect, or twinkling, that can be observed from Earth. For millennia, Aboriginal and Torres Strait Islander Peoples have observed the scintillation of stars and used the observation to predict changes in weather and seasons. On the island of Mer in the Torres Strait, the beginning of the monsoon season (kuki) is characterised by stormy weather and strong winds. The Miriam Elders predict the onset of this season by the appearance of rapidly twinkling stars. When fishing out on the reefs, Peoples of the Torres Strait also use knowledge of stellar scintillation and the correlation with strong winds to gauge when it is safe to travel back to the islands.  

Aboriginal and Torres Strait Islander Peoples’ continuing astronomical observations over millennia have resulted in an abundance of astronomical knowledge of the patterns and relationships between celestial objects and phenomena and events on Earth. Today, much of this knowledge is now recognised by contemporary astronomers and is being used to inform the field of astronomy. This elaboration provides students with the opportunity to research how Aboriginal and Torres Strait Islander Peoples have used and applied this knowledge in a multitude of ways. For millennia, these astronomical knowledges have been applied to successfully make predictions regarding times to travel, seasonal and weather changes, and when to harvest resources. Students can learn that the astronomical knowledge of Aboriginal and Torres Strait Islander Peoples is interwoven into cultural and social aspects and patterns of life.