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NEWS & VIEWS FROM MUSEUM VICTORIA

Total Lunar Eclipse

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by Tanya
Publish date
2 April 2015
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A total lunar eclipse will be visible from across all Australia this Saturday, April 4. But it will be a quick one. Rather than passing deep into the Earth’s shadow, the moon is skimming close to the shadow’s edge, as seen in this animation.

Total Lunar Eclipse - December 2011 The moon moves out of totality as seen from Sydney during the December 2011 eclipse.
Image: Neerav Bhatt
Source: Neerav Bhatt/flicr
 

The period of totality, when the moon is fully enclosed in the Earth’s umbral shadow, will last just five minutes or so. This makes it the shortest total lunar eclipse of the 21st century.

In fact, this eclipse has the shortest period of totality for almost 500 years. Back in 1529, on October 17, there was an eclipse where totality lasted for just 1 minute and 42 seconds.

The moon's passage through the Earth's shadow The moon skims the edge of the Earth’s umbral shadow. Note: this graphic is oriented for the southern hemisphere.
Source: Museum Victoria
 

How to see it?

The great thing about lunar eclipses is that no special equipment is required to view them. Just look for the moon, which will be visible in the north-eastern sky, weather permitting.

Eclipse timings Local circumstances for the eclipse.
Source: Museum Victoria
 

From Western Australia, the eclipse begins shortly after sunset with the moon low to the eastern horizon. However, by the time of totality the moon will have risen to a great vantage point.

For the rest of Australia, the eclipse occurs an hour or two after sunset.

The whole event will last for three-and-a-half hours – it’s only the moment of totality that will be very short.

Total Lunar Eclipse - April 2014 The moon disappears into shadow during the total lunar eclipse of April 2014.
Image: Phil Hart
Source: Phil Hart
 

Watching the moon slowly enter into the Earth’s shadow is always an amazing sight. And it’s during this partial phase of the eclipse that the shadow appears lovely and dark – seen in sharp contrast to the part of the moon which is still in sunlight.

Because totality is very brief and the moon sits so close to the shadow’s edge, this eclipse will not give us a deep red moon. Instead, we will likely see a variation in tone across the face of the moon.

The southern region of the moon – the topmost part as viewed from Australia – travels deeper through the shadow and should take on a reddish-orange glow. Whereas the northern part (or the bottom of the moon) that skims the shadow’s edge, will remain fairly bright.

Total Lunar Eclipse - October 2014 The moment the moon enters totality during the October 2014 lunar eclipse. A similar variation in colour across the moon is expected for this upcoming eclipse.
Image: Martin George
Source: Martin George
 

Where the shadows lie

What’s interesting to note about this eclipse, is that it’s a great test for eclipse modellers. It’s not surprising, that there is no sharp edge to the Earth’s shadow and therefore the timings of this eclipse are highly dependent on the model used to estimate the shadow’s size.

This was first recorded in the early 18th century when the French astronomer and mathematician Philippe de La Hire realised that to match the timings of a lunar eclipse, it was necessary to increase the predicted radius of the Earth’s shadow by 2.4%.

In fact, observations of lunar eclipses over the next 200 years showed that the size of the Earth’s shadow varied slightly from one eclipse to another.

By the late 19th century a standard value of 2% was adopted as the most effective increase to be made to the Earth’s shadow size to produce the best predictions for an eclipse.

The ‘fuzziness’ of the Earth’s shadow is due to a number of factors such as the sun’s apparent size and the transparency of the Earth’s atmosphere. Eclipse models also have to take into account the fact that the Earth isn’t completely round, but flattened slightly towards the poles. And even the Earth’s axial tilt can add a small variation in the size of the Earth’s shadow depending on what season it is on Earth.

But for most lunar eclipses, these variations have a small effect on the eclipse timings, amounting to differences of the order of 20 seconds or so. But because this eclipse occurs so close to the edge of the Earth’s shadow the model used is much more critical.

Timey wimey

For this article, I’ve sourced the eclipse timings from NASA’s eclipse website maintained by Fred Espanek, a retired astrophysicist from NASA’s Goddard Space Flight Center. His Earth shadow model is the smallest and gives the shortest period of totality at 4 minutes and 38 seconds.

But it’s not surprising that other reputable eclipse models are found to give different results. Australian David Herald is the author of the fantastic Occult program that predicts all types of occultation events (such as the Saturn occultations we saw last year), and it also predicts eclipses. The latest version of his program (Occult4), measures totality for this eclipse as lasting 7 minutes and 14 seconds.

While the longest measurement of totality is sourced from the U. S. Naval Observatory. Their lunar eclipse computer gives a prediction of 12 minutes and 18 seconds.

But what will we see?

What this highlights for me, is the beauty of nature. We can do our best to predict what will happen, but sometimes we just don’t know for certain until we see the event itself. And it’s one of the lovely things about lunar eclipses that each one is unique.

With this eclipse, it is the path through the Earth’s shadow which makes it particularly different. But what can also affect eclipses is how dusty the Earth’s atmosphere is at the time. The dustier the atmosphere the more light is blocked.

That’s when the moon can turn a really deep red, like it did 2011 when the atmosphere was full of ash from the eruption of Chile’s Puyehue-Cordon Cualle volcano.

Even nonlocal weather conditions can affect the appearance of a lunar eclipse. Storm systems and poor weather in the part of the world where the sun ‘disappears’ as seen from the moon, will make the atmosphere less transparent. In particular, if it’s a very deep eclipse and the moon passes right through the centre of the Earth’s shadow, such weather systems can help to deepen the Earth’s shadow so that the eclipsed moon becomes almost impossible to see.

So why not try your hand at timing this eclipse event and see which model gives the best prediction for you?

And while you are watching the eclipse, the star to the right of the moon is called Spica, the brightest star in the constellation of Virgo. While in the east Saturn will be visible at the head of Scorpius and over in the north-west Jupiter can be found shining brightly.

But if the weather doesn’t cooperate in your local area, you can also follow the eclipse via live streaming by Sydney Observatory, Slooh or the Virtual Telescope.

Most importantly, this lunar eclipse is well worth a look because it will be a while before we get the chance to see another. The next lunar eclipse to be seen from Australia is a partial one on August 7, 2017 and only 25% of the Moon’s diameter will be in shadow. The next total lunar eclipse won’t occur until January 31, 2018.

Many thanks to Martin George, Curator of Astronomy and Assistant Director, Queen Victoria Museum, Launceston, for very useful discussions that improved this article.

The Conversation

This article was originally published on The Conversation. Read the original article.

 

Six generations of Satchells

Author
by Kate C
Publish date
1 April 2015
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John Satchell grew up with a colour photograph of a model steam train hanging on his bedroom wall. Not uncommon for small boys, perhaps, but John's train had a direct link to his ingenious ancestors. His train—a perfect, working scale replica of a shunting engine from 1857—was built by his great grandfather, also John, and painted by his great-great grandfather James Satchell. The model train itself, eventually donated to Museum Victoria in 1990, is now on display in The Melbourne Story.

  Steam Locomotive Model Steam Locomotive Model - Hobsons Bay Railway Pier Shunting Engine, No.5. (ST 038379)
Source: Museum Victoria
 

John's father Tony hung the photo for his son and often told him the story of the train. "Dad's a genealogist, and he's researched both sides of the family. He just loves history," says John. "He's always made me more than aware that this train exists and took me to see it in the museum. I loved steam trains as a kid and still do."

With Tony's 80th birthday approaching at the end of March, John and his wife Danielle searched for a unique and meaningful gift for him. They thought of the 1868 photograph of the elder John and James Satchell with their magnificent model, and how they might replicate it with the youngest Satchell, their toddler James. Until young James was born, John explains, genealogist Tony was anxious that "the Satchell family name was running out."

James & John Satchell, 1868 Photograph from 1868 of the Hobson's Bay Railway Pier shunting engine model with modelmaker John Satchell, and his father James Satchell. (ST 037829).
Source: Museum Victoria
 

The Satchells recruited a friend to photograph John and James next to the train's exhibition showcase, but the tricky lighting and reflections meant no success. Danielle wrote a letter to the museum asking if there was any way we could open the showcase so they could get a perfect shot. It was an irresistible opportunity to link six generations of Satchell men, so last week before the museum opened, exhibition and collection management staff brought out the train. MV photographer Jon Augier captured the historic moment.

Child, man and model train Young James Satchell with father John posing with the model train built in the 1860s by their Satchell ancestors. Note the authentic Victorian-era gravitas.
Image: Jon Augier
Source: Museum Victoria
 

The senior John and James both worked at Melbourne's first foundry, Langlands, originally established on Flinders lane. John was an apprentice there in the 1860s when he built the model, and his father James was a foreman. The model earned John a medal at the Intercolonial Exhibition of Victoria in 1866, and later, when he sold it, enough money to buy a block of land in Caulfield. The story is recorded in the Satchell family history written by Tony Satchell in 1988.

The surprise birthday gift is sure to delight this family historian. It might continue another family tradition, too. Says John of Tony, "he's brought up a couple of times that he thinks James should have a picture of the steam train in his bedroom. I've been saying 'oh yeah, that's a good idea' but leaving it at that because I don't want Dad to start thinking of getting a picture… it could ruin the surprise!"

Museum Victoria wishes Tony a very happy 80th birthday.

Satchell family The whole family: James Satchell with his mum Danielle and father John.
Image: Jon Augier
Source: Museum Victoria
 

Multilingual Museum Tour launch

Author
by Jen Brook
Publish date
26 March 2015
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Jen manages Humanities programs at Museum Victoria.

To celebrate Cultural Diversity Week, last Friday we proudly launched the Immigration Museum’s Multilingual Museum Tour. This free downloadable app, made in partnership with SBS, is your personal tour of the museum in six languages: Arabic, French, Italian, Japanese and Mandarin and English. The tour features detailed text, audio commentary and stunning historical imagery that reveal the stories of the people, businesses and architecture that have transformed Melbourne and Victoria.

Four people at tour app launch Immigration Museum Manager Padmini Sebastian and MV CEO Dr J Patrick Greene (far right) with launch guests Mr Peter Khalil and Hon Robin Scott MP.
Image: Jon Augier
Source: Museum Victoria
 

The tour was launched by Hon Robin Scott, Minister for Multicultural Affairs, who addressed a crowd of special guests including representatives from the Victorian Multicultural Commission, City of Melbourne, Melbourne Visitors Centre, the Yulgilbar Foundation, Multicultural Arts Victoria and AMES. We also had had the Consulate Generals of Spain, Italy, and France and our project partners SBS. The Minister spoke of the importance in recognising Melbourne as a successful, contemporary multilingual society and the significance of the Immigration Museum as a place to celebrate Victoria’s multiculturalism. Cultural Diversity Week is one of Victoria’s largest multicultural celebrations and, like the Immigration Museum, provides an opportunity for all Victorians to come together to share their culture, faith and language.

Guests at the launch of the tour app Guests at the Immigration Museum to launch the Multilingual Museum Tour.
Image: Jon Augier
Source: Museum Victoria
 

The museum is proud and delighted to have partnered with SBS for this project, an organisation at the forefront of celebrating multicultural Australia, providing high quality, independent, culturally-relevant media to all Australians regardless of geography, age, cultural background or language skills. SBS’s talented radio presenters are the voices behind the Arabic, Italian, Japanese, French and Mandarin guides. The English guide is presented by Immigration Museum Manager Padmini Sebastian.

Six presenters of the app Presenters of the Multilingual Museum Tour app:
MANDARIN: Liu Jiang, SBS Radio
ARABIC: Iman Riman, SBS Radio
ITALIAN: Carlo Oreglia, SBS Radio
FRENCH: Christophe Mallet, SBS Radio
ENGLISH: Padmini Sebastian, Manager Immigration Museum
JAPANESE Miyuki Watanabe SBS Radio
Source: Museum Victoria / SBS
 

The Immigration Museum’s Multilingual Museum Tour builds on the technology initiatives and programs that Museum Victoria has been developing in recent years which assist in increasing audience access to our museums and collections. These include Melbourne’s Golden Mile, Spotswood Industrial Heritage and Carlton Gardens walking tour apps, as well as the Field Guide to Victorian Fauna app, which has been downloaded over 100,000 times,

Guests at the Multilingual Museum Tour launch. Guests at the Multilingual Museum Tour launch.
Image: Jon Augier
Source: Museum Victoria
 

You can download the app free to your own Apple and Android device before your visit, or ask to borrow one of our devices from the Immigration Museum ticketing desk.

Transcribing field diaries

Author
by Nicole K
Publish date
19 March 2015
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Deep in Museum Victoria’s archives lie boxes of notebooks. Notebooks that contain a significant part of our museum’s history. They are the field diaries of our past curators and collection managers, produced on scientific expeditions to explore, research and discover the natural history of Australia (and beyond).

Field diaries from Museum Victoria's collection Field diaries from Museum Victoria's collection
Source: Museum Victoria
 

These field diaries are of great interest to both scientists and historians. They are filled with invaluable data, providing insights into past species’ abundance and distribution, as well as personal descriptions of the trials and wonders experienced on historic expeditions.

A photograph from Graham Brown's field diary: Mt Rufus, Tasmania (1949). A photograph from Graham Brown's field diary: Mt Rufus, Tasmania (1949).
Image: Graham Brown
Source: Museum Victoria
 

Despite the fascinating information contained within the diaries (and the interest in them), they are relatively inaccessible. They were handwritten, often in less-than-favourable conditions (picture a scientist, crouched in the bush, notebook balanced on knee).

Sketch from Allan McEvey's field journal of his expedition to Macquarie Island, 1957. Excerpt from Allan McEvey's field journal of his expedition to Macquarie Island, 1957.
Image: Allan McEvey
Source: Museum Victoria
 

We have therefore started a crowd-sourcing project to transcribe the field diaries in our collection. The pages of each diary are carefully digitised and then uploaded into DigiVol the Atlas of Living Australia’s volunteer transcription portal that was developed in collaboration with the Australian Museum. Once transcribed, the text in the diaries will be searchable. We can create lists of the species mentioned and use this information to better understand and conserve our precious biodiversity.

Our most recent transcription project is Allan McEvey's field diary of his expedition to Macquarie Island in 1957. Museum Victoria's Curator of Birds from 1955, McEvey had a passion for scientific illustration and his field diaries are filled with sketches of birds and other wildlife.

Sketches of Black-browed Albatross, <i>Diomedea melanophris</i>, from Allan McEvey's field journal of his expedition to Macquarie Island, 1957. Sketches of Black-browed Albatross, Diomedea melanophris, from Allan McEvey's field journal of his expedition to Macquarie Island, 1957.
Image: Allan McEvey
Source: Museum Victoria
 

The original diaries, along with their transcriptions, will eventually be available online via the Biodiversity Heritage Library (BHL), the world's largest online repository of biodiversity literature and archival materials.

The Australian component of BHL is managed by Museum Victoria and funded by the Atlas of Living Australia. The project has allowed us to digitise over 500 rare books, historic journals and archival field diaries. This represents over 12000 pages of Australia’s biological heritage that was previously hidden away in library archives.

Interested in becoming a transcription volunteer?

If you would like to help us unlock the observations in our historic field diaries, more information is available on the DigiVol website.

Dawn reaches Ceres

Author
by Tanya Hill
Publish date
5 March 2015
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When NASA’s Dawn spacecraft is captured into orbit around the dwarf planet Ceres on Friday, March 6, there will be no fanfare in mission control. In fact, the spacecraft won’t even be in radio contact. There’s no need, because Dawn’s path is set – this is a spacecraft unlike any other.

What makes Dawn unique is its ion propulsion system, which gives the spacecraft incredible manoeuvrability. Instead of using large bursts of thrust to get where it’s going, Dawn takes the slow and steady approach. Its ion engine delivers a tiny but continuous thrust that can last for days or weeks at a time.

Over the last two-and-a-half years, Dawn has been slowly reshaping its trajectory to bring it near Ceres and, most importantly, to match the dwarf planet’s speed – Ceres travels around the sun at nearly 64,000 kilometres per hour.

For other planetary missions, entering orbit is make or break. It’s an intense moment that hopefully ends in jubilant celebration when all goes as planned and the spacecraft momentously falls into orbit. But Dawn’s slow approach means that it is now right on course to guarantee capture by Ceres’ gravity.

Dawn is captured by Ceres' gravity The spacecraft’s approach trajectory with the white circles spaced at intervals of one day. This indicates the spacecraft’s speed – the closer the circles, the more slowly Dawn is moving.
Source: NASA/JPL
 

Come Friday, if the spacecraft’s propulsion were to be switched off it would remain under Ceres’ influence but would travel around the dwarf planet in a highly elliptical orbit. So over the next few weeks, Dawn will use its ion thrusters, together with Ceres’ gravity, to slowly draw it into a circular orbit – the first of four such orbital positions around the dwarf planet.

Not for the first time

Ceres is the second object that Dawn has orbited. Between July 2011 and September 2012, Dawn was in orbit around Vesta, which, like Ceres, resides in the asteroid belt located between Mars and Jupiter.

This marks the first time that one spacecraft has been able to orbit two different planetary objects. And it’s only possible because of Dawn’s ion engine.

A spacecraft powered in the usual way, using chemical propellant, would require ridiculous amounts of fuel to carry out such a mission. And even if it was possible for a spacecraft to carry that much fuel on-board, the cost of the mission would be astronomical.

Dawn's path to Ceres Dawn was launched in September 2007 and has taken the slow and steady approach to visit Vesta and now Ceres.
Source: NASA/JPL
 

At Ceres, Dawn will eventually travel in a polar orbit, travelling above the north and south poles. As it moves from north to south it will travel over the daytime side of the planet, and then during the second half of its orbit it will fly above Ceres' night side.

In its first orbital position, at a height of 13,500km, it will take 15 days for Dawn to complete one orbit. Since the planet takes only nine hours to rotate on its axis, this will allow Dawn to make a good map of the dwarf planet’s surface.

Throughout its 15-month mission, Dawn will vary its orbit three times, each one descending closer to the planet at heights of 4,400 km, 1,470 km and 375 km. To change orbits it will move through a complex series of spiral trajectories.

The descent to its lowest orbit will take two months and, during that time, Dawn will complete 160 revolutions as it constantly reorientates itself to ensure that one of its ion beams is thrusting in the right direction to continue its slow spiral descent.

Dawn's spiral descent Two months of downward spirals are needed to move Dawn into its lowest orbit - from the High Altitude Mapping Orbit (HAMO) to the Low Altitude Mapping Orbit (LAMO).
Source: NASA/JPL
 

Better than Star Wars

Ion propulsion systems, like the one that powers the Dawn spacecraft, have long been considered the next big thing for space exploration. In fact, they seemed so futuristic that they appeared in the Star Wars movies, powering Darth Vader’s TIE fighters or Twin Ion Engine fighters.

Science fiction to science fact The TIE fighters in Star Wars had twin ion engines, but Dawn does one better, with three ion engines.
Source: NASA/JPL
 

Ion engines were first used by NASA on Deep Space 1, which flew past the asteroid 9969 Braille in 1999 and comet Borrelly in 2001.

The Japanese Aerospace Exploration Agency (JAXA) has successfully used ion engines on its Hayabusa asteroid missions, the second of which was launched in December last year.

The Dawn spacecraft is fitted with three ion engines, although only one engine is used at any one time. And true to what we expect from science fiction, the spacecraft does emit a blue-green glow. This is a result of its xenon fuel.

The inner workings of an ion propulsion system. The inner workings of an ion propulsion system.
Source: NASA
 

Positively-charged xenon ions pass through two electrically charged grids. This accelerates the tiny ions and they shoot out of the engine at 144,000 kilometres per hour, providing the thrust to propel the spacecraft in the opposite direction.

Ion engines are around ten times more efficient than chemical rockets because the ions are ejected at roughly ten times the speed that a propellant is expelled by a rocket. The acceleration, however, is much slower.

It would take Dawn around four days to accelerate from 0 to 100 kilometres per hour but the trade off is that in doing so, it would only use 450grams (or just one pound) of fuel.

Why Vesta and Ceres?

Of course, the reason the technology is so marvellous is because it enables such fantastic science – the exploration of the two most massive objects in the asteroid belt, Ceres and Vesta.

The dwarf planet Ceres New images of Ceres, taken February 19 at a distance of 46,000km, show a mysterious double bright spot.
Source: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
 

Don’t let their location fool you – these are not space rocks like typical asteroids. They are big worlds and, like Earth and the other terrestrial planets, Ceres and Vesta have a layered structure.

Vesta has an iron-rich core, a silicate mantle and a crust made of basalt. While Ceres is thought to have a rocky core, an ice mantle and a dusty surface.

The ice mantle is particularly interesting. It’s thought that around 30% of Ceres’ mass may come from water and potentially some fraction of that could be liquid water. Just last year, the Herschel Space Observatory made detections of what appear to be plumes of water vapour escaping from slightly warmer regions on Ceres.

The Dawn mission will continue until June 2016 and the latest images will be regularly posted here, while the Dawn mission blog is a great way to keep up-to-date on everything that happens.

Dawn of the Solar System

The space mission was called Dawn because if we think of Ceres and Vesta as protoplanets, then by better understanding these objects, we will gain insight into the early history of our solar system.

Vesta and Ceres size comparisons Ceres and Vesta more closely reflect half-formed planets than space rocks like asteroids.
Source: NASA
 

The planets of our solar system formed by a method of accretion. Starting out as specks of dust that collided and stuck together, they then grew bigger and formed rocks until eventually they were large enough to draw in enough material to form planets.

Vesta and Ceres seemed to have halted mid-way through this process. This is most likely due to the formation of Jupiter. Its gravity may have prevented objects in the asteroid belt from coming together to finish off the planet building.

As a result, Vesta and Ceres provide a unique opportunity for understanding the early formation of the planets, because they came so close to becoming planets themselves.

The early solar system The early solar system was born out of a dusty disc encircling the sun.
Source: William Hartmann. Courtesy of UCLA
 

The ConversationThis article was originally published on The Conversation. Read the original article.

MV's new digital exhibits

Author
by Nicole K
Publish date
5 March 2015
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On Tuesday 3 March, Museum Victoria joined 25 Australian cultural institutions at Parliament House to launch the Australian component of the Google Cultural Institute.

Google Cultural Institute launch, 3 March 2015, Parliament House, Canberra Google Cultural Institute launch, 3 March 2015, Parliament House, Canberra
Image: Nicole Kearney
Source: Museum Victoria
 

The Google Cultural Institute is an online collection of millions of cultural treasures from over 670 museums, art galleries and archives around the world. Visitors can explore millions of artworks and artefacts in extraordinary detail, create their own galleries and share their favourite works.

Museum Victoria has been involved in the Google Art project since 2011 and was among the first institutions to partner with Google to create what is now the world's largest online museum.

Featured content on the Google Cultural Institute Featured content on the Google Cultural Institute
Source: Google
 

Tuesday's launch welcomed 14 new Australian contributors, including the Australian War Memorial, the National Portrait Gallery and the Australian Centre for the Moving Image. Over 2000 of Australia's finest cultural works are now accessible online.

Among these treasures are 226 highlights from Museum Victoria's collection. These include Aboriginal bark paintings, photographs depicting early Victorian history, and scientific illustrations that trace the development of scientific art.

In order to tell the fascinating stories behind these collection items, we have created three digital exhibitions within the Google Cultural Institute:

The Art of Science: from Rumphius to Gould (1700-1850)

The Art of Science exhibit The Art of Science exhibit
Source: Museum Victoria
 

Scientific Art in Victoria (1850-1900)

Scientific Art in Victoria exhibit Scientific Art in Victoria exhibit
Source: Museum Victoria
 

A.J. Campbell (1880-1930)

A.J. Campbell exhibit A.J. Campbell exhibit
Source: Museum Victoria
 

These exhibits include stunning photographs and illustrations, curator-narrated videos and in-depth information.

Many of these illustrations come from rare books preserved in our library and, in many cases, accompany the first published descriptions of our unique Australian fauna. The books are available online in their entirety in the Biodiversity Heritage Library, a project funded in Australia by the Atlas of Living Australia.

About this blog

Updates on what's happening at Melbourne Museum, the Immigration Museum, Scienceworks, the Royal Exhibition Building, and beyond.

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