Ireland has opened a new antenna station as part of the €150m Europe-wide Low Frequency Radio Array (LOFAR). The addition of the Irish station, which is located at Birr Castle Estate in County Offaly and operated by Trinity College Dublin, means that the LOFAR network now stretches 2000 km across increasing the telescope’s sensitivity.
The telescope was switched on by John Halligan, Ireland’s minister for training, skills, innovation, research and development. “Membership of LOFAR affords a unique opportunity for research and engagement to young people across the country with astronomy and science in general,” says Halligan. “As minister, it is my distinct pleasure to be here to celebrate the achievement of such a wide section of the Irish scientific community.”
Fifty-one antenna stations
LOFAR is being developed by a consortium led by ASTRON, the Netherlands Institute for Radio Astronomy. It consists of 51 antenna stations, 38 of which are in the Netherlands with six in Germany, three in Poland and one in England, Ireland, France and Sweden.
The telescope operates between 10–240 MHz, allowing scientists to look back to the formation of the first stars, scan the skies for rare transient phenomena and study high-energy cosmic rays.
“Thanks to the new LOFAR station in Ireland, we can observe the universe in even more detail. For example, we can look more closely at objects near and far, from our Sun to black holes, magnetic fields, and the emergence of galaxies in the early universe,” says LOFAR director Rene Vermeulen. “These are important areas of research for astronomers in the Netherlands and partner countries.”
Rising costs have forced scientists to cut back plans for the world’s largest radio telescope, known as the Square Kilometre Array (SKA). The project’s first phase will now contain fewer antennas spread over a smaller area with poorer frequency coverage than was envisaged two years ago. Even though representatives of the 10 countries funding the SKA are confident that the observatory will “deliver transformational science capabilities”, astronomers are nonetheless worried about the impact of a far more compact set of antennas in Australia.
As its name suggests, the SKA will ultimately consist of antennas with a combined collecting area of 1 km2. Its full design calls for thousands of mid-frequency radio dishes spread out across southern Africa and a million low-frequency dipole antennas distributed throughout Australasia. But with a likely price tag of several billion Euros, the partner countries – currently Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, the Netherlands and the UK – are initially building a slimmed-down version known as SKA1.
However, even SKA1 is proving a headache. A first incarnation, consisting of 250 dishes in Africa and about 250,000 antennas in Australia, was proposed in 2013 in response to a cost cap of €674m (in 2016 prices) imposed by the partner countries. Yet a subsequent increase in the estimated cost meant that the proposal had to be scaled back two years later. Now, following a further price rise of about €150m, plans have had to be pared back further still.
Deployment baseline
At a meeting held in the Netherlands on 18–19 July, the SKA council approved a “deployment baseline” drawn up by the project’s management. Compared to the design laid out in 2015, this involves reducing the number of African dishes by three to 130 and spreading those dishes out over just 120 km – as opposed to 150 km. It also halves the number of dishes that are sensitive to all three of the frequency bands foreseen at this stage of the project and reduces equipment used to observe pulsars. The cutbacks also involve slashing computing power by more than 80% with the idea that the shortfall can be made up when processors are cheaper.
Heino Falcke, a radio astronomer at Radboud University in Nijmegen, the Netherlands, says he is “surprised in a positive sense” with what he describes as “fairly modest” changes. He is, however, worried by cuts to the Australian portion of the project. These involve reducing the number of antenna stations from 512 to 476 and squeezing those stations along a “baseline” of 40 km rather than 65 km. Doing so, he explains, might impede astronomers’ ability to remove foreground radio noise when measuring hydrogen emission from the universe’s “dark age” shortly after the Big Bang – one of the SKA’s headline aims. “I hope it would still be possible,” he says, “but the change adds uncertainty.”
According to Philip Diamond, director-general of the SKA Organisation based at Jodrell Bank in the UK, astronomers advising on the cuts had initially said that 40 km would probably be enough, but that after doing additional modelling of the telescope’s likely performance they became “a little bit concerned” about the shortening. “They haven’t finished those simulations yet, but they raised their hands and said they are not sure about this,” he says.
Approval needed
Diamond says that the Australian baseline could be extended back to 50 km at a cost of about €14m, which, he suggests, could be made available if just one of seven possible new partner countries joins the project. As things stand, the existing members have yet to formally approve funding, but Diamond expects them to do so in the first half of 2019, following the setting up of an intergovernmental organization to oversee the project. Construction should then start a few months later and take around five years to complete.
Although the full SKA remains on the back burner for the moment, Diamond is heartened by council’s approval of the reformulated SKA1. “I have always known that [realising the SKA] would be tough,” he says, “but I felt quite buoyant after the meeting.”
On accepting the Institute of Physics (IOP) President’s Medal at the International Conference on Women in Physics (ICWiP), Dame Jocelyn Bell Burnell closed with Laurel Thatcher Ulrich’s infamous quote – “Well-behaved women seldom make history.” And what does she say is the least well-behaved thing she’s done during her scientific career? Become a working mother. Jocelyn battled with stereotyping and bias because she was a woman in a male-dominated field who also dared to have a family and career. She persevered and refused to back down, going on to become an award-winning scientist, Fellow of the Royal Academy and Dame Commander of the Order of the British Empire (keep an eye out for a feature on Jocelyn Bell Burnell in Physics World later this year). Bell Burnell’s story was one of many awe-inspiring tales of ground-breaking women at ICWiP last week, which was held at the University of Birmingham in the UK – and here are some whose stories were too good to keep to myself.
Dame Athene Donald is a trailblazer. The first woman to be professor in a UK university and master of a Cambridge college, she has never been afraid to ruffle feathers or say what she thinks. She is an important member of more committees, assessment panels and boards than most academic departments combined, but still finds time to visit schools. And when she does, she challenges what they think: that physics is the Large Hadron Collidor at CERN and…men.
Donald is humble, observant and inquisitive – characteristics that have contributed to making her one of the world’s finest scientists and communicators. But the road hasn’t always been easy and the most difficult time in Donald’s life was mid-career. From the outside, it looked like she had made it, which is when the professional jealousy of others started to kick in. She was frequently the only woman on committees, where she was ignored, and she felt her research group was suffering from the lack of resources she could pull in. But Athene was not going to give up, instead creating a network of mentors and supporters and channelling anger into gender work. Donald was made the gender champion of Cambridge, which holds the only Athena Swan gold award for a physics department in the country. She began initiatives to support women returning from maternity leave, offered CV advice and frameworks for promotion, ran workshops on confidence and impostor syndrome, and helped postgrads with career advice. But with great power came great responsibility – from broadcast to print media, everyone wants Donald’s comment. Today, she advises everybody, from academia to pre-19 education and even parliament and the hardest part is learning to say no to other people’s requests.
There were several things in Donald’s lecture at ICWiP that particularly resonated with me. Other than a short time in the US, Athene has never left Cambridge. It was here she completed her undergraduate, PhD, first lectureship, first readership, first professorship. Here she became Fellow of the Royal Society and Dame. There is ongoing dialogue in academia that you should move across the country and world to gain an “international reputation” and improve your academic status. Her commitment to her husband, children and parents demonstrates that being successful is not “either/or”.
The Institute of Physics’ president-elect, chemical engineer Dame Julia Higgins was instrumental in establishing the Athena Swan (Scientific Women’s Academic Network) charter in 1999. She began her quest for diversity in the 1990s, “I had always assumed that if I looked over my shoulder there would be more following up behind, but there weren’t.” She was the first woman to become both a Fellow of the Royal Society and of the Royal Academy of Engineering. When Higgins became a professor of polymer science at Imperial College, London, she doubled the number of women at that level. Over her career she has seen the ratio change – there are now more than 50 female professors at Imperial – but she’s still not happy with it. “When we set up the Athena Project, we called it a project because we intended it to be time-limited. There is still a great deal to do.” If you’re interested in Higgins’ research, listen to her on the BBC radio show Life Scientific.
Gabriela González is part of the 1000-person team that detected gravitational waves. In fact, she’s a pretty important part. González is a professor of physics and astronomy at Louisiana State University in the US and the former spokesperson of the LIGO Scientific Collaboration. Her plenary talk at ICWiP was a whistlestop tour into general relativity; starting in a Swiss patent office and ending in a €400m space antenna. González began her career trying to detect gravitational waves from the orbiting neutron stars first observed by Bell-Burnell; an undertaking so complicated even Einstein said it would never be done. They were so determined to detect gravitational waves that her team designed the Laser Interferometer Gravitational-Wave Observatory (LIGO) using technology that hadn’t been invented, with absolute confidence that the scientific community would catch them up. Gradually they pushed the sensitivity of their system further, resolving astrophysical events deeper into outer space. As they tweaked and tested, the physics community was in total suspense – then came challenges to LIGO’s suspension. For statistical certainty, they would need less noise and more light… “Sounds simple right? Well, it’s not very simple – and it’s quite expensive.” The build-up to turning on the detector took over Gabriela’s life: “I was so stressed about preparing for this. I would dream about protocol and analysis – watching out for lightning bolts, reading about earthquakes.”
She wasn’t only concerned whether the accuracy would be good enough – she wanted her team to be good enough too. When you see a page of logos or an author list, it is easy to forget that behind them there are real people living complicated lives. Having such a large team of people from different cultures also makes it easy for bad behaviour to slip under the radar. Gabriela ensured there was an anti-harassment initiative for the LIGO Scientific Collaboration and the Virgo Collaboration (read more here: LVC Allies), along with an active diversity committee that offered training and support. The coalescence of binary black holes detected on 14 September 2015 was the first notes that we have heard of gravity’s symphony. “It has been very exciting, but it’s going to be even more exciting.”
It was difficult to work out how the organizers of ICWiP could make the event even more inspiring following such trailblazers. Enter Nobel laureate Malala Yousafzai.
Star struck: Malala Yousafzai made a surprise appearance at ICWiP. (Courtesy: Jess Wade)
Malala finished her A-levels two weeks ago and from there she jumped on a plane (technically 10 planes) to tour the world on a “Girl Power Trip” with the Malala Fund. So far, she’s had lunch with Justin Trudeau, spent her birthday in Iraq with girls who lived in ISIS captivity, and visited Nigeria, which has the highest number of out-of-school girls in the world. By the end of the adventure, she will have spoken in Africa, North America, the Middle East, Latin America and Europe. And, thanks to the efforts of the Pakistani team, Malala found herself in a conference hall in Birmingham, speaking to 200 excitable physicists. Despite enjoying it when she lived in Pakistan, Malala didn’t study physics at A-level. Next year she will be studying PPE at the University of Oxford (I am sure she could already teach the course, but I’m also keen for her to be prime minister one day, and this degree seems mandatory). She recognizes the need to get more girls into physics, and agrees with much of the IOP’s Improving Gender Balance report. This is an issue for schools, parents and communities to solve. She was graceful, considerate and engaging and she didn’t only talk about her Nobel-prize-winning mission but listened to ours.
So how will we overcome the gender imbalance in physics? For that I turn again to Higgins: “The best thing that I could do for women in science was to be one and to be successful.”
Eclipse America is a one-stop shop for everything concerning next month’s total solar eclipse in the US, as its 70-mile-wide shadow tracks it way from Oregon in the west to South Carolina in the east on Monday 21 August 2017. The event will be witnessed by approximately 12 million people during the late morning through to the mid-afternoon as it passes across this vast country. The website includes a detailed map that illustrates the path of totality, and the best possible locations from which to view the total eclipse. It also shows the degree of partial eclipse visible to the north and south of the Sun’s path (there will be a partial eclipse visible from north-west Europe) and includes advice and information to help viewers enjoy the eclipse safely. The site gives a concise and user-friendly overview of the phenomenon, explaining how this rare and spectacular event will one day no longer be witnessed on Earth, as the Moon moves further away and its apparent size shrinks over time.
Who is behind it?
The Eclipse America website is hosted and run by the American Astronomical Society (AAS) whose large membership is made up of physicists, mathematicians, geologists and engineers with an interest in contemporary astronomy. The society aims to enhance people’s understanding of the universe and advance physical sciences for the benefit of all.
What are some of the topics covered?
Eye safety forms a large section of the website, with a short video and several pages advising viewers how to protect their eyes while viewing the eclipse. The site advocates using eclipse shades or a solar filter on specialist equipment, while also offering advice on how to verify that equipment is safe and complies with ISO12312-2 standards. It also suggests other methods via which the event can be enjoyed and viewed safely such as pinhole projection and instructions on how to make a sun funnel. Guides for educators and community leaders are included in the downloads section along with links to articles about eye care. The Solar Eclipse Experience page provides a detailed account and associated images of a solar eclipse, from “first contact” through every stage until the Sun re-emerges. There is also a helpful glossary that explains eclipse terminology, as well as a description of what to expect when weather conditions are cloudy. A handy resources page forms a collection of further reading, advice, maps and images as well as recommendations of the most up-to-date apps and software.
Who is it aimed at?
As a total solar eclipse is a relatively rare event, the spectacle will undoubtedly generate a lot of public interest. Eclipse America has wide appeal and is aimed at anyone with an interest in witnessing this “cosmic coincidence”, from dedicated eclipse chasers keen to record the event, to educators, community leaders and children. For budding or professional photographers, a section advises how to capture the perfect solar eclipse image or video and also provides valuable advice on copyright and accreditation. The educational materials and videos page are conveniently grouped in age-related collections, which make the resources easily accessible by teachers, lecturers and outreach providers.
How can I take part?
The website encourages people to get involved in various ways, from downloading the instructions to make a sun funnel or becoming a citizen-scientist by signing up to one of the Citizen Science Projects. If you’re in the US, you can search for an eclipse-related event taking place near you by using an interactive map or contacting the AAS to have your lecture, presentation or conference included on the website.
Can you give me a sample quote?
So what is so special about a solar eclipse? More of an experience than an event, the Eclipse America website describes it as “hauntingly beautiful and, without doubt, one of the most awesome sights in all of nature”. And the following description sufficiently raises expectations: “At the beginning and end of totality, the thin middle layer of the Sun’s atmosphere, the chromosphere, blazes in an arc of ruby red. The sky darkens to a deep twilight blue, with yellow, orange, and pink sunrise/sunset colours on the horizon in all directions. Bright stars and planets shine forth, and the air temperature drops noticeably. Birds and farm animals, thinking dusk has settled, return to their nests and barns, and bats come out to feed.” If that doesn’t sell it, then nothing will.
Great myth: Matt Brown debunks science myths, such as that the Great Wall of China is visible from the Moon – it is, but only with a telescope. (Courtesy: iStock/SteveAllenPhoto)
Everything You Know About Science is Wrong – this is the bold claim made by science writer Matt Brown, and it’s also the title of his latest book. Despite its somewhat click-baitey nature, the book’s title is compelling enough to make anyone pick it up and have a look, if only to decide whether you agree with the loaded assertion or not. But don’t let the title fool you, this book is full of extremely accurate science, and what Brown aims to do is bust common science myths that masquerade as facts. “The world is full of pseudoscience – ideas that sound plausible and scientific, but are ultimately worthless. Whole industries are built on the credulity of a trusting public,” writes Brown.
The book is divided into eight sections – science and scientists in pop culture, astronomy, physics, chemistry, biology, geology, the human body and famous scientists. Brown tackles archetypal myths such as the Great Wall of China being the only man-made object visible from the Moon (it’s not, unless you take along a telescope), or that nothing can travel faster than light (this is true only for light in a vacuum that is not interacting with anything else) or that water is a good conductor of electricity (pure water isn’t…it’s the impurities in tap or sea water that act as conductors).
Although this is a book full of nit-picking, I thought that Brown did admirably well to avoid the I-think-you’ll-find tone that would likely annoy readers. Instead, he comes across as enthusiastic and whimsical, while also being glib and funny. Take the chapter on faster-than-light travel: after talking about quantum entanglement (and the instantaneous transfer of information), he ends by pointing out that the British royal family does not seem to obey the laws of relativity given that the transfer of title for a monarch at the death of a previous one is instantaneous. Brown describes a paradoxical scenario where a future monarch dies on Mars and the heir (assumed to still be on Earth) immediately becomes the new king or queen, despite the fact that they won’t know it for the 20 minutes or so it would take for the message to be sent from Mars.
While the science is simple and light, the book is an enjoyable read, particularly the “A–Z of Pseudoscience” towards the end, where Brown lambasts and pokes fun at everything from detoxing and kale to Moon-landing conspiracies and “quantum nonsense”. If you are scientifically up to date, then buy this book for a chuckle and pub-quiz trivia. More importantly though, definitely buy this book for the people in your life who are easily swayed by “alternative” science facts – they will learn something true, new and enjoy themselves while they’re at it.
Remember that scene from the US sitcom The Big Bang Theory when one of the main characters, Howard Wolowitz, is gearing up to go into space and has his first Skype call with a NASA astronaut? The usual hilarity ensues, with Wolowitz’s mother shouting out his breakfast-cereal options midway through the call, which leads the astronaut to give Wolowitz the nickname “Froot Loops”. Despite using his real name in that cameo, few people realized that the astronaut in question was Michael James “Mike” Massimino – a US engineer who served as a NASA astronaut from 1996 to 2014.
Probably best known in the astronomy community for the two space flights that he participated in to fix the Hubble Space Telescope, Massimino says “It’s safe to say that more people know me from [The Big Bang Theory] than anything I ever did in orbit.” Massimino has now told the story of how he ended up on the show, not to mention his long and illustrious career in space, in his new book Spaceman: an Astronaut’s Unlikely Journey to Unlock the Secrets of the Universe.
Currently a professor of mechanical engineering at Columbia University and senior adviser of space programmes at the Intrepid Sea, Air and Space Museum in New York, Massimino’s love affair with space began when, as a little boy of seven, he watched the first Moon landing. He describes meeting Neil Armstrong and refraining from telling the legendary astronaut where he was while Armstrong walked on the Moon (as everyone else was doing), but does describe this scene to the reader with painstaking detail, which suggests just how pivotal this moment was for him.
Massimino may not be the most poignant of writers, but his story is captivating as is his enthusiasm. His descriptions of events are relatable (if a bit US-centric) – he compares going on his first space walk to being picked as a starting pitcher in the World Series but never actually having played the game before. Spaceman is a light and enjoyable read, and a good present for the astro-nut in your life.
Advances in medical imaging enable bespoke tissues and organs to be developed for transplant or engraftment with remarkable resolution and definition using 3D bioprinting. The incorporation of stem cell therapies into these 3D tissue constructs is incredibly promising for the delivery of pioneering stem cell regenerative therapies. Typically, 3D bioprinting requires use of a biomaterial to aid with deposition, which can cause negative host responses. To avoid such problems, US researchers have developed a biomaterial-free cardiac patch (Scientific Reports 7 4566).
Developing a biomaterial-free cardiac patch
Heart disease affects thousands of people every year and effective repair of cardiac tissue would reduce a large medical health care burden. Researchers from the Narutoshi Hibino labat Johns Hopkins Hospital and Johns Hopkins University have devised a 3D-bioprinting procedure that allows for the biofabrication of cardiac tissue patches to deliver regenerative stem cells, without using biomaterials. The process utilises aggregated balls of cardiac cells (cardiospheroids), which are directly printed into a cardiac patch construct. The cardiospheroids are identified, picked up by a vacuum and bioprinted directly onto a needle microarray (a video of the 3D-bioprinting process used is available from JOVE). This novel method allows the patch to be constructed with cells alone and will avoid detrimental effects induced by biomaterial grafts.
Stem cell techniques for tissue regeneration typically rely on biomaterial scaffolds to provide structure and support for cells during grafting. The grafting or introduction of biomaterials to a patient induces an immune response, or can create scar tissue from the graft, potentially damaging the region of tissue intended to be repaired. Through developing a biomaterial-free graft, it is possible to avoid these detrimental factors. And by using a patient’s own stem cells it is possible to create native tissue that is fully biocompatible.
Cardiac patch integrity
3D bioprinting was crucial to the development of effective cardiac patches, with specific spatial distribution being crucial to mechanical integrity. Cardiospheres without specific placement to overlap with other cardiospheres disintegrated after removal from the needle array; although partially disintegrated regions were able to fuse back together eventually. This effect removed the structural definition of the patch, negating the advantages of using bioprinting for developing a cardiac patch of specified dimensions.
In vivo grafts
The researchers grafted patches onto rat hearts and after a week saw signs of blood vessel formation, with viable cells and red blood cells present in the cardiac patch. Tissue protein stains showed that collagen was present in the patch, indicating the deposition of a native extracellular matrix from the cells, crucial to cell integration. Further staining showed the presence of human nucleic acid in rat tissue, implying that the human cell derived patch had successfully grafted with the rat tissue.
This biomaterial-free cardiac patch was developed using pluripotent cardiomyocyte stem cells, cardiac fibroblasts and human umbilical vein endothelial cells (HUVECs), which were aggregated into cardiospheroids for bioprinting. Cardiospheroids were able to develop a functional phenotype after 48 hours, with spontaneous beating and electrical conductivity a week after bioprinting. Cardiomyocytes alone were not able to reproduce this functional phenotype.
Biomaterial-free future?
This process demonstrates a novel approach to eliminating biomaterial-induced damage. Further development of this 3D bioprinting technique in conjunction with stem cell therapies could progress biomaterial-free cardiac patches into the popular domain.
Saturn’s magnetic field has no discernible tilt relative to the planet’s rotational axis, according to data from NASA’s Cassini spacecraft. This unexpected result means the exact length of a day on the planet is still unknown.
Cassini is currently undergoing its Grand Finale phase – 22 weekly orbits of Saturn that take the spacecraft between the planet and its rings. This stage of the Cassini’s mission began on 26 April and it has completed 14 of the orbits. After 22, Cassini will perform its final act and plummet into the planet’s atmosphere on September 15.
Aligned and challenging
Among the vast swathes of data sent back by Cassini, the spacecraft’s magnetometer instrument has revealed that Saturn’s magnetic field is closely aligned to its rotational axis. The tilt is in fact much smaller than the lower limit (0.06°) the magnetometer data indicated before the Grand Finale.
The observation challenges the current understanding of how a planet generates a magnetic field. It is thought that there must be some degree of tilt to sustain currents flowing through liquid metal within the planet. Without a tilt, the currents should subside, causing the magnetic field to disappear.
Unknown day
The result also means the true length of a day on Saturn is unknown, because it is measured by a daily “wobble” in the planet’s interior caused by the misalignment of magnetic field and rotational axis. “We have not been able to resolve the length of day at Saturn so far, but we’re still working on it,” says Michele Dougherty, Cassini magnetometer investigation lead from Imperial College London in the UK.
There is the possibility, however, that the lack of tilt may be rectified with further data. Dougherty and colleagues believe an aspect of Saturn’s atmosphere could be masking the true magnetic fields and Cassini’s plunge into Saturn may reveal further clues.
A potentially explosive phenomenon called superradiance could give black holes hair – according to William East of the Perimeter Institute for Theoretical Physics in Canada and Frans Pretorius of Princeton University in the US. Their claim relies on the existence of an extremely light particle and could be confirmed by detecting gravitational waves associated with the hair.
Black holes famously have “no hair”. This is the conventional idea that a black hole can only be described in terms of three quantities: mass, angular momentum and charge. All other physical properties (the hair) of the stuff that has been sucked into a black hole are lost forever. Evidence for the no-hair theorem has been seen by LIGO, which has detected the gravitational waves produced when two black holes merge.
However, the idea of having no hair does not sit very well with basic principles of quantum mechanics and as a result, the possibility of black-hole hair is an active area of physics research.
Black-hole bomb
Another curious phenomenon associated with black holes is superradiance. This involves particles and electromagnetic radiation scattering from a spinning black hole and gaining energy and angular momentum in the process. If this radiation is reflected back at the black hole, a runaway explosive process called a “black-hole bomb” could develop.
For this process to occur spontaneously there must exist a hitherto unknown boson particle and associated field. Furthermore, the mass of the boson must be extremely low – about 10–17 that of the electron. As a result, the observation of runaway superradiance in black holes could signal the existence of physics beyond the Standard Model of particle physics – perhaps providing an explanation of dark matter.
Quasistable state
Now, East and Pretorius have done detailed simulations of this process for a spinning solar-mass black hole with zero charge. They have found that rather than being explosively unstable, superradiance can settle into a quasistable state in which about 9% of the black-hole’s mass/energy is transferred to a field of hypothetical bosons that becomes trapped around the black hole.
This bosonic halo is called a “Proca cloud” and can be thought of as “long hair” that persists for a relatively long time and also extends out beyond the event horizon of the black hole. Black holes with such hair are expected to broadcast gravitational waves at a specific frequency – and in principle these could be detected by LIGO or perhaps the upcoming space-based LISA gravitational-wave detector.
Scientists have used Archimedes’ ancient principle of water displacement to develop a new 3D scanning and reconstruction technique. The method was developed by an international team led by Kfir Aberman, Oren Katzir, Daniel Cohen-Or and colleagues at Tel-Aviv University in Israel, who have used it to successfully reconstruct complex objects including cavities.
Typically, 3D scanning and reconstruction methods use optical devices that probe the visible surface of an object. While these techniques are reasonably efficient, they cannot capture features of an object that are hidden from the optics’ line of sight. Conventional methods also struggle with glossy or transparent surfaces, which can result in noisy scans.
Archimedes approach
To overcome these limitations, Aberman, Katzir and colleagues took a different approach. Rather than relying on optics they turned to Archimedes’ principle, which states that “the volume of fluid displaced is equal to the volume of the part that was submerged.”
The technique uses a robotic arm to dip an object into a water tank along a controlled direction. As the object is submerged, the water displacement is measured, giving a thin volume slice of the shape. The researchers then repeat this process multiple times by dipping at different angles. Using mathematical models, they convert the volume slices into a dip transform – a 3D representation of the object.
Cat, octopus, elephant
The more often the object is dipped, the greater detail about its geometry can be extracted. Aberman, Katzir and colleagues were able to reconstruct a variety of complex sculptures, including a DNA-like helix, cats, an octopus and an elephant with a rider.
Although the technique does not require expensive equipment or customized environments, it assumes the object has no air pockets when dipped. The team is working on methods to overcome this limitation by measuring the level of water while the object is being vertically lifted out as well as dipped in. This may reveal further details about the object’s geometry.
