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Leonardo da Vinci was a Renaissance genius. Not only did he paint masterpieces of art, but he was an obsessive scientist and inventor, dreaming up complex machines centuries ahead of his time, including parachutes, armored tanks, hang gliders, and robots. On the 500th anniversary of Leonardo’s death, with the help of biographer Walter Isaacson, NOVA investigates the secrets of Leonardo’s success. How did his scientific curiosity, from dissections of cadavers to studies of optics, shape his genius and help him create perhaps the most famous painting of all time, the &quot;Mona Lisa&quot;? (Premiered November 13, 2019)

Discover the science behind Leonardo da Vinci&#x27;s masterpieces—and Mona Lisa&#x27;s iconic smile.

Decoding da Vinci

In a new age of information, rapid innovation, and globalization, how can we prepare our children to compete? Once the envy of the world, American schools are now in trouble. Test scores show our kids lag far behind their peers from other industrialized countries, and as the divide between rich and poor grows wider, the goal of getting all kids ready for college and the workforce gets harder by the day. How can the latest research help us fix education in America? Can the science of learning—including new insights from neuroscientists, psychologists, and educators—reveal how kids’ brains work and tell us which techniques are most likely to engage and inspire growing minds? What role should technology play in the classroom? Teachers, students, parents, and scientists take center stage as NOVA explores a new vision for the “School of the Future.”

How can the science of learning help us rethink the future of education for all children?

School of the Future

Rockets are becoming cheaper and more powerful than ever before thanks to stunning new technologies. As companies like SpaceX and Virgin Galactic make space more accessible, and NASA returns to crewed spaceflight, a new era of space exploration seems to be on the horizon. But will this seeming rocket Renaissance become more than just hype? NOVA explores the latest rocket technologies and the growing role private citizens may have in space. (Premiered February 13, 2019)

With new technologies, NASA and private companies are promising a new renaissance in space travel.

Rise of the Rockets

Koch Foundation

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Draper

Two leading researchers investigate racial bias built into widely used search engines.
Why does a widely used internet search engine deliver results that can be blatantly racist and sexist? Two leading information researchers investigate their discoveries of hidden biases in the search technology we rely on every day, involving pornographic images and ads implying criminal behavior triggered by simple search queries. Both researchers share common concerns about how everyday online searches can reinforce damaging stereotypes, and explore how technology can be made more equitable. (Premiering at 10:30 pm on April 14 on PBS)

Two leading researchers investigate racial bias built into widely used search engines.

Search Engine Breakdown

Despite the efforts of recycling programs and environmental education, it’s still hard for many of us to grasp just how much plastic humans produce. We are on track to produce a billion tons of plastic a year by 2050. Cumulatively, we’ve already produced more than 8.3 billion metric tons since 1950. That’s 20 times the weight of all human beings alive right now. The systems we’ve developed for recycling that plastic are full of logistical, political, and economic obstacles, and the numbers show it. By 2015, three quarters of those <a href="https://www.pbs.org/wgbh/nova/article/76-of-all-plastic-ever-made-has-already-been-discarded/">8 billion metric tons of plastic were already out of use</a>, with 9% of it having been recycled and 12% incinerated. A whopping 79% wound up in landfills or the natural environment, destined to sit virtually unchanged for hundreds, if not thousands, of years.
 

 
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 It doesn’t have to be this way. “Plastic” is a category that encompasses a huge diversity of materials with one thing in common: They’re made of repeating chains of molecules known as “polymers” and can be molded or extruded while soft to take particular shapes. Until recently, we&#x27;ve only looked to petrochemicals (made from crude oil and natural gas) to create plastics with the properties we find so useful: the rigidity of takeout utensils, the flexibility of plastic films, the moisture barrier that contains greasy food. Although some less-common petroplastics are indeed biodegradable, bioplastics—which are often made from plant materials like sugar cane pulp, corn, or cassava and in many cases biodegrade after relatively short periods—may also be able to help address our big plastic problem.Enter polyhydroxyalkanoates, also known as PHAs, polymers used to make biodegradable bioplastics from an unlikely source: bacteria guts. PHAs and other bioplastics seek to challenge our assumptions about what plastic can be, and companies like Danimer in Georgia and Mango Materials in California are betting big that their products can help make a dent in our plastic waste numbers. Danimer’s partnership with Bacardi will see that company unveiling PHA bottles in all of its liquor lines by 2023; it also has partnerships in the works with <a href="https://www.fastcompany.com/90569273/pepsi-nestle-and-bacardi-are-all-using-this-new-plastic-like-packaging-thats-compostable-anywhere">Nestle, Pepsico, and other giants</a> of single-use plastic. Meanwhile, Mango is making inroads into other plastic-reliant industries, like apparel. (Yes, your workout clothes have plastic in them.)But PHAs aren’t new. They’ve been around for 35 years, and doubters like to point to Metabolix, a PHA company that seemed promising, grew quickly, and then collapsed in 2016. Metabolix and other would-be innovators have lived and died trying to “make PHAs happen.” Is now the time for this bioplastic to break through?
 

 
 

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 You might not think plastic and beer have much in common, but in the case of PHAs, there’s some surprising overlap. The bio-based plastic is derived from what amounts to bacteria guts, a polymer the microorganisms use to turn food into energy stored away for a rainy day. To make that polymer into something usable for humans, PHA scientists and entrepreneurs grow the bacteria in big vats under specific conditions, feeding them with vegetable oil, sugar, or methane gas and waiting to harvest the results. So far, kinda like beer.Here’s where it gets a little different. When the bacteria have gotten so full and roly-poly that they’re barely bacteria anymore—when their cells have gone from around 3% polymer to upwards of 95%—they’re subject to a purification process that bursts their membranes and brings the polymer out of solution. The resulting white powder is combined in pellets that then can be made into straws and takeout containers. Voila: plastic that’s not just made without fossil fuels but is also fully compostable, biodegrading in both your backyard and the ocean.We’ve known about bacteria’s capacity to manufacture plastic since the 1920s. But it took until 1983 to figure out how to get the polymers from inside the bacteria into human hands and until quite recently for that to happen on a scale that could be commercialized. “If you think of what we knew in the early 20th century about bacteria, microscopy, evolution, all those things have rapidly evolved,” says Mango Materials CEO Molly Morse. Only in the last decade have we had the tool set to <a href="https://link.springer.com/chapter/10.1007/978-3-642-03287-5_2">make PHAs a reality</a>.
 <figure class="richtext-image full-width"><img alt="small white plastic pellets" class="richtext-image full-width" height="600" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/biopolymer_pellets.width-800.jpg"/><figcaption>Pellets made from PHA biopolymers. Photo courtesy of Mango Materials<div class="credit"></div></figcaption>
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 Now, there are over 150 types of PHAs, which differ based on the length of their molecules, how they’re structured, which microorganisms are producing them, and what those microorganisms are fed. The longer the molecule chains, the more flexible and stretchable the plastic is; the shorter they are, the more brittle the material becomes. PHAs melt and flow like petroplastics and they can be turned into sheets or molded into many forms. That makes them great for all kinds of applications with one thing in common: whether in backyard compost, in industrial composting facilities, or in the ocean, they’ll completely biodegrade within six months. The big difference is that petroplastics are synthetic, and while bacteria may attempt to break them down, those organisms lack enzymes to break the plastics’ carbon-carbon bonds, making full degradation impossible. But since bacteria already use PHAs to store energy, they have built-in ways to both recognize and break them down. That’s what makes PHAs uniquely biodegradable—but only in specific settings. To understand why this is possible, “think about wood,” says Danimer Chief Technology Officer Phil Van Trump. If you build your desk out of wood, it won’t just disappear out of your house one day; it needs the right environment for that. “But in your yard, it’s a different story. Put it back in that environment, and bacteria and fungi will recognize it as food and start in on it.”
 

 
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 Of course, there are some drawbacks. In plastic-nerd parlance, PHAs have a “narrow processing window,” which means that their melting point and the point at which heat transforms them chemically into something else are only 10 degrees apart. That limits the ways they can be processed to stand in for petroplastics—for example, in materials that are subjected to very high heat or need very high mechanical strength, like airplane windshields, car bumpers, or bulletproof vests. But PHAs&#x27; biggest drawback is cost. Production is relatively expensive, especially the part of the process that draws the polymer out of the bacteria, says Amar Mohanty, a polymer and plastics engineer at the University of Guelph in Canada. Though there are different techniques for doing so, they often require large amounts of expensive chemicals like acetone or chloroform. “And to get a really purified polymer, you need to repeat the steps two or three times,” adds his colleague, fellow engineer Manjusri Misra.PHAs, like other bioplastics, also release methane when they degrade under anaerobic conditions (like in landfills). Since methane is a major contributor to greenhouse gas emissions, some critics worry that if PHA products grow popular and then are improperly disposed of, they may end up contributing to the climate crisis. In response, Van Trump and Mohanty stress the importance of developing proper waste-disposal infrastructure along with PHA technology, including industrial composting and digesters. “There’s growing we need to do as a society with how much we stick in landfills,” Van Trump says. In her work at Mango Materials, Morse has taken the methane release issue in a different direction, since Mango’s PHA bacteria actually feed on methane to grow their polymer. Mango has even partnered with Silicon Valley Clean Water in Redwood City, California, to build a digester on site and harness the methane coming off the city’s waste. At just that single location, Mango could produce up to 10 million pounds of PHA plastic per year.And then there’s the question of toxicity. In a <a href="https://www.sciencedirect.com/science/article/pii/S0160412020320213">recent study</a>, Lisa Zimmerman, a biologist at Goethe University in Germany, tested 40 different bioplastics, including one PHA product, and found they were not on average any less toxic than regular plastics. And when chemicals from the bioplastics leached into an environment where Zimmerman was raising microorganisms, many of them (including those from the PHA product) exhibited the potential to simulate hormones and interrupt the organisms’ metabolisms. Since some of the products she tested were not toxic, Zimmerman sees her result as an impetus to increase industry transparency. “The problem is that the product composition is not made openly available, so it’s really hard for other producers to integrate those less harmful chemicals,” she says. “To scale up, it would really help if it was openly communicated what is in the product.” 
 <figure class="richtext-image full-width"><img alt="2 plastic caps and roll of plastic film" class="richtext-image full-width" height="396" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Bioplastic_products.width-800.png"/><figcaption>Plastic caps (left) and film (right) produced from PHA biopolymers. Photos courtesy of Mango Materials<div class="credit"></div></figcaption>
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 Still, all the people interviewed for this article see the current moment as a time with enormous potential for bioplastics. As recently as 2014, when Mango applied for funding through the National Science Foundation to work on marine plastic pollution, their application was denied because the foundation “didn’t believe <a href="https://www.iucn.org/resources/issues-briefs/marine-plastics">plastics in the ocean were a problem</a>,” Morse says. She’s seen huge societal change since then, even noticing a difference just within the period of the COVID-19 pandemic. “People are at home staring at their trash cans wondering where all this stuff is going,” she says. “We’ve seen interest in the past 12 months like never before.”
 

 
 Van Trump also sees a major change in the attitudes of the corporations Danimer is partnering with, like Pepsi, Nestle, and Bacardi, which now seem more willing to invest in solutions to the plastics problem. “We’re growing like a weed,” he says of Danimer, which just opened new facilities in Georgia and Kentucky. And Van Trump and Morse both point out that price and scale are intimately connected. Bioplastics like PHAs are competing against a petroplastics industry producing in simply enormous volumes, with some single plants producing a billion pounds a year—and economies of scale make it possible for petroplastics companies to keep their prices low. “The industry has had 70 to 80 years to optimize and build capacity,” Van Trump says. He holds out hope, though, that “when we get to the scales of the ‘traditional’ polymers, then costs will come down dramatically.”In fact, Mohanty says the current problem for PHAs is the opposite of what it was in the days of Metabolix: too much demand and not enough production capacity. He expects the industry will grow into that demand in the coming decade, <a href="https://www.nytimes.com/2020/08/30/climate/oil-kenya-africa-plastics-trade.html">especially as widespread single-use petroplastic bans go into effect</a>. The key, in the meantime, is to educate consumers about their options and to build enough infrastructure that all those new PHA containers and films and straws don’t end up in landfills. Of our voracious plastic appetite, he says, “If we cannot stay away from it, we have to find ways to handle it.”
 

 
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Drinking straws are one of many single-use plastic products that could potentially be produced using biopolymers. Image Credit: Phichai, Shutterstock

Bioplastics called PHAs grow like beer and biodegrade like wood. And they may be able to help with our plastic waste problem.

Could plastic made from bacteria guts help solve our waste crisis?

The spread of misinformation is influencing human behavior.
Learn the science behind misinformation–how it’s shared, why it&#x27;s believed, and what we can do to address it.
Why Misinformation MattersPublished: February 11, 2021Alex Clark: 2020 was a year packed with challenges in the United States as the COVID-19 virus, national uprisings over police brutality, and a presidential election all took over the news cycle. And through all of these events, the spread of misinformation played a role in raising the tensions, from conflicting messages about masks.Louie Gomert: When I have a mask on, I&#x27;m moving it to make it comfortable, I can&#x27;t help but wonder if that puts some germs in the mask.Clark: To fabricated stories on the victims of police brutality, but things came to a head on January 6th, 2021, when supporters of President Trump stormed the Capitol building in an attempt to overthrow the election results, resulting in the deaths of five people. While people across the country have been struggling to understand how something like this happened, a look at the events and rhetoric over the past few months or years reveals that many of the warning signs were right in the open, and I&#x27;m not just talking about the image boards and forums like 4Chan, Reddit, Parler, where plans were being made to assemble and march on the Capitol. I&#x27;m talking about the interviews I had with people on the day of the election.Voter 1: I&#x27;ve heard lots of information about ballots being discarded. Some polling centers are throwing them in the garbage.Voter 2: To the president, fake news is news that he doesn&#x27;t agree with.Clark: You see, there is a science to how we interpret information about the world around us. Our brains try to make things align with our existing reality and basically try to make sense of it all, but this has become more of a problem in the last decade, simply because we have more choices of where to go when we seek information, and all President Trump needed to reach the supporters was a Twitter account. So misinformation, which is a blanket term for inaccurate communication, can take us further from what&#x27;s actually going on in the world.And when misinformation is spread intentionally in order to disrupt political movements, or sow division among groups, that&#x27;s called disinformation and disinformation is not going away, because bad actors can profit from it and push their causes by sharing it with a click. So that&#x27;s why Nova is starting this new series.It&#x27;s called &quot;Misinformation Nation.&quot; We&#x27;ll speak with experts and news-makers and give real-world examples that explain how misinformation spreads, why it&#x27;s believed, and how our brains strive to make sense of it all, as part of the Nova Science Studio program, where dozens of young science communicators across the country learn the basics of science storytelling.I&#x27;m Alex Clark. I invite you to subscribe to NOVA and NOVA Science Studio, and stay tuned for the episodes. Thanks for watching.

The spread of misinformation is influencing human behavior.

Why Misinformation Matters

In 2018, June Smith takes a consumer DNA test, hoping to solve a longstanding mystery.
Half-sisters share their unlikely story of finding one another through genetic testing, and what they learned about their family history along the way.
Half Sisters Unite Thanks to DNA TestingPublished: January 27, 2021Narrator: June Smith lives in New Jersey, not far from Philadelphia. In 2018, she takes a consumer DNA test, hoping to solve a longstanding mystery. She’s spent years searching for her roots. When June was 16, growing up in Philadelphia, the woman she knew as her mother revealed a secret.June Smith: She said, “Your mother was a white woman.” And I said, “A white woman?” Which was totally shocking to me.Narrator: Her biological mother’s name was Ann D’Amico. June has never learned the identity of her father. When June takes her test with AncestryDNA, she checks the box asking to be linked to any customers with whom she shares DNAThough she knows Ann has died, there’s someone else she desperately wants to find. While digging into Ann’s life story, June learned that she’d given birth to another biracial daughter, who had a different father, a girl, named Joan Moser, June’s older half-sister.Smith: I set out to search for her. And I would go on websites, I would do all kind of people searches looking for Joan Moser. But we could never come up with her.Narrator: One day, June receives a message on her Ancestry page, telling her she has a new match with a close relative, a woman named Sigrid Gilchrist. She’d also grown up in Philadelphia, as the only child of a Black couple active in the civil rights movement. But at 16, Sigrid learned a long-hidden truth from her mother.Sigrid Gilchrist Johnson: She told me I was adopted, that my mother was Italian and my father was Black. It was crushing. I had no idea.Narrator: In the years that followed, Sigrid never connected with any of her biological relatives, until, by pure chance, right around the time that June tests with Ancestry, Sigrid does, too.Ancestry reports that the two women, who share 1,641 centimorgans, may be first cousins. But June can’t help wondering: might Sigrid be someone even closer?The two women agree to talk on the phone.Johnson: She said, “I have three questions to ask you.” I said, “Okay.”Smith: I said, “Were you adopted?” She said, “I was.” I said, “Are you biracial?” She said, “I am.” I said, “Would your birth mother’s name happen to be Ann D’Amico?”Johnson: I said, “Yes, she, that was her name, my biological mother.” She said, “Are you Joan Moser?” And then I said, “That was the name on my birth certificate.”Smith: I said, “Oh, my god, you’re my sister. You’re not my cousin.” We cried, and I just couldn’t believe it. I was on the phone with my oldest sister. Yes.Johnson: It was just like we’ve known each other forever, one-on-one spirit feeling that you can’t describe.Smith: Finding my sister gave me a sense of belonging. It gave me a sense of saying, “Hey, you know, we got the same blood.”Johnson: ...but I do see…Smith: …looks like me…Johnson: Yes.Smith: Look at the chin.Johnson: Yeah.Smith: It’s good having an older sister.Johnson: I don’t like being older, but it’s okay. I love having a younger sister.Smith: She understands.Johnson: Yeah, yeah.

Half Sisters Unite Thanks to DNA Testing Hero

In 2018, June Smith takes a consumer DNA test, hoping to solve a longstanding mystery.

Half Sisters Unite Thanks to DNA Testing

Are DNA ancestry tests equally accurate for all test takers?
Because of the Eurocentric bias of genetic reference databases, DNA ancestry test results for individuals of African and Asian descent are often less detailed than results for individuals of European descent.
How—and why—DNA Testing Uses Biased Reference DatabasesPublished: January 27, 2021Narrator: These 14 people are about to experience DNA ancestry testing for themselves.Cherry Richardson: &#x27;Cause there are so many kids I’m growing up with who are all in the same situation. We don’t know our heritage. We could probably safely assume that our ancestors’ ancestors had something to do with, like, slavery and things like that, but we don’t really know where we came from.Narrator: Cherry Richardson is taking part in a research study, at West Chester University, in Pennsylvania.Bessie Lawton: So, we have a research protocol by which we collect data for this particular project.Narrator: The study is run by two communications professors, Bessie Lawton and Anita Foeman. The question they’re asking is, “How does DNA testing affect our understanding of who we are, and also, our ability to understand what makes us different?”Lawton: And after we receive the results, we bring you together.Anita Foeman: The whole idea is to listen to each other and talk with one another.Narrator: Anita was inspired to start the project because of her experiences as a diversity trainer.Foeman: I thought looking at our DNA was a really interesting way to approach this whole conversation about race and diversity, in a way that was not going to make people defensive. And that has happened.Tyquine Golden: We don’t identify ourselves with Africa. We just say we’re Black. You know, we literally separated from that which we came from.Narrator: In a previous test with Ancestry, Tyquine Golden was told his roots were 80 percent West African, and 20 percent British. In today’s test with FamilyTreeDNA he hopes to learn more.Golden: They got everybody. My suspicions might lead me to say, somewhere in slavery, 20 percent might’ve came in and have been integrated with our DNA And that might not have been voluntary.Tshaka Cunningham: I think, as an African American, it’s a tough thing to grapple with, when you think about the origin of your Caucasian, or white ancestry. That often happened due to rape and mistreatment, but it is part of your history. So you have to confront it on some level and understand it. It’s part of how you got here.Golden: I don’t want to hide from the truth, no matter how bad it could be.Narrator: Now it’s time to collect DNA…Lawton: You can turn it around a little bit, to capture more.Narrator: …and ship the samples off to Houston.So, how do D.T.C.s like FamilyTreeDNA come up with a breakdown of your ancestry? It’s a process that also centers around SNPs, those places in our DNA that most frequently vary between people.The company compares your SNPs with those of people in what are called “reference groups,” people alive today whose DNA has been tested and who share patterns of SNPs that scientists have found to be typical for the region in which they live. Those patterns are compiled into a database.But how well does it represent test takers?Foeman: They’re telling you, “This is your background, based on our database.” Well, if something’s not in their database, they can’t tell you that it’s in your background.Narrator: The D.T.C.s have less data about people of African and Asian descent than they do about people of European descent.Fatimah Jackson: Most of the genetic testing that has been done, has been done on North Atlantic Europeans. So, our reference databases are biased.Foeman: Why don’t we all just take a minute and open your results, and take a look at the map for the first time.Narrator: FamilyTreeDNA has given Nick Pasvanis, whose parents trace their ancestors to Greece, Germany, England and Scotland, a detailed breakdown.Nicholas Pasvanis: I’m 45 percent Southeastern European, which is about what I expected. I’ve always felt like I was just a general European mutt, and that’s pretty much what the map shows.Richardson: So, I was wondering, when I got it, like, if it would say if I was Black. And I am 94 percent West African, so, yeah, I’m pretty Black.Narrator: But Cherry Richardson’s African bubble provides little detail.Hana Wiessmann and Viola Wang, who were both born in China, have even bigger bubbles.Hana Wiessmann: I mean, I have just these giant bubbles, and they’re like, “You’re super Asian.” Like, I kind of already knew that, so…Viola Wang: Basically, people who have huge bubbles are considered the minorities.Jackson: And it’s unfortunate, because it perpetuates a kind of Eurocentrism that has tainted our scholarship, that is a foundation for notions, false notions of white supremacy. And it highlights the disparities that are currently prevalent throughout science and particularly in genetics.

How—and why—DNA Testing Uses Biased Reference Databases Hero

Are DNA ancestry tests equally accurate for all test takers?

How—and why—DNA Testing Uses Biased Reference Databases

At the Neolithic village of <a href="https://blog.historicenvironment.scot/2016/05/3d-4d-digital-monitoring-sea-defences-skara-brae/">Skara Brae</a> off the northern coast of Scotland, serpentine green slopes overlay the remains of a community so complete that many of the houses feature stone beds, dressers, and cupboards—even though the village is older than both Stonehenge and the pyramids of Giza. The site, which was once home to some 50 people, overlooks the blustery Bay of Skaill. Over the millennia, wind and water have slowly eaten into the hills around the ruins, putting them at risk of eventual destruction.
 

 
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 For the last decade, the preservation organization Historic Environment Scotland (HES) has been visiting Skara Brae deveoping strategies to protect what’s sometimes known as the “Scottish Pompeii” from encroaching erosion. One of their most successful efforts has nothing to do with wood or stone and everything to do with light. Every two years, HES conservators bring laser scanners to the remote northern island to gather a 3D image of Skara Brae, including both its structures and the surrounding dunes and cliffs. Comparing the resulting data set to its predecessors has helped them identify to the millimeter how the landscape has changed.“To be able to monitor what’s going on is essential,” says Sophia Mirashrafi, who helps coordinate <a href="https://www.engineshed.scot/about-us/teams/digital-documentation-and-digital-innovation/the-rae-project/">HES’s digital projects</a> and get them ready for presentation to the public. “Scanning doesn’t stop the water from eroding the site, but it can be used to help inform decisions about how it can be protected.” She and her team also used the scans—known as point-cloud models—to create interactive virtual experiences that give the public up-close access to parts of the village.When we think about preserving cultural heritage, Mirashrafi says, we usually think about the physical: propping up carved stone, reconstructing rotted wood, uncovering precious metal. But, just as it’s being used at Skara Brae, laser scanning (also known as LIDAR) has become an essential tool at cultural sites around the world, from Notre Dame to Rapa Nui, in augmenting physical preservation, helping conservators make better decisions, and enriching experiences of the sites for both scientists and the public.
 <figure class="richtext-image full-width"><img alt="Aerial digital map of Skara Brae" class="richtext-image full-width" height="565" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/SkaraBraePlan_Pointcloud.width-800.jpg"/><figcaption>Historic Environment Scotland has used drones equipped with LIDAR scanners and photogrammetry to create aerial 3D models of the Skara Brae Neolithic site, which is older than Stonehenge. Image courtesy of Historic Environment Scotland <div class="credit"></div></figcaption>
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 At the most basic level, a point-cloud model is a collection of 3D coordinates that conservators, art historians, and researchers can use to “sample reality,” says architect and computer scientist Livio De Luca, who heads the vast team of <a href="https://www.sciencemag.org/news/2020/03/scientists-are-leading-notre-dame-s-restoration-and-probing-mysteries-laid-bare-its">scientists racing to preserve</a> Notre Dame Cathedral in Paris after the catastrophic fire that destroyed its roof in April 2019. Laser sensors mounted on rotating heads collect data on more than 100 three-dimensional points per second over a 180-degrees axis by measuring the amount of time it takes for light to leave the sensor, bounce off a given spot on a structure or object, and return.Users move scanners of different resolutions (some for capturing fine details, other for larger landscapes) gradually around the site to produce a digital cloud of points. Each data set overlaps with the last, allowing them to combine those data sets in an algorithmic process called registration, and create a 360-degree “picture” of that site—kind of like doing a 3D jigsaw puzzle. Even though the lasers collect so much data so quickly, the process is still slow and painstaking. It took a team more than two weeks to scan Notre Dame, De Luca says, using some 400 scanning stations to capture as many data points as possible.After the initial puzzle is done, the next step is to turn the cloud of points into a “watertight mesh” using a computer program—converting them from a dense constellation to an interconnected surface. Conservators often combine this mesh with data from another digital data-gathering technique called photogrammetry, which can harvest information about a structure’s texture, color, and general shape from overlapping photos of that structure. LIDAR (which stands for Light Detection and Ranging) “gives you quantifiable accuracy,” says architect and computer engineer John Ristevski, CEO of the digital heritage nonprofit CyArk, whose mission revolves around scanning sites of historical and cultural interest around the world. “In contrast, photogrammetry provides great textures and beautiful geometry, but it’s not completely reliable. We want both.”
 

 
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 As the technology has improved, point-cloud models have come to play an essential role when heritage sites are damaged. Ristevski’s colleagues at CyArk finished scanning one of <a href="https://artsexperiments.withgoogle.com/bagan/">Bagan, Myanmar’s huge stone temples</a> just three months before a 7.1 magnitude earthquake hit the city in 2016. Using <a href="https://www.youtube.com/watch?v=N5Y33-VvsbA">their scans</a>, CyArk was able to create detailed assessments of the damage and help with plans for restoration. Similarly, a Vassar professor, a 3D tourism company, and the company that makes the video game Assassin’s Creed had all <a href="https://www.youtube.com/watch?v=QBzKsTZ81Sw">scanned Notre Dame Cathedral</a> before its fire. “The point cloud represents the main source to rebuild something, using geometrical information in a precise and accurate way,” De Luca says. “If by other kinds of restoration we were able to approximate shapes in the past, now we’re able to reproduce shapes millimeter by millimeter.”Point-cloud modeling can also help conservators do experiments that would be impossible in real life. At Notre Dame, a new phase of reconstruction began this month to rebuild the stone ribs that once held up arches in the ceiling. Before this effort begins in earnest, members of the cathedral team will scan each individual stone, a process that will allow them to rebuild the ribs virtually—ensuring they do not compromise the rest of the structure before they are rebuilt in real life. “We’re able to more safely and, from a scientific point of view, more accurately test how they will behave in rebuilding,” De Luca says.For HES, point-cloud modeling has not just been essential in erosion monitoring; it has also become an important teaching tool. Using LIDAR scanners and drones capable of photogrammetry, the organization has been able to scan the tops of walls (known as “wall heads”), allowing conservators a much more complete view of the structure than ever possible before. “Scaffolding is very expensive, and it’s difficult to get people up there,” says Mirashrafi. Having access to point-cloud models of the upper parts of the buildings has allowed conservators and stone masons working on the many sites HES cares for to get up close to ceilings they couldn’t access otherwise and to better monitor the health of those wall heads—even using their virtual counterparts as teaching tools for masons-in-training.
 <figure class="richtext-image full-width"><img alt="Digital image of row of stone statues" class="richtext-image full-width" height="394" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Ahu_Nau_Nau2.width-800.jpg"/><figcaption>Staffers from the digital heritage nonprofit CyArk traveled to Rapa Nui (Easter Island) in early 2020. There, they taught workshops in point-cloud modeling, which will allow local resource managers and Indigenous groups to monitor the erosion of the island’s 500 moai, or enormous, ancient stone statues. Image Credit: CyArk<div class="credit"></div></figcaption>
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 CyArk was founded by Iraqi-American Ben Kacyra as a way to fight the kind of cultural destruction that was typical of the Taliban and ISIS in Iraq and Afghanistan over the last decades. But as modeling technology has become cheaper and more portable, the company’s mission has changed as well, Ristevski says, with less emphasis on secure data storage and individual projects and more on <a href="https://openheritage3d.org/">open access</a> and education.Since its founding, for example, CyArk has stored copies of each site it scans in a secure facility 200 feet underground—the same facility that, according to urban legend, stores Elvis Presley’s master tapes. “We still do that, but it’s a less interesting piece of our work,” Ristevski says. Two years ago, CyArk also began putting its data sets online under a Creative Commons license. “Things that are burrowed away somewhere is one avenue, but now it’s more about sharing and opening up data,” he says.Similarly, where CyArk once sought to digitize 500 cultural heritage sites under their own steam, Ristevski says what now excites him is the educational workshops the organization runs around the world. “We’ve seen a lot more adoption of this, especially in the last three or four years,” he says. In early 2020, for example, Ristevski and other CyArk staffers traveled to the South Pacific to <a href="https://www.youtube.com/watch?v=79DfInkneRA&amp;feature=emb_title">give a workshop</a> for monument staff and local Indigenous communities at Rapa Nui, also known as Easter Island. That site, much like Skara Brae, faces continual damage from wind and waves, so CyArk did a set of initial point-cloud models to act as a baseline, allowing for annual monitoring of how each of the island’s enormous stone statues is weathering. Helping local authorities monitor their own site makes it possible to scan all 500 sites on the island, he says, whereas CyArk might only have had time or resources for one or two.A technique like point-cloud modeling can also create an opportunity for sorting through and storing many types of information. Notre Dame is a perfect example. “Even if today we are building a lot of data around this physical aspect, we are also building a ‘knowledge cathedral’ at the same time,” De Luca says. For his team, that means building a “digital twin” of the cathedral, a real-time virtual clone of the physical object that records more than just the geometric dimensions of the cathedral before and after the fire. This digital twin also manages the myriad chemistry, physics, art history, archaeology, and engineering data generated by its many restoration projects—from managing the <a href="https://www.pbs.org/wgbh/nova/video/stabilizing-notre-dames-buttresses/">flying buttresses</a> to cataloguing each of the thousands of pieces of tangled, burnt wood that once made up the “forest” in the cathedral’s attic—and makes it available within a few minutes of its collection.
 <figure class="richtext-image full-width"><img alt="Digital model of 2 stone statues" class="richtext-image full-width" height="450" width="800"
 src="https://www.pbs.org/wgbh/nova/media/images/Rob1.width-800.png"/><figcaption>Point-cloud images of huge stone statues at Rapa Nui, also known as Easter Island. Image Credit: CyArk<div class="credit"></div></figcaption>
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 Past Skara Brae, even farther north into the cold reaches of the Atlantic ocean, sits Mousa Broch, a 40-foot-tall Iron Age stone tower built around 300 BCE on a bluff overlooking the sea. Even for the few visitors that make it to the Shetland Islands, Mousa Broch is difficult to access, requiring a strenuous hike. But point-cloud modeling has allowed Mirashrafi’s team not just to gather essential records of the building for posterity but also to open the site (or a version of it) to the public.As part of their scanning efforts, they’ve translated the point-cloud version of Mousa Broch into a version most computers can handle, through a site called <a href="https://sketchfab.com/HistoricEnvironmentScotland">SketchFab</a> (which Mirashrafi calls the “YouTube of 3D models.”) “Sharing for education and interpretation is something we’re equally interested in,” she says. Flocks of storm petrels roost at Mousa Broch at night, so as an extra immersive touch, the team layered recordings of the seabirds over the model animation. The result: a <a href="https://sketchfab.com/3d-models/mousa-broch-shetland-88a87c90cde8477a87523caa511c1796">rich virtual experience</a> that was previously largely inaccessible.In this vein, Mirashrafi says she’s been especially impressed with point-cloud modeling’s potential for storytelling. Being able to digitally recreate a structure or item with such accuracy helps her team fight archaeology’s tendency to strip items of their cultural context. Though the digital can never replace the physical—“When you go out and scan a site, it doesn’t negate the necessity for historians and conservators”—a digital replica is a powerful tool, she says, whether it’s used to help recreate a site before a rock fall or to help the public experience a little bit of new history.Through point-cloud models, a lost or destroyed site can be reconstructed; an artifact can be put back virtually where it was originally found. “So often in museum contexts, it’s hand’s off, don’t touch, don’t talk, don’t question,” she says. “These kinds of virtual environments encourage manipulation and questioning,” in a richer way than you might see behind glass.
 

 
 

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Notre Dame Cathedral on fire in April 2019. Image credit: Wandrille de Préville, Wikimedia Commons

Laser-scanning technology can create exceptionally detailed 3D models of cultural sites, bringing them to life online—and helping experts restore them if disaster strikes.

3D models help preserve landmarks like Notre Dame

Could the cathedral&#x27;s beautiful stained glass collection survive the 2019 fire intact?
Discover the effects the fire had on Notre Dame&#x27;s stained glass, and how one scientist is meticulously cleaning and repairing it.
Saving Notre Dame&#x27;s Stained Glass MasterpiecesPublished: November 20, 2020Narrator: Inside Notre-Dame, scientists begin to gather data and investigate the damage to treasured statues, murals and windows. The cathedral’s most fragile wonder, it’s stained glass, dates back to the thirteenth century. Miraculously, they survive the fire intact.But the intense heat that melted the cathedral’s lead covered roof means that much of the glasswork is now covered in a layer of toxic lead powder. Removing it could damage the delicate glass and be harmful to restorers.Glass Scientist, Claudine Loisel uses a handheld digital microscope to investigate the levels of lead powder on the stained glass. She must then formulate a strategy to clean every single panel; a vast decontamination program.Claudine examines deposits from windows around the cathedral. The samples reveal vital clues about the spread of the lead contamination. The windows of the upper level, in the path of the lead cloud, have been most contaminated.The team takes out and transports these panels to this special laboratory where they experiment with ways to remove the lead. First, Claudine uses a precision vacuum cleaner to remove the hundred years of dust… and most of the lead powder along with it.Claudine Loisel: So this is a good way to protect the conservator. You can control the action, the pressure on the glass and also on the painting.Narrator: Then she uses water and cotton balls to remove the last of the lead.Claudine Loisel: Of course, you need scientific evidence that it’s working.Narrator: Claudine uses x-ray spectroscopy to determine exactly how many wipes it takes to bring the lead down to normal levels.Claudine Loisel: So, we can identify each chemical element we have in the material.Narrator: Too few wipes and the lead will remain. Too many wipes and restoration will take longer than necessary.Claudine Loisel: Ok, now the analysis is finished.Narrator: After five wipes, Claudine checks to see if the glass is decontaminated.Claudine Loisel: Ok, we have different chemical element, calcium, iron, and if we want to see the lead… there is no lead! After nine months, we can see a good solution, a good way to clean and to preserve the stained glass windows from Notre Dame.

Saving Notre Dame's Stained Glass Masterpieces

Could the cathedral&#x27;s beautiful stained glass collection survive the 2019 fire intact?

Topic: Tech & Engineering

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