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(This program is no longer available for online streaming.) On September 11, 2001, an unimaginable horror unfolded that devastated a nation and the world. Fifteen years later, we are still gripped by terror, but it has transformed. The attacks have been coming fast and furious—to Boston, Paris, Brussels, San Bernardino, Orlando, Nice—but they are no longer commanded by a central entity. This is terrorism in the age of the Internet: crowd-sourced violence.In this special report, NOVA traces the evolution of terror strategies from the World Trade Center to today. How have radical organizations grown to make use of modern propaganda and social media tools in order to cultivate an army of self-radicalized killers? What is going on inside the minds of this new breed of terrorist? What new techniques and technologies can help law enforcement cope with this elusive threat? And how can psychology and technology be leveraged to end this dreadful cycle of terror?

From 9/11 to today’s crowd-sourced violence, trace how terrorists’ strategies have evolved.

15 Years of Terror

Alcatraz Island still draws tourists for its history as a federal penitentiary. But it also has a rich past as little-known military base, erected to guard against foreign invasion. Image Credit: MBPROJEKT_Maciej_Bledowski, iStock

Using non-invasive techniques, archaeologists have confirmed the presence of a coastal fortification beneath what was once the prison’s recreation yard.

Ground-Penetrating Radar Reveals Military Structures Buried Beneath Alcatraz Penitentiary

<div class="rich-text">Churchill launches the largest military evacuation in military history. But there's a secret killer in the waters.
 
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<div class="rich-text">Churchill launches the largest military evacuation in military history. But there's a secret killer in the waters. 
</div>

Hitler’s Secret Weapon

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Alcatraz might be best known as a popular tourist destination, the site of the former high-security prison that once held Al Capone. But a team of archaeologists has now unveiled new evidence of this San Francisco Bay island’s often overlooked military history.In the <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/nsg.12031">study</a>, published last Thursday in the journal Near Surface Geophysics, researchers used non-invasive technologies to pull back the curtain on a stunningly well-preserved 19th century coastal fortification that lies beneath the ruins of this infamous federal penitentiary. The work confirms that while prison construction in the early 1900s destroyed much of the former military installation, several structures were buried more or less intact, enshrining a critical sliver of Alcatraz’s colorful past.
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“This really changes the picture of things,” says study author <a href="https://www.binghamton.edu/anthropology/faculty/postdoctoral.html">Timothy de Smet</a>, an archaeologist at Binghamton University. “These remains are so well preserved, and so close to the surface. They weren’t erased from the island—they’re right beneath your feet.”
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<figcaption>Study author Timothy de Smet used non-invasive techniques to create a subsurface map of remains of Alcatraz Island's former military fortification. Image Credit: Timothy de Smet, Binghampton University
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Prior to the mid-1800s, Alcatraz Island was a barren strip of land capable of supporting little more than a raucous population of seabirds. But in the wake of the California Gold Rush, the United States government looked to the rocky outcrop as a potential military base to protect the newly bustling city from foreign invasion. Over the next several decades, a stone- and brick-based fortification was erected, then rebuilt as earthen structures better equipped to handle erosion. But Alcatraz struggled to keep pace with the rapid changes in artillery during and after the Civil War era, and by the late 1800s, the island’s defenses were essentially obsolete. Military pursuits on Alcatraz were abandoned shortly thereafter.
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When the island’s prison was erected around the turn of the 20th century, little physical evidence of its former architecture remained—or so many thought. The new study, led by de Smet, says otherwise. To look beneath the surface, the researchers deployed ground-penetrating radar, which pulses electromagnetic waves into the earth, returning signals that can visualize remains without excavation. The strategy uncovered a labyrinth of subterranean structures, including an earthwork traverse, a kind of defensive trench, running beneath the penitentiary’s former recreation yard.“This really reinforces what several historians and archaeologists had long suspected,” says study author and Alcatraz historian <a href="http://www.johnamartini.com/">John Martini</a>. “Up until this point, we had nothing to go on except for a few visible trace remains and maps—and a lot of suspicion.”In a way, Martini says, the findings reflect just how limited real estate was on Alcatraz, which clocks in at less than 50 acres. “On a small island, there’s only so many places you can build,” he says. “And it’s unlikely they went to the trouble of demolishing all this stuff.”
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<figcaption>A 15-inch Rodman cannon and its gun crew, 1869. These were the largest guns mounted on Alcatraz. Image Credit: National Park Service, Golden Gate National Recreation Area
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Because they’re both sensitive and non-destructive, techniques like ground-penetrating radar are crucial for these kinds of investigations, and can complement historical records that survived the era, says <a href="http://jolenebabyakauthor.com/">Jolene Babyak</a>, an Alcatraz historian who was not involved in the study.With these results in hand, de Smet and his colleagues plan to continue archaeological investigations under Alcatraz. Going forward, only time will tell what this rock will reveal, Martini says. “Below the surface, Alcatraz is still full of mysteries,” he says. “There’s still a whole lot to be learned.”
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<figcaption>Soldiers posing in the island’s ordnance yard. A brick Citadel capped the summit of Alcatraz. 1869. Image Credit: National Park Service, Golden Gate National Recreation Area
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Identifying Lost Crew with Forensics and DNA Analysis

Can a team of forensic archaeologist identify three WWII airmen that disappeared?
In 1944, three WWII airmen disappeared beneath the waves. Now, there may be hope for the return of their remains. The Department of Defense, which operates the largest forensic anthropology lab in the world, does a skeletal analysis to figure out if the recovered remains belong to more than one individual. Then the Armed Forces Medical Examiner System takes over to conduct a DNA analysis using family samples.
Identifying Lost Crew with Forensics and DNA AnalysisPublished: December 3, 2018Onscreen: Dec 17, 1944: A B-24 bomber was shot down off Croatia. Three airmen disappeared beneath the waves: Pilot Eugene Ford, Navigator Russel C. Landry, and Flight Engineer Charles E. Priest.Now, there may be hope for the return of their remains. The Department of Defense operates the largest forensic anthropology lab in the world.Tyler Dunn: It’s my job to do a skeletal analysis blind, so I don’t bias myself.We were presented with 11 teeth; a right humerus, that’s relatively intact compared to everything else; a fragment of a vertebra; a handful of, sort of, non-diagnostic long bone fragments—we can more or less just tell that they’re bone; some fingers, a bit of a toe, and then most of the lower right leg, so a tibia and a fibula.The first question I generally ask is the minimum number of individuals. So, we try and figure out if this could be, or is, more than one person.Based on this case, the skeletal—it’s called M.N.I. or &quot;minimum number of individuals&quot; — the skeletal M.N.I. is one. I have good reason to think that this is one individual.Onscreen: This conclusion is backed up by the dental analysis.Dunn: So, I can tell that this is all teeth from one individual, based on tooth shape, the size of the tooth, and more or less what they look like.Onscreen: It appears that only a single airman was recovered, based on the skeletal evidence. But who was it?Dunn: We more or less measure how long the tibia is. The stature for this individual that we estimated was right around 5 foot 10.Onscreen: Yet the skeletal remains alone cannot provide a definitive ID, so they turn to DNA. The Armed Forces Medical Examiner System now takes over.Timothy McMahon: This is where we take the unknown and we put a name to them.Onscreen: First they extract DNA from the bones and teeth and then sequence many different regions. Then they compare the sequence against family reference samples until finally a match is confirmed.Seven months later…Jim Bell: …so, based on that, the laboratory analysis, established remains of those as First Lieutenant Eugene Ford, serial number Oscar 805804, U.S. Army Air Forces.

Can a team of forensic archaeologist identify three WWII airmen that disappeared?

Finding a Lost WWII Tuskegee Airman

Can DNA analysis ID a Tuskegee Airman missing since WWII?
Named for the Alabama town in which they trained, the Tuskegee Airmen had to &quot;fight just to fly.&quot; Capt. Dickson, whose plane went down in the mountains between Italy and Austria during his 68th mission, is one of 27 Tuskegee airmen missing since WWII. Can DNA analysis identify him?
Finding a Lost WWII Tuskegee AirmanPublished: November 30, 2018Marla Dickson Andrews: This is my father, Captain Lawrence Everett Dickson.Narrator: His daughter Marla was just a child when he disappeared.Andrews: My father was in the third graduating class of the original Tuskegee Airmen.Narrator: Named for the Alabama town where they trained, the Tuskegee Airmen had to fight just to fly.Andrews: The basic sentiment of the country at that time felt that black people were not intelligent enough, they weren’t brave and courageous enough.Narrator: The Tuskegee pilots proved their critics wrong, but at a price: they were asked to fly 70 missions, far more than their white peers. Marla’s father, was on his 68th mission in a distinctive red-tail P-51.Christmas was only days away.Andrews: They expected him to come home very soon, because he only had two more missions to go.Narrator: Just after the new year, they get a telegram.Andrews: It said he was missing in action.Narrator: He was never seen again.Andrews: All through the years, I would ask everybody, &quot;Did you know my father? Were you over in Italy?&quot; And I never had any luck.Narrator: For 50 years, Marla had little more than his medals to remember her father by…Andrews: It’s the Distinguished Flying Cross.Narrator: …until 1998, when she got a letter from her father’s wingman, Robert Martin.The letter revealed that over the mountains between Italy and Austria, her father’s plane began to give him trouble.Andrews: He saw my father having difficulty with the engine. It sputtered out one time, and he got it started again, after trying. And then it sputtered out again, and he got it started again. But the third time, it didn’t work.Narrator: Neither of the two pilots flying with Dickson saw if he got out.Andrews: They went back, and they circled what they thought was the area. And I could tell from the letter how awful he felt.Andrews: I got a call from an army representative, and her specialty was genealogy. At first, I said, &quot;Oh, gosh. I’m going to have to hang up on this person. This is some kind of scam.&quot;Narrator: But it wasn’t a scam. It was legitimate.Andrews: I didn’t know how to handle it. I know that sounds silly because I’m old enough to be able to handle almost anything.Narrator: The remains that were found were sent to the Armed Forces Medical Examiner System for analysis. Here, one at a time, D.N.A. transforms the missing into the found.The D.N.A. is extracted from bones and teeth and then sequenced.Timothy McMahon: Which is a way for us to determine the actual base pairs. So, when I talk about D.N.A., D.N.A.’s made up of four base pairs: G, A, T, C.Andrews: The army asked for my D.N.A, and they asked for my father’s brother’s son’s D.N.A.Narrator: The work is painstaking. It will take some time.Of 27 Tuskegee Airmen missing since World War II, he is the first, and so far only one, to have been recovered.In July 2018, the D.P.A.A. notified his daughter Captain Dickson had been found.Andrews: Because he wasn’t treated properly when he was alive, I’m taking him first class to Arlington. I want to take my CD of Donald Byrd, the jazz trumpeter, ’cause that is so cool. He would really, really like that, and he’d say, &quot;Thanks, Marla. You know how to send a person off.”

Can DNA analysis ID a Tuskegee Airman missing since WWII?

Last B-24

Dive beneath the sea to the wreckage of a WWII bomber. Search for the remains of its fallen crew.

Are We Ready for a Cyber Attack?

<div class="rich-text">Cyber threats from nation states and lone hackers are a persistent threat to America’s critical infrastructure.</div>
<div class="rich-text">According to U.S. intelligence officials and the Department of Homeland Security, state-sponsored Russian hackers have targeted the American electric utility grid. Cyber threats from nation states and lone hackers are a persistent threat to America&rsquo;s critical infrastructure. They can come from anywhere in the world&mdash;and are on the rise.
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 Are We Ready for a Cyber Attack?
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 Published August 23, 2018


 
 Narrator:
 
 Cyber attack scenarios against critical infrastructure have been a concern for the Department of Homeland Security at least since 2007—when the agency commissioned an experiment called Aurora. The question experts wanted to answer was a simple one. Could a purely digital cyber attack disrupt or disable a large generator connected to the power grid?


 
 Perry Pedersen:
 
 I was the director of the control system security program at the Department of Homeland Security. And during that time, I ran the project that many people are familiar with called Aurora.


 
 Narrator:
 
 A team of electrical engineers brought a 27-ton, heavy-duty diesel generator to a specially built testing facility at the Idaho National Lab. After connecting the generator to the power grid, they challenged a team of computer security experts to use computer code to knock the generator off line. The test was monitored via closed circuit TV.


 
 Pederson:
 
 In the video, you’ll see it running, humming along normally. And then you see the first hit...the first jump. You see the generator shudder.


 
 Narrator:
 
 The jump occurred almost immediately after the would-be attackers sent the first packet of malicious computer code.


 
 Pederson:
 
 We wanted to hit it and then wait and collect data and see what was happening and then hit it again, collect some data and kind of watch the progression of the damage to the generator.


 
 Narrator:
 
 After the second attack, the generator lurched again, belched ominous smoke and ground to a halt. Not only was it knocked off the grid – it was rendered completely inoperable.


 
 Joe Weiss:
 
 What they found when they opened the generator was just failures with almost all parts of the generator, both mechanical and electrical. So what you’re really talking about is essentially what you would do with pieces of dynamite.


 
 Pederson:
 
 This was a tough machine. This was heavy duty. And it was designed to run in severe conditions. If you were actually doing that attack, there’s no reason to pause and wait in between. You simply put your software on a loop, and you just keep hitting it until it breaks.


 
 Narrator:
 
 An attack like this could take less than a minute. But leave consequences that would last for months.


 
 Joe Weiss:
 
 If you damage or destroy these, you can't just go down to your neighborhood hardware store and buy another. It could take you maybe six to nine months to get another one of these.


 
 Narrator:
 
 And according to a government study, a coordinated attack on fewer than a dozen power stations could cause a massive outage—far more devastating even than the historic blackout that hit the Northeast in 2003.


 
 Female News Reporter:
 
 The brightness of car headlights is the only visible sight on 42nd Street tonight as thousands wait under a cloud of total darkness.


 
 Kim Zetter:
 
 All you would need to do is take out about nine substations in an attack that could result in a blackout for the majority of the U.S. that could last weeks or months depending on how the attack was designed.
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<div class="rich-text">Cyber threats from nation states and lone hackers are a persistent threat to America’s critical infrastructure.</div>

The Daunting, Dangerous Task of Unearthing Colombia’s Landmines

In 2016, the longest-running conflict in the Western hemisphere drew to a close. Colombian President Juan Manuel Santos signed a peace agreement with the Revolutionary Armed Forces of Colombia, ending 50 years of violence that had seen hundreds of thousands killed and 7 million Colombians driven from their homes—the
 <a href="http://www.unhcr.org/news/latest/2016/6/5763b65a4/global-forced-displacement-hits-record-high.html">
 highest number
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 of internally displaced people the world as of 2016.

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 However, many Colombians still feared returning to the countryside, thanks to war’s other lasting legacy: landmines. While no one knows how many mines pepper the country, from 2008 to 2014, Colombia suffered the world’s second-highest landmine mortality rate. Only Afghanistan had more deaths. Victims have since dropped from a high of over 1,000 per year to fewer than 100, but the country is still considered to be
 <a href="https://reliefweb.int/sites/reliefweb.int/files/resources/Landmine_Monitor_2017_Embargoed.pdf">
 heavily mined
 </a>
 .

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<figcaption>The Colombian military donated deactivated landmines to researchers at the National University of Colombia for testing.
 
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 The first step to eliminating the mines is finding them. Mine detection technologies have progressed very little since they were first developed in the aftermath of World War II and are still almost primarily based on metal detection. This makes Colombia’s predicament even more costly and time consuming than usual. Unlike the majority of affected nations, Colombia’s landmines are homemade and typically contain very low metal content.


 While domestic and international landmine removal groups go about the painstaking task of ridding the country of those stealthy bombs the old-fashioned way—literally digging up suspected mined areas, inch by inch—Colombian researchers have taken it upon themselves to create cutting-edge technological fixes that they soon hope will expedite the process by an order of magnitude.

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<img alt="Colombia photos, July 2015.Manual demining, Colombia." class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/desminadoroliverperezenlafincaelparaiso1.width-990_Ab9SNXo.jpg"/>
<figcaption>A member of the HALO Trust, a nonprofit that removes war debris, treads carefully during a defining operation in Colombia.
 
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 “This is no longer basic research, but application,” says Fernando Cristancho, a nuclear physicist at the National University of Colombia. He and his colleagues have developed a specialized robot that uses neutrons to identify mines buried below the soil, while other colleagues are working on devices that weed out the false positives that frequently bog down landmine hunts. Still others have pursued machines that use electromagnetic waves to remotely detonate and destroy landmines from a distance.


 “We’re putting all of our energy, effort, students, and time into trying to advance this,” says Felix Vega, an electrical engineer at the National University of Colombia. “We’re trying to to solve our own problems.”

<h2>
 A Daunting Clean-Up
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 The conflict in Colombia began on ideological grounds, with disenfranchised rural citizens calling for a
 <a href="http://www.midlandshistoricalreview.com/the-underlying-dynamics-of-colombias-civil-war/">
 transformation to Marxism-Leninism
 </a>
 . As the fighting dragged on, however, guerrillas began to lose sight of their political agenda and focus more on profit-driven crime, including cocaine production and illegal gold mining. Landmines began appearing in the early 1990s, largely as a way to protect smuggling routes, jungle camps, and illicit crops. Around 11,500 people in Colombia have been injured or killed by those hidden explosive devices since then—though experts believe many more deaths have gone unreported.


 Landmines, in general, come in two forms: ones meant to destroy tanks and other vehicles and ones meant to stop humans. Colombia only has the latter: “It’s really difficult to get a car into the middle of a forest,” says Jairo Alexis Rodriguez, a physicist and director of research at the National University of Colombia.


 Even more uniquely, all of the mines left in Colombia today are homemade improvised explosive devices (IEDs) rather than commercially-produced military grade ones. Rebels fashioned them with whatever materials they happened to have on hand, including PVC pipes, plastic bottles, and various chemicals. They purposefully left metal out to prevent the military from identifying them with metal detectors, and the variety of substances they used has also made it more difficult to train sniffer dogs to help with cleanup.

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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/ied-tall.width-990_nVUmd2h.jpg"/>
<figcaption>Many landmines in Colombia are IEDs rather than commercially made and almost entirely devoid of metal, including this one, made from a plastic bottle and plunger.
 
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 That leaves experts with a daunting challenge: how to find mines buried in thick jungles and rugged mountains in a country over twice the size of France with little to no help from traditional demining tools?


 Getting a handle on the scope of the problem is a first step, according to Chris Ince, Colombia country program manager at the
 <a href="https://www.halotrust.org/">
 HALO Trust
 </a>
 , a non-profit organization dedicated to cleaning up debris left over from war. “There is an urban myth that the entire country is mined,” he says. “The reality of the situation is that, until a detailed survey is conducted, the true level of contamination remains unknown.”


 To do this, Ince and other experts hire community members (and, in some cases, former guerrillas) living near suspected mine fields. With their help, they conduct extensive interviews to determine if landmines are indeed present and, if so, where, exactly, they occur. Because guerrillas wanted local people on their side, they often told rural residents where the mines were so the residents could avoid those areas. After interviewing up to 1,000 people at a given site, Ince and his colleagues use those data to home in on an area of likely contamination.


 HALO has cleared more than 500 landmines from over 150 minefields in Colombia. But the task is excruciatingly labor intensive. Some mine fields are a seven-hour walk from the nearest road and require using mule trains to ferry supplies back and forth. Reaching the site is just the beginning. Given that metal detectors have limited use, deminers meticulously dig up the soil of the entire site (sans large shrubs and trees) to a depth of just over a foot. “Up to 70% of our day is spent in vegetation-clearing activities,” Ince says. “You’re literally hand digging the entire area.”


 Cristancho adds that, though certain vegetation is left in place, these operations cannot help but cause significant environmental damage. “It looks like a war zone,” he says. “If you take away 15 centimeters of soil all over the place, the earth gets dry and then the area gets washed away in the next rain.”


 The method also takes forever. Whereas experts working with a metal detector may cover an area of 24 square yards in a day, in Colombia, they typically cover just one to six square yards. “Having all kinds of procedures in place guarantees high standards of safety but makes the process slow and logical,” Ince says. “One of the biggest things we have to do is keep deminers focused, because it’s like finding a needle in a haystack.”

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<h2>
 Modernizing Mine Hunting
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 Yet there could be a better way. As Diego Torres, a physicist at the National University of Colombia, asks, “What if we can develop technologies that immediately identify and destroy mines?”


 For years, Torres and others at universities throughout Colombia quietly pursued landmine-related technologies in near secret to avoid politicizing their work and raising security concerns. After peace came, “we discovered that groups located just 100 meters from each other had been working in the shadows on the same things for ten years,” Torres says.


 For the past decade, Cristancho and his colleagues, for example, have been perfecting a landmine-detecting robot that they believe would spare deminers from having to dig up entire tracts of land. The Alexbot, as they call it, was inspired by existing oil industry technology to measure soil humidity by using neutrons. As Cristancho says, “We didn’t invent this technology, we just put the general pieces together to make it fit a specific task.”

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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/img_2081.width-990_g90Ec5k.jpg"/>
<figcaption>Nuclear physicist Fernando Cristancho demonstrates the features of the Alexbot, a robot that he and his colleagues created to detect landmines using neutrons.
 
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 The six-wheeled Alexbot—which bears a slight resemblance to the Mars rover—sweeps a mechanical arm back and forth above the ground as it slowly proceeds forward in an area suspected of having landmines. The arm holds a container with small amounts of californium-252 which emits neutrons used to map things hidden below. The resulting data are based on the rate and speed at which neutrons backscatter when they encounter carbon, hydrogen, nitrogen, and oxygen—all common components of explosives.


 In
 <a href="http://unperiodico.unal.edu.co/pages/detail/innovador-prototipo-detecta-minas-antipersona/">
 field tests
 </a>
 earlier this year, the Alexbot successfully detected a deactivated IED—donated to the lab by the Colombian military—that the researchers had buried in diverse soils and at different depths and humidities. In other trials, the team was able to detect buried IED-like objects containing just 3.5 ounces of chemicals typically used in landmines. Next steps, Cristancho says, they’ll perform many more field trials and use machine learning to better teach Alexbot what to look for.

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 Cristancho is not the only researcher working on such problems. His university and Los Andes University has produced around half a dozen PhD students whose work specifically focused on demining techniques. Other scientists are pursuing various solutions as well. The key, Torres says, is to design a suite of technologies that not only expedite the process of finding and deactivating landmines but that also add layers of redundancy. “You can always miss something,” he says. “You need to create more techniques if you want to be sure that you have completely eliminated the threat so people can return to their homeland.”


 Vega and his students, for example, are creating another type of landmine detection device that uses ground penetrating radar to map objects buried up to eight inches beneath the soil. They hope this will eventually eliminate the time-consuming problem of false positives, which may constitute up to 99 out of 100 detections using conventional methods.


 But such projects are in need of greater support. “These devices are used to avoid people dying and suffering, but that doesn’t bring in much money,” Cristancho says.


 In one case, Vega and fellow researcher Francisco Roman had created a patented landmine-destroying device that used directed electromagnetic waves to safely activate mines at just over 80 feet away. It was shelved due to lack of funding. “At the end of the day, we developed a concept that worked, but we had to stop at that stage,” Vega says. “Going to the next phase required more money than was available.”

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<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/img_2072.width-990_MvauroU.jpg"/>
<figcaption>Fernando Albarracin-Vargas (left), Sergio Gutierrez, Felix Vega, and Diego Alejandro Torres Galindo at the National University of Colombia's landmine detecting test site. Albarracin-Vargas and Gutierrez are using ground penetrating radar to map objects buried below.
 
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 Given such constraints, Ince doubts that the high-tech devices being developed by Colombian scientists will be ready for deployment in the near future. “Probably in the long term some, of the more esoteric technologies being considered will lead to something capable of helping,” he says. “But the chances of taking something from a prototype to a commercially viable and cost-effective technology—one that doesn’t further complicate security requirements within the framework we operate in—is more difficult.”


 Cristancho argues that the time scale is not a problem—if only funding were available. With $800,000 and eight months of testing, he believes the Alexbot could be deployable. “We have the right people, and we know what we’re doing,” he says.


 Colombia does have an obligation to see that through. The nation is a signatory to
 <a href="http://www.un.org/Depts/mine/UNDocs/ban_trty.htm">
 Mine Ban Treaty
 </a>
 , a United Nations convention that seeks to end the use of antipersonnel landmines worldwide. As part of that treaty, Colombia pledged to become landmine-free by 2021—a goal that HALO and other demining groups are striving to meet. But according to the International Campaign to Ban Landmines, a coalition of non-governmental organizations, Colombia is
 <a href="https://reliefweb.int/sites/reliefweb.int/files/resources/Landmine_Monitor_2017_Embargoed.pdf">
 not on track
 </a>
 for a 2021 victory. Bureaucracy has slowed an already slow process, and certain parts of the country are still under control of organized criminals and the National Liberation Army, another paramilitary group that has yet to agree to peace. Evidence exists that fresh mines are still being planted in those areas, which, for now, remain impossible for humanitarian groups and researchers to reach.


 If some of the technologies come to fruition in the next couple years, though, Colombia may have a chance of demining the parts of the country that are at peace by 2021. Nor is Colombia the only nation that could benefit from better landmine detecting and deactivating technologies, Cristancho points out. “Everywhere where you have some kind of political or military conflict, they use landmines, and in the worst case, they use IEDs,” he says.


 “Will we get there? I don’t know. But we’re doing everything we can to advance science and technology in this country,” Vega says. “At the same time, we’re producing things that may solve other problems tomorrow.”


 Photo credits: Rachel Nuwer, HALO Trust

Ridding Colombia of landmines may require a multi-pronged mix of traditional and ground-breaking technology.

<div class="rich-text">Churchill launches the largest military evacuation in military history. But there's a secret killer in the waters. 
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<div class="rich-text">Churchill launches the largest military evacuation in military history. But there&#39;s a secret killer in the waters.

&nbsp;
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<div class="rich-text"><h3>
 Hilter’s Secret Weapon
</h3>

 Published March 9, 2018


 
 Onscreen: Dunkirk beach, France
 


 
 Winston Churchill:
 
 We shall prove ourselves, once more, able to defend our island’s home. To ride out the storm of war, and to outlive the menace of tyranny. If necessary for years. If necessary, alone.


 
 Onscreen:
 
 Early in WWII—Nazis surround 400,000 British soldiers. If defeated, Hitler will likely conquer all of Europe.


 
 Churchill:
 
 The situation of the British and French armies now engaged in a most severe battle, and beset on three sides, and from the air, is evidently extremely grave.


 
 Onscreen:
 
 Churchill launches the largest evacuation in military history, sending every available ship to rescue the troops.


 But there is a secret killer in the waters. Hitler placed undetectable sea mines that only need a ship’s proximity to detonate, sinking hundreds of thousands of allied ships. The only way to rescue the soldiers is to figure out how Hitler’s secret weapon works.


 
 Simon Foster:
 
 Did they have any idea of what’s inside?


 
 Nigel Froude:
 
 Absolutely not, so they knew nothing about this, so they were going completely blind. These guys were trained in bomb disposal, but this was completely new to them. So a lot of it was just trial and error. The bravery of these guys is phenomenal.


 
 Foster:
 
 So, is this the key to it all? Inside here, this mine is going to reveal its secrets.


 
 Froude:
 
 Yeah. Grand reveal.


 
 Foster:
 
 This would’ve been the moment of truth.


 
 Froude:
 
 And there we have it. This is the trigger that’s going to make the whole mine go bang. If we now remove this place here, we can see the trigger just inside there. If I move it with this screwdriver, you can see the movement of the switch there.


 
 Foster:
 
 And that’s just like a seesaw.


 
 Froude:
 
 Exactly, just like a seesaw. It moves, makes the circuit, and the mine would go bang.


 
 Foster:
 
 Now, what’s making that seesaw move?


 
 Froude:
 
 Magnetism, that was the big secret.


 
 Foster:
 
 The seesaw inside the German, is a dip compass and we’ve got our own version here. Now, unlike a normal compass that moves left or right to indicate the magnetic field, this actually moves up and down.


 The Earth’s magnetic field, which is all around us, it finds it easier to pass through this steel plate than it does in the surrounding area. And this plate here is actually concentrating the magnetic field lines. The magnetic field passing through this is going to be more concentrated here than it is out here. This, this is almost like a lens for magnetism. And as you can see, as it passes over the compass, it’s going to trigger the mine.


 
 Narrator:
 
 This concentrating effect turns a steel ship into a gigantic magnet with its north pole under the ship. It is this strong north pole which triggers the mine. If they can create an artificial magnetic field that generates a south pole under the ship instead, the mine will not go off.


 
 Foster:
 
 The first method they came up with was called Degaussing. If you have a line of cabling like this and run some current through it, it’s going to create a small magnetic field in the opposite direction to the Earth’s magnetic field. Now, if I take my bit of steel and place it over the mine as we did previously, hopefully the mine will no longer be triggered. And this is how they solved the problem. They wrapped a long line of cabling around the outside of the ships, and run huge currents through them. Creating a magnetic field that actually countered the concentrating, the lensing effect of the ship’s hull and prevented the magnetic mine being set off.
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