captioning sponsored by newshour productions, llc >> woodruff: good evening, i'm judy woodruff. on the newshour tonight... >> never again! >> woodruff: ...survivors of the florida school shooting and thousands of others demand change to the nation's gun laws as president trump hol a meeting on school safety. then, a city in scotland reflects on the school shooting that shook its community more than 20 years ago and what itu. could teach th about stopping gun violence. >> you can never say never but i think we've done an awful lot to ske our schools safer pla and i don't go out the door wite f the worries american parents undoubtedly have today. >> woodruff: plus, what freely available open-sourcdata and satellite images can tell us about the true power of north korea's nuclear arsenal. all that and more onht's

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thank you. >> woodruff: calls for action after the school shooting in florida. in tallahassee and around the s country todadents and supporters appealed for an end to the bloodshed. william brangham begins our coverage. >> what do we want? >> change! >> when n we want it? ! >> brangham: the chants began as soon as about 100 of the school shooting survors arrived at e florida state capital in tallahassee. >> never again! never again! >> brangham: from there, they ved inside to lobby the republican-run legislature for some stronger gun control. >> please, i b and i demand that every single person in power who has the ability to change the fear that kids feel going back to school, that they do something. >> no longer can you take money from the n.r.a.

no longer can you fly under the radar doing whatyoer it is that want to do. because we are coming after you. we are coming after every single one of you and demanding that a you taion and demanding that you make a change. >> brangham: the crowds outside ndthe capitol grew to thou for a midday rally. there theyeard an outpouring of anger and grief, over the killing of 17 at marjory stoneman douglas high school, one weekgo today. >> how many more innocent people have to die before we make a change? a change is overdue. and we are the change. when children act like leaders leaders act like childre you know something is about to change!ha >> brang these student activists had traveled more than 400 miles, from parkland, in south florida, to press for a range of solutions. one student called for a ban on semi-automatic weapons like the a-r-15 rifle used in the massacre. >> the only purpose of an assault weapon like this is to kill and to kill as many people

as possible. the a-r-15 is not a self-defense weapon. it is rightly so-called an pon.ults w >> brangham: a day earlier, the florida state house voted against taking up a bill to n assault weapons. today, the democrat who called for that bill to be debated made an impassioned plea for theo studentsep up their fight. >> you are the cavalry we've been waiting for! so to you, let's do it! >> brangham: across the country, thousands of students heededat all, walking out of classes and chanting slogans demanding tougher gun ntrol. washington, d.c., hundr massed outside the u.s. capitol and the white house. inside the executive mansion, president trump held a listening session with high school students and teachers. among them: some who survived the parkland attack, as well as others from school shootings at newtown, connecticut, in 2012 and at columbine high in colorado in 1999. >> we're going to be very strong

on background checks. we'll be doing very strong background checks. very strong emphasis on the mental health of somebody. >> how is it that easy to buy this type of weapon? how do we not stop after columbine, after sandy hook? >> it should have been onein school shoand we should have fixed it! and i'm pissed! because my daughter i'm not going to see again >> until now the president has been a staunch supporter of gun rights. last year, he signed a law that eliminated an obama-eraon regulahich made it harder for some mentally-ill people to get guns. the rule said that anyone receiving social security benefits for mental illness anee who had alsoruled incapable of handling their own finances would be blocked from purchasing weapons. the president vegned the law ing that rule last february.

mr. trump has also repeatedly mainined his allegiance to t national rifle association. last april, he addressed the n.r.a.'s leadership forum in atlanta. >> you came through for me, and i am going to come through for you. >> brangham: the center for responsive politics estimates that during the 2016 election, the n.r.a. spent $30 million to support mr. trump and oppose hillary clinton. during one of the presidential debates, candidate trump argued that strict gun laws don't actually reduce gun violence. >> in chicago, which has the g toughe laws in the united states, probably you could say by far, they have more gun violence than any other city. >> brangham: but yesterday, amid the outcry over parkland, the president appeared to soften his stance. >> just a few moments ago i signed a memorandum ing the attorn general to propose regulations to ban all devices that turn legal weapons into machine guns.

>> brangham: democratsike nator diane feinstein of california urged the president to support her legislation banning bump stocks and to encourage his llow republicans stop blocking it. white house okeswoman sarah sanders also said the president is open to improving federal background checks, and possibly setting a minimum age for buying a-r-15-type rifles. for the pbs newshour, i'm william brangham. >> woodruff: the president also said today letting trained school workers carry weapons might make attackers think twice and, in his words, solve the problem. we'll return to all of this after the news summary. in the day's otherews, president trump charged again that president obama should have done more about russian meddling in the016 election. he also questioned why his attorney general, jeff sessions, is not investigating democrats. meanwhile, house and senate democratic leaders, nancy pelosi and chuck schumer, called for giving the f.b.i. $300 million to fight any meddling in thect

mid-term ens. cities and townsoncross the na mid-section faced severe flooding today, from heavy rain and melting snow. rivers overflowed in michigan, indiana and parts of illinois, submerging roads and naighborhoods. in goshen, indiavernight, crews used boats to rescue people from their homes. and in arkansas, a school bus had to be abandoned dozen students rescued. in syria, the carnage raged on, in a major assault on rebel-held suburbs east of damascus. human rights monitors now say more than 300 people have been killed, just since sunday, and doctors say they are overwhelmed. government air strikes and artillery are blasting the area, and humanitarian groups warned today is a catastrophe the making. >> people are terrified. we know that many are seeking shels r in basementand in dugout makeshift shelters.

we know that children are facing the brunt of this crisis and we are very, very wried for the safety of everyone. >> woodruff: meanwhile, in the north of syria, turkey vowed again to continue its offensive against syrian kurdish fighters around afrin. it also repeated a warning that it will attack fighteried with syria's government, if they try to aid the kurds. new details today on the deadly wreck of an amtrak train that carried dozens of republican congressmen. the train slammed into a garbage truck on tracks in rural virginia last month. now, the national trtation safety board says the truck had tried cross after the safety gates came down. one of the wkers on the truck was killed in the crash. the president's el rejecting criticism that he's profiting from his father being in office. donald trump junior is on a week-long business trip to india that's raised conflict of

interest questions. but he told india's cnbc affiliate that his family is actually missing out on opportunitie t >> when peopk about it these days it's profiteering from the presidency and all thie nons it's like wait a minute-- i can't do deals? i've spent over a decade creating relationships. and we could do so many more and we are not doing those. 'but to one wants k about those kind of deals. l 's sort of a shame. because we put on ese impositions on ourselves and essentially got no credit for actually doing that and for doing the right thing. >> woodruff: the president's son is marketing tru brand luxury homes in india. as president-elect, the elder trump had pledged his real estate business would conduct no new deals while in office. questions today about whether first lady melania trump sponsored her parents for legal resident status in the united states. it's a process that president trump has condemned as "chain migration." "the washington post" reports e slovenian nationals have

their green cards, and will soon become u.s. citizens. the report quotes immigration experts as saying mrs. trump's sponsorsp appears to be the "only reasonable way" that could happen. on wall street tay, stocks swooned late, after mites from the federal reserve's latest meeting signaled more interest rate hikes. the dow jones industrial average lost nearly 167 points to close. at 24, the nasdaq fell 16 points, and the s&p 500 slipped almost 15. and, at the winter olympics in south korea, an important day for american skiers. jessica diggins won the first u.s. gold medal, ever, in cross- country skiing. and lindsey vonn took bronzen the women's downhill. at 33, she's the oldeswoman ever to medal in alpine skiing. r:ill to come on the newsh the backlash parkland, florida, students are facing for speaking

out about gun laws. how scotland tackled gun violence after a school shooting in the 1990s.me ering the life and legacy of billy graham, plus, much more. >> woodruff: as we said at the beginning of the program, stdent-led rallies have pic up a momentum of their own in florida and around the country what should be done about assault-style weapons and other kinds of guns. there were rallies he in washington as well today, in front of the white house and near the capitol. two students who participated after a school walkout join me now. camille richter is a senior at mclean high school in mclean, virginia. d jake bennett is a senior at

h.b. woodlawn in arlington, virginia.k and thu to both of you for coming out here to the studio to talk to us. jake, i'm going to start with you. you walked five miles from your school to the white house. why did you want to be a pa of this today? >> because we live so close to d.c., we felt it wouldn't be the same if we just walked outside, ife just walked to courthouse, which is where our public school headquarters are. we felt driven to march to the white housand to really show we would go this far to voice uour discontent and or anger with congress. >> woodruff: and and, camile, wy is this so important to you? >> i am sick of going to school every day and beingre scafor my life and my friends' lives. we live in a relatively safe

part of virginia in mcln and it's silly we live in a first-world country and, still, first graders, second graders, young kids all through high schoolers are afrd of going to school, and they're afraid of what's going to happen to them. it not right and it really needs to stop. >> woodruff: you wer saying you feel strongly that something has to be done. do you have an idea right now of what you think it suld be? >> i think that universal background checks need to be implemented to buy a gun, and i think that we should ban assault rifles again.ne they were bfor ten years and that really did work. there's no need for americanto civilianave a machine of war. they're not used for hunting orr ection, they're used for murder, and i thinkhose are two steps in the right direction. eyou know, background s are very fast, they take two minulys, and they would re save a lot of lives, my onion.

>> woodruff: yet, a lot of people say since we haven't had that legislation since it expired argue people should be allowed to buy any kind of gun they have to. >> it was ridiculous. in virginia we can only buy one n a month wich some complained is too restrictive. i have a lot of family from wisconsin, hunters. i have been around guns for a long time. i know what it's like. you shoot a g in, you li virginia, it's a pretty regular thing. but there's a difference between a hunting riflele anan assault rifle. there's a different between military grade. it's blatantly understand necessary. >> woodruff: jake, you mentioned the assault weapons and one of the ideas that's being discussed today ngis put an age limit on who can buy an ar-15 or another assault weapon. would something like that, you

think, be acceptable? >> i think part of that would be acceptable. i think that an age limit should be implemented but other restrictionshould be added o to it. i really don't believe that anyone needs an air 15 or other assault weapon. they don't serve any purpose except massacre. it's what the shooters in sandy hook and newtown used and orlando and now stoneman uglas. it's unnecessary. >> woodruff: camile, there have been proposalsre be more guns in schools to protect sudents, thateachers or others be trained and armed to protect students. >> i think it's expensive and unnecessary. you know, how much money does it cost to give every teacher and potentially the students the training and wpoay they need in order to protect themselves? it feels like there is an easier

solution to the problem tha people and lawmakers are kind of avoiding. >> woodruff: jake, i know you were all just watching some of the discussion inside the white house, president trump invited students and some parents who tove been through these tragedies, and edu, do you feel like the message is getting through to the people who can make a difference? >> the message is the florida students are sending, you know, that we were sending, what students all across america are sending, parents, teachers, everyday people are trying to send to congress and to the pr tident arehat, you know, congress needs to stop saying yes to the n.r.a. and start saying yes to the american .hildren and safety and schoo i think that's the message we were trying to send. i think what we did today was set forward a motion that will keepl you know, it wilep building momentum until it does make a change. >> woodruff: what about that,

camileha because ther been school shootings and protests before, but it hasn't lasted or there have been a little bit of change t noa change, these things keep happening. >> we elected congress to be the representatives of the people, not to be the representatives of big lobby firms and of the n.r.a. it feels like when your legislature and representatives ignore thei epdemic of shootings going on across the u.s., it makes you wonder who they are working for. you know, you want to be u represented. nt your voice to be heard. so... e> woodruff: and, you know, some say, well, se young people feel strongly but they're just high school students. >> right. e> woodruff: how much difference can treally make? >> i think we can make a huge difference. there has been some talk from some representatives that, you know, the high school students who are making a stand in florida are plants by the f.b.i. or paid to do this, and it' absolutely ridiculous. again, like we were saying earlier, if you're 18, men areou old to be drafted.

at 16, at least in virginia, you can buy a cars, which is dangerous within itself. why can you buy a gun? you can do these things -- it's just -- it doesn't make sense. we hve a voce and we're clearly, you know, able enough ho use it. you know, we know at we're talking about, to an extent, but... >> woodruff: jake, do you feelri you and yourds are committed to stick with this, with this issue? >> oh, absomutely. we aremit to keep doing whatfer is necessary to afect change whether it's rallies, you know, prtests, whatever it takes, really reaching out to people online. it's not going to be just us that affects thie.s cha it's going to be high schoolers all across america who does. >> woodruff: i know you've managed to get the attention of a lot of people. jacob bennett, camille richter, thank you both. >> thank you.

>> woodruff: we now get a teacher's perspective: mike conrad says the issue of scho shootings has come up repeatedly in his own classroom. he teaches video production at icyal oak high school and joins us from detroit,gan to discuss how educators are confronting this national tragedy. mike conrad, welcome to the program. you wes able to listen to the two students we were speaking with. what did you make of what they had to say? >> well, i applaud them for everything they had to say. the stdents not only camile and jake but students around the country are taking ad stand an they're using the right language, they are using the right vocabulary. they are fed up, and it's time for them to help make change. so i applthd the fact thaey went to the rally today. i enjoyed hearg their thoughts, and i agree with them. >> woodruff: you were telling us that yode own sts are speaking up. what are they saying about the shooting in flrida? >> there's a lot of discussion. the discussion tone has changed in the past couple of days. students are scared. i can give you an example that,

daily, just a generic p.. announcement throughout the school, when the tone goes off, the tension heightens and you hear a student gasp or a student say with fear "oh, no," because they don't know what the announcement igoing to say. that shouldn't happen in the classroom. there are students asking me hot i'm prepardefend them should a shooter come into the school. it's a difficult question to answer because i can talk about all of our drills, all of our lockdowns, iutan talk abo everything we do as a school district and what i do in terms of my owndg know but, at the end of the day, how do you prepare yourself for one of these situations that happened in florida. >> reporter:. >> woodruff: well, what is your thinking about teachers being armed, trained? it came up just this afternoon h at the whiuse, the president raised it with the students and teachers and parents who were -- he was meeting with. what do you think of that idea? >> i think that the moment that you put a gun on the hip of a teacher in a tassrooat we

have accepted a norm that school shootings will not stop, that we are now on the front line to defend against them instead of trying to find a way to stop them. look at a classroom as a safe environment, and i never look at it, when i say that to students or parents, that a safe environment in a classroom means defending against shootings. i look at it as a safplace where a student can talk to me and bring their problems to me. when they come to me and tell me a student is going to harmem lves, they trust they can say those things to me. that's a safe environment. the second i put a gu on my hip, i don't think that relationship continues. >> woodruff: if it's not arming teachers, then what are some solutions, do you think? what's the role thateachers can play to keep students safe and themselves? >> well, i think soit is education and awareness. i think that camile and jake did a great job of explaining some

of the things that have to happen prior to e pont where a shooter ever walks into a school. teachers should not be a line of thdefense. point should never get to the point where they're asked to do so. so i think we as teaers, i teach high school students, 15, 16, 17, 18-year-old students, i should be preparing them to make the decisions vote, to call their legislators, to march should they want to, but i thiny ob as a teacher is to inspire and to educate, and i think that's the best thi that we can do at that point in a classroom, not make it a military zone. >> woodruff: mike conrad is a teacher at royal oak high school, in detroit. thank you very much. we turn now to a darker side of the response to the parkland shootiiv. hari srean explores the anger, lies and conspiracy theories cropping up online.

>> our entire nation is praying for the victs and their families. >> sreenivasan: the immediate response to the school soting in florida was a wave of prayers and condolences from around the country. what qckly followed? a flood of allegations and conspiracy theories about the students calling for gun reform. >> i just know we are being fed something as phony as a three dollar bill. >> sreenivasan: right-wing outlets, like gateway pundit and infowars, and online trolls are promoting the false theory that some of the parkland teens are actually paid actors. the target of many of these attacks is stoneman douglas senior david hogg. he has been called an f.b.i. plant who was coached by his father, and a "crisis actor," after video surfaced of a california cbs story featuring hogg from august. > these people saying this is absolutely disturbing. i am not an actor in any sense, way, shape or form. i was a witness to this. s someone that had to witnis and live through this. >> sreenivasan: many of these

false accounts came from extreme fringes of social mediin but are now amplified by better- known voices. conservative writer dinesh wesouza tweeted that one of the students, intervby a british news program, seemed "coached." onand the president's son,d trump junior, has liked some of these conspiracy tweets. but tuesday, florida senato marco rubio tweeted the accusations against the students are: "the work of a disgusting group of idis with no sense of decency." other republicans stayed away from conspiracy theories about the students, instead accusing democrats and gun control vocates of using the students to push their agenda. former georgia congressman, jack kiston: >> their sorrow can very easily be high-jackedy left-wing groups who have an agenda. let's k ourselves, do we really think, and i say thiser siy, do we really think 17 year olds on their own are going to plan a nationwide rally?

>> sreeniv tucker carlson:chor >> all of a sudden you're seeing these kids involved in calls for very specific pieces of legislation. and the allegation is that they ct with organized anti-gun groups. thpeople who have suggeste have been denounced as immoral and heartless and how dare you on these kids and attack them- which for the record i am certainly not doing. but i think it raises interestingow questions about we make our law. >> sreenivasan: stoneman douglas students are png back against the attacks and criticisms. >> i for one just think, ignore it, first off. because these people are not taking action; we are. we're taking aion and i don't care what a troll says. they're just hiding behind a computer.er we're out on the streets. >> sreenivasan: despite all the criticisms and false accusations, the students still plan to march for gun control next month in washington and around theountry. for the pbs newshour, i'm hari sreenivasan.

>> woodruff: now, the view from a scottish town that knows the horror of n violence first nd. many in dunblane, scotland, have pledged their support to student activists from florida and beyond. britain outlawed hand gun ownership after a massacre at dunblane primary school in 1996. the town has become frustrated byunmerican attitudes toward control. but as special correspondentab malcolm t reports, for the first time in years, some scots see reasons for optimism. >> reporter: in dunblane, a spring flower is in bloom. the snowdrop. it's especially poignant fordo alicherty. she lost 16 of her friends and a teacher in britain's deadliestma shooting. alice, a waitress in her mother's tea shop, has a tattoo immortalizing the snowdrop campaign, a parents movement which led to a nationwide ban on private ownership of handguns. >> once was enough. it didn't need to happen again.

>> reporter: afterast week's massacre in florida, she wishes america would finally learn the lessons of dunblane. >> you'd rather liten to the sound of guns than the sound of children laughing? is that what you're saying thato their lives aronger important? it's all about money it's all about people's right t arms? and i don't think people's right to bear arms is strongn the people's right to have an education and feel safe. and their right to have a life. >> reporter: alice's mother nora was a member of the scho oversight board. three of her children were pupils. they all survived. like many in dunblane, she has become frustrated at the unending cycle of sc shootings in america and the lack of action on gun control. >> your first reaction is "oh, it's another one, and that's ridiculous." and those are two wrong responses to human lives being lost due to guns. but that's what it's beme. the rest of the world is looking at america and thinking why, why are you allowing amerins to

shoot americans, it doesn't make sense. >> reporter: at dunblane cathedral this past weekend, the congregation prayed that america would have a "deep and sober reflection" on its gun laws and that prayer would move beyondnt "sentind words to a deep, growing and active resolve for change." that's a sentiment shared by mick north whose only child, sophie, was killed at dunblane. he is exasperated by america's gun laws. >> athe moment, they are plainly insane. anything that is a gun has the support of the n.r.a. for being available to any citizen of the usa. i mean that is ridiculous. ryu have kids, teenagers being able to buy milityle weapon devastating effect we saw last week. >> reporter: former dunblane pupil malcolm robertso

particularly aggrieved by what he sees as the failure of america's politicians to protect children. he's from a political family. his father george was britain's defense secretary and later the nato secretary general. robertson recalls thomas hamilton, the dunblane shooter, arguing with his father ov a grievance, years before hamilton's anger morphed into carnage. >> i've got three children, three boys. i'm pretty confident that they're safe. i mean you can never say never but i think we've done an awful lot in this country to make our schools much safer places and i don't go out the door with the woies that some american parents undoubtedly have today. >> reporter: here is a statistic that highlights the difference between scotland and the united states. last year, in scotland which has a population of 5.2 million, there were two gun related murders. if such a crime rate applied to america, which has aation of over 320 million, there would

have been 124 murders. but according to the gun violence archive, the number of people killed by firearms in the united statear in 2017 was 16,000. that translates to every single person in dunblane, which has 9,000 residents; plus 7,000 people elsewhe. john carnochan helped to make scotla safer. a former senior detective, he ran the pioneering violence reduction unit, which eradicated glasgow's reputation as europe's murder capital, by targeting all forms of violent behavior. >> start where you are. do what you can. and that will make a difference, you'll start to move towards it if we wait until we have a great plan i suppose, it's never going to happen. if we wait until we have some leader who rides over the hill and says we're going to fix this firearms stuff you're going to be waiting a long time. it's not goinggeo happen. chtarts at an individual level. that's how systems change. heat's how we changed it.

that's what we di in scotland. it doesn't matter where wet, stou will make a difference, and in public health terms, don't make it worse. so i think by reducing access to children to assault rifles, that's a start. >> reporter: at the tilly tearoom, the sense of frustration with america is being replaced by cautious optimism. >> i feel there is a change in momentum. i watched a bwonderful spee emma gonzales, i think is her me. >> if the president wants to come up to me and tell me to my face that it was a terrible inagedy and how it should never have happened and ins telling us that nothing is going to be done about it, i'm goingto appily ask him how much money he received from the national rifle association. >> that young person that i heard speak was the most honest, articulate speech i've heard. and i felt really-- i feel that there's a chance if they hold on to what she said, and people get behind her, at last they can change the corruption from the

n.r.a. and the government. >> reporter: sophie north's bereaved father also feels uplifted bwhat he sees as the inspirational voices emerging from florida. >> keep on talking.ep kesing whatever means you have to publicize your feelings on this. edia.l i hear marches. even walkouts from school. make sure it stays in tell people how it's affected you. don't let the powers that be, divide and rule. kke sure that the average american citizws exactly how this impacts on the average american d. >> reporter: in dunblane, they thbelieve the ballot box i best way to counter the torrent of political donations and lobbng flowing from the gun industry. >> you change it by identifying those peop you can trust in power, by electing those people you can trust in power who will make a difference. the starting this, need to continue doing it.ee

weto get behind them. you that notion that never underestimate a small group ofha people cane the world because that's the way it usually happens anyway. >> ♪ children of love, cover your ears, the bad man is ♪ coming, to take away your >> reporter: eileen barr plays her song about gun violence in the music room of the dunblane center.'s playground, a meeting place, a theatre, a sports hall. symbol of all it's dunblane's rebirth and determination to live. the victims are memorialized in window engravings. there are snowdrops and other images that represent the children. sophie north's motif is her cat. generous donations froms americlped to build this place. in return dunblane offers itswi om. >> my words to the americans s would be to ju where scotland, see where the u.k. has come from taking those actions

jud just moving forward an e ying no more. >> and i would l think we could support america now in trying to change the gs and make america safe. >> reporter: the view from the tearoom is one of tranquility and safety. alice doherty is 27. that's the age her f bends would han, she has never visited america because of its gun culture. >> we got rid of gunand there were people that would have liked guns before. but their lives haven'ged that much. nobody walks around miserable because they don't have a gun. >> repter: the people of dunblane are weary of being defined by tgedy, which is reinforced every time there's a shooting in america. when, they wonder, will america heed the lesson of the snowdrops. for the pbs newshour, i'm malcolm brabant in dunblane.

>> woodruff: the trump administration confirmed last night that vice president pence was scheduled to secretly meet top north korean officials during his recent trip to so korea. e administration said senior north korean officials pulled out of the meeting at the last minute, which would have come siafter pence santly in acknowledge, the north koreans, including kim jong-un's sister, during the olympics' opening ceremony the trump white house considers north korea's nuclear and missile programs the top threat to american national security. st week, miles o'brien looked at the north's ability to make the material required for nuclear bombs. so, how much do we know about those programs? >> reporter: north korea has tested nuclear weapons six time6 since t this mountainous site in punggye-ri.

no one from the outside has witnessed such a test, but the experts believe this propaganda movie produced by the regime offers an accurate, albeit embellished, version of what happens inside. but how much is known about the design and size of this secret arnal? jerey lewis is director of the east asian nonproliferation t program middlebury institute of international studies at monterey. >> so these black spheres are actually the estimated size of the cavities from the north rea's nuclear explosions. >> reporter: he and his team used terrain data gathered by satellites to build a 3d computer model of the punggye-ri test site. >> we estimated where the nuclear explosions had occurred. w were able to use satellite photographs to sre the tunnels went into the mountains. when we finished that, one ofth thgs we realized is that s

the could accommodate a much larger nuclear explosion than we had seen in the past. >> reporter: it led him and his team to predict the north koreans would soon test a bomb ed-kiloton hun yield, much larger than their previous tests. the prediction came at the beginning of 2017. in september, seismometers detected an explosiot that big. even when testing occurs underground some gases can leak out. the united nations, the u.s., south korea, japan and china have surrounded the north with sensors that can detect radioactive isotopes as well as so called noble gases before they decay. the ratio of noble gases xenon 131 and 133 can offer a clue about the design of a bomb. but the north korean site is does not seem to leak very much. >> the south koreans detected a little bit of xenon-133, but not

that much and it didn't detect any other isotopes. >> reporter: physicist and former arms control inspector david albright is president of the institute for science andrn inional security.yo >> not whad expect from a large yield weapon, so they're s early-- they're doing something and it ideal test site location. the explosion is sealing the material inside. >> reporter: but the north koreans do share some tidbits about what their weapons might look like, or so it seems.ve >> so, thectually shown us what are presumed to be photographs of their nuclear devices and they've shown that over the last few years' time frame. >> reporter: nuclear physici sig hecker is with the center for international security and cooperation at stanford universi. he ran the los alamos national laboratory from 1986 through 1997 and has visited north korea

seven times. he believes the first weapon they tested was akin to fat man, the bomb that the us dropped on nagasaki. in it, high explosives implode a plutonium core, causing an instant nuclear chain reaction or explosion. north korea's first test in 2006 was an apparent failure, but in 2009, test number two was a ccess. eance then, the yields have grown ly larger. and that leads experts to believe developed a so called boosted fission bomb.om >> the boostedis one where you take highly enriched uranium or plutonium and yoully put the fusion fuel inside to plutonium or highly enrichedhe uranium. >> reporter: in 1957, great

britain tested a one stage boosted thermonucleabomb. it's yield: 720 kilotons, or about 50 hoshima bombs. >> but the trouble with them is as you increase the yield, it gets bigger and bigger in diameter, and it uses incredible amount of weapon-grade uranium. and so, all the countries are motivated to go to the two-stage weapon. >> this is a 3d model of north eyrea's thermonuclear weapon. eleased a series of pictures and we were able to assess its size. reporter: a two stage, or hydrogen, bomb allows for a much larger yield in a smaller, lighter package. it begins with a plutonium or highly enriched uranium explion, stage 1, that creates enough energy to squeeze hydrogen and its isotopes, causing fusion, stage 2. the u.s. tested more than 100 hydrogen bombs in the pacific. the largest was 15 megatons or 15,000 kilotons, more than 1,000

hiroshima bombs.la after th north korean test, the regime released a picture of a what looks like a two stage device. >> it looks as if this last test, the yield, the explosive yield of that is large enough that in most likelihood, my view bomb which we call a two-stage bomb. >> reporter: but are these weaps small, light and robus enough to be efficiently delivered on a missile? the expeevrts bethe north koreans have designed their bombs with all of this in mind from the outset. >> the first bomb was mostly, i think, they had to prove to themselves, essentially a proof of principle that they can actually make an efficient bomb. and from that point on, they were determined towards making that bomb deliverable. >> so, they've to spend time, i think, worng on getting the yield up and not increasing the size too much, and i think that they've done.te >> rep so it is likely the

north koreans have bombs small enough to be delivered oshort range missiles. but weapons that are mounted on medium range or interconnental ballistic ssiles are a much bigger challenge. >> they have to be smaller. they ought to have to be lighter. they have to be more robust. >> reporter: and what about the missiles themselves? what can they deliver, and where? nethe rocket science in ou report. i'm miles o'brien for the pbs newshour. >> woodruff: one of thetr cos most significant evangelical voices, and religious leads, of the past century died today. billy graham preached to hundreds of millions of people around the world over decades, was a counselor to pnts,

died at the age of 99. hari sreenivasan has this look back at his life. >> and god warns every man and every woman and every boy, outside of jesus christ, to prepare to meet almighty god! >> sreenivasan: billangraham, the list who became known as "america's pastor," first attracted national notice in 1949 when thousands flocked to his revival meetings in los angeles. this scene was repeated again and again over the next half century, as the faithful thronged events dubbed "crusades." >> welcome to madison square garden and the billy graham new >> sreenivasan: his were the first religious services to be inlevised nationally, rais millions of dollars that helped spread his brand of evangelism. billy graham was born on a dairy farm in north carolina in 1918 to presbyterian parents.

he began preaching while attending florida bible college, and a few years later in illinois, he met his wife, ruth bell. their marriage lasted4 years until her death in 2007 dudang the tumultuous early ys of the civil rgrhts movement, am demanded his audiences be physically integrad, once removing a rope barrier that separated the worshippers by color. >> when god looks at you he doesn't look at the outward appearance, the bible says he looks at your heart. >> sreenivasan: and, he carried his message of peace and equality to millions around the world, traveling to 185 countries. >> at sydney airport, evangelist dr. billy graham arrives to begin an australia-widcrusade. >> sreenivasan: over the years graham ministered popular world leaders, as well as those reviled by many, such as north korea's kim il sung. though a life-long democrat, the

evangelist said he never favored one party over the other, and that gave him credibility with both democratic and republican presidents.sa >> if things publicly and preached to the president from some pulpit somewhere, i'd never get another opportunity to talk to them privately. >> sreenivasan: in 1991 as the first gulf war got underway, graham was in the white house with president george h.w. busfa and hily. >> i turned to her and i said, barbara, i said, is this the beginning of the war? and she didn't say anything, buy i could senshe way she looked that she knew something that i didn't know, that this was the begiing. >> sreenivasan: but his relationships with the powerful also diticism. in 2002, tapes recorded in the nixon ite house revealed a conversation between graham and aresident nixon in which both made disparaging r about jewish people. graham apologize in his later years, he said he was less concerned with political matters and more with spirituality.

millns of ordinary americans also felt personally connected with graham through his regular television appearances, as when he consoled the nation after the attacks of september eleventh. >> as a christian, i have hope, not just for this life, but for heaven and the life to come. there is hope for eternal life, for christ has conquered evil and death, and hell. cos, there is hope. sreenivasan: grahainued his crusades, drawing thousands to his final one, in new york city, in june 2005. >> and tonight i'm going to say it is great to be back in new york. >> sreenivasan: at the 2007 dedication of his librriy, followers,ds, family and three former presidents paid tribute. >> he was the first evangelist of any stature that penetrated the iron n. >> sreenivasan: ia 1992

interview on the newshour, graham tried to explain his enduri appeal. >> it took me a long time to learn that there are certain elements true in every audience i speak to. there's always thoseeople who are lonely. there's a sense of guilt. and then there's also fear of death. it's unconscious maybe, but it's there. and those are elements that one can touch on and speak to in the services. and i try to bring that into every sermon that i preach, that christ is the answer, he the hope. >> sreenivasan: the reverend billy graham lived out his final years at his home in montreat, north carolina outside asheville. and for more on the life of billy graham and his influence, we turn to randall balmer, a historian and professor of religion at dartmouth college. he is the author of numerous books on american religion, including "evangelicalism in america," and producer of the pbs documentary, "crusade, the life of billy graham."

>> tell me, what's the legacy of billy gram going to be? >> i think he will go down in history as certainly the towering religious figure of the 20th century. n,rtainly in american religio i suppose some people would argue that various popes mighton cnd for that, but i think he's also very important for two reasons. first of all, he broughtli evanlism out of the shadows in the middle of the 20th century. in the early decades of th 20th century, evangelicals were feeling quite battered asgh thhe larger culture had turned against them, andilly graham, beginning around 1949, 1950, begins to bring them into the public spotlight and begins to make evangelicalism acceptable to larger public. part of that had to do with his personality, the force of his

personality,ut part of it w that he used media quite successfully and brilliantly, in many ways, to bring that message to the larger public. i think that the second legacy of billy graham -- and this is feally quite remarkable -- that, over the coursea career that spanned more than half century, he was never seriously charged with any scandal. it's not to say he didn't misstep from time to tme, he certainly did. but in comparison with other televangelists, for example, billy graham emerged with his integritand his character in tact. >> sreenivasan: you mentioned he largely lived scandal-free. one of the few things mentioned the obituary wasthe recorded conversations he had with president nixon which heater apologized for in siding with some of the anti-semitic views that the president had held. >> he di, and i ink mr. graham was genuinely shocked byauhis, bec he had no

recollection of the conversation. richard nixon had a way of kind of bringing -- pulling people into his orbit, into his dark personality in some ways. that's not to excuse mr. graham at all. i think what he saiwas unforgivable, as he acknowledged, but it's one of the dark marks on his life and on his career, yes. >> sreenivasan: do you think that he was aware of how politically powerful evangelicalism had become in america or hasecome in america? >> he was, and he was not happy about that. when the religious right emerged in the late 1970s in opposition to desesegregation, billy graham was uneasy about it and madseveral statements to the fact that he was afraid that those on the far right would try to co-op evangelicalis for their political ends, and he was not happy about thant.

>> sreenivand you also bring out the important point that he did this barn storming and evangelizing in an area pre-youtube, you know, in an era unlike the evaningelical mers we see today who are using television and the internet to ach these wide audiences, he actually physically went to alle tcountries. >> he did. he was a very prepared evangelist but used media along the way to amplifyhis influence and make himself really into a religious celebrity in the 20thntury. >> sreenivasan: do you think that there is an heir apparent to -- is anybody doing wh billy graham is able to do or is that even possible in this era? >> i donth think so. nk there really will be only one billy graham, and i say that because think he came to prominence at a uniqumoment in history when there are various new media technologies reaching

the public. radio had been around for several years, certainly, and other evangelists had used radio, but grahaseized on television, he seized onic puion with his magazine, the hour of decision, or decision magazine, r, and he exploited mediya brillian in order to make himself into a household name and, as i said earlier, a relious celebrity probably without peer in the 20th century. >> randall ballmer, dartmouth college. thank you. >> thank you. >> woodruff:nd a news update before we go: the sheriff in florida's broward county says deputies will begin to carry rifles on school grounds throughout the county, site of the deadly shooting th parkland. an's the newshour for tonight. i'm judy woodruff. join us online and again here tomorrow evening. for all of us at the pbs newshour, thank y and see you soon.

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