“From Army Private to Atomic Physicist for the Manhattan Project”

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– My name is Diane Call. I have the privilege of
leading this institution as president, and I wanna welcome you to the Fall 2015 Presidential Lecture. 15 years ago, it’s been that long, my predecessor Dr. Eduardo Marti established the
Presidential Lecture Series and in the fall we bring
a noted figure nationally who has an affiliation with
our wonderful university, The City University of New York. And in the spring we showcase one of our own outstanding faculty. Our Presidential Lecture
Committee is here with us and I want to thank them. Dr. Karen Steele, Dr. Sasan
Karimi, Dr. Amy Traver, Dr. Mark Van Ells, and I want
to welcome Ms. Betty Bederson who is here as our guest as well. Our special lecturer is
Dr. Benjamin Bederson, a scientist, an educator,
and a participant observer in a significant moment in history. In World War Two in 1942
the world was at war with Europe and Africa
and Asia the main areas, main theaters of conflict. A competition to create the
next generation of weaponry and a fear of what might in fact come spurred a group of
scientists to work together to research and develop the next weapon, in this case the atomic bomb. This international team of
scientists was quite unique and Dr. Bederson became a member through a most unusual route. He’ll tell you how young they all were. The team was led by Robert Oppenheimer, who himself was, I believe 41 or 42. And this group worked in
Los Alamos, New Mexico to create the atomic bomb. Its use in Nagasaki in Japan
really brought to light the reality of this incredible
power, powerful weapon. Dr. Bederson was recruited
as a very young person, probably as young as many
of the students in this room and that’s how he began his journey to this particular point. He went on, of course,
to earn many degrees and he was a professor
for many years at NYU and is in fact a Professor
Emeritus from that institution, but he began at The City
University of New York at CCNY. Since then, of course he’s
gone on as an atomic physicist in many ways, he’s been editor-in-chief of the American Physics Society and he has ushered in
the world of electronics for journalists in physics. I was fascinated to meet him. I am so happy that he and his
wife are here this evening. His moment in time, his moment
in history is extraordinary. So we bring to you a glimpse
into history and into science and welcome Dr. Benjamin Bederson. (audience applauding) – Thank you. Can you hear me from? Yeah. – [Audience Member] Yes. – I wanna thank Dr.
Call for having me here. To be in this wonderful
campus is a very, very feisty, exciting campus, I’m delighted to be here, and I’m delighted to talk
about my experiences, mostly about World War Two. But I’ll put it in the context of the rest of my life as well. I want to point out that
what I’m talking about in World War Two that
was roughly 70 years ago. That’s a long time ago. For students, that’s
three generations ago. I think of myself when I was a student, I was one generation
away from World War One, and that seemed to me
to be ancient history. I certainly didn’t believe
that it had any direct effect on me, but of course my life
and everybody else’s lives were very importantly
affected by World War One. What we lived through during World War Two was a direct result of World War One. So although it’s 70 years
ago and it’s ancient history, the impact on us today of World
War Two is equally important so it’s really relevant
to what’s going on today. So I’ll start by just first of all giving a little bit of
background of my own life up to when I got to Los Alamos. I’m a Lower East Side kid. My parents were immigrants from Russia. They met at a night school
in the Lower East Side. My first few years were
in the Lower East Side. We gradually moved
further north to The Bronx and then to Brooklyn. And then a very important
event occurred in my life very similar to what’s going on here. I got a free education from City College. That was probably the most important thing that happened to me. A gift from New York City to me, which of course had a fundamental
importance in my life. So I did start City
College, but the war started while I was at City College. After two years, two and
a half years I actually, Pearl Harbor had already occurred. I quit City College to take a defense job. And from this defense job I was drafted into the army in 1943. I had various experiences in the army. I had basic training of three
days worth of basic training. I ended up finally going back to college in an army college program,
but the army college program ended during the Battle of the Bulge and from there just as I
was about to be shipped off with my buddies to Belgium I happened to be interviewed by a visiting committee. I was encouraged by my commanding
officer to be interviewed because he knew I was a New Yorker, and he figured I’d get back to Manhattan. So I got interviewed for something called the Manhattan Project. Thinking that it would get me back. (audience laughing) But in fact I did get an interview. And my first indication that this was something
extraordinarily unusual is that in this interview they
asked me about Newton’s Laws. And I thought, what did a soldier need to know Newton’s Laws for? But anyway, I passed the question. I did know Newton’s Laws. I got shipping orders and I shipped to a town in Tennessee, Knoxville, Tennessee,
from Knoxville Tennessee I got shipped again to
Oak Ridge, Tennessee. And when I got there I
saw a new city being built right in front of my very eyes. It was construction everywhere. Orange-red mud on the ground. I knew there was something going on, and I knew it had something
to do with Newton’s Laws. So I was very puzzled
about what was going on. I took a bunch of tests again and it turned out that
it was a very interesting because the tests were all about science. They knew that I was intending
to be a physics major at City College, so I passed the interview again
and ended up traveling with travel orders to another small town somewhere in the middle of New Mexico. That was Los Alamos. I still of course had no idea what it was, but it was obviously
something to do with science, probably something to do with
physics because my friends who had been shipped to
Oak Ridge originally, the chemists stayed in Oak Ridge and the physicists went to Los Alamos. So I knew that Oak Ridge had
something to do with chemistry and Los Alamos had something
to do with physics. At Los Alamos I was of course a soldier. I was assigned to a barracks. And in the barracks there
were a lot of other soldiers of my age, many of whom had
already had college degrees as physics majors, some
of whom hadn’t had, but we were all obviously science-oriented in some way or another. We were treated as
soldiers part of the time, but part of the time we were given jobs. I got a job on something called Jumbo. I was assigned to something called Jumbo. Now I’ll show you a few slides. That’s the one thing I learned in my life is I don’t understand everything, or anything for that matter. To go back a little bit,
I just wanted to show you the role that chance plays in one’s life. My mother came to America
in 1913 on this very ship. And the very next passage across
the Atlantic Ocean it sank. So I’m here because my mother by accident took the voyage to
America one month earlier than she would have
taken if she had taken it in the following month. When I got to Los Alamos I became a member of what they called the SEDs, the Special Engineering Detachment. It was made up of a bunch of kids like me. We weren’t what you would
call typical soldiers. We were basically ex-students or potential students
and we weren’t really what you would call good soldiers because we didn’t have the background that made for real good
soldiers, we were kinda sloppy. This was the forming document
which formed the SEDs, which described what the SEDs,
why the SEDs were organized. They were organized because
the army needed hands to work on the atomic bomb. They had these famous,
world-famous scientists, but world-famous scientists by themselves, just like college
professors without students, couldn’t really do much. You need hands to do these things. So they invented something called the Special Engineering Detachment. And this was the formative
document which created them. One of the two reasons that they listed as the reasons for forming these SEDs was that it would save the
government a lot of money. Because once you’re in the army you got army pay instead of civilian pay. So that made a big difference to them. When I got to Oak Ridge, Tennessee I wrote a letter to my parents. This is a letter, one of the
letters that I wrote them in which I describe the mysteries that were obviously surrounding
me at Oak Ridge, Tennessee. I knew that there was
something very special about it because we had young girls
cleaning our barracks up and it’s unheard of in the army. We knew there was
something really going on if they would clean up
our barracks for us. So I did tell them that there
was something mysterious going on, but of course I
had no idea what it was. Then when I got to Los Alamos our role in Los Alamos
was very mysterious. We had no idea what we were doing. I was assigned, this,
I’ll come back to that. This is the insignia that we were given after August 6th, 1945. This is a picture of us in a rare case where we were actually in
uniform and at attention. This is what I was assigned to. It was a big steel container. My job was to blow up little
models of the container to see how strong they were and how much explosives were needed to destroy these little containers. I had no idea why I was doing this. It turned out that the
reason for this container was that the atomic bomb,
which they were gonna test, the first atomic bomb was gonna be put inside that container. If it fizzled, it would
keep radioactive material from scattering all over Los Alamos and destroying basically the entire site. So that was why they had this huge container called Jumbo. Incidentally, it’s still there. In Alamogordo where the test bomb was first exploded this container is still there. They don’t know what to do with it. At some point a month or two
after I got to Los Alamos they decided that the atomic
bomb was probably gonna work OK and they thought that
it was a waste of time to build a container, so they disbanded the research on Jumbo and they assigned
me to another project. The other project they assigned me to had to do with blowing things up with the little switches, little switches that we manufactured out of pins. Again, I had no idea why we
were blowing these things up. And about three months after I
got there apparently they had been back to The Bronx and
they given me a security check back in The Bronx and for
some reason or other I passed. Now that’s not a trivial thing. In 1945 in The Bronx politically speaking it was a pretty leftist
place and many of my friends were leftist to say the very least. But somehow I managed to
pass my security clearance and when I got back,
when they abandoned Jumbo they assigned me to the design, testing, and construction of switches that actually would operate the compression fission bomb made out of plutonium. Now I’ll say a few technical words. Not much but just enough to
explain what was going on there. Nuclear fission had been
discovered in Germany in the early 1930s not
very long before 1945 and it didn’t take long
for physicists to decide that fission could be used to
actually cause an explosion and release nuclear energy. The energy in a nuclear reaction is thousands of times greater
than a similar reaction in the chemical world. So if you could create a bomb where nuclei disintegrate
and release energy you can cause an explosion
that is thousands of times greater than any
chemical explosion you could make. The ultimate design of
the bomb is shown here. It turned out that several elements when they absorb neutrons
give off additional neutrons, disintegrate and in the
process of disintegrating release millions of times more energy than in a typical chemical reaction. And so the bomb that was
eventually developed, oops. The bomb that was intentionally developed consisted of a core of
fissionable material which was plutonium,
a man-made new element heavier than was uranium. And in the form of a sphere. Surrounding it were
conventional explosives. And if you trigger these
conventional explosives simultaneously around the entire sphere then the sphere of plutonium
in the center compresses and the density increases
and the chain reaction in which neutrons are released runs away so that each reaction
produces more and so on. So before you know it you’ll have millions of
nuclear reactions occurring within a small fraction of a second. That means microseconds. And so in microseconds you
could have a nuclear reaction involving millions of plutonium nuclei, each one releasing millions
of tons more energy than in a chemical reaction. So that turns out to be
equivalent of many tons of TNT. It turned out that I
was assigned to design, to help design, I shouldn’t I designed, but I should say I helped design. You see the apexes of those triangles, there was switches placed
on each of those apexes. And the idea was that when
you throw a single switch and all of these switches
around the entire sphere ignites at the same time,
the plutonium is compressed by the ordinary explosives
and causes a chain reaction and the energy released is equivalent of thousands of tons of TNT, 10,000 tons of TNT in this particular case. And to my surprise, I was
working with a senior physicist on the design of the
triggers that triggered these chemical lenses, they were called that compressed the plutonium. In other words, I was working
directly on the design of the triggers of the plutonium bomb. You can see, this is the apex
where the trigger was placed and there were 32 such lenses
surrounding the plutonium. Next to my bunk where I lived as a soldier with 60 other soldiers in a barracks there was another boy from Brooklyn whose name was David Greenglass who actually slept in the bunk exactly to the right of my bunk. David Greenglass, as you probably know, turned out to be a spy for the Russians. When he was caught… I’m going backwards. When he was caught, it turned out that he was a machinist who was actually machining
the explosive lenses that were placed in the bomb. And the drawing on the top is the drawing that he gave to his Russian handlers, which as you see is somewhat similar to the actual bomb, although
it was relatively crude. This was my boss who three months after I came to Los Alamos
told me what I was doing. To my great surprise, I think it was probably March of 1944 he took me into a room and explained an entire history of nuclear fission and of what they were trying
to do with the atomic bomb. And that was because
I was given clearance. That was George Kistiakowsky, a chemist. This is actually the atomic bomb that was dropped on Nagasaki. You can see that, if you can imagine it, that it’s somewhat spherical
because the bomb itself is a sphere, consisting
of a sphere of plutonium in the middle and surrounded
these spherical lenses that caused the implosion. That’s a barracks where I lived. This is not quite true,
because our barracks were double bunks and this is
only a single bunk barracks. Now I wanna show you probably
the world’s only existing secret document about shoes. That permits me to wear a pair of shoes, a pair of civilian shoes. When the bomb had reached
a certain level of design the next step was to bring in the Air Force. The Air Force had a base
in Wendover Field, Utah and the crew that was to
drop the atomic bomb on Japan was to be trained on how
to use the atomic bomb. Since I knew all about the switches I actually was ordered
to go to Wendover Field to help teach the Air Force aviators on how to arm the bomb and how to keep it from going off prematurely. And then somebody
discovered that everybody who worked on the airplane
that was to drop the bomb were officers and I was a lowly private. And so they had a conference to decide on what to do about having a lowly G.I. be teaching captains,
generals, and even a major. And everybody decided that the army doesn’t
do that kind of thing. You can’t have a G.I. teaching
a whole bunch of officers. That’s the way the army works. So they decided to make me a civilian. (audience laughing) So what they did was they gave me $200 and they said, “Go to
Santa Fe and buy yourself “some civilian clothes and then
you can go to Wendover Field “and teach the aviators on
how to active the switches “that need to be activated for the bomb.” But I turned out that
I was able to do that. I was able to go to Santa Fe and buy a bunch of civilian clothes, but I needed civilian shoes. The G.I.’s had long shoes,
goes up to the ankle and the leather was inside out so you could spot a G.I. a mile away by just looking at their shoes. So they said, “Oh, you have
to buy civilian shoes.” And I said, “OK.” But I went to Santa Fe and
they wouldn’t sell me any because I needed a ration coupon because shoes were rationed in 1944. So I went back to my security
officer and they said, “OK, we’ll give you a document “that will enable you to buy
a pair of civilian shoes.” So they gave it to me, but they said, “You can’t tell anybody.” So they marked it secret.
(audience laughing) So that’s the reason that you’re looking at probably the only document
in all of the billions of documents in the United States Archives that are secret that is only for shoes. But it does tell you the story. This is just a bunch of photographs of G.I.’s having fun with the civilians. The senior civilians at Los
Alamos were really senior. It was Enrico Fermi, there was Niels Bohr. Niels Bohr by the way was
the only senior scientist who had a pseudonym, he
was called Nicholas Baker. So everybody knew that
Nicholas Baker was Niels Bohr. If you look here, that’s Enrico Fermi right up there. That’s Enrico Fermi, and he was just one of the regular guys. The senior scientists
and the G.I.’s got along just like ordinary professors and graduate students got along. The senior scientists
thought of the G.I.’s, these sloppy G.I.’s as being
like graduate students. A few years ago Sam Roberts, a New York Times reporter, wrote a book called The Brother. This is about David Greenglass. And in it he writes a little bit about me. David and Bederson had bunked
within whispering distance of each other, but the pinup episode. That was a pinup I had of (audience member coughs) a newspaper called P.M. which
you probably never heard of, but it was a leftist newspaper
that was pretty popular in New York in those days. I had a front page
illustration of P.M. on my bunk and David Greenglass, that
was one of the reasons why David Greenglass thought
that I might be sympathetic to his politics. (audience member coughs) David’s first insight into
Bederson’s priorities. I was supposed to be tall
and blond from the Bronx and 23 years old. As a child I lived in Russia. So David Greenglass thought
that I might make a good spy. Fortunately for me and for him, his handler told him to lay off. He said that’s too dangerous. Just to give you an idea of
how Greenglass thought of me, he said, uh this is from the FBI file. I somehow managed to get some
of the real FBI’s files using, just getting it released. Bederson was a good fellow and Greenglass thought he
had left wing tendencies because he had collected money for the Roosevelt campaign at Los Alamos. So Greenglass thought that I might be a good target for espionage
because I was for Roosevelt. This is just a piece from one
of Richard Feynman’s books. Richard Feynman explained
how the soldiers, the SEDs, once they were
told what they were doing worked much more efficiently
than they did before where they didn’t know
what they were doing. Here, by the way, are some
of the soldiers like me who were at Los Alamos. Many of these soldiers went on
to very distinguished careers after and partly because of the start they got at Los Alamos. I want you to look at two of these soldiers, look at that. Jesse Kupferberg and Ken Kupferberg were two of the SEDs just like
me who worked at Los Alamos. There were actually three of them, right. The third brother was a civilian, but two of the Kupferbergs
were my army buddies at Los Alamos, isn’t that
an amazing coincidence? (audience applauding)
(laughs) No, no, I’m going the wrong way. Just to give you an idea of how
important these grunt people the grunts were, that’s
us, we’re the grunts. This is a picture of one of
the G.I.’s and look what, he’s carrying just,
you think he’s carrying just an ordinary thing. He’s carrying the bomb. (laughs) This is the bomb. This is the plutonium for the
Alamogordo bomb right here. That’s really amazing how
personal the whole thing was when we were there. I just showed this as just an example of the G.I., Arnold Kramish
was just one of them who was a famous, he was a famous diplomat after the war. And this is the a story,
this is part of a story. This is Val Fitch describing
his experiences as an SED. Val Fitch was a G.I. just
like me or the Kupferbergs. He won the Nobel Prize many years later. And he describes what a strange bunch of guys these G.I.’s were. He’s telling here the bagel story. I was so homesick that I had tied a bagel to the fluorescent light
string over my bed. And one Saturday morning, we
had these miserable inspections every Saturday morning
and one Saturday morning a commanding officer bumped
his head on the bagel and he said, “What’s this?” And I explained to him what it was. And he ordered me to remove it. So I actually had to remove the bagel, And Val Fitch talks
about that in his memoir. This is an interesting photograph. After the Wendover Field adventure the next step was to bring the bomb to the operating theater. A Air Force base had been
established in the South Pacific in an island called Tinian. Tinian was a Japanese protectorate. It had a shape which was
very similar to Manhattan. And you’ll see another coincidence in a little while about that. And so this island was where the Air Force bombing operation was being used to bomb Japan. And there were hundreds of these B-29s that were operating all from this island. It was the same island
that was going to be used for the atomic bomb. And so somewhere around
May or June of 1945 after my experience at Wendover I was part of the crew that
went to this island of Tinian to help assemble the bomb
there, the real bomb there. This is, it’s very interesting. There are 51 people in this picture. 51 is exactly the number of people who went to Tinian who
were entirely responsible for those two atomic bombs
that were dropped on Japan. They varied from Nobel Prize winners. There are two Nobel
Prizes in this picture. There are three field officers
of rank admiral or general and there’s me. Let’s make a better, this
is a better photograph. This is me, this is a Nobel
Prize winner Norman Ramsey. This is another Nobel
Prize winner Alvarez. A couple of, here’s a general, a major, a few other big shots. This was the entire crew
that was responsible for both atomic bombs. I said that the island
of Tinian was similar to the island of Manhattan, it
kind of looks like Manhattan and another one of
those weird coincidences that you wouldn’t believe, you
really wouldn’t believe it. The SEDs that built the
Air Force base on Tinian decided that it looked like Manhattan so they were gonna name the
streets after Manhattan streets. This was a half a year
before anybody ever dreamed of an atomic bomb coming there. So they actually have it laid out like Manhattan. Here’s Broadway. 9th Avenue, and all of these other streets are named after Manhattan streets. That’s another one of those mysteries that makes no sense whatsoever, but it did happen that way. It’s very interesting to
note that all of the soldiers that had been working on the atomic bomb. It’s an untold story. You read all about the senior scientists but you don’t realize that there were all of these younger guys who
were actually doing the work just like graduate students,
that’s an example of that. This is a couple of photographs. These are the only two
photographs that I have of me at Tinian. This is a bombed out civilian house. This would be a Japanese family’s house. And this is me at a
Japanese Shinto shrine. This is in case you’re interested these are a couple of
sources you get from ’em. Just to prove that I actually was there this is a letter from Rob Oppenheimer and another one from the big brass. This is a picture of the front page of the Santa Fe newspaper
on August 6th of 1945. You have to understand, there
was this city, Los Alamos that was 20 miles away from Santa Fe. There was coming and going all the time. There was a continual stream of traffic and it was called The Hill. Nobody had any idea what it was. Santa Fe, there were all
kinds of rumors of course in Santa Fe of what it really was, but nobody had real knowledge of it. The day that the atomic
bomb was dropped, of course, the secret was out and
this is the headline, this is the paper of the Santa
Fe Mexican describing it. This was the first time
that people at Santa Fe knew about the atomic bomb. And here in New York here is
what happened on August 6th. You have to understand that
that was a moment of history like no other, that the world was changed within a fraction of a
second from before and after. The world is different
now than it was before. And of course it was known. This is the paper, this is the Times just after the Hiroshima bomb was dropped. That was the first of the two. This Hiroshima bomb came first and the Nagasaki bomb came next. Before it there was a
testing bomb at Alamogordo. So there were really ultimately
three bombs that were made. One was a test bomb, the
other two were the real bombs. I kept a diary. It was obvious from the very
beginning that it was important that I was on to something important. And from the day that I arrived on Tinian to the day I left on
Tinian I kept a diary. This is one of the pages, August. August 5th just before
the bomb was dropped and then afterwards. I’m showing you this because
of an interesting incident. It happened that I got so excited
after the bomb was dropped that in the diary I actually wrote some of the details of the triggering that caused the bomb to explode. Then a couple of weeks after that I looked at it again, I said,
my God, what have I done? I got really worried
that I had written down some actual secrets, which,
I was a smoker at the time I burnt it out, some of
the crucial items up here. You can see them up there. Come on, yeah. So that I wouldn’t end
up in jail if I did that. After the bomb was dropped, I went back to Los Alamos. I waited for my turn
to get out of the army. I went back to City
College, got my degree, and then went to graduate school. Became a professor at NYU. And this is a typical picture of me as a professor at NYU. Everybody knows that
experimental physicists do plumbing, wiring, all
kinds of stuff like that. That’s me up there with plumbing as a professor at NYU. Years afterwards, especially during the
late ’60s and early ’70s when there was very
strong student upheavals in the United States, a lot of it having to do with the rise of the military and technical advances, I decided to invent a course called Physics and Society. And this is a flyer for the course. I gave the course many years describing the impact that physics had on society. And of course everybody
knows what that is. Not only because of the atomic bomb, but I was thinking of what happened with solid state physics, how
many transistors there are in this device invented by physicists just like the atomic bomb
caused the revolution, caused the revolution that
we’re living in today. OK, so it comes to the moral aspects of the atomic bomb. I’m sure everybody concerned about that. It seems to me, I seem to almost sounding as though we had did something wonderful. Well in fact, we didn’t
think of it that way. We thought of it as being a
device that would end the war. We thought that was wonderful. But everybody that I knew at Los Alamos felt that what they were doing
was going to end the war. The war was causing
thousands of deaths everyday. Many tens of millions of people
were already been killed. The proposed invasion of Japan would probably cause
another million casualties. We thought that the atomic bomb, although it would certainly
cause deaths in Japan, we nevertheless, the net result would be an immense
savings in human lives. And I think history has
shown that that’s correct. Three days after the
Nagasaki bomb was dropped the Japanese surrender. It’s pretty clear that the
atomic bombs ended the war and caused lives to be saved. As ridiculous as that
sounds, dropping the bomb, in my opinion anyway, saved lives. Now of course the ultimate consequence of the atomic bomb’s another story. We’re faced with problems
related to the atomic bomb, which I did not address
about the bomb’s future, about the roles the bombs
could play in future wars. Clearly it remains possibly
the world’s greatest danger, but the period in which
the bomb was created it made perfect sense. What we knew at the time
that future generations would have to worry about. Even more important thing, how to prevent further use of the atomic bomb. I wanna say a few more words about the situation that existed then compared to the situation today. It’s important to notice
that in 1944, 1945 when Los Alamos was at its heyday, I would say that almost without exception every single person in the United States approved of what was happening. When the bomb was dropped
there was universal approval that it was the right thing to do. It had to do with that fact that there was a unified
opinion in the United States for every American. Every American believed in the war. It was a truly well-defined war in which there was a well-defined villain and we were the good guys. And it’s really true, we were. Today is very different. Today we’re dealing with a country which is divided just about equally. And we cannot say that we have that
unified feeling any more. That’s too bad because you can see what the unified feeling in the country, how it worked to create
the Manhattan Project. The Manhattan Project
was a national event. Hundreds of thousands
of people participated and millions of people
cooperated in one way or another. It could not happen today. I think that’s very sad. But from the point of view of 1945 it was the right thing
to do in my opinion. I think that’s all I have
to say, thank you very much. (audience applauding) – [Audience Member] Could you tell us why it was called the Manhattan Project. Why Manhattan? – Oh. – [Audience Member] Do
you know why the project was called the Manhattan Project? – It’s another accident of history that the engineering district that created the Manhattan Project got its start in a building
in Lower Manhattan, and that’s how it was called
the Manhattan Project. It’s strictly an accident, and
nothing to do with anything. – [Audience Member] I was
wondering if you might be part superhero perhaps because
you were working very closely with all of these fissionable
materials, very closely, and a lot of your compatriots
are no longer with us, so to what do you
attribute your longevity? – Oh.
(audience laughing) I’m only 93 years old.
– Only! (audience applauding) – These days that’s no big deal. (audience laughing) – [Audience Member] Question,
sir, I have a question. So in Manhattan Project I
think there are two strategies of atomic bombs, one is explosion and one is gun assemble. Your project is explosion. So between these two different strategies, what’s the relationship? You work together, or
you are like compete? – Well, I didn’t go into
technical details at all. The first bomb, the Hiroshima bomb, it was not an implosion bomb. It was a gun bomb, it
was a primitive bomb. And it was made, the fissionable
material was uranium, U-235, a rare isotope of
uranium which actually fissions. The principle isotope of
uranium does not fission, but U-235 does, and
that explains Oak Ridge, because Oak Ridge was the
place where U-235 was created by distillation plants. So what happens, simply
for the Nagasaki bomb, was that there was a gun, a real gun. The inside which was
coated with Uranium-235 and then there was a shell, a real shell was made out of U-235 and the
shell was fired into the gun. Just as simple as that,
and the combination of the two together caused a
critical mass and the explosion that was very primitive. The Nagasaki bomb was a
very sophisticated bomb which had tried implosion, the
implosion, the compression. That’s the one I worked on. So there were different
technologies completely. – [Audience Member]
Yeah, so my question is, your job is like racing of the time. The quickly you make the bomb, so most people can
saved in the war, right? So in these two strategies,
what’s the military choose? So they have difference
like 90% the gun finished and 50% the explosion finished, or you just like working in the same time, or you just work together or
you just compete together like? – The gun bomb was made
first because it was easy. – [Audience Member] Oh, OK. – It was sure to work ’cause
it’s just simply blowing. A real gun, it was a gun barrel that was actually taken from the navy that was used for the Hiroshima bomb. So it was quite simple to use,
and there was only enough, the material that was made for it was manufactured by distillation
in Oak Ridge, Tennessee and that’s all the uranium-235 they had. The plutonium actually was
made in nuclear reactors in Hanford, the state of Washington where there were three principle units of the Manhattan Project. There were many more,
but three principle ones. Los Alamos where the research
and development was going on. Oak Ridge where the manufacture of U-235 or the distillation plants were
built for U-235 from U-238. And Hanford, Washington where
nuclear reactors were built to produce plutonium in nuclear reactors from uranium piles. So there are three different elements. When I came to Oak Ridge and I
saw those plants being built, huge plants, there were vertical plants with pipes on the side I thought they were distillation plants. My first thought was
that they were building sour mash whisky plants. This was Tennessee, you understand. I thought they were building sour mash plants to drop on the Germans and to get them drunk.
(audience laughing) That’s what I thought at
first, but then I realized they were distillation
plants, OK, they really were, but they were distilling U-235 from U-238. Just a pure distillation,
so I was wrong in one way and right in another way. – [Audience Member] Yes, Dr. Benjamin, how long did it take you
after the bomb was dropped to feel comfortable enough to reveal that you were part of the secret project? – Sorry, I can’t hear you. – [Audience Member] How long
after the bomb was dropped it took you to feel comfortable enough to reveal that you were
part of the secret project to ordinary people? – How long?
– Yes. – Did it take?
– No, now long did it took you to feel comfortable to reveal that you were part of the secret project? – [Diane] When could you let people know that you were part of the project. – Oh. (laughs) Well, let me think. I wrote an article for a physics journal some years later. That was the first time
that I actually revealed what I was doing. It was sort of a memoir in a journal called Physics in Perspective in which I wrote about
it for the first time. That was in the ’70s after I invented my Physics and Society course I decided at that time to
write about the atomic bomb. But in my course I taught
about nuclear explosions right away from the beginning, right there in the course
that I had invented as the result of the student
troubles of the ’60s and ’70s. – Any other questions? I want to thank Dr. Bederson.
(audience applauding) And thank you for being here. As our custom we have some
light refreshments outside. And I thank you for coming out on this less than ideal weather
day, but a perfect day to listen to both history
and science, so thank you. (audience applauding)

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