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Language: en
Jay Robert Oppenheimer might be the most
important physicist to have ever lived
he never won a Nobel Prize but he
changed the world more than most Nobel
Prize winners under his leadership the
best physicists of the 20th century
built the atomic bomb forever changing
the course of history if there is
another world war this civilization may
go under he has affected every war waged
and every peace settled since the end of
World War II he also created a way for
Humanity to destroy itself now I am
become death the destroyer of
worlds this video is about how to build
an atomic bomb the life of Oppenheimer
and why serious scientists were worried
about the explosion setting fire to the
atmosphere ending all life on
Earth part of this video is brought to
you by Ren
when Jay Robert Oppenheimer was 21 he
placed an apple laced with toxic
chemicals on the desk of his physics
tutor the tutor Patrick blackett was an
experimentalist and he had hounded
Robert to do more of what he thought
Robert wasn't very good at experimental
work Oppenheimer had already been
spending his days in a corner of JJ
Thompson's basement laboratory
attempting to make thin films of burum
which were used to study electrons but
Oppenheimer was clumsy and not good at
this
work he was soon avoiding his duties in
the lab spending his time listening to
lectures and reading physics journals it
was 1925 and the 21-year-old Oppenheimer
was becoming fascinated by the new field
of quantum
mechanics despite being surrounded by
brilliant physicists like Rutherford and
Chadwick Oppenheimer was deeply unhappy
he wrote I'm having a pretty bad time
the lab work is a terrible boy and I'm
so bad at it that it's impossible to
feel that I'm learning anything a friend
walked in on him lying on the floor of
his room which he called a miserable
hole groaning and rolling from side to
side in emotional anguish it was in this
state that Robert attempted to poison
blackett the specifics are lost to
history there are conflicting reports if
Oppenheimer used cyanite or something he
found in the lab which would have just
made blacket sick this story sounds
unbelievable but Oppenheimer himself
confirmed it luckily blackett did not
eat the apple but the attempted
poisoning became known to the Cambridge
University authorities Robert's parents
were visiting their son from the us at
the time and Julius Oppenheimer
successfully lobbied Cambridge not to
press criminal charges due to his
family's wealth Robert wasn't even
expelled from Cambridge on the condition
that he had periodic counseling sessions
with the psychiatrist in London
[Music]
[Applause]
in the summer of 1926 Robert traveled to
the University of gingan the chairman of
the department was Max Bourne who just 2
years earlier had coined the term
quantum mechanics Bourne was reportedly
a thoughtful and gentle teacher and had
nurtured the work of verer Heisenberg
Wolf Gang poy enrio fmy and Eugene
wigner basically the who's who of
quantum mechanics the class that
Oppenheimer was in was also
extraordinary including luminaries like
Paul ra and John Von noyman where the
academic culture at Cambridge focused on
experimental physics goodan was all
about theoretical physics and under Max
borne's mentorship Oppenheimer thrived
his mental health improved and he found
a community of people who were as
obsessed with physics as he was on
November 14th 1926 Robert wrote to Frank
his younger brother you would like
Gooding gun I find the work hard thank
God and almost Pleasant
Robert was thriving and his talent was
being recognized borne later wrote he
was a man of great talent and he was
conscious of his superiority in a way
which was embarrassing and led to
trouble when Oppenheimer was 23 he
graduated with his PhD in physics he
wrote his thesis in German on the
quantum theory of continuous Spectra all
in all he published more than a dozen
papers in the 2 years he was at goodan
many of them expanded upon the work of
ver Heisenberg who was just 3 years
older than Oppenheimer the two
eventually met in 1927 the same year
Heisenberg published his groundbreaking
paper on the quantum uncertainty
principle by all accounts the pair got
along well there was no way to know that
just 15 years later they would be deadly
Rivals attempting to build the first
nuclear bomb Oppenheimer for the USA and
Heisenberg for Nazi
Germany at the time it was thought that
getting significant amounts of energy
out of radioactive atoms was impossible
ever since the discovery of
radioactivity by AR Beckel Marie and
Pierre K in the late 1890s it was known
that radioactivity was a passive process
unstable atoms would just Decay at
random unpredictable times and surely
there was no way to control
that in 1933 Ernest Rutherford
oppenheimer's old boss from Cambridge
wrote that anyone who expects a source
of power from the transformations of
these atoms is talking moonshine that
same year Albert Einstein said that
there is not the slightest indication
that nuclear energy will ever be
obtainable it would mean that the atom
would have to be shattered at
will so how would you break an atomic
nucleus well you could take a proton and
accelerate it through a large electric
field and then smash it into a nucleus
this is exactly what John cockroft and
Ernest Walton did in
1932 they accelerated protons into
lithium nuclei breaking them apart the
pair would later win a Nobel Prize for
this work but a proton is positively
charged so it's repelled by all nuclei
which are also positively charged so to
give them a hope of overcoming this
barrier cockroft and Walton had to use
250,000 volts to accelerate the protons
even then only about 1 in a billion
protons actually hit split a lithium
nucleus so this would not be an
effective way to get
energy but there is another
way in 1932 the neutron was discovered
this subatomic particle that's about .1%
heavier than a proton and it has no
electric charge so a neutron would not
be repelled from a nucleus and in 1933
Leo zard was thinking about how you
could use neutrons to split nuclei it
suddenly occurred to me that if we could
find an element which is split by
neutrons and which would emit two
neutrons when it absorbed one Neutron
such an element if assembled in
sufficiently large mass could sustain a
nuclear Chain Reaction but the thing is
nobody knew if there was an element that
had a kind of nucleus that would do
that on the 29th of January 1939 Louise
Alvarez a promising young physicist was
getting a haircut while reading the San
Francisco Chronicle and suddenly he got
out of the chair halfway through the
haircut and ran to oppenheimer's office
Alvarez read an article about how two
German chemists OT Han and Fritz stman
had successfully split an atom of
uranium by bombarding it with neutrons
Oppenheimer was not impressed that's
impossible he reportedly told the young
alvas proceeding to mathematically prove
on his Blackboard why fion could never
be achieved
but the next day Alvarez had repeated
the experiment and invited Oppenheimer
to see it Alvarez later recalled that in
less than 15 minutes he not only agreed
that the reaction was authentic but also
speculated that in the process extra
neutrons would boil off that could be
used to split more uranium atoms and
thereby generate power or make
bombs when a single atom of uranium 235
splits apart it loses a little bit of
mass which is released as energy
following Einstein's mass energy
equivalents that is a tiny amount of
energy about 20 times less than the
amount required to raise a grain of sand
the thickness of a piece of paper but
atoms are also tiny in a 1 kg lump of
uranium there are about a trillion
trillion atoms so the energy quickly
adds up soon almost everyone was
convinced in August of 1939 Einstein who
just six years earlier believed that
nuclear bombs were impossible signed his
name to a letter addressed to President
Franklin Roosevelt the letter actually
written by zard warned Roosevelt of the
possibility of nuclear weapons it also
pointed out that Germany had access to
uranium from the mines in Czechoslovakia
which was recently taken over by the
Nazis Roosevelt began an informal
uranium committee to discuss this topic
but then for 2 years nothing
happened in 194 1 Roosevelt upgraded the
informal uranium committee to the S1
committee which would report directly to
the White House the explicit goal was to
develop an atomic bomb and in May 1942
Oppenheimer was hired onto the committee
to be the coordinator of Rapid
rupture so why was he
selected well after completing his PhD
Oppenheimer became a physics Professor
first at Berkeley and then at Caltech
the Brilliance he had shown under Max
borne's tutelage didn't fade indeed it
blossomed into a remarkable but strange
physics career in the 15 years after
finishing his PhD Oppenheimer made
important contributions to everything
from Nuclear Physics to Quantum field
Theory and even astrophysics he had a
number of Nobel prizewinning ideas one
of his students Willis lamb became a
Nobel laurate but Oppenheimer himself
was nominated three times but never
actually won the Nobel
Prize when asked why he thought that
Oppenheimer never won the Nobel Prize
Murray Gman said that he didn't have
sits fles a German word that translates
to sitting flesh the ability to sit down
in a chair for a long time and do the
hard work he never wrote a long paper or
did a long calculation he didn't have
the patience for that Wolf Gang pal also
said his ideas are very good but his
culations are always
wrong but Oppenheimer was amazing with
people he was a natural and charismatic
leader and this combination his Charisma
and his ability to generate great ideas
would serve him well in the next phase
of his
[Music]
life on the 18th of September 1942
General Leslie Groves was put in charge
of the Manhattan Project I was
responsible for the development of the
atomic bomb on day one he ordered 1,200
tons of uranium ore the next day he
ordered to buy the Oak Ridge site where
the ore would be refined the next month
in a surprising move he chose
Oppenheimer to be the science director
of the soon Tobe established Los Alamos
laboratory Oppenheimer had just been
selected to be the Chief Architect of
the atomic
bomb the military establishment had
concerns Oppenheimer did not have a
Nobel Prize so would the scientists
hired for the project respect his
opinion and follow his leadership
Oppenheimer also had no prior
administrative experience over a large
project like this furthermore he was a
theoretical physicist who according to
Isidor Rabbi was a very impractical
fellow he didn't know anything about
equipment and then there was the problem
of oppenheimer's political stance he had
links to the Communist party including
his wife Catherine who was a member of
that party but Groves was impressed by
Oppenheimer he valued his overwhelming
ambition he also knew that oppenheimer's
ability to understand problems not just
in physics but chemistry engineering and
Metallurgy would be invaluable Groves
thought that Oppenheimer was a real
genius saying that why Oppenheimer knows
about everything he can talk to you
about anything you bring up well not
exactly he doesn't know anything about
sports the two men couldn't have been
more different Oppenheimer weighed half
as much as Groves despite both of them
being nearly 6 feet tall ideologically
Oppenheimer was a communist Groves a
staunch conservative but Groves was
convinced that Oppenheimer would be the
person that would build the atomic bomb
before the Nazis and that was all that
mattered Isidor Robbie later commented
that hiring Oppenheimer for this role
was a real stroke of Genius on the part
of General Groves who was not generally
considered to be a genius
the Manhattan Project needed a location
somewhere isolated to keep the project
Secret Safe from enemy attack and while
no one wanted to admit it somewhere that
was sparsely populated just in case
there was an
accident Oppenheimer proposed Los Alamos
New Mexico he had fallen in love with
the harsh desert and the mountains of
New Mexico when he was in his 20s in
1929 Oppenheimer wrote to a friend my
two great loves are physics and New
Mexico it's a pity they can't be
combined but Oppenheimer had severely
underestimated the logistical challenge
ahead in 1943 Oppenheimer estimated that
he'd need about six scientists supported
by a handful of Engineers and
technicians to make a
bomb he was off by two orders of
magnitude 764 scientists would end up
working for the Manhattan Project 302 of
which would work at the Los Alamos
site over 600,000 people in total were
involved with the making of the atomic
bomb by this point making the atom bomb
didn't seem impossible it seemed
likely on the 2nd of December 1942 a
team of physicists at the University of
Chicago led by enrio FY created the
world's first artificial nuclear reactor
pile one it consist consisted of 45 tons
of uranium and uranium oxide and 330
tons of graphite blocks horrifyingly
enough it was located under the stands
of the football field it generated about
half a watt of power and if you can make
a nuclear power plant you can make a
bomb the only real difference between
the two is how many neutrons hit the
next atom causing it to split and
release more neutrons if on average that
number is one there will be a stable
self sustaining Chain Reaction but it
won't grow if it's less than one the
reaction will die down and if it's more
than one the reaction will grow this is
known as the multiplication Factor K
nuclear reactions are similar to
pandemics in this
way the simplest way to make a nuclear
bomb is to get enough Phile material
close together that it creates a runaway
chain reaction that amount is known as
the critical mass with your uranium 235
you need about 52 kg forming a sphere
with a diameter of 17 cm if you use
plutonium 239 the critical mass is much
smaller only around 10 kg which would
create a sphere only 10 cm wide for the
first few years the scientists worked on
a bomb with a gun type design inside a
gun type bomb you have two slabs of
uranium 235 both of which are below the
critical mass then using a con
conventional explosive like cordite you
rapidly fire one towards the other so
the combined mass is higher than the
critical mass when the uranium bullet is
about 25 cm away the nuclear chain
reaction begins resulting in an atomic
explosion despite the simple design it
is not very efficient only a small
percentage of the uranium under goes
Vision so the total yield of the bomb is
much smaller you also run into some unex
expected problems like how do you make
sure the uranium slides smoothly through
the barrel well you use oil to lubricate
the barrel but all the synthetic oils
the scientists tried would dry up in the
end the only oil they could find that
would work was the oil from sperm
whales only about 7% of naturally
occurring uranium is u235 the file fuel
for nuclear bombs when u235 absorbs a
neutron it briefly becomes
u236 and then it rips itself roughly in
half and releases on average 2.4
neutrons per Vision but when you get
uranium out of the ground most of it is
u238 which doesn't undergo fision so to
make a nuclear bomb the scientists used
gigantic Mass spectrometers to separate
out and concentrate the
u235 and the resulting substance was
uranium with a much higher concentration
of u235 in other words it was
enriched there was another option though
in early 1941 a new element was
discovered or rather synthesized when a
neutron is absorbed by a nucleus of
uranium 238 it turns into uranium 239
u239 is unstable so it decays into
neptunium which then becomes
plutonium there are three things that
matter for this story first is the that
plutonium 239 is a great fuel for a
nuclear bomb it has a critical mass of
only about 10 kg second it is cheaper to
make than to separate uranium 235 and
third it reacts too quickly to be used
in a gun type device it would fizzle
meaning only a tiny fraction of the fuel
would undergo fion but there is a way to
make a bomb using plutonium critical
mass changes depending on the density of
the material under normal pressure
conditions 6 kg of plutonium 239 won't
explode but if you compress it the atoms
get closer together and the chance of a
stray Neutron hitting the nucleus
increases so the higher the density the
lower the critical mass so if you set
off conventional explosives around a
ball of plutonium you can get it
compressed enough to start a nuclear
chain reaction and this was the whole
idea behind the implosion bomb design
there are a couple ways to cheat
lowering the critical mass for one thing
you surround the sphere with a material
that reflects neutrons decreasing the
amount of nuclear fuel you need to start
a chain reaction you can also have a
neutron Source something that kickstarts
the chain reaction for the first
implosion bomb scientists created a
device called the urchin which was a
tiny pellet weighing just 7 G and it
would sit at the heart of the bomb it
was made of buril and polonium separated
by a layer of nickel and gold the idea
was that when the explosives detonated
the shock wave would mix the burum and
polonium together and then the alpha
particles from polonium would cause the
burum to release a flood of neutrons
which would set off the nuclear Chain
Reaction at least that was the hope an
atomic bomb had never been made before
Oppenheimer and the rest of the
scientists at Los Alamos needed to act
quickly it was already 1945 and Truman
wanted to test the weapon before the
start of the pot Stam conference that's
where Truman Churchill and Stalin would
come together to plan the post-war peace
the conference began on the 17th of July
the earliest date that everything could
be ready for the bomb was just one day
earlier so that is when the test was
scheduled it was codenamed
[Music]
Trinity the night before Oppenheimer was
nervous there were so many things that
could go wrong the last test firing of
the explosives without the actual
plutonium core was a failure to calm
himself he recited a stanza from the
babad Gita the sacred Hindu poem he had
actually translated the Gita from the
original Sanskrit himself in battle in
Forest at the precipice in the mountains
on the dark great sea in the the midst
of javelins and arrows in sleep in
confusion in the depths of Shame The
Good Deeds a man has done before defend
him perhaps more terrifying than the
idea of the bomb not working was that it
would work too
well around 1942 Oppenheimer discussed
with Arthur Compton a terrible
possibility that a nuclear test could
end the world the worry was that the
nuclear bomb would create temperatures
so hot that Fusion would
occur a tiny fraction of the atmosphere
just one part in 2 million is hydrogen
gas but the worry was that at high
enough temperatures and pressures that
hydrogen could fuse together releasing
energy this energy would fuse more
hydrogen it could also break apart the
hydrogen from water vapor causing that
to fuse as well that would release even
more energy causing yet more Fusion
until the entirety of the Earth's
atmosphere would become a giant fusion
bomb recalling his conversations with
Oppenheimer in 1959 Compton said nor was
this all that Oppenheimer feared the
nitrogen in the air is also unstable
though in less degree might not it too
be set off by an atomic explosion in the
atmosphere most of the science quickly
realized how unlikely this scenario was
and they continued on with the project
so no one took the idea too seriously
but the thought of starting a fusion
reaction with a fision weapon would
become very important after the
war the Trinity test was scheduled for
4:00 a.m. but it was delayed due to a
storm so at 529 and 21 seconds the
gadget the world's first nuclear bomb
detonated the high explosive squeezed
the core of plutonium inwards the shock
wave mixed the burum and polonium
releasing a flood of neutrons the urchin
worked it jumpstarted the nuclear
reaction and now there was no way to
stop it just 6 kg of plutonium created
an explosion that was equivalent to
nearly 25,000 tons of TNT the New Mexico
mountains were illuminated brighter than
than in daytime the shock wave was felt
from over 160 km away the mushroom cloud
Rose to 12 km into the sky it was so hot
that the desert sand melted into a
glassy mineral now known as trinitite
fortunately the blast did not set fire
to the
atmosphere on August 6 1945 the Boeing
b29 Flying Fortress dropped Little Boy a
Gun type nuclear bomb with 64 kg of
enriched uranium the nitr cellulose
ignited pushing the Slugs of uranium 235
together tipping it over its critical
mass the blast from the explosion
equivalent to 15,000 tons of TNT killed
nearly 70,000 people another 7,000 would
die from Burns and radiation poisoning
in the following months 3 days later an
implosion type bomb like the gadget was
dropped on Nagasaki killing an estimated
880,000 more
people more than 95% of the 225,000
people killed in the bombings of
Hiroshima and Nagasaki were civilians
most were women and
children in 1965 recalling the moments
after the Trinity test Oppenheimer said
that he thought of another verse from
the gaita we knew the world would not be
the
same few people
laughed few people
cried most people were
silent I remembered the line from the
Hindu scripture the Bhagavad
[Music]
Gita
Vishnu is trying to persuade the prince
that he should do his duty and to
impress him takes on his multi-armed
form and
says now I am become death the destroyer
of
worlds I suppose we all thought that one
way or
another after the war Oppenheimer was a
national hero his portrait was on the
cover of Time Magazine and he became a
household
name in 1947 he became the director of
The Institute of advanced study at
Princeton he also became the chairman of
the general advisory committee where he
became an adviser on nuclear weapons
related issues he used his position to
argue for arms
control in August 1949 the Soviet Union
tested their first atomic weapon
and the US military quickly decided that
the best course of action was to develop
a more powerful bomb the hydrogen bomb
known as the super Oppenheimer was
against the development of the super on
ethical grounds and the worry that it
would start an arms race but Truman's
Administration pushed through and 3
years later Ivy Mike the first Hydrogen
Bomb was tested in the Marshall Islands
it had a yield of 10.4 megatons of TNT
that's 400 times more powerful than the
Trinity
[Music]
test a hydrogen bomb is actually three
bombs in one a conventional bomb a
fision bomb and a fusion bomb the
conventional explosives trigger a fision
reaction which increases the temperature
and pressure enough to fuse dyum and
tridium together releasing a huge amount
of energy in 1961 the Soviet Union
tested the SAR bomba the most powerful
explosion ever detonated it was another
five times more powerful than Ivy Mike
around 2,000 times more powerful than
Trinity this kind of arms race was
exactly what Oppenheimer had feared in
part due to his opposition to the
hydrogen bomb and due to his calls to
avert a nuclear arms race Oppenheimer
was essentially put on trial to revoke
his security clearance he had been
surveilled while he was working for the
Manhattan Project but that surveillance
didn't stop after he left many of the
wir Taps were legal and warrantless
Oppenheimer was questioned about his
ties to the Communist party including
his affair with Jean tatlock a Communist
Party member while he was leading the
Los Alam lab he was essentially accused
of treason and
Espionage in December 1953 Oppenheimer
had his security clear
suspended his face now grim and in black
and white was once again on the cover of
time his security hearings were
international
news in 1964 German playwright hinar
kiphart wrote a play about oppenheimer's
life Oppenheimer was sent a copy of this
script and he hated it so much that he
threatened to sue he especially despised
the final scene where the character of
Oppenheimer realizes the EV of his work
and I quote we have been doing the work
of the devil to Oppenheimer it was
always more complicated than that I
think that it probably was assumed it
certainly was always assumed at Los
Alamos that if the war were not over and
not
clearly to be brought to a
conclusion by diplomatic means
uh this weapon would play a part at the
time the
alternative the campaign of invasion was
certainly much more terrible for
everyone
concerned I think
that hirosima
was far more costly in life and
suffering
inhumane than it needed to have been to
have been an effect
Ive argument for ending the
war this is easy to say after the fact
in 1965 he was asked about the recent
proposal of talks with the Soviet Union
to Halt the proliferation of nuclear
weapons and his response was it should
have been done the day after Trinity
later that same year he was diagnosed
with throat cancer he was a lifelong
smoker and he died on the 18th of
February
1967 aged
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