The Last Man Who Knew Everything: Enrico Fermi

The Last Man Who Knew Everything: Enrico Fermi

Author
David N.Schwartz
Year
2017
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Review

I’ve been interested in Enrico Fermi since I heard about his ability to estimate anything. I loved this deep dive into him as a person - he wasn’t just a brain, it seems he was quite the character. I often find that biographies don’t have a high-enough number of insights per page to justify a recommendation, this is no exception. That said if you’re into science, the Manhattan Project or the art of estimating things then I’d recommend this one.

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Key Takeaways

The 20% that gave me 80% of the value.

  • Enrico Fermi was the father of the Nuclear age and the MVP of the Manhattan Project. He lived in the golden age of Physics, and was at the centre of it. He built the first working reactor, which demonstrated self sustained chain reactions were possible and controllable. He was first to unlock the energy inside the atom for human kind.
  • Fermi mastered all the sub-disciplines of Physics. A feat that's unlikely to be repeated given the sprawling complexity of the subject today. His super power was getting to answers quickly. He was great at both theoretical and practical physics, few of his piers could say that.
  • He seemed to have a great life. He was social, fit, competitive and funny. He won many friends and was uniquely loved by the community (see 'To Fermi with love' eulogies).
  • He was a prolific teacher and mentor. He practiced by explaining complex physics to those without traditional STEM backgrounds.
  • He taught himself physics from books (selected and sequenced by a mentor). Daily he worked through proofs in the library until he understood them. Larger books could take a year to complete. He wrote everything into a notebook. Clearly determined, he learnt German to read the best physics papers.
  • Fermi had a great understanding of probability and fundamental physics. He was famous for being able to estimate almost anything to within an order of magnitude.
  • He would reason from truths, guess probabilities and values. He'd undershoot some, and over shoot others... but often got accurate outcomes. These are now called 'Fermi estimation problems.'
  • Fermi was able to calculate anything to within an accuracy of 10% within a day, but to improve accuracy 3x could take a further 6 months. As entertaining as this talent was, it seemed to be what made him great at physics too. He understood the theory, predicted outcomes and designed experiments to test them.
  • He made regular predictions with a group of scientists for fun, Fermi was the most accurate (97%). He stuck to the theory that next month would look like this month.
  • Fermi invented the Monte-Carlo method for analysing probability’s on the way to solving a different problem. It turned out to be a massive contribution to statistics.
"Never make something more accurate than necessary" Enrico Fermi
  • He founded the Rome School of Physics with the principles of:
    • Equal importance to theory and experiment
    • Conservatism when claiming results
    • Division of labour to achieve major results
    • Steer clear of religion and philosophy
  • He got an Academia Italia award (Galileo got one) which gave him a salary for life. He was indirectly supported by Mussolini was supporting him in his early days.
  • Fermi received 39 nominations for the Nobel Prize from his peers. He won in 1938 for demonstrating the existence of new radioactive elements, produced by neutron irradiation and the discovery of nuclear reactions brought about by slow neutrons.
  • He fled to the USA via boat after collecting the prize. His wife was Jewish, and it was clear that Hitler and Mussolini's were going to persecute them.
  • Soon after, scientists understood they'd split the atom and that a nuclear bomb maybe possible. Fermi gave it a low probability of success (10%). He tried to convince Heisenberg to stay in the US but he returned to Germany to lead the nuclear program for Hitler.
  • Fermi tested the assumption with experiments that identified that 2 neutrons were released when the atom split, only 1 was needed to make a chain reaction.
  • Fermi and others briefed the US military explaining that a nuclear bomb could be a million times more powerful per pound than existing explosives.The Navy started to fund the research.
  • Oppenheimer started the Manhattan Project.
    • Many streams of critical work in parallel:
      • Fermi in Chicago: Chain reaction and plutonium production
      • Oppenheimer: Theoretical work on fast neutron fusion:
        • How much material would the critical mass of the bomb need to be
        • Best material for fission reaction (plutonium)
        • Production of U235 for fusion reaction
  • In Jan 1942 a simple and ambitious timetable was drafted.
    • Determine the feasibility of a chain reaction (+ 6 months)
    • Achievement of a controlled chain reaction (+ 12 months)
    • Product of plutonium of the bomb (+24 months )
    • A working bomb (+36 months)
  • Over 3 years Fermi wrote 50 papers on chain reactions. Fermi bet on graphite to be the right material to slow down neutrons and moderate the reaction. This turned out to be a crucial bet, the German effort went for heavy water and never got to a working reactor.
  • Fermi had full security clearance (despite the FBI recommendation) and worked under the alias Eugene Farmer
  • Fermi designed the first reactor in his head. A large pile of graphite bars with room for uranium cores. If he got the geometry right, the neutrons will be captured by the uranium and cause a chain reaction. They added control rods that would speed up and slow down the reaction. The reactor was to prove that chain reactions were possible, and to produce plutonium for weapons. The first reactor was built under a squash court, after 29 prototypes.
  • Fermi was a showman. They started up the reactor by removing safety rods and edging out control rods. Each rod movement caused spikes and drops in radioactivity, Fermi accurately predicted them. He shouted "this will do it" when he gave the order to remove the last rod. Colleagues were scared. Fermi hadn't communicated the plan ahead of time. The reaction quickly became critical, and grew exponentially (as planned). Fermi waited 28 minutes before yelling "ZIP" and dropping the rods back in. Fermi showed that a controlled fission reaction was possible. Humans could now control the release of energy embedded in the nucleus of the atom. The weight of the moment was clear. They were on a path to a nuclear bomb.
  • There was a lot left to do. Begin plutonium production, determine critical mass and conceive of a detonation method. Von Neumann worked out how to detonate to bomb, by working through complex pressure wave calculations. Explosives of different densities would be required.
  • When Hitler was defeated many called to stop the program but Truman wanted the bomb to end the war with Japan. Fermi thought inviting the Japanese to a demonstration would be enough. Oppenheimer convinced the panel (inc. Fermi) to back immediate military use.
  • The first bomb was tested in March 1945. Fermi watched from the desert, lying facedown away from the blast with eye protection. The bomb produced the brightest manmade light. Fermi dropped paper into the shockwave, and declared the force must have been 10 kilotons of TNT (it was 18). An hour later they drove to the site, the tower had evaporated, the sand had turned to glass.
  • They debated if they should tell their allies. Truman updated Stalin, who showed little interest.
  • Lil boy and Fat man were dropped on Hiroshima and Nagasaki, killing 70k and 80k people respectively. Japan surrendered 5 days later. Secrecy was lifted, a book on the Manhattan project was already ready for publication and it sold 100k copies.
  • Fermi had patented the nuclear reactor and slow neutrons before this all stared. Those patents were priceless but he was only given pennies on the dollar by the US.

Micro Insights:

  • He categorised people into 4 categories. Lower than average, average, intelligent and exceptional.
  • He bought a silly yellow car that became a character in the families life.
  • He had a daily routine. 2 hours of work before breakfast. Broke the day up with sport and lunch.
  • Leona Wood was the only female researcher on his team in the Manhattan project. He and his colleagues hid her pregnancy so she could continue. Fermi researched how to deliver a baby just in case.
  • Dirac named Fermions after him.
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Deep Summary

Longer form notes, typically condensed, reworded and de-duplicated.

  • Fermi should be more well known, based on his achievements
  • Life spanned 2 world wars, and 2 big discoveries. Relativity and quantum theory.
  • In Fermi’s early work, he’d been spilling atoms without knowing it
  • He built the first working nuclear reactor. Fission.
  • He played an important role in the manhattan project, witnessed the first atomic bomb test
  • Very few have a legacy like Fermi. Many scientists gave him glowing obituaries
  • He spoke out about the h-bomb but worked on it
  • In terms of a teacher and mentor, he was probably the most prolific. His students won many Nobel Prizes
  • Fermi Problems - estimate probability, values to within an order of magnitude
  • Never make something more accurate than necessary
  • Physics was the most important thing his life
  • He wasn’t a great dad
  • His lack of self promotion and dying before TV was popular is probably why he had less of a profile
  • He confined his science to real physics problems that could happen in the real world. He didn’t engage in the only theoretical
  • His dad worked for the railway. Italians are proud of their rail system.
  • Lost his older brother as a young boy
  • How he learnt physics and maths:
    • Studied by himself at the library everyday
    • Worked through books - sequenced by a mentor
    • Worked through every proof. He mastered the material. Deriving everything from first principles before moving on
    • Some of the larger books took him a year
    • He could remember the content
  • He learnt advanced mathematics and german, so he could learn the best physics
  • At university. The lectures didn't take much time. He spent most of his time in independent study. He got perfect grades in Physics, Mathematics, Chemistry and German. He got perfect grades in everything but drawing. Which he got 24/30.
    • He only really had to work at chemistry as he had no background in that
    • The rest of his time was spent reading papers in the library. On quantum physics etc
  • Fermi was a bit of a prankster.
  • He enjoyed leading hikes into the hills with friends at the weekends.
  • He ridiculed the intelligence of women around him
  • His knowledge of relativity became stronger than his teachers, he used to give lectures
  • Fermi practiced pedagogy, giving lectures on complex relativity to people without the usual background to understand it
  • He recorded all of his knowledge into notebooks. His 1919 notebook is 102 pages long and has lot's of different advanced physics.
  • He would fiddle with things whilst solving equations. Cutting himself with a pen knife, leaving a scar on his face
  • Fermi wanted to do real applied experiment physics, he didn't focus on theory. He mixed the two.
  • Fermi loved probability and physics. He loved to gamble. Loved to set riddles.
  • Fermi problems. Guessing the probability of events, plugging in numbers within a order of magnitude, getting to a sensible answer.

Quantum Breakthroughs:

  • Plank proposed that energy was in packets. Not waves.
  • Energy came in discrete packets.
  • Electrons and protons were discovered around this time
  • Things were changing fast
  • Fermi and Wolfgang Pauli were opposites
    • Pauli was a drunk, had an ass hole vibe , hung out with artists etc
    • Pauli - exclusion principle.
    • Suggested electron spin (which he didn't believe)
  • Paul Dirac was the opposite of Pauli
    • Dirac was probably autistic.
    • Dirac: why do you dance?
      • Heisenberg: "When there are nice girls its a pleasure"
      • Dirac: "How do you know beforehand if the girls are nice?"
    • Student: "I don't understand the equation on the blackboard"
      • Dirac: {silence - as it wasn't a question he didn't know to respond}
  • Pauli's exclusion principle could be extended to atoms
  • It was an answer to degeneracy
  • Dirac read Fermi's paper... but didn't reference it when he created an alternative approach. Fermi wrote to him. Dirac later always credited Fermi.
  • Fermions and Bosons. They got Fermi's name.
  • Interesting how ides are morphed and used in different contexts to solve different problems.

Part 2 the Rome Years

Family Life

  • He organised 2 physics conferences
  • Fermi had the analytical skills to analyse almost anything
  • Fermi grouped people into 4 categories of intelligence:
    • Lower than average
    • Average
    • Inteligent
    • Exceptional
  • Bought a silly yellow car, became a character in the families life
  • Fermi worked in a routine. Got up early, 2 hours in study before breakfast, off to work until 1 PM for lunch, 2 hours of tennis or activities, back to work, return home for dinner about 8pm.
  • He even had a yearly routine - skiing etc
  • Fermi wanted to move to the US - it would help his career, research and hiking per suits
  • He wrote a physics textbook with his wife to make more money and substitute his academic incom

The Rome School of physics

  • Principles:
    • Balance of theory and experiment
    • Development of expertise
    • Conservative about results claimed
    • Publicity
    • Focus on import so approach
    • Division of labour to achieve major results
    • Nothing about philosophy or religion
  • Fermi was the leader. He was called the pope by his ‘disciples’
  • Fermi has a charisma and leadership
  • Students were choosing engineering not physics
  • He was teaching people to think how he thought
  • A group endeavour and a social endeavour. They’d spend weekends together
  • Held conferences - got the best minds together
  • Fermi got a reward, entrance into a society, gave him a salary for life on top of the university one
  • Academia Italia (Galleleo and early one)
  • Came with a title of ‘his excellency’, he found the fancy dress embarrassing, didn’t like spending time at functions. Wanted to get back to studies
  • Fermi - was therefore supported by the regime. Musolini. Gave him stability. They claimed his work as Italy’s. Deal with the devil.

Beta radiation

  • Computed probability density of where the electrons would be in orbit at any one time
  • Took ideas developed in one concept, applied them to another
  • Dirac produced QED. Theory of Qauntum Electro Dynamics
  • Laid the foundation for Fermis beta radiation work
  • Dirac - Before: electro magnetic field - they feel a force and interact with each other. There was a relationship between magnetic and electrical fields. Maxwells equations quantified it.
    1. Maxwell:

    2. If you understand the strength of the field you can understand how an electron will behave
    3. A field exerts a force that varies throughout the field. Influenced by distance from source and type of source. Allowed for repulsive and attractive.
    4. The particle is not a manifestation of the field
  • Dirac discovered. World not entirely predictable at very small levels. The world is not continuous, energy comes in irreducible packets. There is granularity.
  • Dirac- the particle and the field are a single system. They are coupled. Built on all t
  • They knew that beta radiations particles were omitted, but they violated the rules of conservation of energy.
  • Pauli proposed that there must be another particle, that couldn't be seen because it had no charge. This must be ejected at the same time as the Beta particles.
    • People thought this was crazy, and that it was more likely the conservation of energy rule would be violated in this instance
    • It turned out to be the Neutron and the Neutrino
  • Nature- said no to Fermis weak force paper. It seemed to be impossible to prove.
  • Fermi invented the Monte-Carlo method for analysing probability’s .... just as a means to working on physics. It was a massive contribution to statistics

Nobel Prize - Anyone can submit a nomination

  • Records show Schrödinger received 41 nominations before getting one
  • Fermi received 36 nominations, 3 for chemistry, 36 for physics
  • Great scientists nominate each other
  • Fermi 1938 won the Nobel Prize
  • Fermi was asked if he'd be able to accept the prize, or if the regime (Mousolini would stop it)
  • He knew he'd be able to accept it
  • But he went to live in America afterwards, he wouldn't have been able to keep the money if he returned to Italy - but he fled for other reasons too.
  • They went around Rome for one last time
  • They were waiting for call from the committee. At the time, news of new antisemetic laws came over the radio. Jews were not able to attend school etc.
  • The call came, he won the Nobel prize on his own for
    • Demonstrations of the existence of new radioactive elements, produced by neutron irradiation
    • and discovery of Nuclear reactions brought about by slow neutrons
  • He had a celebratory dinner
  • They had to get through Germany. His wife had to convert from Jewish to Catholic to travel through Germany.
  • They had to flee in secrecy. To exile. They were conflicted about leaving. Were they fleeing. They sailed across the Atlantic

By the time he got to the united states, things had really moved on

Other scientists had realised that they'd split the atom

A lot of energy would be released.

Enough to cause a potential chain reaction. Some of them realised how dangerous this was.

Fermi thought there was only a 10% chance it was possible. Therefore he didn't think that they should keep it secret, just say there was a lower probability. The others disagreed.

Fermi started on measuring the number of neutrons released. The number of neutrons would determine if a chain reaction was possible. He measured and estimated that 2 were emitted for each reaction, making a chain reaction possible.

They knew it could be used to make a weapon, they knew they had to brief the US military.

Fermi meets the US navy

  • Experiments at Columbia university reveal that conditions can be found where uranium might be able to deliver its large excess of atomic energy and this might mean that uranium could be used as an explosive which might be 1 million times more powerful per pound than any known explosive.
    • The probabilities are against us, but our colleagues feel that the possibility should not be ignored.
    • We're in Washington tomorrow lecturing, you're welcome to come
  • Fermi kept the letter, as a from of insurance to prove his loyalty to the US
  • They were still undecided on secrecy, they sent a paper to a journal, but asked them to hold fire on publishing whilst they thought about the implications of it

The navy meeting - he spoke for about an hour

  • Slow neutron fission, the emission of neutrons from fission, chain reaction
  • He said they were checking the numbers on neutron emmissoin
  • He also said critical mass would be important. The head of the navy asked how big would it need to be?
    • Fermi said: It could have to be the size of a small star
    • He also said they'd need to separate u235 from the other isotopes and they don't know how to do that yet
    • He didn't want to spur them into a frenzy of action
  • The navy did then start looking into using nuclear power to power submarines
  • The navy sent a cheque to Columbia

Natural Uranium has 2 isotopes in it.

  • U238 - Difficult to spilt, 99.3% of natural uranium
  • U235 - Readily splits, good for reactions, just 0.7% of uranium

A cain reaction would require tons and tons of uranium if they couldn't separate the isotopes.

New measurements were 1.5 Neutron emissions. Anything over 1 would allow a chain reaction.

They started doing experiments in water, but the water absorbed some of the Neutrons.

U238 actually has a dampening effect on neutrons emitted from U235.

Heisenberg was in the US, Fermi had fled to the US. The debate was all about if you could do science under the regime if war broke out. Heisenberg thought you could.

Heisenberg felt like leaving Germany would be a betrayal.

Heisenberg and Fermi spoke about the possibility of a nuclear bomb. They tried to convince him to stay in the US. However, Heisenberg was too patriotic. Fermi said, that's a shame, I hope we meet again after the war (which hadn't started yet)

Fermi had previously nominated Heisenberg for a Nobel Prize.

When Heisenberg returned to Germany, Hitler asked him to build a bomb, put him in charge of the project.

Fermi respected Heisenberg enough to know that they would now have to do the same in the US.

If water wasn't the best place for the reaction, what was? Graphite?

Hydrogen was the lightest. Uranium was the heaviest (at the time)

They started looking for moderators.

Graphite was machinable, they set about substituting water for carbon

  • The idea being that carbon would slow down and absorb kinetic energy, long enough to create a chain reaction
  • The scheme would require a lot of graphite

Roosevelt agreed to start the manhattan project.

It all started with Fermi at Columbia

In the fall of 1939 he wrote 47 papers, describing the experimental work leading to the first controlled self sustained chain reaction on December 2nd 1942.

  • He pursued other academic interests at the same time
  • Fermi thought he could calculate anything to within an accuracy of 10% within a day
  • To improve the accuracy by a factor of three could take 6 months
  • He would sometimes get frustrated if he couldn't immediately solve a problem
  • Get got together with a bunch of people. They made predictions about the future. Fermi was the most accurate. About 97% of the time. But he sticked to the theory that next month would look largely like this month

Compton was brought in by Bush to lead the Manhattan project.

He met with key people brought teams together, to centralise the effort and made 2 decisions (Jan 1942)

First the timetable of the development of the bomb:

  • Determine the feasibility of a chain reaction (July 1st 1942 - 6 months)
  • Achievement of a controlled chain reaction (Jan 1943 - 12 months)
  • Product of plutonium of the bomb (Jan 1944)
  • A working bomb (Jan 1945)

Decision to centralise the work:

  • UCL Berkley would remain in California
  • Everyone else including Fermi would come to Chicago
    • Fermi wasn't happy, as he had a good team and complete control at Columbia

The FBI were following Fermi. 1940:

  • He left Italy because his wife is Jewish
  • He has been a nobel prize winner
  • He is a facist
  • He shouldn't be employed on secret work without further assessment
  • His colleagues like and respect him professionally and personally

The government allowed him to work on the secret stuff, as most of it has originated from his brain.

  • Fermi complained when he discovered his main was being read

Teller using Fermi’s beta decay maths worked out that a fusion bomb could have unlimited energy, you could just add s’more material

  • Everyone was working on fission
  • Teller proposed fussion

Fermi was fun, always up for a game.. which helped him make friends and build relationships

  • 40 physicists were working on the chain reaction in Chicago
  • Fermi was given more and more responsibility until he complained that he was doing physics by phone (too much admin)
  • In contrast to today. The first reactor was designed by Fermi in his head, based on his guess about how the neutron flow would develop in the pile
    • He was working out how long it would take until it got too hot etc in his head
  • Before they built the first serious reactor, they'd built 29 experimental prototype pile
  • The job of the first reactor, was to prove the chain reaction would be possible, but also to produce plutonium (alternative to U235) for fusion weapons
  • the Fermis hosted parties for new physists, played parlor games, made great friends, built a social bond
    • Large pile of graphite bars, with uranium in between
    • If the geometry is right, the neutrons will be captured by the uranium, and cause a chain reaction
    • He built prototypes under the squash courts
  • He needed new instruments to help understand the reaction
  • He had a material that he could use to stop it getting out of control
  • To start the reaction, you would take out the strips
  • Finally, pulling out the control rod would start the reaction
  • The plan was to complete the pile by October 20th 1942.
  • They didn't know if you could control a chain reaction
  • Key personal couldn't travel by air. They now also had body guards. They needed to use code names
    • Henry Farmer was his code name
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The manhattan project had different streams of critical work. Planning moved ahead assuming that Fermi would deliver. A number of tracks that depended on each others success were working forward simultaneously

  • Fermi in Chicago: Chain reaction and plutonium production
  • Oppenheimer: Theoretical work on fast neutron fusion:
    • How much material would the critical mass of the bomb need to be
    • Best material for fission reaction (plutonium)
    • Production of U235 for fussion reactoin
  • They built the pile under the squash court despite the risk
  • Graphite bars and uranium were arriving at a furious pace
  • Machining graphite into proper shapes, boring holes for uranium
  • 3 shifts of 8 hours
  • Built it inside a rubber bloom built by Goodyear so they could suck the air out
  • They needed 76 layers, 27 feet high
  • December 2nd 1942
    • 3 safety rods were removed
    • ZIP removed the first control rod, the reaction started up then faded
    • the last one was pulled, the reaction was huge, but sub critical
    • they removed it 6 inches at a time, as Fermi checked calculations
      • each time the reaction was lasting as long as Fermi thought before leveling off
    • at 11:35 a safety trigger set off, and a vertical rod dropped
    • they went for lunch
    • about 3:25PM Fermi ordered another foot of the rod to be withdrawn
      • this will do it he declared
      • now it will become self sustaining, it will climb and continue to climb
      • the reaction grew largely, the curve was exponential
      • he gave no indication of next steps as he looked at measurements
      • everyone was waiting on his word
      • 28 minutes into criticality he called ZIP and they dropped the rods back
    • History had been made, but it was a sombre mood. They noted that they'd made history but that this would go down in history as a black day
    • Only after the war would his wife learn what happened that day

It was the first time that humans tricked nature in a controlled and sustained way into releasing the energy embedded into the nucleus of the atom. Fermi showed that a controlled fission reaction was possible. He also led the way for the exploration of uranium for peaceful purposes. The first nuclear reaction.

The program then moved onto the second problem. The design and realisation of a large reactor that could produce the nuclear explosive plutonium.

He had done enough experiments and mastered the theory that he could predict what would happen at each 6 inch removal of a control rod.

  • Fermi made it a spectacle. He was a showman, he did what others wanted him to do

It was years of hard work. The German effort was years behind them. They never constructed a working reactor.

  • This is largely because of the early decision from Fermi to use graphite. Rather than heavy water.
  • Pure graphite was key. Germans experimented with graphite but it was impure, and they didn't think that it could be purified.
  • Heavy water was really hard to make in bulk, which tripped up the Germans

Fermi learned how to think like a neutron.

He was a brilliant and inspirational leader.

He was easily accessible to senior and junior scientists alike

He could understand any problem thrown at him.

He simplified experimental setups

He was utterly unafraid of using quick and dirty solutions

Chapter 18

  • Chicago Pile 1 was reconstructed in a new way
  • Chicago Pile 2 had a central core that could be removed.
    • It took CP1 a minute to double its reaction when it went critical
    • It took CP2 about 5 seconds
  • CP2 gave him neutrons at will
  • He developed new detectors

Leona Woods: the only female scientist.

  • One night Fermi was driving her home, she suggested they stop and sleep
    • Fermi said he couldn't because of his reputation
    • She was pregnant at the time and said what about mine???
  • The health and safety officers would have stopped her from experimenting if they knew about her baby
  • She was however able to hide her pregnancy with baggy clothes
  • Fermi researched how to deliver a baby, just in case
  • Fermi took at the request of a colleague, looked at his watch which wouldn't keep good time.
  • Fermi took it for 3 minutes, took some measurements, and was able to explain the phenomena and predict its future inaccuracy
  • They created a newer bigger pile.
  • They started out on plans to productionize plutonium
  • fast neutrons were the secret to the bomb
  • Oppenheimer and Fermi started to working together
  • Von Neumann
  • Oppenheimer planned the devision of labour
  • Los Almos was were they all came together to build the bomb
  • There was a large site, with a plutonium production reactor
    • Hundreds of buildings, thousands of people
    • 3 plutonium production reactors, and a huge chemical treatment plant
  • They lost a reactor - a reaction stopped - poisoned
    • the reactor produced a rare element (Xenon-135) that absorbed neutrons
    • however, when running at full speed that wouldn't happen
  • The plan was to use plutonium in an implosion which would cause a chain reaction
  • But there were doubts about using plutonium
  • Spontaneous fission was going to be a problem
  • The only was to do it was going to be plutonium implosion
  • They would need it to be a perfect sphere so the shockwaves behave evenly
  • The waves deform the sphere
  • Scientists would need to reverse the shape of the waves quickly after it happened

Critical Mass was an important question

  • The British government was doing something similar to the Manhattan project. They joined forces but it took a while to talk to each other
  • The critical mass problem needed to be brute forced. They used lots of women and calculators
  • Feynman looked after them
  • High explosive lensing could change the shape of the material, explosives would have different densities
  • Von Neumann was responsible for the calculations
  • Fermi used the punch cards
  • Von Neumann built the first truly programmable computer after the war
  • Fermi would trek in the hills
  • March 1945 - Plutonium production and uranium production in full swing
  • U235 critical mass = progress was being made
  • Fermi became worried about building a bomb
  • The initiator became the difficult problem
    • The urchin - on implosion would emit 100 neutrons
    • They would seed the fusion explosion
    • Fermi conceded that it would work
  • Fermi pushed the project for 5 years, but he had growing internal panic
    • both of being successful and failing

The war with Germany effectively ended, in April 1945

  • The germans tried but didn't get there because they went for heavy water not graphite
  • Heisenberg said he did that deliberately to slow them down
  • they never achieved a chain reaction

Many now believed that the project should be slowed or stopped, as nobody else was close.

The bomb if developed should not be dropped on Japan.

Truman wanted to get the bomb to quickly end the war with Japan

Fermi, Oppenheimer and others were asked to advise the president on:

  • Current status of project
  • Estimates of weapons effectiveness
  • Where, when and how to let the soviets know about the project
  • How to manage the technology in a post war world
  • How to use the weapon to end the war with Japan

Fermi suggested a dramatic demonstration to the Japanese (in a desert)

Oppenheimer disagreed, and thought that nothing would persuaded them.

  • Oppenheimer thought it would be no worse than the traditional bombing campaigns

They decided to hit Japanese military targets in cities.

They knew they would only have a few bombs in the near future, they didn't want to waste one on a demonstration for Japan

  • Fermi had never got this high up in politics before
  • Many signed a letter, asking to keep the bomb secret, or only use it as a demonstration

June 15th 1945: Oppenheimer held another meeting and made recommendations:

  • continue nuclear research
  • manhattan project should be extended to the end of the war to oversee the technology
  • Oppenheimer 350 word report on behalf of the 4 scientists.
    • Allies should be told of progress
    • Opinions differed they leaned toward immediate military use to end the war as soon as possible
    • As scientists, they had no specialty in deciding what to do with atomic weapons
  • Fermi was the last hold out
  • Fermi thought it was best to keep the bomb secret for as long as possible
  • Oppenheimer pressured Fermi - he only conceded because he was not a politician
  • It didn't matter anyway though, the president had already decided to use it

Unholy Trinity

  • March 1945 - the number one priority became to test the weapon
  • Halt all other work, divert all scientific resources to the test
  • Fermi arrived by car (on its last legs)
  • Fermi got in trouble, as he was taking odds on the atmosphere burning up. Some of the military got worried and reported it
  • They modified tanks with lead so they could take soil samples after the blast
  • Iron tower held the device
  • The VIPs got front row seats on a small hill
  • Most of the scientists viewed from within the bunker
  • Fermi wanted to be out in the open
  • With as little as possible between him - he went to the desert with some other physicists
  • 5:30AM
  • The detonators went off
  • The explosions pushed the device in on itself
  • The urchin emitted the neutrons
  • leading to an explosive chain reaction of plutonium fission in less than a millisecond

Fermi was lying facedown, with welding glasses, looking away from the explosion

For a few seconds, everything went white. It was the brightest light ever created on the planet.

They stood and turned. Fermi started counting from the white flash

He held paper above his head, he counted off the seconds and dropped them into the blast wave

They went 2.5m, Fermi announced that the blast was 10 kilotonnes of TNT

He prepared the experiment the night before

Instrumentation specialists to days to confirm it was 18

They went to the site within an hour

The hole was 5 ft deep and 30ft wide

The tower had evaporated, the sand was turned to glass

63 ranches were within 30 miles. Residents weren't evacuated.

They have not been competed.

July 24th, 1945. Truman told Stalin about his new weapon.

  • Stalin didn't show much interest, but congratulated them, and hoped they would use it against the Japanese
  • Stalin would have had some intel already - they knew it was plutonium

The United States warned Japan that they needed to surrender immediately, or there would be dire consequences. They did not mention the bomb.

  • Lil boy, and fat man were flown to a south pacific island held by the US
  • Lil boy was dropped on Hiroshima , killed 70k, levelled the city
  • Some Japanese tried to contact the US and surrender, but the senior military leadership decided to fight on
  • Fat man was dropped on Nakazaki - 80k people died.
  • Between the blasts, Stalin declared war on Japan.
  • It took 5 days for the Emperor to surrender without condition
  • The bombs were seen to have been a success at ending the war

The news was out, the manhattan project became public.

Fermi's wife only understood what he was doing after the bomb

  • One of the people had written a book about the whole project
  • It sold 100k copies
  • Fermi was a strange kind of famous

Fermi's lectures were written up and published in 1945 - they were classified until 2009.

Fermi was ready to return to Chicago.

Fermi is called the father of the nuclear age

  • He came up with the first crucial experiments in 1939 to explore how chain reactions might be created using uranium, they noted that graphite would be the right moderator
  • The pile was the first working reaction was important
    • showed chain reactions were possible and controllable
    • produced the neutrons and plutonium they needed
  • The next two reactors were crucial in understanding the purity that is required
  • Finally the reactors were used to test the critical mass assumptions
  • He was the go to physicist when others were stuck.
  • He saw quick solutions
  • Oppenheimer relied on his scientific guidance
  • He did not design the bomb
  • He wasn't working on fast collisions either
  • He wasn't working on uranium enrichment either
  • Von Neuman did the pressure wave calculations for the detonation
  • Fermi missed a major technical issue in Xenon-135 poisoning of the reactor

Thousands of people were working on the project, many didn't know what they were working on. Groves and Oppenheimer were crucial too. Hundreds of Physicists came.

Never make something more accurate than necessary.

Fermi began doing astrophysics, everything to do with radiation in space.

Late March 1948 - QED

  • Feynman discovered it at the same time as 2 others (Julian Schwinger was one)
  • Fermi preferred Julian Schwinger's approach and nominated him for the nobel prize
  • Feynman liked Fermi
  • Helped create the Atomic Energy Agency: to make it civilian and not military
  • Fermi became interested in computers
  • MonteCarlo simulations were Fermi's math tool
  • Fermi started working on computational theory
  • And hydro dynamics
  • Fermi was involved in early particle accelerators
  • Discovered a new short lived particle. Delta++
  • Fermi enjoyed working with others and helping them, he started to step back and let others take the lead and the credit
  • Fermi's clearance file stated he was the greatest living physicist
  • The hydrogen bomb, nuclear reactors and refinement were all still being discussed by GAC
  • There were no minutes in these meetings
  • News got through that the soviets were also working on nuclear weapons
  • They said no to the hydrogen bomb. They didn't see the need.
  • They could do 100x more damage. What was the point?
  • They wanted the US to forbid the development of these weapons
  • They were asked to develop the hydrogen bomb before the Russians
  • Many vital flaws were discovered in the early designs
  • November 1952 - on an Island, they proved that it would be possible
  • Fermi wanted to leave the H bomb project
  • Fermi wanted to avoid public policy questions
  • Fermi stood with Oppenheimer and defended him when they were removing his security clearance
  • Oppenheimer faced humiliation and disgrace.
  • Fermi had a number of nuclear patents
    • Before the Maanhatten project
    • Zalard had chain reaction patent
    • Fermi had a patent on the nuclear reactor
    • Fermi had a slow neutron patent
    • The commercial value of them was incalculable
  • They settled with Fermi - he got a lot of money, but pennies on the dollar of the value
  • He got to go back to Italy, he went to Lake Como for a lecture series and was joined by old friends, family and many physicists
  • Fermi began to get ill. Was told he had 6 months.
  • in 1964 he died.
  • Fermi was stoic, and calm about dying
  • Fermi won a prize from AEC - $25,500
  • Died of a heart attack in his sleep. Chicago.
  • Had cancer - stomach cancer.
  • Many spoke at his funeral
  • Nothing altered his simplicity
  • Nothing altered his love for science
  • He was a great teacher
  • Scientists wrote him a book, 'To Fermi with love'
  • He was loved. He was one of the best physicists that has lived
  • The Fermi award is awarded for best energy science contributions
  • It's a huge honour among scientists
  • His strong force experiments helped identify quarks and gluons
  • The Monte-Carlo technique is really important
  • Fermis text books live on
  • More than 200k people died at the hands of nuclear weapons in Japan
  • Fermi put probability at the front of physics, it was important for quantum mechanics
  • Energy locked inside matter, he unlocked it, he gave man the ability to destroy the world
  • He was the last man who knew everything
    • This was meant to refer to physics
    • He was the last man to know all of physics
    • He mastered
      • Astro
      • Nuclear
      • Particle
      • Condensed
      • Geo
    • He was great at theory and experimentations
    • He knew about matter, energy, time and how they interact
    • He knew everything about how the physical world works
    • Our knowledge has evolved since he died.
    • For one person to master all the physics of his day was a unique achievemen
    • Today, it wouldn't be possible to be at he edge of many subdisciplines