Author: Not Decided
Status: In Research
Please post any ideas or research for this episode that you want to contribute in this topic. If the episode hasn’t been assigned to an author yet, you can note your intent to write in the string too, and we will contact you to discuss.
I’ll begin writing this asap, probably on the weekend.
Something else science related that would be nice to mention somewhere is the discovery of antibiotics leading to penicillin becoming available during WW2. Might go nicely as a quick note at the end of this episode.
Saw your reply in the transport episode. Do you want to work together on the atom episode? I’ve got a chemistry and physics background, so someone who has an idea of the practical uses of the pure science science would be great. As a start I’ll put together a timeline of the development of the atomic model and related discoveries such as quantum theory, general relativity (e=mc2) and of course nuclear physics. Once that is together we can start discussing some of the practical uses of the science to try and liven up the episode a bit.
Yeah sure. I have a background in electrical engineering, so that would make me a bit more practically oriented then. However, since I did this in uni it is still quite abstract, but I am very interested in the engineering side of things. Nowadays I work with lasers, which were invented later than the period we are discussing but also rely on quantum mechanics.
I guess if you want to shape it a bit more into a general science and engineering episode with a catchy title one should start to explain that physics was more or less completed at the turn of the century. Only then they started with all of this interesting stuff, which is, of course, the reason why pretty much anything done before this time period is called classical physics.
I reckon the entire timeline of modern physics could be woven in together with the important engineering aspects of those discoveries. For the physics side of things, you could think of atom models, quantum theory, relativity and nuclear physics. Engineering that this enabled could be X-ray scanners (already in the WW1) and ultimately, of course, the atomic bombs dropped in 1945. This could give you a timeline where Modern Physics created the opportunity to create the atomic bomb.
However, I do think much more important stuff went on here that changed our lives. We owe more in our current lives to this leap in physics. The interest in the atom model also accelerated the research into semiconductors since they finally had a way to explain what was going on in there. This of course together with code-breaking efforts sort of morphed into current day computers (massively oversimplifying things). Also, the photovoltaic effect, which kick-started quantum mechanics, enabled many optical innovations. One I could think of is the night vision equipment already used in World War 2. Furthermore, radio, although the Maxwell equations and its subsets are Classical, went through a huge boom in the interwar years. Think about what radio did for communications, radar, etc. After WW2 many of these creations really came to life with the invention of the transistor, lasers, computers (although electronic computers were also used in WW2, for example at Bletchley Park)
@Spartacus What role do you envision for “science and technology” or “physics and engineering” in this B2W series? I also see an episode called “Radio Days”, I guess that is cultural instead of technological, am I right? I believe we can write a lot about both physics and engineering in the interwar years. Although, I must admit most of these inventions go anywhere from late 19th century (mainly the physics) up to mid 20th (mainly the engineering). Importantly, I do think that these inventions are very important for both the war (think about radio, radar, sonar, night vision) and our current lives (think about the device you are reading this on).
PS I guess you can sense that I went on a Wikipedia spiral writing this comment.
My vision (although this may differ from Sparticus and Indy’s) is that the physics would be the backbone of the episode with the engineering/technology advancements spinning from that, though we could quite easily do it the other way and decide what technologies we ant to cover and cover the physics around those. Looking at Sparticus’ comments on other episodes they are quite hapy for us to go outside of the immiedate timeframe of the episode, so covering late 19th century through to the start of WW2 should be fine. Yes, there is lots that could be covered.
From a pure Physics perspective, I’m thinking that the following should be covered:
There are also a large number of medicine related discoveries in this time period. Think things like penicillin and the tetanus shot. These may be nice to mention, but we probably have enough to cover as it is.
It doesn’t differ from our vision at all, this is in fact how we discussed it when we listed the episodes.
I’m going to break the major scientific discoveries down into decades so as not to be too long. Feel free to ask about any of the terminology that doesn’t make sense, I’ve tried to give an explanation for anything I think needs it. Here is some discoveries from the 19th century:
19th century – physicisists believe that the job is just about done, just need to make some minor adjustments and then we will know how everything works
1859 – Gustav Kirchhoff introduces the concept of a blackbody (an idealised system where all radiation entering the system is emitted – many large celestial bodies such as stars closely match the behaviour of black bodies) and proves that its emission spectrum depends only on its temperature.
1877 - Ludwig Eduard Boltzmann suggests that the energy levels of a physical system could be confined to specific values based on the properties of the system (work based on statistical mechanics and mathematical arguments). He also produces the first atomic model of a molecule in terms of the overlapping molecular orbitals (as they would later be called) of the constituting atoms.
1885 – Johann Jakob Balmer discovers a numerical relationship between visible spectral lines of Hydrogen, the Balmer series.
1887 - Michelson Morely experiment. Albert Michelson and Edward Morley attempt to find the ether (the medium through which light waves were thought to travel) using inteferance patterns in light. Despite numberous attempts at the experiment, no evidence for the ether was found.
1887 – Heinrich Hertz discovers the photoelectric effect (the emission of electrons when light shines on an object)
1888 – Hertz demonstrates experimentally that electromagnetic waves exist.
1888 – Johannes Rydberg modifies the Balmer formula to include all spectral series of lines for the hydrogen atom, producing the Rydberg formula which is employed later by Niels Bohr and others to verify Bohr’s first quantum model of the atom.
1895 – Wilhelm Conrad Röntgen discovers X-rays.
1896 – Antoine Henri Becquerel accidentally discovers radioactivity while investigating the work of Wilhelm Conrad Röntgen; he finds that uranium salts emit radiation that resembled Röntgen’s X-rays in their penetrating power.
1896-1897 – Pieter Zeeman first observes the Zeeman splitting effect (splitting of spectral lines in a magnetic field) by applying a magnetic field to light sources.
1896–1897 Marie Curie investigates uranium salt samples using a very sensitive electrometer device to measure electrical charge. She discovers that rays emitted by the uranium salt samples make the surrounding air electrically conductive and measures the emitted rays’ intensity. In April 1898, through a systematic search of substances, she finds that thorium compounds, like those of uranium, emitted “Becquerel rays”.
1897 – J. J. Thomson’s experimentation with cathode rays led him to suggest a fundamental unit more than 1,000 times smaller than an atom, based on the high charge-to-mass ratio. He called the particle a “corpuscle”, but later scientists preferred the term electron.
1899 to 1903 – Ernest Rutherford investigates radioactivity. He uses the terms alpha and beta rays in 1899 to describe the two distinct types of radiation emitted by thorium and uranium salts. Rutherford is joined at McGill University in 1900 by Frederick Soddy and together they discover nuclear transmutation when they find in 1902 that radioactive thorium is converting itself into radium through a process of nuclear decay giving off a gas (later found to be a He nucleus); they report their interpretation of radioactivity in 1903.
1900 – As an explanation of black body radiation Max Planck suggests that electromagnetic energy could only be emitted in quantized form, i.e. the energy could only have set values.
1902 – Gilbert N. Lewis develops the “cubical atom” theory in which series of 8 electrons are positioned at the corner of a cube. The model predicts that single or double bonds result when two atoms are held together by 1 electron for each bond located between the two atoms. This model can not explain a triple bond, but suggests that a quadruple bond is possible.
1905 – Albert Einstein explains the photoelectric effect. He postulates based on Planck’s quantum hypothesis for black body radiation, that light itself consists of individual quantum particles (photons).
1905 – Einstein publishes his Special Theory of Relativity dealing with objects moving at very fast speeds but at steady motion (i.e. not accelerating). Einstein conducted a thought experiment where he watched someone on a train looking at a mirror moving at the speed of light, did they see their own relfection, or did it never reach the mirror, and if it did reach the mirror did the person outside the train see the light from the person’s face moving towards the mirror move at twice the speed of light. Einstein decided that the speed of light must be constant leading to a number of strange side effects such as mass, time and length changing with speed. Additionally, 2 people may not agree on events happening simultaneously depending on their point of view. Also produces a universe wide speed limit equal to the speed of light.
1907 to 1917 – Ernest Rutherford: To test his planetary atomic model (later known as the Rutherford model), he sent a beam of positively charged particles (alpha radiation particles) onto a gold foil and noticed that although most passed through the foil some bounced back, thus showing that an atom has a small-sized positively charged atomic nucleus at its center.
1909 – Geoffrey Ingram Taylor demonstrates that wave like interference patterns of light were generated even when the light energy introduced consisted of only one photon i.e. a single particle is behaving like a wave.
1909 – Einstein shows that, if Planck’s law of black-body radiation is accepted, the energy quanta must also carry momentum, making them particles.
1911 – Lise Meitner and Otto Hahn perform an experiment that shows that the energies of electrons emitted by beta decay had a continuous rather than discrete spectrum (i.e. they absorb at all wavelengths rather than set wavelengths. This is in apparent contradiction to the law of conservation of energy. These and other anomalies are later explained by the discoveries of the neutrino and the neutron.
1911 – Einstein theoretically derives the equivalence of matter and energy (e=mc2). This equation states that enrgy and mass are two sides of the same coin and is why nuclear fusion (as seen in stars) and nuclear fision (as seen in the nuclear bomb) give off so much energy. The more stable the nucleus is, the lower the average energy of its constituents is, as atome decay or fuse, they form more stable nuclei and the excess mass is converted to energy.
1913 – Robert Andrews Millikan publishes the results of his “oil drop” experiment, in which he precisely determines the electric charge of the electron. This makes it possible to calculate the Avogadro constant (the number of atoms or molecules in one mole of any substance) and thereby determine the atomic weight of the atoms of each element.
1913 – Niels Bohr introduces his version of the atomic model. Neils Bhor introduces the idea of electrons in set stable orbits. Electrons could jump between orbits, thus changing their energy but could not be in an area that was not a stable orbit. The difference in orbital energies would thus give rise to the discrete spectral lines observed.
1915 – Einstein first presents what are now known as the Einstein field equations. These equations specify how the geometry of space and time is influenced by whatever matter is present, and form the core of Einstein’s General Theory of Relativity. General relativity is our best understnading of how garvity works but does not work with quantum mechanics which operate on a much smaller scale.
1916 – Gilbert N. Lewis conceives the theoretical basis of Lewis dot formulas, diagrams that show the bonding between atoms of a molecule and the lone pairs of electrons that exist in the molecule.
1916 – To account for atomic absorption or emission spectral lines changing when the light source is subjected to a magnetic field, Arnold Sommerfeld suggests there might be “elliptical orbits” in atoms in addition to spherical orbits.
1917 – Ernest Rutherford notices that, when alpha particles are shot into nitrogen gas, signatures of hydrogen nuclei were detected. He determines that the only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggests that the hydrogen nucleus, which is known to have an atomic number of 1, is an elementary particle, which he determines are protons.
1919 – Building on the work of Lewis (1916), Irving Langmuir coins the term “covalence” and postulates that coordinate covalent bonds occur when two electrons of a pair of atoms come from both atoms and are equally shared by them, thus explaining the fundamental nature of chemical bonding and molecular chemistry.
1922 – Bohr updates his model of the atom to better explain the properties of the periodic table by assuming that certain numbers of electrons (for example 2, 8 and 18) corresponded to stable “closed shells”, presaging orbital theory.
1923 – Pierre Auger discovers the Auger effect, where filling the inner-shell vacancy of an atom is accompanied by the emission of an electron from the same atom.
1923 – Louis de Broglie extends wave–particle duality to particles, postulating that electrons in motion are associated with waves. He predicts that the wavelengths are dependent on the momentum (and thus mass) of the particle.
1923 - Edwin Hubble is able to prove that the Andromeda galaxy is too far away to be part of the milky way. Thus first proving the existence of other galaxies.
1924 – Wolfgang Pauli outlines the “Pauli exclusion principle” which states that no two identical fermions may occupy the same quantum state simultaneously (i.e. each electron subshell may only have a 2 electrons in it, 1 spin up and the other spin down), a fact that explains many features of the periodic table.
1925 – George Uhlenbeck and Samuel Goudsmit postulate the existence of electron spin.
1925 – Friedrich Hund outlines Hund’s rule of Maximum Multiplicity. This states that when electrons are added successively to an atom as many orbits are singly occupied as possible before any pairing of electrons with opposite spin occurs. In addition, the inner electrons are paired and only the valence electrons floolw this rule.
1926 – Erwin Schrödinger uses De Broglie’s electron wave postulate to develop a “wave equation” that represents mathematically the distribution of a charge of an electron distributed through space, being spherically symmetric or prominent in certain directions. This introduces the idea of an “electron cloud” as opposed to electrons in certain fixed orbitals.
1927 – Werner Heisenberg formulates the quantum uncertainty principle. It states that there is a maximum precision of which cetrain pairs (such as position and momentum) of physical properties can be known
1927 – Walter Heitler and Fritz London introduce the concepts of valence bond theory and apply it to the hydrogen molecule.
1927 – Walter Heitler uses Schrödinger’s wave equation to show how two hydrogen atom wavefunctions join together, with plus, minus, and exchange terms, to form a covalent bond.
1927 – Robert Mulliken works, in coordination with Hund, to develop a molecular orbital theory where electrons are assigned to states that extend over an entire molecule and, in 1932, introduces many new molecular orbital terminologies, such as σ bond, π bond, and δ bond.
1927 - Georges Lemaître proposed on theoretical grounds that the universe is expanding, thus first predicting the big bang.
1928 – Linus Pauling outlines the nature of the chemical bond. He outlines the quantum mechanical basis for all types of molecular structure and bonding and suggests that different types of bonds in molecules can become equalized by rapid shifting of electrons, a process called “resonance” , such that resonance hybrids contain contributions from the different possible electronic configurations.
1928 – Friedrich Hund and Robert S. Mulliken introduce the concept of molecular orbitals analagous to orbitals in atoms.
1929 – John Lennard-Jones introduces the linear combination of atomic orbitals approximation for the calculation of molecular orbitals.
1929 – Fritz Houtermans and Robert d’Escourt Atkinson propose that stars release energy by nuclear fusion.
1930 – Dirac hypothesizes the existence of the positron, a positively charged analogue of the electron.
1930 – Pauli suggests that atoms must contain an extremely light neutral particle which he called the “neutron.” He suggests that this “neutron” is also emitted during beta decay and has simply not yet been observed. Later it is determined that the particle emitted is actually the almost massless neutrino.
1931 – Ernst Ruska creates the first electron microscope.
1931 – Ernest Lawrence creates the first cyclotron.
1932 – Irène Joliot-Curie and Frédéric Joliot show that if the unknown radiation generated by alpha particles falls on paraffin or any other hydrogen-containing compound, it ejects protons of very high energy. This is not in itself inconsistent with the proposed gamma ray nature of the new radiation, but detailed quantitative analysis of the data become increasingly difficult to reconcile with such a hypothesis.
1932 – James Chadwick performs a series of experiments showing that the gamma ray hypothesis for the unknown radiation produced by alpha particles is untenable, and that the new particles must be the neutrons hypothesized by Fermi.
1932 – Mark Oliphant: Building upon the nuclear transmutation experiments of Ernest Rutherford done a few years earlier, observes fusion of light nuclei (hydrogen isotopes). The steps of the main cycle of nuclear fusion in stars are subsequently worked out by Hans Bethe over the next decade.
1932 – Carl D. Anderson experimentally proves the existence of the positron.
1933 – Following Chadwick’s experiments, Fermi renames Pauli’s “neutron” to neutrino to distinguish it from Chadwick’s theory of the much more massive neutron.
1933 – Leó Szilárd first theorizes the concept of a nuclear chain reaction. He files a patent for his idea of a simple nuclear reactor the following year.
1934 – Fermi publishes a very successful model of beta decay in which neutrinos are produced.
1934 – Fermi studies the effects of bombarding uranium isotopes with neutrons.
1935 - Schrödinger develops the Schrödinger’s cat thought experiment. It illustrates what he saw as the problems of the interpretation of quantum mechanics, namely that subatomic particles can be in two contradictory quantum states at once.
1936 – Carl D. Anderson discovers muons while he is studying cosmic radiation.
1938 – Otto Hahn and his assistant Fritz Strassmann report that they have detected the element barium after bombarding uranium with neutrons. Hahn calls this new phenomenon a ‘bursting’ of the uranium nucleus. Simultaneously, Hahn communicates these results to Lise Meitner. Meitner, and her nephew Otto Robert Frisch, correctly interpret these results as being a nuclear fission. Frisch confirms this experimentally on 13 January 1939.
1939 – Leó Szilárd and Fermi discover neutron multiplication in uranium, proving that a chain reaction is indeed possible.
That’s a (short) breakdown of physics up to the start of the war. There really is lost going on in those 50 or so years. Some of it is really heavy and will need a much simpler explanation between now and the episode being produced. Yes, so much of this discovery led to so many technological advancements that it is difficult to know where to begin with those and much of the rest is fundamental to understanding the physics of the breakthroughs.
@Spartacus
As you can see above there is a lot going on, some of it can easily be cut but I’ve left it in there for completeness and just in case there is some kind of technology that sprang from it that I’m unaware of. Do you want to focus say nuclear physics (leading to the atomic bomb in WW2), or make it a really brief overview of all of this physics and the technological advancements that went alongside it. The problem with science is that many people make small incremental steps towards a (or in this case many) large discoveries.
Dduring this time mathematicians are developing theories for computing machines, which would lead directly to todays computers. Alan Turing is at this time working on models for a computing machines. I’m not sure if this is place to bring up this topic but it wil lead to technology that will change the world
@apj868
I think we should focus on two intertwined lines of research: quantum physics and nuclear physics. Those two lines have much in common since they both booked enormous progress using the improved understanding of the atomic model. They also accelerated each other’s advancements, hence they are intertwined. I think you need to explain both of them together to paint a decent picture. I guess we all agree the nuclear physics story needs to be told because of the atomic bomb. However, I think quantum physics captures the imagination.
A very short start to the engineering side:
For such a counter-intuitive theory, quantum physics was quickly put to engineering use. In 1923, Louis de Broglie postulated that moving particles can be described by waves. An electron microscope, which works by this very principle, was already prototyped in 1931. In 1938, the first commercially available electron microscope was produced by Siemens.
I have to think about this for bit - the timeline is an awesome start as it gives us a springboard for starting to tell the story. What we need now is to make it personal. Obviously, when we start WW2 we will deal with both the Manhattan project the Uranium Club. The question is who the main characters in that are. Bohr and Heisenberg come to mind as they are close friends that end up on opposite sides. That being said I’m a bit reluctant to dive too deep into the controversial meeting between the two in Copenhagen in 1941, but there is one element in that meeting that fascinates - the claimed objective and anti-war stance of more or less all of the scientists and how they still ended up working to create the ultimate weapon of mass destruction (while Heisenberg always maintained that he was stalling and many of the other Uranium Club members like Otto Hahn were openly anti-Nazi and still continued their research…).
I know this is super vague, I’m carrying on in running thought here. Basically the question is what the human interest angle of the story is, and if the reluctance to create weaponry, but still doing it could be an angle the leads us to Manhattan.
If that is the case we have to find a way to end in 1939 with what was being done with the discoveries listed, and we need a protagonist and and antagonist to exemplify the two stances…
Ideas?
I was well aware that the timeline would be a starting point of the discussion rather than the end. The potential end used of science is a major concern even today, we often don’t know what potential technologies fundamental research can create when we are performing it. I have a few ideas to liven up the story:
Technological improvements that come from the research. Problem is that these tend to lag behind the pure scientific research, so many are WW2 era or later. Sjoerd has already mentioned a number of technological advancements that have come from research at this time. Things like GPS and nanotechnology also have their theoretical roots here but don’t come about until much after the war.
Controversy over the research/scientist rivalries. There was much push-back to modern physics, particularly in the early days. By the main timeline of the story just about all scientists were on board with the new concepts. The Michelson Moorely experiment (1887), for example, was repeated numerous times with ever more sensitive equipment. The scientists that did not want to believe the results came up with ever more desperate explanations for the results.
Awards (particularly the nobel prize as the most widely recognised). A couple of notables. Marie Curie was the first female recipient of the prize and is the only person to have won it in 2 scientific fields (physics and chemistry). The Curie family has in fact been involved in 4 nobel prizes (2 of which were won jointly by 2 members of the family). Albert Einstein won only a single nobel prize despite having at least 4-5 works that very easily could have won. Interestingly, what he won it for (his explanation of the photoelectric effect) is probably lhe least publicly recognised out of all of his big works.
De Brogile’s work on extending wave-particle duality to particles (1923) was his phd. I remember in lectures being told that he was kicked out of the university for having such a crackpot idea. It was later on that Niels Bhor (one of the leading physicists in the world at the time) came to the university and was told about this strange phd student and his ideas. Bhor asked to have a look at the work and realised that it was proof of his atomic model (1913). The university then sent De Brogile a sincere apology and the phd was accepted. I have never been able to find this story anywhere else, but might be an interesting side note if we can prove its truthfulness.
Weird conclusions from the work. Relativity has lots of them (touched on these in special relativity, 1905). A couple of others include quantum mechanic/statistical mechanic’s implication that everything is possible, some things are just highly, highly improbable and the well known thought experiment Schrodinger’s cat.
I’ll do some digging into the scientists involved in both the Manhattan project and also the uranium club, see what we can do to point the story towards them. I know that there were a number of scientists that defected to the allies (or at least stoppped working with the Nazis), Albert Einstein being one although he did not work directly for the allies. Not sure how many of them worked on one, both or no projects.
If you would like that and want to go into controversial territory you could talk about Wernher von Braun. Although that would probably make more sense as a special on the WW2 series.
How much WW2 stuff do you want packed into this B2W episode? The direct history of the Manhattan project to me seems more like a special for the WW2 series.
Since this B2W series seems to take all kinds of aspects other than the direct leading up to WW2 into account, I think the story of the tremendous achievements in physics and engineering needs to be told as well.
We try to stay on topics relevant to WW2 to not go completely out of hand. In this case it’s obvious as this is the basis for how the war ends 
But we shouldn’t go past 1939 into the war itself. I’m thinking more of creating continuity by introducing characters that play a central part both before WW2 and during the war. If we can find an angle that will continue into the war (like with Bohr and Heisenberg) that’s great.
The issue with their ‘conflict’ is that it’s unclear what happened, even if it was a conflict at all, and what Heisenberg’s motives were. Moreover, while Heisenberg was a leading figure in the Uranium Club, Bohr was not officially part of the Manhattan Project, although he made significant and direct contributions once he had fled from occupied Denmark.
Here is what our scientists were doing throughout the war. Something interesting that I didn’t know about was the exedous of Jewish scientists from (especially) German institutions to other institutions from 1933 onwards, that is probably something that we want to mention in the episode. They were either forced to leave or discredited by the nazi party. None of the scientists involved in discoveries pre 1900 were active during the war, so I left them off. Also left off scientists involved in discoveries that are in no way related to the atom (e.g. Hubble).
Max Plank – (mostly pre-war under Nazi rule) Tried to talk other scientists out of leaving Germany. Succeeded in allowing a number of Jewish scientists to continue working in Nazi Germany. Met Hitler in 1933 to discuss Jewish scientists, Hitler went on a rant, Plank could only remain silent and then take his leave.
Gilbert Lewis – Not really working on anything to do with atoms/nuclear physics. More of a traditional chemist, research not involved in the war.
Albert Einstein – Born a Jew, emigrated to the US in 1933. Tried to get fellow Jewish scientists jobs in places like Turkey. 1935 decided to stay in US permanently and applied for citizenship, granted in 1940 despite some resistance. Wrote a letter to US president Roosevelt a few months before WW2 after pressure from Leo Szilard warning of the dangers of Germany developing the atomic bomb, something Einstein hadn’t considered, urging the US to begin work on their own project using his connections with the Belgian royal family to get contacts in the oval office. Believes that writing the letter was his 1 great mistake in life. Wasn’t directly involved with the Manhattan project, but did give the US navy guidance with development of some weapons.
Ernest Rutherford – Died 1937
Geoffrey Ingram Taylor - Solved military problems such as the propagation of blast waves, studying both waves in air and underwater explosions. Taylor was sent to the United States in 1944–1945 as part of the British delegation to the Manhattan Project. At Los Alamos, Taylor helped solve implosion instability problems in the development of atomic weapons particularly the plutonium bomb used at Nagasaki on 9 August 1945.
Lise Meitner – Jewish, saved from the exodus of Jewish scientists in Germany by her Austrian citizenship. Her response was to bury herself in her work. Got too difficult and departed for the Netherlands in 1938. Despite being one of the first people to experimentally discover nuclear fission, refused to work on the bomb for either side.
Otto Hahn – Suspected by the Allies of working on in the Uranium club, but did not. His only connection was working on nuclear fission. Taken into custardy by the British in 1945. Was said to be in despair when he learnt about the use of the bomb. Allowed to return to Germany early 1946.
Robert A Millikan – Not involved in WW2, peace activist. Served as vice chairman on the US national research council during WW1 (yes 1, not 2).
Niels Bhor – Concluded based on his liquid drop model of the nucleus that it was U-235 and not the more abundant U-238 responsible for fission with thermal neutrons. Parents were Jewish, so he was considered Jewish. Found many Jewish scientists work in many institutions across the world. Working in Denmark at the beginning of the war, to prevent the Germans from discovering Max von Laue’s and James Franck’s gold Nobel medals, Bohr had de Hevesy dissolve them in aqua regia. In this form, they were stored on a shelf at the Institute until after the war, when the gold was precipitated and the medals re-struck by the Nobel Foundation. Famous meeting with Heisenberg September 1941. Had a hand in getting Sweden to accept Danish Jewish refugees in September 1943. Encouraged to come to Britain, arrived October 1943 but kept out of sight. Paid a series of scientific visits to the US and the Manhattan project, described as a father figure to the younger scientists. Quoted as saying “they didn’t need my help to make toe atomic bomb” but credited with an important contribution to the work on modulated neutron initiators. Tried to get the Anglo-Ampericant to work with the Soviets on the bomb (he believed that they were aware of the project) but the British and Americans refused.
Arnold Summerfeld – Once said to be a nationalist. Wrote to Einstein shortly after Hilter’s rise to power saying “I can assure you that the misuse of the word ‘national’ by our rulers has thoroughly broken me of the habit of national feelings that was so pronounced in my case. I would now be willing to see Germany disappear as a power and merge into a pacified Europe.” Not involved in WW2.
Irving Langmuir – In WW2 worked on improving naval sonar for submarine detection, and later to develop protective smoke screens and methods for de-icing aircraft wings. Not involved in the Manhattan project.
Pierre Victor Auger – Continued his research through WW2, not involved with the war.
Louis De Broglie - Continued his research through WW2, not involved with the war.
Wolfgang Pauli – Jewish born, became a German Citizen after the German annexation of Austria, tried to get Swiss citizenship to keep his job in Switzerland, but eventually moved to the US in 1940, became a US citizen in 1946. Continued his research through WW2, not involved with the war.
Samuel Goudsmit - He was also the scientific head of the Alsos Mission and successfully reached the German group of nuclear physicists around Werner Heisenberg and Otto Hahn. Goudsmit concluded that the Germans did not get close to creating a weapon (published 1947).
George Uhlenbeck – 1943 to 45 led a theory group at the Radiation Laboratory in Cambridge, Massachusetts which was doing radar research.
Fredrich Hund - Continued his research through WW2, not involved with the war.
Erwin Schrödinger – Known opponend to Naziism, fled Germany in 1934. Worked in the UK and India. In 1940 helped found the Institute for Advanced Studies in Dublin, remained there for the remainder of the war. Continued his research through WW2, not involved with the war.
Werner Heisenberg – Large part of the uranium club (investigating both nuclear energy and the bomb). Incarcerated for his work on the uranium project 3 May 1945, eeleased 3 Januray 1946.
Walter Heitler - Jewish born German citizen. Lost his job in Germany in 1933. Continued his research in UK and Ireland form 1933 and through WW2, not involved with the war.
Fritz London – Jewish born German citizen. Lost his job in Germany in 1933, after various positions in England and France emigrated to the US in 1939 and became a US citizen in 1945. Continued his research through WW2, not involved with the war.
Robert Mulliken - Continued his research through WW2, not involved with the war.
Linus Pauling - Continued his research through WW2, not involved with the war. Later became an anti-nuclear bomb activist.
John Lennard-Jones- British citizen, at outbreak of war, seconded as Chief Superintendent of Armament Research to the Ministry of Supply which took over the mathematical laboratory for ballistics calculations, developed a team of mathematicians for this purpose. Director-General of Scientific Research (Defence), Ministry of Supply. Member of the Advisory Council of the Department of Scientific and Industrial Research.
Fritz Houtermans – Communist, left Germany for Britain after the rise of Hitler. Continued his research through WW2, not involved with the war.
Paul Dirac - Continued his research through WW2, not involved with the war.
Ernest Lawrence – Worked on uranium enrichment in the Manhattan Project.
Irène Joliot-Curie – (Marie Curie’s Daughter) Contracted tuberculosis and was forced to spend several years convalescing in Switzerland. Concern for her own health together with the anguish of leaving her husband and children in occupied France was hard to bear and she did make several dangerous visits back to France, enduring detention by German troops at the Swiss border on more than one occasion. Finally, in 1944 Joliot-Curie judged it too dangerous for her family to remain in France and she took her children back to Switzerland.
Frédéric Joliot-Curie (Husband of Irene, above) - At the time of the Nazi invasion of France in 1940, Joliot-Curie managed to smuggle his working documents and materials to England with Hans von Halban, Moshe Feldenkrais and Lew Kowarski. During the French occupation he took an active part in the French Resistance as a member of the National Front. During the Paris uprising in August 1944 he served in the Prefecture of Police manufacturing for his fellow insurgents Molotov cocktails, the Resistance’s principal weapon against German tanks.
James Chadwick - In July 1941, Chadwick was chosen to write the final draft of the MAUD Report, which, when presented to President Franklin D. Roosevelt, inspired the U.S. government to pour millions of dollars into the pursuit of an atomic bomb. One of the head British scientists on the Manhattan project.
Mark Oliphant – 1938 to 1940 worked on the development of radar. From Mrach 1940 worked on the Manhattan project. Had no misdirections that he was working on a bomb and nothing else like power generation. Inspired Lawrence to convert his 37-inch cyclotron into a giant mass spectrometer for electromagnetic isotope separation. Headed a team assisting his friend Lawrence at the Radiation Laboratory in Berkeley to develop the electromagnetic uranium enrichment—a vital but less overtly military part of the project. A meeting with Major General Leslie Groves, the director of the Manhattan Project, at Berkeley in September 1944, convinced Oliphant that the Americans intended to monopolise nuclear weapons after the war, restricting British research and production to Canada, and not permitting nuclear weapons technology to be shared with Australia, discussed starting a 100% British nuclear weapons project which was rejected. Remarked about the bomb that he felt “sort of proud that the bomb had worked, and absolutely appalled at what it had done to human beings” and “I, right from the beginning, have been terribly worried by the existence of nuclear weapons and very much against their use.”
Carl D. Anderson – Did research at Caltech on rocketry during WW2.
Enrico Fermi - Fermi left Italy in 1938 to escape new Italian Racial Laws that affected his Jewish wife Laura Capon. He emigrated to the United States where he worked on the Manhattan Project during World War II. Fermi led the team that designed and built Chicago Pile-1, which went critical on 2 December 1942, demonstrating the first artificial self-sustaining nuclear chain reaction. At Los Alamos he headed F Division, part of which worked on Edward Teller’s thermonuclear “Super” bomb. He was present at the Trinity test on 16 July 1945, where he used his Fermi method to estimate the bomb’s yield.
Leo Szilard - After Adolf Hitler became chancellor of Germany in 1933, urged his family and friends to flee Europe while they still could. Moved to England, where he helped found the Academic Assistance Council, an organization dedicated to helping refugee scholars find new jobs. Foreseeing another war in Europe, Szilard moved to the United States in 1938, where he worked with Enrico Fermi and Walter Zinn on means of creating a nuclear chain reaction. He worked for the Manhattan Project’s Metallurgical Laboratory on aspects of nuclear reactor design. He drafted the Szilard petition advocating a demonstration of the atomic bomb, but the Interim Committee chose to use them against cities without warning.
Fritz Strassmann - contributed to research at the Kaiser-Wilhelm Institute on the fission products of thorium, uranium and neptunium. Involved in the uranium club.
Thought this might be useful. The entire site’s about the Manhattan project and subsequent nuclear weapons, but this specific page deals with scientists leaving Germany pre WW2 in this time period.