Book Review: "The Pope of Physics"

The Pope of Physics is a 2016 biography of Enrico Fermi (1901-1954), written by Gino Segre and Bettina Hoerlin. Segre's uncle Emilio was a student of Fermi's in Rome, whereas Hoerlin's father knew Fermi from Los Alamos, New Mexico in the post-World War II years.

I began reading the book earlier this year, before I knew that the movie Oppenheimer was coming out. Both The Pope of Physics and Oppenheimer chronicle the United States' development of the atomic bomb through nuclear fission and its use against Japan in World War II, along with the associated ethical questions. There is a Fermi character who makes brief appearances in Oppenheimer, whereas The Pope prominently discusses the real-life Robert Oppenheimer. I would urge anyone with an interest in the subject matter to read The Pope, either before or after seeing Oppenheimer, to obtain a better understanding of the movie and the physics underlying the atomic bomb.

The Pope tells the life story of Fermi, growing up and establishing his career in Italy, then moving to the US when Mussolini began implementing policies in the 1930s against Jewish people (which included Fermi's wife). Fermi taught at Columbia University in New York City and then worked on the bomb project at the University of Chicago, before dying prematurely of cancer. 

The book details Fermi's exceptional abilities in many areas: "the only twentieth-century physics genius to be entirely self-taught" (p. 16), someone who "considered himself an experimentalist as well as a theorist" (p. 32), and "probably the only person with expertise in every aspect of the physics problems being faced in the [Los Alamos] laboratory" (p. 224).

Fermi's early work included his theories of beta-decay and the weak force. However, he and his colleagues also discovered nuclear fission -- the process behind the atomic bomb -- but did not realize it! Instead, Fermi and colleagues thought they had discovered a chemical element with 93 protons, surpassing uranium (92). In this regard, Fermi, like Albert Einstein with his general-relativity equations in an earlier era, showed that even the most brilliant scientists are not immune from major blunders.* 

Early efforts at understanding the nature of atoms and nuclei involved firing certain kinds of particles at other particles (see this article on Ernest Rutherford's legacy). Fermi's team, known as The Boys, had bombarded many different kinds of chemical elements -- from hydrogen to uranium -- with neutrons, finding particles they thought were the heavy elements. As Segre and Hoerlin explained, however, German chemist Ida Noddack was correct in suggesting that "the supposed transuranic might be the nucleus of an element that lay far down the periodic table, a fragment produced by the splitting of the uranium nucleus" (p. 106). That splitting was, of course, nuclear fission.

Two other researchers, Hahn and Strassmann, had found a seemingly anomalous result from collisions of neutrons and uranium: "a radioactive isotope of barium. Since the barium nucleus has only 56 protons while uranium has 92, this seemed impossible" (Segre & Hoerlin, p. 129). Hahn and Strassmann's colleagues Meitner and Frisch then came up with a stunning interpretation, namely that fission had occurred and the missing mass had been converted to energy via Einstein's E = mc-squared. As the book elaborates, Meitner "realized that the sum of the two fragments' masses was less than the uranium mass. A rapid estimate showed her that the difference in mass was roughly equal to the energy of motion needed" (p. 130).

Initial fission experiments produced only a ripple of energy on laboratory detectors. Producing enough energy for the kinds of bombs used in Japan required chain reactions. As Fermi envisioned as a possible reaction between neutrons and uranium, "if an initial fission were to produce two neutrons, those two would generate four neutrons by colliding with other uranium nuclei. From 2 to 4 to 8 to 16 to 32 to 64 to... It would be a chain reaction. And if each collision generated the amount of energy Frisch and Meitner had estimated a month earlier, the end product would be a mammoth source of power" (p. 144-145). Oppenheimer was among the fastest to realize that fission could eventually lead to an atomic bomb (p. 146).

Though Fermi lived a long time ago and may be best known for the bomb, his and his colleagues' contributions in other areas have made an indelible impact on modern life. As Segre and Hoerlin note, "... without understanding the Pauli Principle, quantum mechanics, and Fermi-Dirac statistics, the world would not have been able to produce semiconductors, transistors, computers, MRIs, lasers and so many of the other inventions that shape our life" (p. 55). 

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*Fermi received the 1938 Nobel Prize in physics, with the award notice reading, "To Professor Enrico Fermi of Rome for his identification of new radioactive elements produced by neutron bombardment and his discovery, made in connection with this work, of nuclear reactions brought about by slow neutrons" (Segre & Hoerlin, p. 95). The book acknowledges that, "Some detractors say Fermi got the Nobel for a faulty discovery. But his years of productive research, particularly showing the world the power of slow neutrons, suggest otherwise. Nevertheless, he never quite forgave himself for his mistake about transuranics [elements heavier than uranium]" (p. 123).

Vox Explains Henrietta Leavitt's 1908 Discovery of How to Measure Distances to Stars and Galaxies

Vox provides a very clear explanation of Henrietta Leavitt's 1908 discovery that allows us to estimate the distance to stars and galaxies. 

The book Einstein's Greatest Mistake (which I previously reviewed here) also discusses Leavitt's contributions (pages 137-142). This section of the book explains why stars differ in their degree of pulsation: "We're used to our sun shining pretty evenly, at just about the same intensity day after day. But that's because the layers of fuel in the sun burn fairly evenly. In some very different stars, the burning is highly uneven" (pp. 138-139). The latter type of stars alternate between states of hot, bright, expansion and, after the expansion releases pressure, a dimmed and slimmed down appearance.

2022 Nobel Physics Prize to Quantum Entanglement Researchers

The 2022 Nobel Prize in physics has been awarded to three researchers for their work in quantum entanglement and its applications. This posting from Daily Kos features a compilation of links, explanations, video tutorials, and other material pertaining to the prize-winning research. I wrote a watered-down introduction to quantum entanglement back in 2005, which is available here.

Physicist Alan Nathan on Baseball Podcast

My friend Alan Nathan, a retired professor of physics at the University of Illinois Urbana-Champaign and one of the leading experts on the physics of baseball, appeared on the Society for American Baseball Research's SABRcast several weeks ago. The archived audio is available here (you have to scroll down a bit when the new page comes up). Professor Nathan discusses both historical and current trends in the study of bats (and bat swings), baseballs (and their spin, flight, etc.), and baserunners.

Book Review: "Einstein's Greatest Mistake"

David Bodanis begins his 2016 book Einstein's Greatest Mistake with a depiction of a once-great scientist who had become a forlorn figure in his later years. He was usually alone when he walked home after a day at the Institute for Advanced Study in Princeton, New Jersey, isolated intellectually and socially from other scientists, many of whom "no longer took his ideas seriously" (p. xii). How Einstein got to that place in his life is for Bodanis to explain. The author's account is plausible, in my view, and reveals interesting facets of Einstein's personality along the way.

There actually are two major scientific mistakes Einstein made in his scientific career, his response to the first likely affecting his response to the second. Among Einstein's many accomplishments -- including the five momentous discoveries of his annus mirabilis (miracle year) of 1905 -- his 1915 general-relativity conception of gravity arguably is his best-known scientific contribution (along with E = mc-squared). The offshoots of general relativity, according to Bodanis, include "explaining why black holes exist, showing how the universe began and how it will likely end, and even laying the foundation for revolutionary technologies such as GPS navigation" (p. xii-xiii).

But there seemed to be a problem with general relativity. Conventional wisdom among astronomers at the time was that the size of the universe was constant. Yet, Einstein's general-relativity equations allowed the possibility of the universe expanding or collapsing (see pp. 115-116). To align with notions of a static universe, therefore, Einstein introduced a new term -- known as the cosmological constant or lambda -- into his formulation. 

Unfortunately for Einstein, that was not the end of the story. As the book describes, in 1929 Edwin Hubble and his associate Milton Humason determined from observations of the movement of stars and galaxies that the universe was indeed expanding. Einstein's equations were right the first time and now lambda could be eliminated (see pp. 135-154). A valuable aspect of this part of the book is its reporting on the work of less well-known scientists whose work informed the debate, such as Father Georges Lemaitre (click here for my review of The Day Without Yesterday, about Lemaitre's work), Alexander Friedmann, and Henrietta Leavitt.

The general-relativity/universe-expansion debacle only seemed to harden Einstein's resolve to stick to his own theories no matter what. As Bodanis noted, "When [Einstein's] critics tried to bring in evidence against his later beliefs, he ignored them, confident that he would be vindicated again" (p. xiii). From this stance emanated Einstein's second major mistake.

As Bodanis describes, from the early 1910s through the early 1930s, the study of quantum mechanics (QM) at the microscopic level of matter developed alongside the study of relativity at the large level of stars and galaxies. QM had a number of odd features, such as probabilistic predictions that a particle might end up in one place 70% of the time and in another place 30%. Einstein objected vigorously to this proposition, leading to his famous statement about God not playing dice with the universe.

At first, Einstein engaged with the ideas of quantum mechanics -- in an attempt to discredit them. Particularly interesting, as the book recounts, were the Brussels conferences of 1927 and 1930. Each morning, as the elite coterie of physicists (including QM proponent Niels Bohr) gathered for breakfast, Einstein would issue a daily challenge to QM, proffering some kind of thought-experiment that seemed to undercut the logic of the theory. Bohr and like-minded colleagues would then spend large amounts of time, sometimes deep into the early-morning hours, trying to rebut Einstein. Ultimately, the pro-QM group successfully answered Einstein every time.

According to Bodanis, "Einstein never again attended such a meeting; never again attempted to refute Bohr or [Werner] Heisenberg in public debate. Nor, however, did he change his beliefs." (p. 204).

The rest of Einstein's career, until his death in 1955, was largely an intellectual waste, according to Bodanis. These years were filled with missed opportunities. Potential collaborations with other leading physicists either fell through or did not interest Einstein in the first place. Princeton faculty “worshipped Einstein and would have relished the chance to collaborate with him. Their studies ultimately helped lead to the creation of the transistors that today operate inside all our phones and electronic devices. But Einstein couldn’t bring himself to grapple with these strange consequences of the new quantum mechanics“ (p. 219)

Even when Bohr visited Princeton in 1939, gone were Einstein's spirited and detailed challenges to Bohr. As the book notes, Einstein avoided most opportunities to interact with Bohr and when the two were together, "Einstein would speak only in banalities" (p. 226).

For laypersons interested in a  non-technical exposition of Einstein's and his intellectual opponents' ideas -- along with the human drama of Einstein's career arc -- it would be a great mistake not to read this book!

Vox on Olympic Ski Jumping

Vox explains "Why ski jumpers hold their skis in a V," as opposed to the older style of keeping their skis parallel (link).

Vox on 2021 Nobel Physics Prize to Climate-Change Researchers

Voxexplains the climate-change modeling -- "account[ing] for the roiling randomness present in everything from materials to the motion of the atmosphere, and still mak[ing] useful predictions" -- that earned three researchers this year's Nobel Prize in physics.