Field of Science

Oppenheimer's folly: On black holes, fundamental laws and pure and applied science

On September 1, 1939, the same day that Germany attacked Poland and started World War 2, a remarkable paper appeared in the pages of the journal Physical Review. In it J. Robert Oppenheimer and his student Hartland Snyder laid out the essential characteristics of what we today call the black hole. Building on work done by Subrahmanyan Chandrasekhar, Fritz Zwicky and Lev Landau, Oppenheimer and Snyder described how an infalling observer on the surface of an object whose mass exceeded a critical mass would appear to be in a state of perpetual free fall to an outsider. The paper was the culmination of two years of work and followed two other articles in the same journal.

Then Oppenheimer forgot all about it and never said anything about black holes for the rest of his life. 

He had not worked on black holes before 1938, and he would not do so ever again. Ironically, it is this brief contribution to physics that is now widely considered to be Oppenheimer’s greatest, enough to have possibly warranted him a Nobel Prize had he lived long enough to see experimental evidence for black holes show up with the advent of radio astronomy.

What happened? Oppenheimer’s lack of interest wasn’t just because it was published on the same day on which World War 2 was launched. It wasn’t because he became the director of the Manhattan Project a few years later and got busy with building the atomic bomb. It also wasn't because he despised the freethinking and eccentric Zwicky who had laid the foundations for the field through the discovery of black holes' parents - neutron stars. It wasn’t even because he achieved celebrity status after the war, became the most powerful scientist in the country and spent an inordinate amount of time consulting in Washington until his carefully orchestrated downfall in 1954. All these factors contributed, but the real reason was far more mundane – Oppenheimer just wasn’t interested in black holes. Even after his downfall, when he had plenty of time to devote to physics, he never talked or wrote about them. The creator of black holes basically did not think they mattered.

Oppenheimer’s rejection of one of the most fascinating implications of modern physics and one of the most enigmatic objects in the universe - and one he sired - is documented well by Freeman Dyson who tried to initiate conversations about the topic with him. Every time Dyson brought it up Oppenheimer would change the subject, almost as if he had disowned his own scientific children.

The reason, as attested to by Dyson and others who knew him, was that in his last few decades Oppenheimer was stricken by a disease which I call “fundamentalitis”. Fundamentalitis is a serious condition that causes its victims to believe that the only thing worth thinking about is the deep nature of reality as manifested through the fundamental laws of physics.

As Dyson put it:

“Oppenheimer in his later years believed that the only problem worthy of the attention of a serious theoretical physicist was the discovery of the fundamental equations of physics. Einstein certainly felt the same way. To discover the right equations was all that mattered. Once you had discovered the right equations, then the study of particular solutions of the equations would be a routine exercise for second-rate physicists or graduate students.”

Thus for Oppenheimer, black holes, which were particular solutions of general relativity, were mundane; the general theory itself was the real deal. In addition they were anomalies, ugly exceptions which were best ignored rather than studied. As Dyson mentions, unfortunately Oppenheimer was not the only one affected by this condition. Einstein, who spent his last few years in a futile search for a grand unified theory, was another. Like Oppenheimer he was uninterested in black holes, but he also went a step further by not believing in quantum mechanics. Einstein’s fundamentalitis was quite pathological indeed.

History proved that both Oppenheimer and Einstein were deeply mistaken about black holes and fundamental laws. The greatest irony is not that black holes are very interesting, it is that in the last few decades the study of black holes has shed light on the very same fundamental laws that Einstein and Oppenheimer believed to be the only thing worth studying. The disowned children have come back to haunt the ghosts of their parents.

Black holes took off after the war largely due to the efforts of John Wheeler in the US and Dennis Sciama in the UK. The new science of radio astronomy showed us that, far from being anomalies, black holes litter the landscape of the cosmos, including the center of the Milky Way. A decade after Oppenheimer’s death, the Israeli theorist Jacob Bekenstein proved a very deep relationship between thermodynamics and black hole physics. Stephen Hawking and Roger Penrose found out that black holes contain singularities; far from being ugly anomalies, black holes thus demonstrated Einstein’s general theory of relativity in all its glory. They also realized that a true understanding of singularities would involve the marriage of quantum mechanics and general relativity, a paradigm that’s as fundamental as any other in physics.

In perhaps the most exciting development in the field, Leonard Susskind, Hawking and others have found intimate connections between information theory and black holes, leading to the fascinating black hole firewall paradox that forges very deep connections between thermodynamics, quantum mechanics and general relativity. Black holes are even providing insights into computer science and computational complexity. The study of black holes is today as fundamental as the study of elementary particles in the 1950s.

Einstein and Oppenheimer could scarcely have imagined that this cornucopia of discoveries would come from an entity that they despised. But their wariness toward black holes is not only an example of missed opportunities or the fact that great minds can sometimes suffer from tunnel vision. I think the biggest lesson from the story of Oppenheimer and black holes is that what is considered ‘applied’ science can actually turn out to harbor deep fundamental mysteries. Both Oppenheimer and Einstein considered the study of black holes to be too applied, an examination of anomalies and specific solutions unworthy of thinkers thinking deep thoughts about the cosmos. But the delicious irony was that black holes in fact contained some of the deepest mysteries of the cosmos, forging unexpected connections between disparate disciplines and challenging the finest minds in the field. If only Oppenheimer and Einstein had been more open-minded.

The discovery of fundamental science in what is considered applied science is not unknown in the history of physics. For instance Max Planck was studying blackbody radiation, a relatively mundane and applied topic, but it was in blackbody radiation that the seeds of quantum theory were found. Similarly it was spectroscopy, the study of light emanating from atoms, that led to the modern framework of quantum mechanics in the 1920s. Scores of similar examples abound in the history of physics; in a more recent case, it was studies in condensed matter physics that led physicist Philip Anderson to make significant contributions to symmetry breaking and the postulation of the existence of the Higgs boson. And in what is perhaps the most extreme example of an applied scientist making fundamental contributions, it was the investigation of cannons and heat engines by French engineer Sadi Carnot that led to a foundational law of science – the second law of thermodynamics.

These days there is a lot of valid discussion about how the pursuit of pure science usually leads to unexpected applied results, but sometimes the opposite is also true: the pursuit of what Subrahmanyan Chandrasekhar called “derived science” leads to new horizons in pure science. Derived science consists of exploring the implications and results of pure science, but as the history of science has regularly demonstrated, this investigation can also feed back into the advancement of pure science itself.

Today many physicists are again engaged in a search for ultimate laws, with at least some of them thinking that these ultimate laws would be found within the framework of string theory. These physicists probably regard other parts of physics, and especially the applied ones, as unworthy of their great theoretical talents. For these physicists the story of Oppenheimer and black holes should serve as a cautionary tale. Nature is too clever to be constrained into narrow bins, and sometimes it is only by poking around in the most applied parts of science that one can see the gleam of fundamental principles.

As Einstein might have said had he known better, the distinction between the pure and the applied is often only a "stubbornly persistent illusion". It's an illusion that we must try hard to dispel. 

Seeing the 2016 election through Jonathan Haidt's moral foundations theory

One of the best social science books that I have read is NYU psychologist Jon Haidt's "The Righteous Mind". Recently Haidt has become well known for opposing what he sees as clampdowns on free speech and dissenting views on college campuses, the paucity or suppression of conservative views on these campuses and the coddling of students, but he is still primarily known for his writings on political psychology. As someone who describes himself as a moderate libertarian, I largely agree with Haidt's views on these matters.

The basic premise of "The Righteous Mind" is that liberals, conservatives and libertarians use different moral metrics to judge the veracity and fitness of political candidates and of their world views in general. Their outrage or praise at statements that politicians make depends on how well or badly these statements score on their spectrum of moral values. Haidt's point is that most of the disagreement on political issues between liberals and conservatives boils down to a subset of six moral 'foundations' that they score politics on. 

The six moral foundations are: care/harm, liberty/oppression, fairness/cheating, loyalty/betrayal, authority/subversion and sanctity/purity. Based on several studies conducted by him and his colleagues, Haidt has concluded that in general, liberals value the first three values disproportionately while conservatives value all six values equally. Thus as an example, liberals get very worked up about the oppression of minorities because it scores very badly on the "care/harm" and "liberty/oppression" metrics, while religious conservatives get very worked up by LGBT rights because it scores very badly on their "sanctity/degradation" and "liberty/oppression" metrics. Libertarians view the liberty/oppression axis as being as overwhelmingly important.

The following chart neatly illustrates these differences:

Haidt also refers to these moral foundations as sacred values, considering how intensely liberals and conservatives often cling to them. Seen through this lens of sacred values, it's very interesting to look at the Giant Conflagration of 2016 (otherwise known as the 2016 US election). When Trump said all those obnoxious things about Hispanics or women or Muslims, he scored very low on liberals' main moral values (the three on the left): by insulting certain racial or demographic groups, he was showing that he did not care about them, he was purportedly infringing on their liberties and he was also not being fair to them. As the chart shows, concern for the care and liberties of victims of oppression is liberals' most sacred value, although it is also valued highly by conservatives. Minorities and women are often thought to fall in this category, and so the violation of this value disqualified Trump in the eyes of liberals right away.

What they failed to realize was that he was still scoring very high on the three conservative values on the right. Many conservatives who supported him disavowed his words, but that wasn't why they would have a big problem supporting him. He was clearly showing loyalty to disgruntled working class whites, he was being an authority figure to them, and in some sense he also seemed to be preserving the sanctity of their way of life. It's not that conservatives didn't care about the left three values, it's just that all the supposedly disqualifying things he said still made him score very high on the values on the right. On balance he thus still scored favorable.

The mistake liberals made was in thinking that his words would be as important to conservatives as they were to them, but because those words didn't really affect the three major values on the right that conservatives found important, they didn't matter much to them. It's a good case of missing the forest for the trees, and hopefully liberals won't make the same mistake next time. All six foundations are important, however, so liberals cannot be faulted for being angry at Trump's shoddy treatment of the three on the left; as Haidt says, even conservatives value these foundations.

The next four years are going to be a giant experiment in testing all these moral foundations. If the worst that everyone thinks about Trump comes to pass, this country will be in bad shape. That would be because he would have failed on all six foundations: for instance, if he does not deliver on promises to bring jobs to the white working class, the moral foundation of betrayal/loyalty and authority/subversion which they have largely staked their support for him on would take a potentially existential hit. He would have then failed both liberals and conservatives. If on the other hand, he manages to actually follow up on the positive promises that he has made, especially regarding job creation, and also manages not to significantly hurt the other moral foundations on the chart, who knows, perhaps everybody would have been wrong about him after all. For now the best strategy is the one recommended by the Zen Master: "We'll see".

Richard Feynman on our difficult times: "Whatever else is going on, we've always got our physics."

At this unfortunate moment, one of the best things I can think of is an anecdote about Richard Feynman from Stephen Wolfram's new book "Idea Makers". Wolfram was a graduate student with Feynman, and he recounts an episode from one of his visits to Feynman's place.
"If there's one moment that summarizes Richard Feynman and my relationship with him, perhaps it's this. It was probably 1982. I'd been at Feynman's house, and our conversation had turned to some kind of unpleasant situation that was going on. I was about to leave. And Feynman stopped me and said, "You know, you and I are very lucky. Because whatever else is going on, we've always got our physics."
To which I may add, we also have friends, family and our hobbies. Whichever direction the maelstrom of political winds blows our ship, we may take solace in these relative constants of our life. 

It does not mean that we lose ourselves in them to the extent of completely withdrawing from the larger national dialogue - the next few years more than any others demand our participation in that dialogue - but it's very reassuring to know that a carbon-carbon bond, or a supernova, or a protein molecule, or a semiconductor, or an equation, simply don't care who the president of the United States is. Moreover, as Einstein once said, time itself is no more than a "stubbornly persistent illusion", and if time might be illusory, then politics is a vanishingly transient ghost in the grand scheme of things.

I find cool succor in this pristine, untouched domain of science and ideas, and I hope most of us will in the difficult days ahead.

BAGIM event on computational chemistry careers

I want to note an event organized by BAGIM - a Boston area group that organizes talks and discussions on computational chemistry and related topics. It's being held on November 10th and will feature a panel discussion on careers in computational chemistry.

The event should be of special interest to postdocs and graduate students. It's a topic that's interesting partly because it's kind of tricky. It's tricky because computational chemistry is a very interdisciplinary field and its practitioners come from a variety of backgrounds - most commonly from organic and physical chemistry but also increasingly from biology and computer science. 

These days the definition of the field has also greatly expanded to include analysis of large-scale data and bioinformatics. What part you exactly need to know and what employers are looking for are facts that you would probably know only after talking to a few people in the field.

That's why I think these kinds of panel discussions might be useful, especially for people who are just getting into industry and academia. It's worth checking out if you are in the area.

Lise Meitner's 48 Nobel Prize nominations

It's Austrian physicist Lise Meitner's birthday today. Meitner was one of the most remarkable scientific figures of the twentieth century. After doing massive scientific work in radioactivity, she figured out the mechanism of nuclear fission with her nephew Otto Frisch in the depressing winter of 1938, after her colleagues Otto Hahn and Fritz Strassmann observed uranium improbably breaking up into barium.

Meitner continues to be one of the most notable scientists not to have won a Nobel Prize. The omission stands out especially because Hahn won it in 1945. By all accounts Meitner and Hahn enjoyed a very productive working relationship for almost thirty years before the tide of fascism tore their lives apart. Their relationship was warm and friendly, but still formal; both were after all products of the rigid and hierarchical German society of their time.

Meitner's lack of a Nobel Prize is stark not only because of the seminal importance of nuclear fission, but because a search of the Nobel Prize nomination database reveals a striking fact: Meitner was nominated for the Nobel Prize in physics or chemistry no less than 48 times between 1937 and 1948 alone. That's almost five nominations a year. Other great scientists have also received dozens of nominations - for instance the chemist R. B. Woodward had 92 before he finally won - but Meitner's is certainly on the higher side. The database runs to 1965, and it's rather curious to see no nominations after 1948.

The list of scientists nominating her is a roster of the who's who of twentieth century physics: Max Planck, Niels Bohr, Werner Heisenberg, Arthur Compton and Max Born all nominated her multiple times. Hahn nominated her once. Curiously, Albert Einstein who thought highly of Meitner does not seem to have nominated her even once; given Einstein's freethinking views and liberal persona this is rather strange.

Given the number of prominent personalities advocating her work, Meitner's omission from a Nobel Prize will continue to be a blot on the history of the prizes. This hole stands out even more because Meitner was otherwise highly decorated and publicly recognized, receiving for instance the prestigious Enrico Fermi Award from the United States Atomic Energy Commission. A combination of factors likely contributed to the failure of the prize committee. Sexism, certainly, but I don't think sexism played as prominent a role as it did in the careers of some other deserving female scientists. Part of the reason why I don't think it played an overriding role is that nuclear physics was the only field until then in which two women - Marie Curie (who shares a birthday today with Meitner) and Irene Joliot-Curie - had received Nobel Prizes. The physicist Maria Goeppert Mayer would very soon become only the second woman to win a physics Nobel Prize, again for nuclear physics. Also, Otto Frisch and Fritz Strassmann who were instrumental in both discoveries also did not receive the prize, and their omission of course cannot be ascribed to gender discrimination.

The real reason remains muddy and is likely a collage of fuzzy factors. Some have speculated it was anti-semitism, although given the number of Jewish prize recipients until then it would appear to be a minor determinant. Others think that the relatively low opinion of her work held by some prominent members of the Nobel committee might have contributed. Personally I also think it might have been an honest albeit misguided view of the contributions of the four scientists involved in discovering fission: Hahn's work might have been regarded as a proper "discovery" while Meitner and Frisch's might have been regarded as a mere "explanation". Strassmann could have been omitted because he was presumably Hahn's "assistant" (which he wasn't).

All these factors likely played a role, and no single factor might have been dominant. At the very least, Meitner's lack of a prize is as disappointing as Frisch and Strassmann's. In fact I always think that if there is an underappreciated hero of the nuclear fission story, it's not Meitner but Fritz Strassmann. This quiet and industrious man did much of the tedious grunt work that was key to solving the puzzle of the breakup of uranium. The kind of craftsmanship that he exhibited is too often overlooked, by the public as well as by prize committees. Morally too he was a hero; during those perilous years he hid a Jewish friend in his apartment for many years at considerable risk to his life. 

Meanwhile, Frisch was instrumental in helping his aunt work out the exact mathematics of the fission process and then performing the first fission experiment outside Berlin. Working with Rudolf Peierls in Birmingham, he later established the first value for the critical mass of a bomb and helped convince key members of then slow-moving Manhattan project that nuclear weapons were possible. He also fine tuned this critical mass value at Los Alamos by performing dangerous experiments which were christened 'tickling the dragon's tail'.

Niels Bohr rightly suggested that the physics Nobel Prize should have been split between Meitner and Frisch, the chemistry prize between Hahn and Strassmann. But the prize is a human institution after all, and a fallible human committee created by fallible human beings does not always obey the logical dictates of history. Hahn and Meitner are now largely remembered, Strassmann and Frisch are now largely forgotten. But Meitner stands out, for her brilliance and experimental acumen, for her perseverance and doggedness, for her stoic will during tumultuous and painful times, for great personal fortitude. She may not have won a Nobel Prize, but her 48 nominations provide a tribute to her remarkable personality as a scientist and human being. She deserves to be constantly remembered and celebrated.

Jack Roberts and Dorothy Semenow - Caltech's first female graduate student

The New York Times has an obituary today of pioneering Caltech chemist Jack Roberts who passed away last week at the ripe age of 98. Roberts was a truly incredible organic chemist, contributing massively to a diversity of fields that most scientists can only dream of crisscrossing. Even a short listing of the fields he enriched includes NMR spectroscopy, molecular orbital theory, reaction mechanisms and kinetic isotope effects. 

But one of Roberts' most notable achievements was human - when he moved from MIT to Caltech, he brought with him Caltech's first female graduate student, Dorothy Semenow.

Roberts certainly played an important role in admitting the institute's first woman, but Semenow's transition would likely have not been possible without the intervention of one of the world's greatest scientists, Linus Pauling, who was then chairman of Caltech's chemistry department. Here's what Roberts says in his autobiography about Pauling's stamp on this historic change:
"Caltech, unlike MIT, did not admit women as students, although there were a few female postdoctoral fellows. I talked to Linus about Dorothy and her strong desire to come to Caltech. To my surprise, he showed immediate interest. He told me that the question of admitting women had been raised not many years earlier, and that the faculty had voted not to change. Furthermore, he said that the Institute's trustees had taken note of the faculty action and had endorsed it. But he said he wanted to try again with a specific case, and asked that Dorothy submit an application as soon as possible. 
I wasn't on hand and had no idea what happened at Caltech during the decision-making process. It was certainly to the credit of both Caltech and Linus that the matter was settled by the end of the academic year, including approval by the trustees. There were stories that I had said I would not come if Dorothy was not admitted. That was not true. I only presented the case and others carried the ball, but it was wonderful to be associated with an institution that could act so quickly to change a very strong tradition."
It is certainly to Roberts' credit that he pressed for the change. It is also to his credit that he admits at the end that his role in the whole affair was not as gallant as the New York Times and others think it was. At Caltech Semenow did very strong work validating one of Roberts' key contributions to chemistry, the discovery of benzyne which is a very unusual benzene double with a triple bond. After an academic career in which she also acquired a PhD in psychology, she now seems to be advancing chemical education through games.

Interestingly, I found a reference to Dr. Semenow in a 1953 Caltech publication which seems to be some kind of monthly campus newsletter. After acknowledging her admission, the newsletter curiously says the following:
"This gallant action is not, however, an open invitation to the ladies. It applies only to "women of exceptional ability who give promise of great scientific contributions." And, before she can enroll, a woman must get the approval of the academic division in which she intends to work, as well as that of the Committee on Graduate Study.' With such hurdles as these, it is hardly likely that the campus will ever be swarming with female students. Most admissions of women, in fact, will probably involve the use of unique or outstanding research facilities here."
Yes, that charming second paragraph does seem to put a dent into the unprecedented event which it heralds, reassuring its readers not to worry about the campus "swarming" with the ladies (who understandably would of course distract all the gents). In fact, until 1967, Caltech's catalog proclaimed that female students would be admitted, "but only in exceptional cases". Now I am willing to cut Caltech some slack here - it was 1953 after all - but it does show how far they still had to go even after Semenow moved there from the more egalitarian MIT. 

How times have changed. Today Caltech has about 30% female graduate students, and while there clearly can be an improvement in this number, it was Dorothy Semenow, Jack Roberts and Linus Pauling who blazed that trail.

Steve Jobs on what happens to companies when sales people take over product people

Here's a great quote from Steve Jobs (from this interview) about what happens when technology companies, and especially ones with a monopoly, pivot from being product-driven to sales-driven. The italics are mine.
“The technology crashed and burned at Xerox. Why? I learned more about this with John Sculley later on. What happens is, John came from Pepsico. And they—at most—would change their product once every 10 years. To them, a new product was a new sized bottle. So if you were a ‘product person’, you couldn’t change the course of that company very much. So, who influences the success at Pepsico? The sales and marketing people. Therefore they were the ones that got promoted, and they were the ones that ran the company. 
Well, for Pepsico that might have been okay, but it turns out the same thing can happen at technology companies that get monopolies. Like IBM and Xerox. If you were a ‘product person’ at IBM or Xerox: so you make a better copier or better computer. So what? When you have a monopoly market-share, the company’s not any more successful. So the people who make the company more successful are the sales and marketing people, and they end up running the companies. And the ‘product people’ get run out of the decision-making forums. 
The companies forget how to make great products. The product sensibility and product genius that brought them to this monopolistic position gets rotted out by people running these companies who have no conception of a good product vs. a bad product. They have no conception of the craftsmanship that’s required to take a good idea and turn it into a good product. And they really have no feeling in their hearts about wanting to help the costumers.”

I have noted a similar quote by Jobs regarding the decline of Microsoft before, but this quote really fleshes out the problem in detail. What Jobs is saying about technology companies applies equally or even more to science-driven companies like pharmaceuticals and biotechnology. Nobody is saying that sales and marketing are not important, but when your company's basic foundation is fundamentally based on new products like drugs, then sales people can only get you so far, and beyond a point they can even destroy your raison d'etre. Interestingly, Microsoft itself is a good recent example of how a product-driven strategy can actually shore up a company's fortunes: a lot of the recent uptick in Microsoft's recent stock price and performance has come from the development of a new product - their cloud computing platform Azure. 

OpenEye CEO Anthony Nicholls has noted how the decline of Big Pharma's fortunes from the 90s onwards tracks well with the replacement of product people at the helm with sales people and lawyers. That seems to be too much of a coincidence. CEOs and CSOs definitely set the tone for what's important, and it's hard to see how a lawyer from a company that has nothing to do with making drugs can truly appreciate how to improve a drug-making company's core competency. Nor does being product-driven entail sucking up other firms in mergers and acquisitions. The problem is that while your company's fortunes may get a brief shot in the arm because of new products developed by other companies, at some point those companies' products may themselves run out. More importantly, if your primary goal is to simply acquire other companies, then you are no longer a pharmaceutical R&D organization, you are more like a holding house for other companies' products which you simply acquire and sell. At the very least you should then call yourself a holding house.

Of course, all this is more comprehensible (although still not excusable) when you consider how skewed the incentive systems are. When a new CEO is given a mandate to make a hefty profit in five years by impatient investors, their goals are totally limited to satisfying that narrowly defined demand, and since drug discovery (new product creation, that is) almost always looks at ten year horizons, the likelihood of that particular activity meeting their requirements is slim. Instead, acquiring the small neighborhood biotech and keeping investors happy for five years is the primary goal; after that you and your ten million dollar bonus are out anyway, so who cares?

In some sense Jobs' wisdom can be summed up very simply: if your company is based on a product, you should make better and more product. Selling it is important, but that comes next. If you invert the order or make sales your exclusive focus, then the very thing you are selling will one day cease to exist.

A really bad year for chemistry and chemists

The shocks just keep on coming. Monday brought news of University of Illinois computational chemist Klaus Schulten's demise. Schulten was a student of Martin Karplus who made great strides in using molecular dynamics to simulate the behavior of not just single proteins but giant protein assemblies like viruses. He contributed to both the science and the technology, popularizing parallel MD calculations along with their impact on key biological systems.

What's troubling is that news of Schulten's passing comes on the heels of similar bad news about two other chemistry and biology leaders - Jack Roberts and Susan Lindquist...and that's just in the last two days.

And these aren't even the first world-class scientists in the field to pass into the great beyond this year. There's also Harry Kroto, Ahmed Zewail and Roger Tsien, all Nobel Laureates. As far as the passing of great chemists into history goes, this has been as bad a year as any that I at least can remember.

If I believed in an all-powerful deity, I would probably think that some malevolent deity who failed high school chemistry and has held a grudge against all things chemical since is tampering with the lifelines of chemistry's leading practitioners. The more mundane but still depressing explanation is that this unfortunate set of coincidences is just that, a bad set of coincidences compounded with the raw fact of people dying at the end of a natural life span.

The one thing we can say is that all these giants have left their indelible footprints on their fields. These are fields that span a vast landscape: physical and organic chemistry, spectroscopy, chemical biology, cancer and neurodegenerative disease research, materials science. The fact that even such a small sampling of chemists corresponds to such a large sampling of scientific topics is a testament both to their intellectual prowess and the versatility of chemistry. 

They have all left us a lot of work to do.