Would nukes have helped in Vietnam?

by Alex Wellerstein, published July 25th, 2014

That night I listened while a colonel explained the war in terms of protein. We were a nation of high-protein, meat-eating hunters, while the other guy just ate rice and a few grungy fish heads. We were going to club him to death with our meat; what could you say except, “Colonel, you’re insane”? … Doomsday celebs, technomaniac projectionists; chemicals, gases, lasers, sonic-electric ballbreakers that were still on the boards; and for back-up, deep in all their hearts, there were always the Nukes, they loved to remind you that we had some, “right here in-country.” Once I met a colonel who had a plan to shorten the war by dropping piranha into the paddies of the North. He was talking fish but his dreamy eyes were full of mega-death.

So wrote Michael Herr in his masterful and classic book of Vietnam War journalism, Dispatches. I recently re-read Herr’s book, and this passage stuck out to me today more than it did when I first read the book a decade ago. “There were always the Nukes…” is an attitude that one sometimes sees expressed in other contexts as well, the idea that if it came to it, the USA could, of course, “glassify” any enemy it so chose to. The bomb in this view is the ultimate guarantor of security and strength. But of course Vietnam, among other conflicts, showed very clearly that being a nuclear state didn’t guarantee victory.

A napalm attack in the Vietnam War. Source.</a

Napalm in Vietnam. Source.

Would nukes have helped with the Vietnam War? It is a somewhat ghastly idea, to add more slaughter to an already terrible, bloody war, but worth contemplating if only to consider in very tangible terms what nuclear weapons can and can’t do, could and couldn’t do. It was a question that was studied seriously at the time, too. In early 1967, a JASON committee consisting of Freeman Dyson, Robert Gomer, Steven Weinberg, and S. Courtney Wright wrote a 60 page report on “Tactical Nuclear Weapons in Southeast Asia,” considering what could and couldn’t be done with the bomb. The whole thing has been obtained (with redactions) under the Freedom of Information Act by the Nautilus Institute, who have put together a very nice website on the subject under the title “Essentially Annihilated.”

The motivation for the report, according to Ann Finkbeiner, came from a few of the JASON consultants hearing off-hand comments from military men about the appeal of using a nuke or two:

“We were scared about the possible use in Vietnam,” said Robert Gomer, a chemist from the University of Chicago who was probably Jason’s first nonphysicist. During the 1966 spring meeting Freeman Dyson was “at some Jason party,” he said, and a former chairman of the Joint Chiefs of Staff who was also close to President Johnson “just remarked in an offhand way, ‘Well, it might be a good idea to throw in a nuke once in a while just to keep the other side guessing.’”

Gomer took initiative on the report, but it is Dyson’s name that is most closely associated it, in part because he (alphabetically) is listed as the first author, in part because Dyson is much more famous. Finkbeiner, who interviewed the authors of the report, says that it was not a report that was specifically requested by the military or government, and that it hewed closely to analytical/tactical questions as opposed to ethical ones.

Which is to say, as you probably have figured out, they set out to show from the start that tactical nuclear weapons would not be a good thing to introduce into the Vietnam War. So they weren’t exactly neutral on the question, but neutrality and objectivity are not the same thing.

1967 - Tactical Nuclear Weapons in Southeast Asia

The report is a fascinating read. It serves as a wonderful lens into how strategic thinking about tactical weapons worked at the time, because the authors, perhaps in an attempt to make sure it was taken seriously, couch all of their reasoning in the language of other, official studies on the issue. So it offers insights into the kinds of issues that were popping up in war-gaming scenarios, and assumptions that were apparently taken as valid about what a tactical nuclear weapon could and couldn’t do. And by deliberately avoiding any discussions of politics and morality (and with that, strategic nuclear weapons use), it does allow them to get into the nitty gritty of the tactical questions without getting overwhelmed by larger and often more nebulous debates about the propriety of nuclear arms.

The basic conclusions are pretty simple. The main one is that even if the US did use tactical nuclear weapons, and such use was entirely unilateral, it wouldn’t get very useful results. Tactical nuclear weapons were thought to be most useful against large massed troops or columns of armor, such as an invading Red Army moving into Western Europe. The problem is, that didn’t describe the situation in Vietnam very well at all, where the Viet Cong and North Vietnamese Army typically operated in smaller groups under forest cover. You could use nukes to destroy their bases, but you’d have to locate their bases first — and by the time you’ve done that, you could have just bombed them conventionally. In general, in a war like Vietnam, tactical nuclear weapons appeared to offer little advantage over conventional arms in most situations. The one special addition of the nukes — the fallout — was too difficult to predict and control, and fallout that would be a useful barrier to troops would necessarily become a problem for civilians as well.

There are some interesting numbers in the report. One is a citation of a conclusion from a RAND study that in a complex war environment, a tactical nuclear weapon is “on the average, equivalent to about 12 nonnuclear attack sorties.” The JASON authors conclude that if you wanted to do something like the Rolling Thunder campaign using nuclear weapons, under this rubric it would require 3,000 tactical nuclear weapons per year. They also note another war-gaming conclusion, that even in the presumedly “Soviet” tactical nuclear weapons environment — large, massed troop and armor concentrations —  “the average number of enemy casualties per strike was about 100.” This probably assumes that some strikes are outright misses while others are very effective, but that’s an impressively low number. The JASON authors note that this would be considerably less in a Vietnam-style environment, because the ability to locate targets of interest would probably be much lower.

There are, they acknowledge, a few cases where specific uses of tactical nuclear weapons might be advantageous. Bridges, headquarters, and underground tunnel complexes could be more easily taken out with tactical nukes than conventional weapons. Such conclusions are somewhat underwhelming, and maybe that is the point: when you do figure out what good the weapons might do, it seems much less impressive than the fantasies.

Map of the Tet Offensive, 1968; the JASON authors would perhaps have us consider what this would have looked like if the North Vietnamese had been supplied tactical weapons from the Soviets or Chinese. Source.

Map of the Tet Offensive, 1968; the JASON authors would perhaps have us consider what this would have looked like if the North Vietnamese had been supplied tactical weapons from the Soviets or Chinese. Source.

The strongest argument they make against using the weapons, though, is not so much that they would be ineffective against the Vietnamese. Rather, it is that the weapons would be really effective against American troops in Vietnam:

If about 100 weapons of 10-KT yield each could be delivered from the base perimeters onto all 70 target areas in a coordinate strike, the U.S. fighting capability in Vietnam would be essentially annihilated. In the more likely contingency that only a few weapons could be delivered intermittently, U.S. casualties would still be extremely high and the degradation of U.S. capabilities would be considerable.

This is often the argument made today whenever the idea of using nuclear weapons — tactical or otherwise — re-raises its head. Since World War II, the US has the strongest interest in not breaking the “nuclear taboo” because once nukes start becoming normalized, the US usually stands to lose the most, or at least a lot. Massed troops, heavy armor, and fixed bases? That’s how we prefer to fight wars. Massive urban cities conveniently located on coasts? Check. Economy highly reliant on communications, transportation, and other infrastructure? Yeah. Which is probably one of the deep reasons that the US, for all of its lack of willingness to commit to a no-first use policy, has always managed to find a way so far to avoid using the tens of thousands of nuclear weapons it produced in the years since Hiroshima and Nagasaki.

The report convincingly concludes:

The use of TNW [tactical nuclear weapons] in Southeast Asia would be highly damaging to the U.S. whether or not the use remains unilateral. The overall result of our study is to confirm the generally held opinion that the use of TNW in Southeast Asia would offer the U.S. no decisive military advantage if the use remained unilateral, and it would have strongly adverse military effects if the enemy were able to use TNW in reply. The military advantages of unilateral use are not overwhelming enough to ensure termination of the war, and they are therefore heavily outweighed by the disadvantages of eventual bilateral use.

When I teach to students, I try to emphasize that there are some deep paradoxes at the core of nuclear weapons policies. Deterrence is a tricky-enough strategic issue, a mixture of  military logic and raw fear. Tactical nuclear weapons add complicated wrinkles. Were they merely a means of making deterrence more credible, by showing the Soviets (and whomever else) that we were not willing to let the threat of nuclear annihilation become paralyzing? Or were they really intended to be military weapons that could be usefully employed, regarded as a sort of scaling up of conventional capabilities? In terms of their doctrine and literature, it isn’t clear: they are spoken of as both, in part because a stated willingness to use them is core to their deterrent value. (That is, if you are going to be convincing in your statements that you are willing to use them, you have to look like you are willing to use them, even if you don’t want to use them.)

How much of tactical nuclear weapons was just swagger? Above, the Davy Crockett weapons system, in full-swagger mode.

How much of tactical nuclear weapons was just swagger? Above, the Davy Crockett weapons system, in full-swagger mode.

Thinking through, in a concrete way, what would happen if nuclear weapons are used, and what the long-term consequences would be (politically, tactically, environmentally, economically, etc.) is an important exercise, even if it is sometimes labeled as morbid. Too often, I think, we close our minds to the very possibility. But “thinking the unthinkable” is valuable — not because it will make us more willing to use them, but because it highlights the limitations of their use, and helps us come to grips with what the actual consequences would be.

So would nuke have been useful in the Vietnam War? I think the JASON authors do a good job of showing that the answer is, “almost certainly not very useful, and possibly completely disastrous.” And knowing, as we do now and they did not in 1967, how much of a long-term blot Vietnam would be to US domestic and foreign policy in the years that followed, consider how much of a danger it would have posed if we had started letting little nukes fly on top of everything else.

News and Notes

John Wheeler and the Terrible, Horrible, No Good, Very Bad Day

by Alex Wellerstein, published July 14th, 2014

Just a quick plug: as noted previously, I’m moving out of the Washington, DC, area very soon, to start a new job at the Stevens Institute of Technology in the New Jersey/NYC area. My last talk as a DC denizen is going to be next Monday, July 21st, at the American Institute of Physics in College Park, Maryland, from 12-1:30pm.


Here’s the information:

The AIP History Programs invites you to an ACP Brown Bag Lunch-Time Talk:

John Wheeler’s H-bomb blues:
Searching for a missing document
at the height of the Cold War

by Alex Wellerstein, Postdoctoral Fellow at the Center for History of Physics

Monday, July 21, 2014
12–1:30 pm

Conference Room A
American Center for Physics
1 Physics Ellipse
College Park, MD 20740

There’s never a right time to lose a secret document under unusual circumstances. But for the influential American physicist John Archibald Wheeler, there might not have been a worse time than January, 1953. While on an overnight train ride to Washington, D.C., only a month after the test of the first hydrogen bomb prototype, Wheeler lost, under curious circumstances, a document explaining the secret to making thermonuclear weapons.

The subsequent search for the missing pages (and for who to blame) went as high as J. Edgar Hoover and President Eisenhower, and ended up destroying several careers. The story provides a unique window into the precarious intersection of government secrecy, competing histories of the hydrogen bomb, and inter-agency atomic rivalry in the high Cold War. Using recently declassified files, the AIP Center for History of Physics’ outgoing Associate Historian will trace out the tale of  how Wheeler ended up on that particular train, with that particular document, and the far-reaching consequences of its  loss—or theft—for both Wheeler and others involved in the case.

It’s a very fun paper, drawing heavily on John Wheeler’s FBI file, and one that I will be turning into an article fairly soon. It is open to the public if you RSVP. If you’re in town and want to see me before I go, please feel free to come! To my knowledge it will not be live-streamed or recorded or anything like that.


Who smeared Richard Feynman?

by Alex Wellerstein, published July 11th, 2014

One of the many physicists who came under official FBI scrutiny during the Cold War was Richard Feynman. Feynman’s work on the bomb at Los Alamos, combined with his fame, penchant for telling stories about safe-cracking, and occasional consideration for being on government committees led him to be investigated a few times, to see where is loyalties lay. In March 2012, the website MuckRock filed a Freedom of Information Act (FOIA) request to obtain and release Feynman’s full FBI file (minus deletions). It got a lot of Internet buzz when it first came out, but from the look of most of it, the articles about it didn’t read it very carefully — they just mined it for a few good quotes.

Would you give this man a security clearance? From the Emilio Segrè Visual Archives.

Would you give this man a security clearance? From the Emilio Segrè Visual Archives.

And good quotes it has. Like most FBI files for people who had security clearances at one point or another, it is mostly concerned with interviews with friends and colleagues about Feynman’s “character and loyalty.” Most of the file was filled out in 1958, when Feynman was apparently being considered for a position on Eisenhower’s President’s Science Advisory Committee (PSAC), a very high-level advisory board created in the wake of Sputnik. Most of the testimonies look like this:


“…a brilliant physicist… discreet, loyal American citizen of good character and associates and recommended him for a position of trust…” And so on.

And sometimes you can figure out the basics of what the blank spots say from the context. The first blank spot is someone who Feynman worked with during a summer of 1956 visit to Brookhaven National Laboratory, and we can deduce from the text that: 1. the person is a man, and 2. the person is not someone Feynman knew well before that period. We could if we were really tempted to, try to figure out (from archival files or databases), the names of several candidates based on these properties, and then see if they fit into the blank spot (since it is a fixed-width font). The second blank spot is the name of the interviewing FBI agent (SA = Special Agent). In this case, it is such a boring endorsement that it doesn’t seem worth the effort. (The b7C and b7D on the right are FOIA exemption references that indicate that the blanked out parts have been done so to protect the “privacy” and hide the name of the confidential informant.)

Feynman smear 1

But there is a much more interesting letter in the file, and it is one that several blogs and news sites picked up on at the time. It is dated August 8, 1958, and is an epic 9-page attack on Feynman’s character, written directly to J. Edgar Hoover. It argues that “Feynman is a master of deception, and that his greatest talent lies in intrigue, not physics”:

I do not know—but I believe that Richard Feynman is either a Communist or very strongly pro-Communist—and as such as a very definite security risk. This man is, in my opinion, an extremely complex and dangerous person, a very dangerous person to have in a position of public trust… In matters of intrigue Richard Feynman is, I believe immensely clever—indeed a genius—and he is, I further believe, completely ruthless, unhampered by morals, ethics, or religion—and will stop at absolutely nothing to achieve his ends.

You can read the least-redacted version of the letter here. A lot of the sites which posted it did so in sort of a confused way — talking about how it reflected that the FBI was dubious about Feynman (the FBI do not issue opinions of this sort, and the letter is just part of his file), and wondering which of his colleagues would be mean enough to write such a thing.

Feynman smear letter, 1958

I’ve read a lot of FBI files of physicists, and plenty of them are full of anonymous, smearing letters to Hoover. This one sticks out as unusual, though, both in its vehemence and its personal specificity. The author of the letter is not some anti-Communist nut who writes nasty letters as a hobby. It hits much closer to home than most smears.

So who smeared Feynman? What can we infer about the letter’s author, reading between the lines?

  • The author is someone who knew Feynman pretty well. This is a letter written by someone who has heard a lot of Richard Feynman stories — they are well-acquainted with his lock-picking Los Alamos stories, for example. (And this was several decades before those stories appeared in books.) They know that he’s very handy with mechanical devices, they know his friends, they claim to know how Feynman has talked about his political positions over the years and how he is registered to vote (Republican).
  • The author is religious and conservative. Among the author’s criticisms of Feynman is that he is irreligious and a fake Republican. The author repeatedly invokes Eisenhower’s name in awe and respect, and offers to swear either on a Bible or to the President himself. The author talks of Feynman’s “long hatred of Republicans,” but knows that Feynman registered as a Republican in 1956 — which the author believes to have been part of a long-game deception to infiltrate the government. The author could be faking it, of course, but it doesn’t read like that to me.
  • The author knows a lot about his scientific contacts and knows he is considered brilliant by his peers, but is probably not a physicist. On page 6 of the letter, the author names lots of Feynman’s scientific associations and acknowledges that they would all give Feynman high marks. But the author also makes some rather elementary errors: some of the names are obviously misspelled — “Enerico Fermi” and “Claus Fuchs.” It is hard for me to believe that any of his Los Alamos peers would misspell those names in 1956, much less that of Fermi’s. Of course, we all make typos. But the tenor of the letter suggests someone who was pretty closely connected with Feynman’s scientific world, but was not a member of it.
  • The person is someone who the FBI had already identified as worth interviewing, prior to the letter. This is obvious from the first sentence (“On July 28, 1958, I was interviewed by a representative of the FBI…”) but was missed by a lot of the sites that wrote on the file. This tells us a few things. For one, it tells us that this person was already someone whose connection to Feynman was superficially obvious — again, not an anonymous ranter, but someone relatively close. For another, it lets us trace through the file and figure out where the interview happened. And indeed, we find that on 7/28/58, an FBI agent from the Butte office interviewed someone in Boise, Idaho, who talked about Feynman’s lock-picking stories, and had a rare negative conclusion about his suitability. Probably the same person.
  • The person who wrote the letter is a woman. Wait, what? Indeed! Despite a lot of redaction to keep the identity of the letter writer and interviewee a secret, there are a few tiny slips: a reference to “her” and “she” in a few of the FBI memos. This is the sort of subtle thing that must make file redactors kick themselves, because it’s the sort of little slip-up that gives away a lot of information.

So who smeared Feynman? I submit a theory: I suspect it was his second wife, Mary Louise Bell, to whom he was married from 1952 until 1956. That’s not a long marriage, but it’s plenty of time to hear someone’s stories ad nauseam, and plenty of time to learn to hate someone. From James Gleick’s Feynman biography, Genius:

His friends refused to understand why he finally chose to settle down with Mary Louise Bell of Neodesha, Kansas, who had met him in a Cornell cafeteria and pursued him—they said cattily—all the way to Pasadena and finally accepted his proposal by mail from Rio de Janeiro. … They married as soon as he returned from Brazil, in June 1952, and they honeymooned in Mexico and Guatemala, where they ran up and down Mayan pyramids. He made her laugh, but he also frightened her with what she decided was a violent temper. … She nagged him, they thought. She liked to tell people that he was not “evolved” to the point of appreciating music and that sometimes she thought she was married to an uneducated man with a Ph.D. … Politically she was an extreme conservative, unlike most of Feynman’s colleagues, and as the Oppenheimer security hearings began, she irritated Feynman by saying, “Where there’s smoke there’s fire.” He, too, voted Republican, at least for a while. Divorce was inevitable—Feynman realized early that they should not have children, he confided in his sister—but it was nearly four years before they finally separated.

Further evidence from the file: Feynman’s only connection to Boise, Idaho, is through Bell (they were married there in late June 1952). The final divorce settlement was rendered only in May 1958 — two months before the FBI interviewed the letter writer. It was an extremely ugly, long (2 years!) divorce hearing: it made the newspapers because of Bell’s allegations of “extreme cruelty” by Feynman, including the notion that he spent all of his waking hours either doing calculus and playing the bongos.

Another approach to these files is to try and guess missing words based on the fixed-width font size. One possible fit shown here, for example. I am always a little un-sure about this approach, though, since lots of other things could fit, as well.

Another approach to these files is to try and guess missing words based on the fixed-width font size. One possible fit shown here, for example. I am always a little un-sure about this approach, though, since lots of other things could fit, as well.

Of course, there’s always another possibility, such as the idea that it might not be Bell herself, but her mother, sister, close friend, etc. But there’s a level of personal animosity in the letter that is quite deep. There’s a sense that this letter writer is the only person in the entire FBI file who is fed up with Feynman’s self-serving stories and not engaged in any form of hero-worship just because he is a well-respected genius. It really does read like someone who just went through a very messy divorce with the guy.

As an aside, I talked about this with my own wife, and she noted how gendered a lot of the Feynman stuff is. His “smartest man in the room” stories are an awfully common male trope, and the emotional self-denial that comes through in his stories (e.g. about his first wife, Arline) reflects a guy who is trying very hard to put on a public face that is strongly within typical American masculinity. Many of the traits discussed in the smear letter are ones Feynman himself would own up to gladly, but were turned on their head — Feynman’s anti-secrecy exploits at Los Alamos are not seen as evidence of the inefficiency of secrecy, but as evidence of Feynman’s own juvenility. Somehow I don’t see Feynman’s male colleagues making that sort of twist. This isn’t to be essentialist, or to claim that men couldn’t smear — but the male smears usually had more emphasis on the Communism and less emphasis on his emotional stability.

Feynman never became a member of PSAC. Was it because of this letter, the one piece of strongly negative testimony in his file? We would need more records (and not the FBI’s) to know that: the FBI did not make recommendations as to whether someone should be hired, it simply produced a summary of the information it received (often with an emphasis on the derogatory information, though), and let the agency in question decide what it wanted to do about it. Feynman’s lack of PSAC participation may have had to do with other factors; it is not clear that he would have even wanted to be on the committee, given his avowed distaste for government work in the Cold War period. But it’s a strong letter, so it might have had an effect — it’s a letter from someone who knew Feynman, and his flaws, very well.


A bomb without Einstein?

by Alex Wellerstein, published June 27th, 2014

If Albert Einstein had never been born, would it have changed when nuclear weapons were first produced? For whatever reason, I’ve seen this question being asked repeatedly on Internet forums, as odd as it is. It’s kind of a silly question. You can’t go in and tweak one variable in the past and then think you could know what the outcome would be. History is a chaotic system; start removing variables, who knows what would happen. Much less a variable named Albert Einstein, one of the most influential physicists of the 20th century, and whose importance extended well past the equations he wrote… and those were pretty important equations, at that!

1946 - Einstein Time magazine - detail

Einstein’s 1946 cover of Time magazine. The mushroom cloud is a beautifully executed combination of the Trinity and Nagasaki mushroom clouds.

On the other hand, this kind of science-fiction counterfactual can have its usefulness as a thought experiment. It isn’t history, but it can be used to illustrate some important aspects about the early history of the atomic bomb that a lot of people don’t know, and to undo a little bit of the “great man” obsession with bomb history. Albert Einstein has been associated with the bomb both through his famous mass-energy equivalence calculation (E=mc²) and because of the famous Einstein-Szilard letter to Roosevelt in 1939. On the face of it, this gives him quite a primary role, and indeed, he usually shows up pretty quickly at the beginning of most histories of the Manhattan Project. But neither E=mc² nor the Einstein-Szilard letter were as central to the Manhattan Project’s success as people realize — either scientifically or historically.

In terms of the science, E=mc² gets a lion’s share of attention, most perfectly expressed by Einstein’s portrait on the cover of Time magazine in 1946 (above) with his equation emblazoned on a mushroom cloud. A lot of people seem to think that E=mc² played a key role in the development of the bomb, that the weapon just falls out of the physics. This is wrong. The equation can help one understand why atomic bombs work, but it doesn’t really tell you how they work, or whether you would expect them to even be possible.

The way I like to put it is this: E=mc² tells you about as much about an atomic bomb as Newton’s laws do about ballistic missiles. At some very “low level” the physics is crucial to making sense of the technology, but the technology does not just “fall out” of the physics in any straightforward way, and neither of those equations tell you whether the technology is possible. E=mc² tells you that on some very deep level, energy and mass are equivalent, and the amount of energy that mass is equivalent is gigantic. But it says nothing about the mechanism of converting mass into energy, either whether one exists in the first place, or whether it can be scaled up to industrial or military scales. It gives no hints as to even where to look for such energy releases. After the fact, once you know about nuclear fission and can measure mass defects and things like that, it helps you explain very concisely where the tremendous amounts of energy come from, but it gives you no starting indications.

Eddington's famous plate of the 1919 solar eclipse, which helped confirm Einstein's theory of General Relativity. Very cool looking, and interesting science. But not relevant to atomic bombs. Source.

Eddington’s famous plate of the 1919 solar eclipse, which helped confirm Einstein’s theory of General Relativity. Very cool looking, and interesting science. But not relevant to atomic bombs. Source.

What about the rest of Einstein’s main theoretical work, both Special and General Relativity Theory? They are pretty irrelevant to bomb-making. The physical processes that take place inside atomic bombs are what physicists call “non-relativistic.” Relativity theory generally only shows its hand when you are talking about great speeds (e.g. large fractions of the speed of light) or great masses (e.g. gravitational fields), and neither of those come into play with fission bombs. You can neglect relativity when doing the math to make a bomb.

An intelligent follow-up question might be: “well, just because relativity theory didn’t play a role in the bomb process itself doesn’t answer the question of whether it started physics on a path that led to the bomb, does it?” Without getting into a long timeline of the “science that led to the bomb,” here, I think we could reasonably summarize the situation like this: Einstein’s 1905 papers (of which E=mc² was one) did indeed play a role in the subsequent developments that followed, but perhaps not as direct a one as people think. E=mc² didn’t inspire physicists to start looking into processes that converted mass to energy — they were already looking into those through an entirely separate (and earlier) line of development, namely the science of radioactivity and particle physics. The fact that huge amounts of energy were released through nuclear reactions, for example, had already been studied closely by the Curies, by Ernest Rutherford, and by Frederick Soddy prior (but only just) to 1905.

Arguably, the most important work Einstein did in this respect was his work on the photoelectric effect (for which he was awarded the Nobel Prize in Physics for 1921), which helped establish the physical reality of Max Planck’s idea of a quantum of energy, which helped kick off investigations into quantum theory in earnest. This had a big influence on the later direction of physics, even if Einstein himself was never quite comfortable with the quantum mechanics that developed in subsequent decades.

The Hahn-Meitner-Strassman experiment apparatus, at the Deutsches Museum in Munich. My own photo.

The Hahn-Meitner-Strassman experiment apparatus, at the Deutsches Museum in Munich. My own photo.

Did any of the relativity work lead, though, down the path that eventually arrived at the discovery of fission in 1939? I don’t think so. The experiments that Hahn, Meitner, and Strassman were doing in Berlin that lead to the discovery of fission in uranium were themselves careful replications of work that Fermi had done around 1934. Fermi’s work came directly out of an experimentalist, nuclear physics context where physicists were bombarding substances with all manner of subatomic particles to see what happened. It was most directly influenced by the discovery of the neutron as a new sub-atomic particle by Chadwick in 1932. This came out of work on atomic theory and atomic modeling that was being done by Rutherford and his students from the early 1910s-1920s. And this early nuclear physics came, most directly, out of the aforementioned context of radioactivity and experimental physics of the late 19th century.

None of which has a strong, direct connection to or from Einstein’s work in my mind. They have some overlaps of interest (e.g. Bohr was a student of Rutherford’s), but the communities working on these sorts of experimental problems are not quite the same as the more theoretical circle that Einstein himself worked in. If we somehow, magically, removed Einstein’s early work from the equation here, does the output change much? There would be some reshuffling, probably, but I sort of think that Rutherford would still be doing his thing anyway, and from that much of the other work that led to the bomb would eventually come out, even if it had a somewhat different flavor or slightly different timeline.

My least favorite way of depicting the fission process, where energy (E) is a magic lightning bolt coming out of the splitting atom. In reality, most of the energy comes in the form of the two fission products (F.P. here) repelling from each other with great violence. Source.

This is my least-favorite way of depicting the fission process, where energy (E) is a magic lightning bolt coming out of the splitting atom. In reality, most of the energy comes in the form of the two fission products (F.P. here) repelling from each other with great violence. Source.

Do you even need to know that E=mc² to make an atomic bomb? Perhaps surprisingly, you don’t! There are other, more physically intuitive ways to calculate (or measure) the energy release from a fission reaction. If you treat the fission process as being simply based on the electrostatic repulsion of two fission products, you get essentially the same energy output in the form of kinetic energy. This is how the physics of fission is often taught in actual physics classes, because it gives you a more concrete indication of how that energy is getting released (whereas E=mc² with the mass-defect makes it seem like a magical lightning bolt carries it away). There are other more subtle physical questions involved in making a bomb, some of which have Einstein’s influence on them in one way or another (e.g. Bose–Einstein statistics). But I think it is not totally crazy to say that even if you somehow imagine a world in which Einstein had never existed, that the physics of an atomic bomb would still work out fine — Einstein’s specific technical work wasn’t central to the problem at all. We also have not brought up the question of whether without Einstein, relativity in some form would have been discovered anyway. The answer is probably “yes,” as there were people working on similar problems in the same areas of physics, and once people started paying a close attention to the physics of radioactivity they were bound to stumble upon the mass-energy relationship anyway. This isn’t to denigrate or underestimate Einstein’s influence on physics, of course. What makes Einstein “Einstein” is that he, a single person, pulled off a great number of theoretical coups all at once. But if he hadn’t done that, there’s no reason to think that other people wouldn’t have come up with his theoretical insights individually, if slightly later.

A postwar re-creation of the genesis of the Einstein-Szilard letter.

A postwar re-creation of the genesis of the Einstein-Szilard letter.

What about Einstein’s most direct role, the famous Einstein-Szilard letter of 1939 that influenced President Roosevelt to set up the first Uranium Committee? This is a tricky historical question that could have (and may at some point) an entirely separate blog post relating to it. Its writing, contents, and influence are more complex than the standard “he wrote a letter, FDR created the Manhattan Project” understanding of it that gets boiled down in some popular accounts. My feeling about it, ultimately, is this: if the Einstein-Szilard letter hadn’t been written, it isn’t clear that anything would be terribly different in the outcome in terms of making the bomb. Something like the Uranium Committee might have been started up anyway (contrary to popular understanding, the letter was not the first time Roosevelt had been told about the possibility of nuclear fission), and even if it hadn’t, it isn’t clear that the Uranium Committee was necessary to end up with a Manhattan Project. The road from a fission program whose primary output was reports and a fission program whose primary output was atomic bombs was not a direct one. By early 1941, the Uranium Committee had failed to convince scientist-administrators that atomic bombs were worth trying to build. They had concluded that while atomic bombs were theoretically feasible, they were not likely to be built anytime soon. Had things stayed there, it seems unlikely the United States would have built a bomb ready to use by July/August 1945.

The “push” came from an external source: the British program. Their MAUD Committee (an equivalent of the Uranium Committee) had concluded that a nuclear weapon would be much easier to build than the United States had concluded, and sent an emissary (Mark Oliphant) to the United States to make sure this conclusion was understood. They caught Vannevar Bush’s ear in late 1941, and he (along with Ernest Lawrence, Arthur Compton, and others) wrested control of the uranium work out of the hands of the Uranium Committee, accelerated the work, and morphed it into the S-1 Committee. The name change is significant — it is one of the more vivid demonstrations of the increased degree of seriousness with which the work was taken, and the secrecy that came with it. By late 1942, the wheels for the full Manhattan Project were set into motion, and the work had become a real bomb-making program.

Einstein wasn’t involved with any of the later work that actually led to the bomb. He almost was, though: in late 1941, Bush considered consulting Einstein for help on the diffusion problem, but opted not to push for it — both because Einstein wasn’t regarded as politically reliable (he had a fat FBI file), and his approach to physics just wasn’t very right for practical problems. Bush decided that Einstein would stay out of the loop.

Usual, rare anti-Nazi propaganda postcard from 1934, showing Hitler expelling Einstein from Germany, titled "The Ignominy of the 20th Century." It is one of the most blatant visual renderings of Einstein as a "scientific saint." Source.

Unusual, rare anti-Nazi propaganda postcard from 1934, showing Hitler expelling Einstein from Germany, titled “The Ignominy of the 20th Century.” It is one of the most blatant visual renderings of Einstein as a “scientific saint.” Source.

Let’s sum it up. Did Einstein play a role in the creation of the atomic bomb? Of course — his physics isn’t irrelevant, and his letter to Roosevelt did start one phase of the work. But both of these things are less prominent than the Time-magazine-cover-understanding makes them out to be. They weren’t central to what became the Manhattan Project, and if you could somehow, magically, remove Einstein from the equation, it isn’t at all clear that the atomic bomb wouldn’t have been built around the time it actually was built. I don’t think you can really credit, or blame, Einstein for the atomic bomb, in any direct fashion. Einstein did play a role in things, but that role wasn’t as crucial, central, or direct as a lot of people imagine. If you could magically drop him out of history, I think very little in terms of atomic bombs would have been affected.

So why does the Einstein and the bomb myth persist? Why does everybody learn about the Einstein letter, if it wasn’t really was sparked the Manhattan Project? There are two answers here, I think. One is that Einstein was, even before the war, one of the best-known, best-recognized physicists of the 20th century, and was synonymous with revolutionary science and genius. Having him “predict” the atomic bomb with equations in 1905 — 40 years before one was set off — is the kind of “genius-story” that people love, even if it obscures more than it enlightens. It also has a high irony quotient, since Einstein was forced to flee from Germany when the Nazis took power.

But there’s another, perhaps more problematic aspect. In many early copies of the Smyth Report that were distributed by the government, copies of the Einstein letter were mimeographed and loosely inserted. The magnification of Einstein’s role was purposefully encouraged by the government in the immediate period after using the weapon. (And it was even a convenient myth for Einstein, as it magnified his own importance and thus potential influence.) Hanging the atomic bomb on Einstein’s head was an act of self-justification, of sorts. Einstein was the world’s greatest genius in the eyes of the public, and he was a well-known pacifist, practically a scientific saint. After all, if Einstein thought building a bomb was necessary, who could argue with him?


Feynman and the Bomb

by Alex Wellerstein, published June 6th, 2014

Richard Feynman is one of the best-known physicists of the 20th century. Most of those who know about him know he was at Los Alamos during the Manhattan Project — some of the best “Feynman stories” were set there. But Feynman’s own stories about his wartime hijinks were, like most of his stories about himself, half just-for-laughs and half lookit-mee! Feynman’s always got to either be a lucky average Joe, or the one brilliant mind in a sea of normals. His Los Alamos antics are mostly just tales of a genius man-child running around a secret laboratory, picking safes and irritating security guards. They aren’t very good gauges of what he actually did towards making the bomb. So what did Feynman actually do with regards to making the bomb? And does it matter, for thinking about his later career, especially the work that won him a Nobel Prize two decades later? 

Los Alamos colloquium from 1946, featuring (foreground, from left-to-right), Norris Bradbury, J. Robert Oppenheimer, John Manley, Richard Feynman, and Enrico Fermi. This version is cropped from the scanned copy at the Emilio Segrè Visual Archives. I will note that unlike the more common copies of this photo that have circulated, you can actually get a sense for how many other people were in the room — it looks like a really packed house.

Los Alamos colloquium from 1946, featuring (foreground, from left-to-right), Norris Bradbury, J. Robert Oppenheimer, John Manley, Richard Feynman, and Enrico Fermi. This version is cropped from the scanned copy at the Emilio Segrè Visual Archives. I will note that unlike the more common copies of this photo that have circulated, you can actually get a sense for how many other people were in the room — it looks like a really packed house.

Feynman’s own stories of his wartime work are centered around things other than the work itself. So he describes doing calculations, but doesn’t really say what they were for. He describes going to Oak Ridge, but only as a pretext for a story about dealing with generals and engineers. He describes the Trinity test, but a lot of that is about his claim to being the only person who saw it without welding glass on. And so on. These give glimpses, but not a very complete picture.

The historian of physics (and my advisor) Peter Galison wrote an article on “Feynman’s War” several years back, looking closely at what it actually was that Feynman was doing at the lab, and how it played into the style that he later became famous for in physics. Galison argues that Feynman’s postwar work is uniquely characterized by being “modular, pictorial, and proudly unmathematical.” He contrasts this with the work of several of his contemporaries, including Julian Schwinger, who came up with equivalent solutions to the same physical problems but through a very different (much more mathematical) approach. Feynman’s famous diagrams, which had a huge influence on the teaching and practice of postwar physics, exemplify this approach. What in Schwinger and Tomonaga’s hands (the other people Feynman shared his Nobel Prize with in 1965) was solvable only through massive, lengthy, laborious math could, in Feynman’s hands, be solved through a series of clever diagrams which came up with equivalent results. Feynman’s solutions to quantum electrodynamics weren’t the only way to do it — but they were easier to comprehend, to teach, and to apply to new questions.

The first Feynman diagram, published in R. P. Feynman, "Space—Time Approach to Quantum Electrodynamics,"Physical Review 76 (1949), 769-789, on 772.

The first published Feynman diagram, from Richard P. Feynman, “Space-Time Approach to Quantum Electrodynamics,”Physical Review 76 (1949), 769-789, on 772.

OK, so what does this have to do World War II? Well, Galison’s argument is that you can see the same sort of thinking at work in what Feynman did at Los Alamos, and he argues that it is during the war that he really started applying this mode of physics. He divides Feynman’s work into several “projects.” They were:

  • Neutron measurements for determining critical mass (including the famous “tickling the dragon’s tail” experiment” involving creating brief, barely-subcritical masses)
  • Work on the “Water Boiler” reactor at Los Alamos, which provided further data on nuclear chain reactions
  • Work as a safety supervisor at Oak Ridge, Tennessee, at Oppenheimer’s request (which in his own writings is distilled down to a single humorous anecdote where Feynman is simultaneously clueless and brilliant)
  • Developing formulae relating to criticality and implosion efficiency (including the Bethe-Feynman formula)
  • His work on the hydride bomb, an abortive, Teller-inspired approach to make a “cheaper” fission weapon which involved devilishly difficult calculation (because not all of the neutrons produced in the weapon would be of the same energy)

Galison argues that in each of these instances, you can see the germs of his later approaches. He credits this to both Feynman’s own personal scientific style and inclinations as a theorist (Feynman didn’t seem to like to work with fundamental equations, but with “shortcuts” that lead to quicker, more efficient solutions, for example), but also to the requirements of the wartime goal, where theorists had to come up with tangible, practical results in a very short amount of time.  For example, Galison notes that the formulae relating to how the implosion bomb worked “brought the abstract differential equations to the bottom line: how hot, how fast, how much yield?” The practical needs of the war favored a particular “theoretical style” in general, Galison argues, one that could be most easily meshed with engineering concerns, rapid prototyping, and the lack of time to ruminate on fundamental physics questions.

The "Water Boiler" reactor at Los Alamos. Source: Los Alamos Archives (12784), via Galison 1998.

The “Water Boiler” reactor at Los Alamos that Feynman worked on. Source: Los Alamos Archives (12784), via Galison 1998, p. 404.

Galison’s article is fairly technical. He goes through Feynman’s work (what of it that is declassified, anyway) and tries to follow his thinking in a very “internal” way, and then match that up with the requirements imposed by the specific wartime context. If you are well-versed in physics you will probably find the details interesting. I’m more of a big-picture person myself, and I like the structure of Galison’s argument even if I don’t feel fully capable of digesting all of the physics involved. One small example of Galison’s work can probably suffice. Feynman was sent to Oak Ridge, as noted, to serve as a safety supervisor. He was taking over for Robert Christy, who got pneumonia in April 1944. The safety question was not a general one, but a very specific one: how many barrels of uranium (in various degrees of enrichment) could be safely stored in a room without running a risk of a criticality accident? Feynman himself relates the problem like this in his famous bit, “Los Alamos from Below” (reproduced in Surely You’re Joking, Mr. Feynman):

It turned out that the army had realized how much stuff we needed to make a bomb — twenty kilograms or whatever it was — and they realized that this much material, purified, would never be in the plant, so there was no danger. But they did not know that the neutrons were enormously more effective when they are slowed down in water. In water it takes less than a tenth — no, a hundredth — as much material to make a reaction that makes radioactivity. It kills people around and so on. It was very dangerous, and they had not paid any attention to the safety at all.

In Feynman’s account, he more or less walks in and figures out what the problems were and how to fix them. The story is about ignorance — in particular systemic ignorance due to secrecy — and Feynman’s attempts to cut through it.

Feynman's diagrammatic sketch of storage of barrels of uranium at Oak Ridge, prepared for his "Safety Report." Source: Galison 1998, p. 408.

Feynman’s diagrammatic sketch of storage of barrels of uranium at Oak Ridge, prepared for his “Safety Report.” Source: Galison 1998, p. 408.

Galison’s account is more technical. Feynman told them that pretty much any amount of unenriched uranium could be stored safely in the facility, but that 5% enriched and 50% enriched had to be handled fairly carefully. 50% enriched uranium in water, for example, would dangerous at a mere 350 grams of material unless there was a neutron absorbing material (cadmium) present. Feynman developed a series of safety recommendations for all grades of enrichments, and had to use reasonable safety margins to make up for potential errors in the calculations. He became the “point man” for safety questions involving fissionable materials, and developed (as Galison puts it) “visualizable” methods for answering basic (but important) questions about hypothetical systems (e.g. for “Gunk storage tanks,” whether they had to be coated with cadmium or not). His methods, Feynman himself emphasizes, were “only approximate, as accuracy has been sacrificed to speed and simplicity in calculation” — the kind of computational “short cut” that was both needed for the practical requirements, but also was common to Feynman’s general approach to physics. Galison concludes the section thus:

The admixture of approximation methods, neutron diffusion, nuclear cross sections, floods, fires and wooden walls marked Feynman’s correspondence with the Oak Ridge engineers. From April of 1944 to September 1945, whatever else Feynman was doing, he was also deeply enmeshed in the barely-existing field of nuclear engineering. Out of this interaction came characteristic rules and modular reasoning: visualizable, approximate, from-the-ground-up calculations applied to neutrons, pans, sheds and sludge. Visionary statements reinterpreting established laws of physics ceded to the exigencies of living in a world he had to reach outside the home culture of theoretical physics as he knew it before the war. Now a billion dollar plant was churning out U-235, and only a calculation stood between thousands of workers and nuclear disaster.

Which is a lot more serious-sounding that Feynman’s own somewhat jokey accounts of the work. In the latter part of the article, Galison connects all of these methods for thinking — and sometimes even the specific problems — with Feynman’s postwar work, showing the influence of his time at Los Alamos.

Diagram of neutron fluctuations from a report by F. de Hoffmann, R.P. Feynman, and R. Serber. Galison notes: "Significantly, Feynman and his collaborators captured the situation in a spacetime diagram drawn with time in the vertical direction and space horizontal. Such an image must be kept in mind when viewing Feynman's early postwar spacetime 'Feynman diagrams,' where again particles are absorbed, emit other particles, and scatter as reckoned by a concatenation of independent algebraic rules." Galison 1998, 405-406.

Diagram of neutron fluctuations from a report by F. de Hoffmann, R.P. Feynman, and R. Serber. Galison notes: “Significantly, Feynman and his collaborators captured the situation in a spacetime diagram drawn with time in the vertical direction and space horizontal. Such an image must be kept in mind when viewing Feynman’s early postwar spacetime ‘Feynman diagrams,’ where again particles are absorbed, emit other particles, and scatter as reckoned by a concatenation of independent algebraic rules.” Galison 1998, 405-406.

Feynman stayed at Los Alamos until the fall of 1946, when he relocated to Cornell University. He never worked on weapons again, but he never took a particularly strong stand on it. What did Feynman think about nuclear weapons, and his role in making them? There is some evidence in his private correspondence, much of which was published not too long ago, but it is scant. Most of his responses to inquiries were along the lines of “we feared the Nazis would get one first.”That’s it. No comment on their use at all, or the end of the war, or any of the other common responses from Los Alamos veterans. When asked in the 1970s about his thoughts on nuclear weapons in general, he demurred: “Problems about the atomic bomb and the future are much more complicated and I cannot make any short  statement to summarize my beliefs here.”

Feynman gave an interview in 1959 where he was asked directly about the bomb. His response was a little lengthier then, but still said very little:

Now, with regard to our own things as human beings, naturally—I myself, for example—worked on the bomb during the war. Now how do I feel about that? I have a philosophy that it doesn’t do any good to go and make regrets about what you did before but to try to remember how you made the decision at the time. …if the scientists in Germany could have developed this thing, then we would be helpless, and I think it would be the end of the civilization at that time. I don’t know how long the civilization is going to last anyway. So the main reason why I did work on it at the time was because I was afraid that the Germans would do it first, and I felt a responsibility to society to develop this thing to maintain our position in the war.

This, of course, ignores the question of “so why did you continue when the Germans were known not to have made much progress?” and much more.

Charles Critchfield, Richard Feynman, J. Robert Oppenheimer, and an unidentified scientist, at Los Alamos. Source: Emilio Segrè Visual Archives, via Los Alamos.

Charles Critchfield, Richard Feynman, J. Robert Oppenheimer, and an unidentified scientist, at Los Alamos. Source: Emilio Segrè Visual Archives, via Los Alamos.

During the interview, Feynman was asked, point blank, whether he worked on any secret projects. Feynman said no, and that this was “out of choice.” Pushed further, he elaborated:

I don’t want to [do secret work] because I want to do scientific research—that is, to find out more about how the world works. And that is not secret; that work is not secret. There’s no secrecy associated with it. The things that are secret are engineering developments which I am not so interested in, except when the pressure of war, or something else like that, makes me work on it. … Yes, I am definitely anti-working in secret projects. … I don’t think things should be secret, the people developing this. It seems to me very difficult for citizens to make a decision as to what’s going on when you can’t say what you’re doing. And the whole idea of democracy, it seems to me, was that the public, where the power is supposed to lie, should be informed. And when there’s secrecy, it’s not informed. Now, that’s a naive point of view, because if there weren’t secrecy, there’d be the Russians who would find out about it. On the other hand, there’s some awfully funny things that are secret. It becomes secret that we know what the Russians are keeping secret from us, for instance, or something like that. It seems to me that things go too far in the secrecy.

After that point in the interview, he steered away from political opinions, explaining that he had strong ones, but he didn’t think they were any more valuable than anyone else’s opinions.

There were those, of course, who did try to recruit Feynman for military work. John Wheeler, his doctoral advisor at Princeton, and the man who had roped him into Los Alamos in the first place, appealed to him strongly to join the Princeton work on the hydrogen bomb (Matterhorn) in late March 1951. Wheeler had heard the Feynman was trying to spend his sabbatical in Brazil, but Wheeler thought the chance of global war was “at least 40%,” and that Feynman’s talents might be better spent helping the country. It was a long, emotional letter, albeit a variation on one that Wheeler sent to many other scientists as well. Wheeler tried to win him (and others) with flattery as well, telling Feynman that “You would make percentage-wise more difference there than anywhere else in the national picture.” In response to Wheeler’s long, many-pointed letter, Feynman simply responded that he didn’t want to make any commitments until he found out whether the Brazil idea would work out. End of story. Nothing specific about the hydrogen bomb one way or the other.

High resolution detail of Feynman's Los Alamos security badge photograph. A this resolution you can see a lot more strain on his face than the one I posted awhile back. Source: Los Alamos National Laboratory Archives.

High-resolution detail of Feynman’s Los Alamos security badge photograph. At this resolution you can see potentially more strain on his face than the one I posted awhile back. Source: Los Alamos National Laboratory Archives.

What should we make of this? Feynman is a complicated man. Much more complicated than the zany stories let on — and I suspect the stories themselves were some kind of defense mechanism. As Feynman’s friend Murray Gell-Mann said at Feynman’s memorial service, Feynman “surrounded himself with a cloud of myth, and he spent a great deal of time and energy generating anecdotes about himself.” They were stories “in which he had to come out, if possible, looking smarter than anyone else.” He was not a moralizer, though. His work on the bomb fit into his stories only as a context. He no doubt drew many lessons from his work on nuclear weapons, and he no doubt had many opinions about them in the Cold War, but he kept them, it seems, much to himself.

Oppenheimer famously said that, “In some sort of crude sense, which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin…” Perhaps Feynman agreed — perhaps no more humor could be wrung out of the bomb after Hiroshima and Nagasaki. Maybe it’s harder to write a zany story about the hydrogen bomb. And maybe he was just truly not interested in them from a technical standpoint, or, as he said in 1959, just didn’t think his opinions on these matters, one way or another, were worth a damn, going against the notion held by many of his contemporaries that those who made the bomb had a special knowledge and a special responsibility. To me, he’s still something of an enigma, just one that wrapped himself in jokes, rather than riddles.