Monday, October 27, 2008
Today, October 27, 2008, marks the 40th anniversary of the death of Lise Meitner. She became in her lifetime, and still ranks as, one of Germany's greatest physicists...better said, one of the world's great physicists. She played a key role, perhaps the pivotal role, in the discovery of nuclear fission in 1938 and 1939, and in so doing became known for a time as the Mother of the Nuclear Age and, sometimes, the Mother of the Atomic Bomb. She was asked to come to the U.S. and work on the Manhattan Project, but she refused because she considered it a perversion of her science. She died in 1968 in Cambridge, England, just a few days short of her 90th birthday.
Meitner was born in Vienna on either November 7 or November 17, 1878 -- no one seems sure. She was ethnically Jewish but was baptized a protestant in 1908 and remained one throughout the rest of her life. In 1906 she became only the second woman to receive a doctorate in physics from the University 0f Vienna. There was little future for a woman physicist in Austria, so in 1907 she departed for Berlin, then the vital center of German physics. She began by attending lectures by, and then serving as assistant to, the great Max Planck, but was soon introduced to a young chemist by the name of Otto Hahn. They hit if off and began a collaboration in radioactivity, she doing the physics and he doing the chemistry, that endured off and on until July 1938 when she was forced to flee from Nazi Germany. Even then it continued in correspondence and one secret meeting in Copenhagen until January 1939.
What is remarkable to an observer in the current age, looking back upon the dark ages of gender equality, is how irresistibly Meitner seems to have bubbled to the surface of the physics community in Berlin and indeed in all Europe notwithstanding the pervasive prejudice of most of the men in that community against women in science. She endured professional and personal obstacles to her career of the most absurd and inexcusable variety: for example, when she began working with Hahn she was required by Emil Fischer, the director of the Kaiser Wilhelm Institute for Chemistry, to work only in a basement room with a separate entrance, no toilet facilities and no access to the laboratories upstairs. Worse yet, for many years she had to work without pay and without academic status because the Prussian university and research institute system had no places for women. This photo of Lise at the Summer Physics Colloquium at Niels Bohr's Physics Institute in Copenhagen in 1935 illustrates what she was up against (Max Born and Werner Heisenberg are with her in the front row):
Although her official academic status was lowly, Meitner's brilliance was evidently widely recognized and she inexorably became one of the elite physicists in Europe. Just consider the list of some of the physicists with whom she had professional and sometimes personal relationships: Max Planck, Albert Einstein, Max von Laue, Wolfgang Pauli, James Franck, Neils Bohr, Max Born, Erwin Schroedinger, Werner Heisenberg, James Chadwick, Enrico Fermi, Irene Curie.
The embedded backwardness of turn-of-the-century Prussian civilization gradually gave way through the 20's to more egalitarian values and in 1926 Lise became the first woman physics professor in Germany. She was by then so advanced in her standing in the scientific community that the requirement of an Habilitation thesis was waived -- she had already written and published more than 40 papers.
The Deutsches Museum in Munich is thought by many to be the leading science museum in Germany, and maybe it is. It has, however, like many German institutions, had some difficulty coming to terms with its own history. The museum's treatment of Lise Meitner is illustrative.
What you see in the photo above is an exhibit to be found today in the Chemistry section of the Deutsches Museum. It is captioned:
The Experimental Apparatus with which the Team of Otto Hahn, Lise Meitner and Fritz Strassmann Discovered Nuclear Fission in 1938
As it happens, the Deutsches Museum is even now in the process of producing a scholarly history of itself during the Nazi era. This would be an excellent occasion for the museum to make amends for its past mistreatment of Lise Meitner and bring its website properly up to date.
The end result of the combined experimental and theoretical efforts of Lise Meitner and Otto Hahn from 1934 through early 1939 was to split the atom, discover and describe the process of nuclear fission and launch the nuclear age. It counts as one of mankind's great scientific achievements and would richly deserve the ultimate prize for achievements in physics and chemistry. The Nobel Prize would count as that ultimate prize if only it were what the public thinks it is, namely, a prize awarded by a qualified panel of certified experts adjudicating the merits of scientific work in an atmosphere free of scientific, political, racial and gender prejudice and pressure. This definition, unfortunately, does not apply to the Nobel Prize.
The Nobel Prizes for Physics and Chemistry (and perhaps for all other fields as well) are dispensed by a small panel of Swedish persons meeting behind closed doors who may or may not be qualified to judge what they are judging and who often bring to bear upon their judgments all imaginable forms of prejudice, incompetence, whimsy and small-mindedness. To take just one example -- Albert Einstein was nominated ten times, all in vain, for the Nobel Prize in Physics before finally receiving it on the eleventh go-around in 1921 -- sixteen years after his discovery of special relativity in 1905 and six years after his discovery of general relativity in 1915. Almost every man, woman and child on the planet knew by the mid-teens that Einstein was one of the scientific giants of human history. Though few understood it, the language of relativity had become part of everyday conversation in all corners of the globe. After the solar eclipse observations by Eddington in 1919, confirming that light bends going around the sun, Einstein was practically deified. Nevertheless, it took the five Swedes on the physics committee until 1921 to catch up. One of the reasons given by one of the five, by the way, was that relativity was about philosophy not science! Five Swedes off the street locked in a room with a bottle of acquavit could have done better.
With this in mind it will come as no surprise to the reader that Lise Meitner and Otto Hahn did not share a Nobel Prize. On the contrary, Otto Hahn alone was awarded the 1944 Nobel Prize in Chemistry "in reward for his discovery of the fission heavy atomic nuclei." (From the Presentation Speech of Professor A. Westgren, Chairman of the Nobel Committee for Chemistry, given on December 10, 1944.) Hahn was not permitted to leave Germany in 1944 to receive the prize and so did not actually receive it until 1946.
Beginning in the early 1930's Enrico Fermi in Italy had been experimenting with the bombardment of nuclei of various elements on the periodic table with neutrons. In 1934 Lise Meitner wished to undertake a project at her institute in Berlin to replicate, clarify and extend Fermi's work. She needed the assistance of chemist so invited Otto Hahn to join her in the project, and he agreed to do so. Over the space of the next four years the two of them, with the added participation of an analytical chemist named Fritz Strassmann, carried out a series of experiments in which they bombarded nuclei, uranium nuclei in particular, with neutrons, using the devices now exhibited by the Deutsches Museum. Meitner inspired the project and according to Strassmann was its intellectual leader.
The project and the experimental neutron bombardment work of Meitner, Hahn and Strassmann continued into the first half of 1938. As we have seen, Meitner was forced to flee for her safety in July of 1938. That left Hahn and Strassmann behind in Berlin to carry on the work, using, of course, the devices and instruments Meitner necessarily left behind when she fled. From her new post in Sweden, however, Meitner continued to direct the experimental work of Hahn and Strassmann through correspondence. In our present era of instant Internet communication it comes as a bit of a surprise surprise to learn how fast and efficient was the postal service in Germany and Sweden in 1938. Letters posted in Berlin were often delivered in Stockholm within one or two days. Through written correspondence Lise could thus closely direct and follow the experiments in Berlin, and Otto could quickly report his results to her.
In addition to their correspondence, Meitner and Hahn had one secret meeting in Copenhagen in November 1938. He went there to deliver a lecture and she quietly came over from Stockholm. They met in private and did not disclose the meeting to their friends. He told her of some strange results he was getting as the result of neutron bombardment of uranium, using increasingly sophisticated and exact methods. The results were such that neither of them could believe in their accuracy, and Meitner instructed him to go back to Berlin and do it over again with even greater care. In hindsight we can recognize that the results in question, which troubled them so, showed that the neutron bombardments were splitting the uranium nuclei.
Hahn and Strassmann continued this line of experimentation for the remainder of November and on into December. Hahn bore down hard and his methods became increasingly clever and refined. He was a talented chemist and he knew they were on the verge of an exciting discovery (without knowing what it was), he was under constant pressure from Meitner and they both knew that others, notably Curie and Savitch in Paris, were working along similar lines. Meitner and Hahn naturally wanted to get there first. Scientific research, it turns out, is a highly competitive field in which the players are interested not only in the discovery of truth but also in winning the race and enjoying the glory and rewards which come to the victor. Ego vies with intellect for primacy in scientific work.
As the experimental work continued into December it resolved itself into a puzzle over the persistent presence of barium in the dish containing the substances resulting from the neutron bombardment of uranium. Hahn, Meitner and everyone else working in the field expected the neutron bombarment of uranium to result in neutrons being captured in the uranium nucleus, thus adding to its weight and resulting in a new and heavier element, a so-called transuranium element. In this schema barium had no place. Barium (element 56) is a lighter not a heavier element than uranium (element 92). Common sense tells you that you cannot add weight to uranium and get a lighter element as a result. You must necessarily get a heavier element. Where, then, was all this barium coming from?
Hahn and Strassmann knew that some of the barium was coming from the barium chloride they themselves had introduced into the mixture to serve as a carrier agent in aid of the experiment. This was an accepted chemistry technique. The two chemists did not think for a moment that any of their barium was resulting from the neutron bombardment process. To the contrary, they believed that the resulting substance must some kind of isotope of radium. Therefore they concentrated on the attempt to separate out the "resulting substance" from the barium carrier. Hahn and Strassmann tried a series of ingenious and refined methods of accomplishing this separation, but every one of them failed and they were left time and again with a bowl full of barium. It is easy for the observer today to say, "So be it. Your bombardment of uranium has evidently produced barium. Now go to work and figure out why." But this was not Hahn's mind-set. He believed, as did most every other chemist and physicist on earth, that the laws of physics do not permit barium to result from neutron bombardment of uranium. It simply cannot happen. This was why Lise told him in Copenhagen in November to go home and try it again. He did, and the result was the same.
This left Hahn in a dilemma: the facts of the experiments told him one thing, but his mind told him another. Should he publish the results of his experiments, even though he was not sure of them and could not explain them, or should he wait until Meitner could get up to speed and provide an explanation?
The timing of events now becomes critical. On Monday, December 19,Hahn wrote to Meitner describing his results: "Our radium isotopes act like barium...Perhaps you can suggest some fantastic explanation. We understand that it really can't break up into barium.... So try to think of some other possibility." She received that letter in Stockholm on Wednesday, December 21, and replied immediately saying it was "difficult to accept....but not impossible." She also informed Hahn that she would be leaving on Friday, December 23, for the village of Kungalv in the Swedish countryside for a week's vacation. She did not in that letter attempt an explanation of the barium.
On the same day that Meitner received and replied to his letter (Wednesday, December 21), Hahn and Strassmann completed one final test -- they subjected the mystery substance to a process of beta decay, which produced the element lanthanum rather than actinium, which in turn meant that the substance in question was not a radium isotope but was barium. Otto decided at this point to publish, without waiting for further input from Lise. He thereupon contacted Paul Rosebaud at Der Naturwissenschaften and told him he had an important paper for the next edition. Rosebaud bumped another article to make space and offered to print Hahn's article in the January 6, 1939, edition of the journal.
This was a fateful decision by Hahn at a critical moment in the history of science. On the one hand, he was really not ready in his own mind to accept the results of the experiments, i.e., that he had produced barium. He had doubts. On the other hand, he knew his results were important, or might be, however strange, and he wanted to get into print before Curie and Savitch did so. He was evidently not willing to wait until Lise could come aboard and provide the needed explanation. His haste to publish and his taste for glory overcame his uncertainty about his results and his loyalty to Lise. We can mark this moment as the point at which Hahn decided to become a Bonze (German for "big man").
Otto wrote to Meitner again that evening (Wednesday), lamely asserting (knowing he was about to push off without her), "We cannot hush up the results even though they may be absurd in physical terms. You can see that you will be performing a good deed [if you can provide an explanation]." "A good deed?" What kind of condescending expression was that? He promised to send her a manuscript copy of the article he was about to write.
Hahn completed his write up the next day, Thursday, December 22, and delivered it personally to Rosebaud that evening. The article, as we know, bore the names of Hahn and Strassmann but not of Meitner. Later that evening Hahn mailed a copy to Meitner, addressed to her in Stockholm because he had not yet seen her letter advising him she was leaving for Kungalv.
In retrospect it is fair to criticize Hahn's rush to publish. The article was, after all, not truly ready for publication (see below). Did he have any reason to think Curie and Savitch were really so close behind? Was it not in fact the beginning of the Christmas holiday season when most everyone can be expected to slack off in any event? Did he not have a moral obligation to Lise, who had been driven out of her home and her laboratory by the Nazi's, and who had in fact inspired and directed the project which had led to the barium results, to wait at least a few days for her to receive his article and work out the theoretical explanation of what had happened? The addition of such an explanation would have made the paper far more professional and scholarly. These questions continue to overhang Hahn's legacy.
Let us consider, then, the Hahn-Strassmann article which was published by Rosebaud on January 6, 1939. On the face of it it is an awkward, incomplete and hesitant piece of work. Hahn pulled his punches and stepped back from the conclusions that were implied by the experimental results. He apparently lacked the courage of his own convictions, making his rush to publish look all the more nakedly opportunistic.
The article begins with the title,
"Ueber den Nachweis und das Verhalten der bei der Bestrahlung des Urans mittels Neutronen entstehenden Erdalkalimetalle"
("On the Detection and Behavior of Alkaline Earth Elements Derived from the Neutron-Irradiation of Uranium").
It should better have read "Barium" rather than "Alkaline Earth Elements." The entire course of experiment had been about the baffling presence of barium. Why not say as much? Bear in mind he later received a Nobel Prize precisely because he had produced barium.
The article then proceeds in a hesitant, subjunctive mood: "we ought to...," "we should...," "there could be...," and weakest of all, "we cannot bring ourselves...to take such a drastic step." The facts reported in the article point squarely to barium, i.e., to the splitting of the uranium nucleus, but Hahn lacked sufficient confidence (or courage) to say it. The article cries out for the theoretical explanation that Lise Meitner could have given.
The article concludes on this limpid note:
Als Chemiker muessten wir aus den kurz dargelegtenVersuchen das oben gebrachte Schema eigentlich unbenennen und statt Ra, Ac, Th die Symbole Ba, La, Ce einsetzen. Als der Physik in gewisser Weise nahestehende “Kernchemiker” koennen wir uns zu diesem, allen bisherigen Erfahrungen der Kernphysik widersprechenden, Sprung noch nicht entschliessen. Es koennten doch noch vielleicht eine Reihe selstsamer Zufaelle unsere Ergebnisse vorgetaeuscht haben.Believe it or not this cautious article, this blatant hedging of his bet, this steadfast refusal to say, "we have split the atom," won the Nobel Prize for Hahn. Other factors may have entered in, but this was the springboard to the prize.
As chemists we should restate the above-mentioned scheme resulting from our briefly-described experiment and instead of Ra [radium], Ac[actinium], Th[thorium] insert the symbols Ba [barium], La [lanthanum], Ce[cerium]. As “nuclear chemists” working close to the field of physics we are not ready to take this step, which contradicts all previous experience of nuclear physics. It could perhaps be that an unusual series of coincidences has falsified our results.
The explanation Hahn craved and could not himself give was in fact given by Lise Meitner and her nephew Otto Robert Frisch 2 days after Hahn completed and submitted his article. Meitner and Frisch met in Kungalv for their Christmas holiday week, and on the morning of December 24, Christmas eve day, began to discuss Otto Hahn's letter of December 19. They had not yet even received and read his letter of December 21 or the manuscript copy of his article. The December 19 letter sufficed, however, to show Meitner and Frisch that Hahn had apparently split a uranium nucleus.
On that December 24 morning, in a scene that might have come out of a Hollywood movie, Frisch put on his new cross-country skis and Lise put on her hiking boots and the two of them set out on a tour through the snowy Kungalv countryside. As they progressed along the trail they tried to make sense of what Hahn had reported. How was it possible to form barium out of uranium? As their conversation gained momentum their tour lost momentum and they sat down on a log along the trail. Lise pulled out some scraps of paper from her bag and they began to calculate and draw diagrams.
In a short time the two of them had taken a giant step: using the metaphor proposed by Niels Bohr which suggests that an atomic nucleus is like a drop of water they asked, what if that drop should pull or be pulled apart into two separate drops? It happens easily with water when shaken. Could it happen to a nucleus when hit and de-stabilized by a neutron? Suppose it did and the two drops were pushed apart by the mutual repulsion of their respective collections of protons. Frisch, a better draftsman than Meitner, diagrammed how it might look. They realized, however, that it would take enormous energy to push the fragments apart, so Meitner, a better calculator than Frisch, began to calculate. She concluded that it would take 200 million electron volts to push the two nuclear fragments apart. Now where might that energy come from? Was such energy available in the nucleus? Meitner remembered some earlier numbers concerning the mass defects of nuclei and calculated that when a nucleus splits in two it loses one-fifth the mass of a proton. Then in a beautiful application of Einstein's equation E = mc² she calculated that loss of the mass of one-fifth of a proton would generate approximately 200 million electron volts of energy, just enough to push the two drops of the nucleus apart. It all fit together. It must have been a thrilling moment for the two of them.
Meitner and Frisch thus had derived the theoretical explanation of Hahn's and Strassmann's experimental results precisely three days after Meitner received Hahn's letter of December 19 and two days following the submission of Hahn's article to Der Naturwissenschaften. As they sat in Kungalv continuing to discuss their conclusions they did not know that Hahn's article was due to be published on January 6. Unlike Hahn, they did not rush to publish.
Among other reasons, Frisch wanted first to take their results back to Copenhagen and discuss them with Niels Bohr. He did so on January 3. In a scene one would die to have witnessed, Bohr slapped his forehead and exclaimed, "Oh what idiots we have all been! Oh but this is wonderful! This is just as it must be!" On that same day Meitner received the revised proofs of Hahn's article and wrote to him acknowledging that she was now certain that he had split the uranium nucleus and produced barium. Three days later, on Friday, January 6, 1939, Meitner and Frisch worked out the outline of their paper on the telephone and Frisch thereupon drafted it. Ironically, this draft of the Meitner-Frisch paper explaining the result was written on the same day that the Hahn-Strassmann paper was published reporting the result. So close yet so far.
In the course of the next week, the week beginning January 9, Frisch constructed and conducted an experiment designed to test the conclusions he and Meitner had reached by searching for telltale nuclear fragments that would indicate the nucleus had split. He began his measurements on that Friday, January 13. The results showed the anticipated fragments and confirmed the theoretical model he and Meitner had developed.
In the immediate aftermath of his experiment Frisch had a chance conversation with one William A. Arnold who was a visiting biologist from the Hopkins Marine Station in Pacific Grove, California. Frisch asked Arnold what biologists call it when cells divide. Arnold said "binary fission." Frisch dropped the "binary" and adopted the "fission," thus arriving at the name by which the process of splitting the nucleus has ever since been known, "nuclear fission." Thanks to a Californian.
Meitner and Frisch now had a theory, experimental confirmation of the theory and a new name for the process explained by the theory. Unlike Hahn they had not precipitously rushed to publish, and as a result they had a more satisfying article to present. Meitner and Frisch again conferred by telephone and agreed on the final form of their paper. In addition, Frisch separately wrote up the results of his experiment. Frisch finished the drafting of both papers on Monday, January 16, and mailed them to the journal Nature in London the following morning. The Meitner-Frisch paper, "Disintegration of Uranium by Neutrons: a New Type of Nuclear Reaction," wherein the name "nuclear fission" appeared for the first time in print, was published in Nature on February 11, 1939, just 36 days after the publication of Hahn's and Strassmann's paper.
I have spelled out these dates in order to illustrate the essential unity of the combined work of Meitner, Frisch, Hahn and Strassmann. They did their work in same time frame and would have done it in the same location had not the Nazis driven Meitner out of Berlin. All of their efforts were directed at the same subject and their work was complementary. Hahn and Strassmann produced the physical results in the laboratory but could not explain them. Indeed, they doubted them. Meitner and Frisch took over the results and created the theoretical framework which explained them and in so doing laid the foundation for the nuclear age. Had Hahn acted with a little bit more courtesy, consideration and collegiality their combined work would have been presented and published in a unified article and science would have been the better for it. Instead, Hahn jumped the gun and in retrospect made himself seem crassly opportunistic. He acted not in the interests of science, but in his own interest.
From this complex mix of experimental and theoretical work by four German scientists five errant Swedes plucked out Hahn alone for recognition and gave him the Nobel Prize in Chemistry. From the date his paper was prematurely published, January 6, 1939, until the end of his life Hahn played the Bonze and sought recognition to the exclusion of his three colleagues, especially of Lise Meitner. If the five Swedes wished to honor him alone he was fine with that. He did, in fairness, give a nod, however minimal, in Meitner's direction in his Nobel Lecture of December 13, 1946, but later on when, as a laureate, he was entitled to participate in the Nobel Prize process he did not do what a man with better character would have done -- press for an award of the physics prize to Lise.
(The records of the Nobel Prize deliberations by the Royal Swedish Academy of Science are kept closed for 50 years following an award. The records of the award to Hahn were opened to scholars in 1996 and were the subject of an extensive article reviewing the process by Elizabeth Crawford, Ruth Lewin Sime and Mark Walker, "A Nobel Tale of Postwar Injustice," Physics Today, Volume 50, Issue 9, 26 - 32 (1997). )
Looking back now 40 years after her death, Lise Meitner's reputation has grown and continues to grow, while Hahn's reputation remains tarnished by the one-sided award of the Nobel Prize and his opportunistic and selfish conduct before and after the award. Unjust though the denial of the Nobel Prize was, Lise Meitner has been honored in many, many other ways: numerous German schools and streets bear her name; element 109 in the periodic table is called "meitnerium;" both Germany and Austria have issued Lise Meitner stamps;
a crater on Venus has been named for her;
likewise a crater on the moon; she received the Max Planck Medal (with Hahn), the Otto Hahn Prize (!) and the Enrico Fermi Award (with Hahn and Strassmann); and in 1946, the year Hahn received the Nobel Prize, she was named Woman of the Year in the U.S. by the Women's National Press Club and was seated next to Harry S Truman, President of the United States, at the award banquet.
Thursday, October 16, 2008
I knew the course the debate would take as soon as I saw the ties the candidates wore.
Obama wore the same tie he wore in his acceptance speech in Denver. It does not suit him. He doesn't do red. It was a poor choice. His performance was likewise poor, at least during the first half of the debate. Fortunately, he eventually settled down and slipped into his professorial mode, solid but somewhat dull. Playing safe, making no serious mistakes, taking few risks and reaching only one high point -- his moving and courageous statement about abortion.
McCain, on the other hand, who desperately needs some color, but apparently doesn't know it, had the bad judgment to show up in a colorless blue-gray striped banker's tie -- well-tied, I admit, but unimportant and unsuited to the occasion. McCain needed to shine, but did not. He stayed on his message, such as it is, aimed at his hard core conservative constituency. He stayed in character, grim though it is, as a humorless, up-tight, bad-tempered, grouchy and mean SOB. After the selection of Sarah Palin it is almost pointless to say anything more about McCain's poor judgment, but it surpasses all understanding that he continues to swing and miss. For example:
- Hammering on Joe the Plumber, as though anyone, including Joe himself, gives a damn. Joe admitted later that he is not even registered to vote. And the press discovered Joe is not Joe, is not a licensed plumber and is in fact a numbskull.
- Absurdly comparing Obama, once again, to Herbert Hoover.
- Pointlessly citing nuclear submarines as somehow relevant to ending our dependence on foreign oil.
- Asserting he has no litmus test for choosing Supreme Court judges, but in the next breath admitting that he would consider a judge who was favorable to Roe v. Wade as unqualified.
- Continuing to talk about Bill Ayers even though the overwhelming evidence of the public opinion polls shows that it is hurting him not helping him.
- Artlessly using the phrase "I am not President Bush," apparently not remembering, or remembering but not understanding, that this is a derivative of the deadly quip Lloyd Bentsen used against the witless Dan Quayle in their vice-presidential debate: "You're no Jack Kennedy." The phrase works to diminish not enhance the person targeted by it.
- Failing to maintain his composure when Obama was speaking by allowing himself to be shown on camera rolling his eyes, contorting his face and looking like a jerk not entirely in control of himself.
- To his credit, slight though it is, he restrained himself from mentioning Pastor Wright. That was the high point of his performance.
Hold your breath.
Monday, October 13, 2008
I’ve read Obama’s books, and they are first-rate. He is that rara avis, the politician who writes his own books. Imagine....
But having a first-class temperament and a first-class intellect, President Obama will (I pray, secularly) surely understand that traditional left-politics aren’t going to get us out of this pit we’ve dug for ourselves. If he raises taxes and throws up tariff walls and opens the coffers of the DNC to bribe-money from the special interest groups against whom he has (somewhat disingenuously) railed during the campaign trail, then he will almost certainly reap a whirlwind that will make Katrina look like a balmy summer zephyr.
Obama has in him—I think, despite his sometimes airy-fairy “We are the people we have been waiting for” silly rhetoric—the potential to be a good, perhaps even great leader. He is, it seems clear enough, what the historical moment seems to be calling for.