Here is the abstract of the Oppenheimer-Snyder paper, with some technical details omitted:
When all thermonuclear sources of energy are exhausted, a sufficiently heavy star will collapse. In the present paper we study the solutions of the gravitational field equations which describe this process. The radius of the star approaches asymptotically its gravitational radius. Light from the surface of the star is progressively reddened, and can escape over a progressively narrower range of angles. The total time of collapse for an observer comoving with the stellar matter is finite, and for typical stellar masses, of the order of a day. An external observer sees the star asymptotically shrinking to its gravitational radius.
The paper is written in the same unsensational style as the abstract. Oppenheimer and Snyder did not conclude their paper by saying, “It has not escaped our notice that these collapsed objects may play a fundamental role in the dynamics and evolution of the universe,” as Francis Crick and James Watson similarly said fourteen years later at the conclusion of a similar paper.
Black holes are familiar objects to modern astronomers. We know that they exist all over our own galaxy and in the central regions of other galaxies. We see them as sources of X-ray radiation emitted by gas as it falls into them and is heated to temperatures of millions of degrees by their overwhelmingly strong gravity. At the center of our own galaxy we see a black hole weighing as much as a few million suns, with massive stars orbiting around it like moths around the flame of a candle. Black holes are not rare, and they are not an accidental embellishment of our universe. They are a fundamental driving force of its evolution. They are a dominant source of energy. For every ounce of matter consumed, they yield more than ten times as much energy as the nuclear reactions of fusion and fission that cause our sun to shine and our hydrogen bombs to explode. To a modern astronomer, a universe without black holes makes no sense.
To a modern physicist, black holes are also objects of transcendent beauty. They are the only places in the universe where Einstein’s theory of general relativity shows its full power and glory. Here, and nowhere else, space and time lose their individuality and merge together into a sharply curved four-dimensional structure precisely delineated by Einstein’s equations. If you imagine yourself falling into a black hole, your local perception of space and time will be detached from the space and time of an observer watching you from outside. While you see yourself falling smoothly into the hole without any deceleration, the outside observer sees you coming to a halt at the horizon of the hole and remaining forever in a state of permanent free fall. Permanent free fall is a situation that can only exist by virtue of the distortion of space and time predicted by Einstein’s theory.
This is the central paradox of Robert’s life as a scientist. His theoretical prediction of black holes was by far his greatest scientific achievement, fundamental to the modern development of relativistic astrophysics, and yet he never showed the slightest interest in following it up. So far as I can tell, he never wanted to know whether black holes actually existed. I tried sometimes to talk with him about the possibilities for observing black holes and testing his theory. He impatiently changed the subject and talked about something else. I also met Hartland Snyder from time to time at the Brookhaven National Laboratory where he spent most of his life. He too was uninterested in black holes. He had a distinguished career as a designer of accelerators.
We now know that the Oppenheimer-Snyder calculation is correct and describes what happens to massive stars at the end of their lives. It explains why black holes are abundant, and incidentally confirms the truth of Einstein’s theory of general relativity. And still, Robert was not interested. The question remains: How could he have been blind to the importance of his greatest discovery? I have no answer to this question. It remains as a paradox in the life of a genius. Perhaps if the Oppenheimer-Snyder calculation had not happened to coincide in time with the Bohr-Wheeler theory of nuclear fission and with the outbreak of World War II, Robert would have paid more attention to it.
2. Oppenheimer as Administrator
I do not have much firsthand experience of Robert as administrator. My chief witness here is Lansing Hammond, a friend of mine who worked for the Harkness Foundation. In 1947, when I came to the United States from England, Hammond was in charge of programs and placements for the Commonwealth Fund Fellows. In those days, Commonwealth Fund Fellows were young Brits who came to America to study at American universities with fund support. I was one of them, and Hammond made the arrangements for me to come first to Cornell University and then to the Institute for Advanced Study at Princeton. Thirty years later, in 1979, Hammond wrote me a letter about Oppenheimer. I replied to his letter, “It is sad that in the official memorials to Robert there was never anything said or written that gave such a fine impression of Robert in action. I hope there may still be a chance sometime to make your story public.” Hammond died a few years later. Here is his story:
I’d just received copies of the application papers—sixty of them—for the 1949 awards. Among them were four or five in that, to me, shadowy borderline realm between theoretical physics and mathematics. I was in Princeton for a couple of days, asking for help on all sides. Summoning all the courage I could muster, I made an appointment to see Robert Oppenheimer the next morning, leaving the relevant papers with his secretary. I was greeted graciously, asked just enough questions about my academic background to put me at ease. One early comment amazed me: “You got your doctorate at Yale in 18th century English literature—Age of Johnson. Was Tinker or Pottle your supervisor?” How did he know that?
Then we got down to business. In less than ten minutes I had enough facts to support trying to persuade candidate Z that Berkeley was more likely to satisfy his particular interests than Harvard; he would fare well at the Institute; would be welcome; but Berkeley was really the best choice. I was scribbling notes as fast as I could; occasionally a proper name produced wrinkles on my forehead. Oppenheimer would flash me an understanding grin and spell out the name for me: “That may save you some time and trouble.”
As I was gathering up my papers, feeling I’d already taken up too much of the great man’s time, he asked gently: “If you have a few minutes you can spare, I’d be interested in looking at some of your applications in other fields, to see what this year’s group of young Britons are interested in pursuing over here?” I took him at his word, and was completely overwhelmed by what ensued: “Umm—indigenous American music—Roy Harris is just the person for him, he’ll take an interest in his program. Roy was at Stanford last year but he’s just moved to Peabody Teachers’ College in Nashville. Social psychology, he gives Michigan as first choice—Umm—he wants a general, overall experience. At Michigan he’s likely to be put on a team and would learn a lot about one aspect. I’d suggest looking into Vanderbilt; smaller numbers; he’d have a better opportunity of getting what he wants.” (The candidate was persuaded to try Vanderbilt for one term, with the option of transferring to Michigan if he wasn’t satisfied. He spent two years at Vanderbilt, with profit and enthusiasm.) “Symbolic logic, that’s Harvard, Princeton, Chicago or Berkeley; Let’s see where he wants to put the emphasis. Ha! Your field, 18th-century English Lit. Yale is an obvious choice, but don’t rule out Bate at Harvard, he’s a youngster but a person to be reckoned with.” (My field, and I’d not yet even heard of Bate, but I took pains, the next time I was in Cambridge, to meet and talk with him.) We spent at least an hour, thumbing through all of the sixty applications. Robert Oppenheimer knew what he was talking about. He pleaded ignorance about two or three esoteric programs. Every positive comment or recommendation was right on target. And so, when it finally came time to leave, I couldn’t resist saying that if I could only bribe him, once a year, to repeat what he’d just done, it would save me months of sweating. He really grinned at that. “That wouldn’t be fair to you, Dr. Hammond. It would take away the satisfaction and excitement of talking with lots of other people and finding out fo
r yourself.” I left, walking on air, head abuzz, most of my problems solved. Never before, never since have I talked with such a man. No suggestion of trying to impress. No need to. Robert Oppenheimer’s was just genuine interest in all fields of the intellect; a fantastically up-to-date knowledge of what was going on in US graduate schools and research centers; an intuitive understanding of where a given person with definite interests would best fit in; and taking pleasure in being of help to someone who badly needed it.
The Robert Oppenheimer that Hammond saw that morning in 1949 was the same Robert Oppenheimer who had mastered every detail of the bomb project at Los Alamos five years earlier, and had fitted the most appropriate task to each scientist and engineer in his army of subordinates. He was equally at home in the world of literature and the world of science, in the eighteenth century and the twentieth.
The year 1942 was the turning point in Robert’s life, when he suddenly changed from a left-wing academic intellectual to a practical and brilliantly successful administrator. When he accepted in 1942 the job of organizing the bomb laboratory at Los Alamos, it seemed to him natural and appropriate that he should work under the direct command of General Leslie R. Groves of the United States Army. Other leading scientists wanted to keep the laboratory under civilian control. Isidor Rabi of Columbia University was one of those most strongly opposed to working for the army. Robert wrote to Rabi in February 1943, explaining why he was willing to go with General Groves:
I made in Washington a strong and extremely painful attempt to have our project transferred to … a special committee established for that purpose. I did not get to first base.… I do not know whether the arrangements as now outlined will work, for that will take in the first instance the good will and cooperation of quite a few good physicists, but … I am willing to make a faithful effort to get things going. I think if I believed with you that this project was “the culmination of three centuries of physics,” I should take a different stand. To me it is primarily the development in time of war of a military weapon of some consequence. I do not think that the Nazis allow us the option of not carrying out that development. I know that you have good personal reasons for not wanting to join the project, and I am not asking you to do so. Like Toscanini’s violinist, you do not like music.
That letter to Rabi is the only place in Robert’s correspondence where he says explicitly why he pushed ahead with building the bomb and was willing to place its fate in military hands.
Late in 1944, as the Los Alamos project moved toward success, tensions developed between civilian and military participants. Captain Parsons of the US Navy, serving as associate director under Robert, complained to him in a written memorandum that some of the civilian scientists were more interested in scientific experiments than in weaponry. Robert forwarded the memorandum to General Groves, with a covering letter to show which side he himself was on: “I agree completely with all the comments of Captain Parsons’ memorandum on the fallacy of regarding a controlled test as the culmination of the work of this laboratory. The laboratory is operating under a directive to produce weapons: this directive has been and will be rigorously adhered to.” So vanished the possibility that there might have been a pause for reflection between the Trinity test and Hiroshima. Captain Parsons, acting in the best tradition of old-fashioned military leadership, armed the Hiroshima bomb himself and flew with it to Japan.
In later years I found a key to the character of Robert by comparing him with Lawrence of Arabia. Lawrence was in many ways like Robert, a scholar who came to greatness through war, a charismatic leader, and a gifted writer, who failed to readjust happily to peacetime existence after the war, and was accused with some justice of occasional untruthfulness. Lawrence’s book The Seven Pillars of Wisdom is a vivid and subtly romanticized history of the Arab revolt against Turkish rule, a revolt which Lawrence orchestrated with an extraordinary mixture of diplomacy, showmanship, and military skill. The Seven Pillars begins with a dedicatory poem, with words which perhaps tell us something about the force that drove Robert Oppenheimer to be the man he became in Los Alamos:
I loved you, so I drew these tides of men into my hands,
And wrote my will across the sky in stars
To earn you Freedom, the seven pillared worthy house,
That your eyes might be shining for me
When we came,
and with words which tell of the bitterness which came to him afterward:
Men prayed that I set our work, the inviolate house,
As a memory of you.
But for fit monument I shattered it, unfinished: and now
The little things creep out to patch themselves hovels
In the marred shadow
Of your gift.
3. Oppenheimer as Poet
Robert Oppenheimer was also something of a poet. The best place to find the poetic Robert is in the book Robert Oppenheimer: Letters and Recollections,1 a collection of personal letters, with recollections contributed by his friends and recorded by the editors Alice Smith and Charles Weiner. I quote three snippets to give you a taste of the young Robert. The first was written when he was a nineteen-year-old sophomore at Harvard, to Miss Limpet (actually his boyhood friend Paul Horgan) from Celia (himself) describing the antics of Celia’s son Henley (also himself). The letter ends with a parody by Henley of Eliot’s recently published The Waste Land:
What does it mean?
Decaying hag
Shrewish in the wilted sheen
Of a stoop; raucous stag
Boasting loot in flesh and waistcoat,
Pretty penny, Henley, Ascot,
Left ’em not a rag.
No, that is not what it means.
Four years later Robert was back at Harvard as a postdoc, having finished his Ph.D. with Max Born at Göttingen in record time. At the age of twenty-three he published a poem of his own with the title “Crossing.” It describes the landscape of New Mexico which he had come to love:
It was evening when we came to the river
With a low moon over the desert
That we had lost in the mountains, forgotten,
What with the cold and the sweating
And the ranges barring the sky.
And when we found it again,
In the dry hills down by the river,
Half withered, we had
The hot winds against us.
There were two palms by the landing;
The yuccas were flowering; there was
A light on the far shore, and tamarisks.
We waited a long time, in silence.
Then we heard the oars creaking
And afterwards, I remember,
The boatman called to us.
We did not look back at the mountains.
My third snippet comes from a letter of Robert to his brother Frank, written when Robert was twenty-eight, teaching physics and building a first-rate school of research in California. Frank was eight years younger and was then an undergraduate at Johns Hopkins. Here is some of Robert’s fatherly advice:
The fact that discipline is good for the soul is more fundamental than any of the grounds given for its goodness.… But because I believe that the reward of discipline is greater than its immediate objective, I would not have you think that discipline without objective is possible: in its nature discipline involves the subjection of the soul to some perhaps minor end; and that end must be real, if the discipline is not to be factitious. Therefore I think that all things which evoke discipline: study, and our duties to men and to the commonwealth, war, and personal hardship, and even the need for subsistence, ought to be greeted by us with profound gratitude; for only through them can we attain to the least detachment; and only so can we know peace.
It comes as a shock to see that little word “war,” among the things that we should be grateful for. This may help to explain how easily Robert slipped into the role of the good soldier ten years later.
These letters give some insight
into Robert’s character, showing us the flaw which made his life ultimately tragic. His flaw was restlessness, an inborn inability to be idle. Intervals of idleness are probably essential to creative work on the highest level. Shakespeare, we are told, was habitually idle between plays. Robert was hardly ever idle. His restlessness appears already in the early Harvard letters, outpourings of words written by a young man unable to stop when he has nothing more to say. Restlessness was at the root of the craving for discipline that is revealed in his letters to his brother. Restlessness drove him to his supreme achievement, the fulfillment of the mission of Los Alamos, without pause for rest or reflection. Without his restlessness, the pace at Los Alamos would have been slower. There would then have been a chance for the Second World War to have ended quietly in a Japanese surrender with Hiroshima and Nagasaki spared.
Robert was well aware of his own weakness. In later life he never spoke of himself directly, but he occasionally expressed his inner thoughts obliquely by quoting poetry. Especially from George Herbert, his favorite poet. In my Oppenheimer file there is a letter from Ursula Niebuhr, who knew Robert better than I did. She was the wife of the famous theologian Reinhold Niebuhr, who was invited to the institute by Robert and lived here as a member. Here is Ursula writing:
The last comment is about George Herbert. It was another lunchtime. This one was at the Oppenheimers’ house, on a beautiful spring day, and Kitty had masses of daffodils about the house. The Kennans and we were invited. Robert was at his most charming and hospitable best. After lunch, over coffee in that old part of their living room on the lower level, with Robert’s favorite books in the black-painted bookcases at the back, and the sunlight on the daffodils, and the smell of the wood fire, somehow Robert discovered that George Kennan did not know George Herbert. He turned to me and said, “But you, of course, do.” My father had been named for George Herbert, as there had been some distant connection over two hundred years ago, at least according to my pious grandmother. Robert went to his bookcase and drew out a rather nice old edition of Herbert and read in that sympathetic voice of his “The Pulley”:
The Scientist as Rebel Page 23
