Читать книгу Einstein Wrote Back - John W. Moffat - Страница 12

3

NIELS BOHR

ON THE MORNING of my appointment with Niels Bohr, I took a tram to Blegdamsvej 17 in Copenhagen, carrying my manuscripts in a large brown envelope. By this time, I had written a second manuscript about unified field theory. I paused for a few moments outside the three-storey building with its red-tiled roof and little courtyard facing the street, and gazed at the tarnished brass letters spelling out “Niels Bohr Institutet 1920.” I suddenly felt my heart palpitating. What was I going to say? How should I address Niels Bohr? Could he really help me?

Bohr had mapped out the structure of the atom in 1913, and later in the 1920s had helped to develop the quantum revolution. After Ernest Rutherford discovered that there was a hard core in the centre of atoms, consisting of a positively charged nucleus, Bohr produced a model of the atom in which the energy associated with the spectral line radiation* was quantized, or occurred in discrete quantum units. This followed the important discovery by Max Planck in 1900 that radiation emitted by a hot body was not continuous, as had been assumed in classical physics, but came in discrete parcels of energy. In effect, Bohr succeeded in making the atom stable. Previously, the classical model of the atom could not prevent the orbiting electron from spiralling in towards the nucleus. Bohr pictured his atom as a mini-solar system, with the positively charged nucleus playing the role of the sun and the electrons swirling in stable, planet-like orbits around it. However, Bohr’s young assistants, Werner Heisenberg and Wolfgang Pauli, were not able to apply his model of the atom to more complicated spectral line data.

Eventually physicists gave up on the Bohr model as a true visual picture of the atom and developed the modern version of quantum mechanics, which described the electrons and protons in the atom as waves. This new view interpreted the emission of the spectral lines from the atom in terms of probability theory. That is, light, consisting of photons, had only a certain “chance” of being emitted from the atom at any particular time. This new description of the atom gave birth to what is now called quantum mechanics, which revolutionized physics by overthrowing the whole notion of classical physics applying at the subatomic level.

Because of his pioneering work in atomic physics, by 1953, when I met him, Niels Bohr was certainly the most famous scientist in Denmark, and was one of the most famous physicists in the world. He had won the Nobel Prize in physics in 1922.

I opened the gate, entered the courtyard and rang the bell next to a door that said “Administration.” A buzzing noise answered me. I pushed the door open and climbed the stairs to an office where a secretary sat at a large oak desk overlooking the gardens and park at the back of the institute building. It was a clear spring day and through the window I could see a soccer game in progress in the park, with young men kicking a ball around the field. Through the glass I could hear their muted shouting and birds in the nearby trees as well. The secretary smiled at me and asked in Danish what my business was. I explained that I had an appointment with Professor Bohr at ten-thirty. “Ah, yes, you’re the young man who is working on Einstein’s unified field theory,” she said, fixing me with a curious gaze. “You may sit in that chair over there and wait for Professor Bohr.”

As I waited, my nervousness increased. I could feel my palms becoming moist. I tried to concentrate on the shouts of the soccer players, and block out all other thoughts. After several minutes a short, stocky, middle-aged man with curly black hair opened the office door and walked over to the secretary, ignoring me. She said, “Dr. Rosenkrantz, this young man has an appointment with Professor Bohr.”

The man turned and looked at me for the first time. “Ah, you’re the young man who is working on Einstein’s unified field theory,” he said.

“Yes,” I replied. “My name is John Moffat.” I stood up and we shook hands.

“Do you have your manuscript on the unified field theory with you?” he asked.

“Yes, I do,” I said, holding up my large brown envelope, which shook slightly in my trembling hands.

“Well, then,” he said, “let’s go in and see Professor Bohr.”

We walked down a long dark corridor and came to an office. When Rosenkrantz opened the door, the strong smell of tobacco smoke wafted out. A tall man with a dome-shaped head and wearing a rumpled brown suit stood in the far corner of the room looking out the window at the soccer game in the park. His hair was thinning, accentuating his large ears.

Rosenkrantz beckoned me into the room and performed the introductions. “Professor Bohr, this young man is John Moffat.”

Niels Bohr removed a pipe from between his thick lips and said in softly spoken Danish, “So, you’re John Moffat?”

I said yes, I was.

“Do you have your manuscript on Einstein’s unified field theory with you?”

“Yes,” I replied. Again, I lifted the envelope. “I have two manuscripts, Professor Bohr. One has to do directly with Einstein’s classical unified field theory. The other attempts to quantize his unified field theory.” *

Bohr then crossed the room to his desk, sat down and contemplated a wooden rack holding pipes of various sizes, standing next to a large Danish matchbox and several tins of tobacco. He took his pipe out of his mouth and, pointing the stem at me, said, in English this time, “Please, sit down, sit down.” I took one of the chairs in front of his desk. Dr. Rosenkrantz sat in a chair next to mine, and placed a notebook on his knee. He took a pen out of his breast pocket, unscrewed the cap and began writing scratchily. I realized that he must be about to take notes, and my palms started sweating again. Was he actually going to record everything that was said?

There was a silence while Bohr picked up one of the tobacco tins from his desk, removed the lid, and poked his bear-like hand inside to pull out a lump of tobacco. He removed his pipe from his mouth and shoved the tobacco into the bowl. Then he carefully took a metal instrument from his pipe stand, tamped the tobacco down into the bowl with it and put the pipe back into his mouth. Next, he picked up an oversized box of matches, took out a match and lit the pipe, making dry sucking sounds as he drew in the smoke. Printed on the matchbox was the familiar Danish trademark H. E. Gosh & Co., with the famous picture of Tordenskjold, the eminent Danish-Norwegian naval hero of the seventeenth century. Everyone had these matchboxes in their kitchens. Bohr sat back in his chair and studied me for a while. The room was silent except for the birds singing outside. The shouting of the soccer players had ceased. Bohr said, “Let’s see the manuscript on unified field theory.”

I opened my envelope, took out the manuscript and leaned across the desk to hand it to him. I had managed to make copies of the two papers on my parents’ old Royal typewriter with faded carbon paper, and had written in the equations with a pen. Bohr put the pipe down on what looked to me like an antique Royal Danish porcelain dish, and spent several minutes quietly reading my paper. He then said, “Hmm!” and looked up and smiled at me.

While he had been reading, his pipe had gone out. He took another one from the stand and followed the same routine again: filling the pipe, tamping down the tobacco, lighting it and sucking it into life. Then he leaned back in his chair staring at the ceiling while the blue smoke rose up from his pipe and filled the room with its strong, sweet aroma. Thus we sat for at least five minutes waiting, while Bohr thought about what he had read. Rosenkrantz sat quietly with his fountain pen poised over his notebook.

Finally, Bohr levelled his gaze at me and ruminated, “So, you’ve been working on Albert’s unified field theory.”

“Yes,” I said.

Bohr took the pipe out of his mouth, as apparently it had gone out again. It joined the first pipe on the porcelain dish. I wondered if he was going to light another pipe before we proceeded with the business at hand. And indeed he did. He removed a third pipe from the stand and performed the same ritual yet again, while I counted up the pipes still in the stand. I thought that if we were going to go through those remaining ten pipes, I would be in Professor Bohr’s office for the rest of the day.

After he succeeded in lighting the third pipe, he asked me in a mumbling voice, “What is your opinion about Einstein’s efforts to unify electromagnetism and gravity?”

Now Dr. Rosenkrantz’s pen began scratching rapidly in the notebook. I sensed that something serious was finally about to happen in my meeting with Niels Bohr.

“I think it’s a logical extension of his gravity theory,” I replied.

Bohr smiled, removed the pipe from his mouth and said, “Are you aware of the fact that Albert has become an alchemist?”

I was taken aback by this obvious slight of one of the great physicists of the twentieth century. I said, “You mean someone who tries to turn base metals into gold?”

Bohr smiled again, and mumbled, “Yes, something like that.” Bohr’s derogatory comment indicated that he felt strongly that Einstein was wrong in denying the probabilistic nature of quantum mechanics. Einstein did not believe that quantum mechanics formed a complete description of reality, whereas Bohr did. Instead of Einstein working to develop quantum mechanics further, he had been focusing on extending his theory of gravity to include the electromagnetic forces, but without including the nuclear forces, which in the opinions of contemporary physicists, played a more significant role than gravity in the subatomic realm. I had to concentrate on catching his words because Bohr mumbled even more disturbingly than most Danes do when they speak, whether in Danish or English. Evidently Dr. Rosenkrantz, who was also Danish, was used to Bohr’s inaudible mumbling and was able to follow his conversation more easily than I.

I sat for a few moments, wondering how to respond to this rebuke of Einstein. “I understand, Professor Bohr, that you do not believe that Einstein is following a satisfactory path in his physics.” Miraculously, my initial nervousness had disappeared, and I was now entirely focused on the conversation and on figuring out Bohr’s attitude towards Einstein.

Bohr put down the pipe, which had now gone out, took another one from the rack and began the ritual. I now understood why he had such a large box of matches. When he had finished lighting the pipe, he said, with the pipe stem still in his mouth, “I feel that Albert has been wasting his time. You cannot ignore quantum mechanics and hope to achieve any success by unifying the classical gravitational and electromagnetic fields, in the way he attempts to do this.”

I said, “Well, Professor Schrödinger has also been attempting to unify gravity and electromagnetism, using the same formalism as Einstein, the nonsymmetric theory.”

Bohr removed the pipe from his mouth, looked at me sternly and said, “Well, Erwin is also an alchemist these days. He is pursuing this foolish denial of the successful development of quantum mechanics, and has also gone down this blind alley of trying to unify the classical gravitational and electromagnetic fields.”

Then I asked, “So, Professor Bohr, you believe they should be following a quantum mechanical interpretation of these fields?”

He then mumbled, “We already have a quantum mechanical interpretation of electromagnetic fields, which has been quite successful. As for gravity, I do not see that a classical unified theory of gravity and electromagnetism can ever solve the problems of atomic physics.”

“I understand,” I said, “that Professor Einstein does not agree with your interpretation of quantum mechanics. In fact, he seems to be opposed to quantizing the gravitational field.”

“Well,” Bohr said, “it saddens me to see that Albert has taken the wrong path in recent years. We have disagreed about this issue for years, and he refuses to accept the success of the quantum theory. He insists on being pigheaded about this.”

We sat in silence for a while again, and I waited for Bohr to put down his pipe and start over again with another. And indeed he did. I wondered if he went through this ritual every time he granted an interview. When he succeeded in lighting the fifth pipe, he leaned back in his chair and looked at me. “Anyway,” he said, “how did you come to write this manuscript? I understand from Mr. Page at the British consulate that you’ve been studying mathematics and physics by yourself.”

I nodded, and shifted in my seat. Now that the conversation had turned from physics to me, I began feeling nervous again.

“When did you leave school?”

“I finished high school in Kaptain Johnson’s school in Copenhagen when I was sixteen and then pursued an art career in Paris.”

“So you didn’t go to a gymnasium?” Bohr asked.

“No,” I said.

“And you haven’t attended the university in any way?”

“No,” I said again.

“So where did you get the books to learn mathematics and physics?”

“At the university library. The science textbook and periodicals section of the university library is open to the public.”

I saw Bohr and Rosenkrantz exchange glances.

“How long did it take you to learn mathematics and physics, such that you could write this manuscript?”

“About a year,” I answered.

“By yourself?” he asked incredulously.

“Yes.”

“So what do you plan to do now?”

“I’d hoped that I could pursue an academic career and study physics, possibly in England. I am a British citizen.”

“Well,” said Bohr, removing his pipe from his mouth, “you couldn’t pursue an academic career in Denmark without going through the usual channels. That is, you have to take your student exam at a gymnasium and then enter the physics curriculum at the University of Copenhagen. Would you want to do this?”

“I think that I would prefer to go to England if possible, to an English university.”

“Well, then,” he said, “you would find that you would have to proceed through the same kind of academic channels that you would here, but it is possible that it would be easier for you than here in Denmark.”

I then plucked up my courage, and said, “Professor Bohr, would it be possible for me to give a talk here at the institute? I have been working on some quantum mechanical interpretations of gravity, using Julian Schwinger’s approach to quantum field theory.”

As we were talking, I had suddenly had the rash thought that if I could give a convincing talk to the physicists at the institute, they might accept me as a promising young physicist and I could perhaps bypass those “usual channels” that Bohr had referred to. During my private studies of physics, I had gone beyond quantum mechanics and learned about quantum field theory, combining quantum mechanics and the special theory of relativity.

Again, Bohr exchanged a glance with Rosenkrantz, who was still busy recording all that we were saying.

“Do you think you are capable of giving such a talk here at the institute?” Bohr asked.

I shifted nervously in my seat and replied brashly, “Yes, I think I am, Professor Bohr.”

“Will you be using Einstein’s unified field theory?” he asked.

“Yes, I think I will, as well as some ideas I have about quantizing his theory,” I responded.

“I’m afraid that you will meet much skepticism,” Bohr said. “Professor Christian Møller, who is our expert here at the institute on gravity, is also skeptical about Einstein’s program, but we can arrange for you to speak to him and see if he can arrange for you to give a seminar.”

Bohr put down his pipe, to join the others in the porcelain dish, and directed Rosenkrantz to arrange a meeting with Møller.

“Also,” Bohr said, addressing me again, “I will speak to Mr. Page at the British consulate and see whether they can help you with possibly pursuing your studies in England.”

Bohr stood up, signalling the end of the interview, and Rosenkrantz and I also rose from our chairs. I shook Professor Bohr’s hand and thanked him for his kindness in having this meeting with me. Rosenkrantz and I left the smoke-filled room together.

*Atoms emit photons when an electron makes a transition from a particular discrete energy level to a higher one, and they absorb photons when changing to a lower energy state. The emissions or absorptions occur as coloured or dark lines, respectively, within the radiation spectrum. These spectral lines are highly specific to different atoms, and can be used to identify elements, for example, in the composition of stars.

*By “quantizing,” I meant that the energy associated with a field such as the electromagnetic or gravitational field must also come in quantum packages of energy. This is accomplished by “quantizing” the classical field theory through the application of the mathematics of quantum mechanics and relativity theory.