Preface
The following lecture was written out completely before the actual talk. In the real presentation, because there was, first, no PPT to assist me and, second, my on-the-spot performance was not up to par, I ended up saying much less than I had intended, and did not do very well. Looking at this script should make up for some of that. 《Does God Play Dice》 can be read online at http://book.sina.com.cn/nzt/liangzishihua/.
Let’s Begin
Because I prepared too thoroughly—I had already written out the whole script—when speaking I might be a bit constrained, and since I can’t use PPT, I’ll have to keep glancing at the text, so please forgive me. What I say will all be posted later on my blog—EPR.yculblog.com. Do you know what EPR is? It is also my Unknown Realm ID, and after hearing this talk you will at least know roughly what that thing is.
As for this “pp,” I originally wanted to keep it a bit suspenseful, but ZXM went ahead and helped me promote it. I didn’t originally want to come up with such a flashy name; actually, in our department, it’s just for our own amusement, and even without a name it would be fine. Anyway, as long as everyone knows it’s about little gǔ and science, that’s enough.
First, PP stands for “popularity”—the “popularization of popularization.” My main purpose this time is not to popularize scientific knowledge. Of course, if anyone wants to chat with me about some scientific knowledge, I’d be very happy to do so when there’s a chance. My purpose, I feel, is rather like that of a salesperson—I’m selling popular science books. Popular science books popularize science, but at present popular science books themselves are not very popularized; people all keep their distance from them. What I want to talk about first is how to regard popular science books, how to read them, and I hope to arouse a bit of your interest.
Second, when people see “pp,” the first thing they may think of is “ppmm,” pretty young ladies. That is also the scientific impression I hope to bring you—stunning, mysterious, lovable beauties. I hope to stimulate everyone’s interest, so that you will actively draw near to her and get to know her.
Third, “tie-pp” means posting photos. What I want to introduce to you are some peripheral impressions. We do not need to go deep ourselves, to climb those rocks in person; through those beautiful photographs, we can still get some impressions of science. Although it can never compare with making the trip oneself, even if we do not personally engage in science, looking at photos can still let us understand the fun of science and the marvels of nature.
PP is also an abbreviation for “a little bit.” The time is only a little bit, and my ability is only a little bit; anyway, I’m just pointing out a little bit of something, and I hope everyone can feel there is at least a little bit of interest in it, that’s all.
PP is also an abbreviation for “philosophy of physics,” but in fact I will try my best to avoid dragging philosophy into it. In truth, there are quite a few “philosophers” on the market now who have only a literal, superficial half-understanding of physics, and there they are, talking grandly about philosophy; to be honest, I rather look down on that. I’m just chatting casually; everyone can do philosophical reflection, of course, but when your fire isn’t hot enough yet, don’t go shouting about it.
ZXM added one more thing for me at the time, saying there was also the meaning of beating pp, cough.
First Story: The Harvest of Not Understanding
When it comes to science, people may not be interested, but precisely for that reason I think it is all the more necessary for me to talk to you about popular science.
Modern science and the humanities are increasingly diverging, just as Academician Xu Kuangdi, the former mayor of Shanghai, sternly put it: scientists are generally uncultured, and humanists generally don’t understand science.
Admittedly, modern natural science and the humanities are both becoming more and more specialized. A person’s energy is limited, and it is difficult to study everything comprehensively. However, Murray Gell-Mann once angrily pointed out—perhaps occasionally you may encounter a scientist who doesn’t know Shakespeare, but you will never encounter a scientist who is proud of not knowing Shakespeare; yet in the fields of art and the humanities and even the social sciences there are often people who take pride in almost not understanding science or mathematics! This is rather harshly put, but we can observe and reflect on it: is it really without reason to say this? For many people in the arts and humanities, is the reason they are not interested in science because their capacity is limited, or because they simply disdain learning about it? In China, this situation is even more serious—the scientific community and the humanities community mutually despise and look down on one another. In our department, is there also such a situation among the various specialties? Of course we cannot expect everyone who studies Western philosophy to be like Professor Zhang Xianglong, who bridges China and the West; but I hope those who study Western philosophy will not take pride in not understanding Chinese philosophy, those who study logic will not take pride in not understanding philosophy of science, and so on.
I do not expect people in the sciences all to be like Schrödinger, who was thoroughly conversant with classical literature and philosophy, mastered reading and writing in English, French, Italian, and Spanish as well as in Greek and Latin, translated the Homeric epics into English, translated French poems into German, published a personal poetry collection in 1949, enjoyed drawing and sculpture, was particularly fond of drama, loved nature, liked mountain climbing… Nor do I expect humanists to have any especially high scientific background. But at the very least there should be a little more mutual respect. If you have never heard of Schrödinger just as you have never heard of Whitehead, that is not strange, but that is certainly nothing to be proud of!
ZXM heard that I not only wanted to talk about science, but also about quantum mechanics, and was frightened out of his wits, saying that this topic was too deep and it would be better to make it more universally applicable, reach a broader audience, something like that. I felt quite helpless. In fact, quantum physics is certainly profound—probably there is nothing deeper than quantum physics! But popular science books really cannot be called too profound, especially for those of us who study philosophy. If we dare to read Husserl, would we still be afraid of this popular science reading matter? The book I’m recommending to everyone is one of the trashiest books I’ve read recently; it is not only popular literature, but internet literature as well. In my personal feeling, this book is simply popular to an extreme. Personally, I am not the biggest fan of this style. My favorite popular science book on quantum mechanics is still John Gribbin’s Searching for Schrödinger’s Cat—this was the first popular science book on quantum theory that I read. Although the quality of the Chinese translation is extremely poor, if you are just reading casually in your spare time, the muddled terminology does not matter much. Gribbin’s book is excellent, and among the Phaedrus of Stone series there are several of his books, all very splendid. There is also a recently published book in the fourth installment of The First Push, The New Quantum World, which is also good. Excellent popular science books on quantum physics are very scarce both in China and abroad, because they are simply too hard to write!
When it comes to these so-called “high-end popular science” books, the one people are most familiar with is probably Hawking’s A Brief History of Time. By the way, A Brief History of Time is actually rather ordinary. Of course Hawking wrote it very splendidly, but I would not recommend it first to everyone. For themes such as relativity, Kip Thorne’s Black Holes and Time Warps is the best I have read, and Gribbin’s In Search of the Big Bang is also very good. Of course, the biggest advantage of A Brief History of Time is that it is relatively thin, more popular and concise, but it is not as clear as Thorne or Gribbin.
People say that A Brief History of Time sells a lot, is read by few, and even those who read it do not understand it, because it is too profound. Actually, that’s not quite right. Physics is profound, but those popular science books are not profound; you only need a middle-school physics foundation to read them. I finished A Brief History of Time in two or three days when I was in the third year of junior high. In fact, you do not even need to master middle-school physics very well; just knowing a few conservation laws is more or less enough. The first is conservation of mass-energy; if you don’t know this and keep thinking about building perpetual motion machines, that won’t do. The second, for example, is charge conservation. Actually, it is enough just to know that besides conservation of mass-energy there are other conservation laws as well. Several of the pseudo-scientists I’ve seen know conservation of mass-energy, but not the others; they think that if you compress 1,800 electrons together, that makes a proton, and that won’t do. Having a rough grasp of such physical common sense is enough, so that after reading popular science books you don’t turn into a pseudo-scientist. But actually pseudo-scientists ought all the more to read quantum mechanics. I see many pseudo-scientists shouting about overthrowing Einstein, but I really have seldom seen any pseudo-scientist try to give a new interpretation of quantum mechanics. When I was a freshman in high school, I corresponded with a pseudo-scientist, and at the time I recommended that very book Searching for Schrödinger’s Cat to him.
In short, I can guarantee with my reputation that the popular science books I recommend are all very accessible—at least much more accessible than most people who have never read them imagine.
But why does everyone say A Brief History of Time is unreadable? That is normal too, because physics is profound—wouldn’t it be strange if you could read it and understand it? If you read two popular science books and then say, “I’ve figured out relativity and quantum mechanics!”—congratulations, you’ve already become a pseudo-scientist!
It seems that the legendary Liu Bing once came up with an advertising slogan for A Brief History of Time: “Read Hawking; whether you understand it or not, it’s a gain.” This slogan was very successful. Someone named Simpli made some objections to it, and what he said was not without reason, but as for what else there can be to gain from not understanding, I have my own view.
Actually, first of all, there is the issue of a change in thinking habits. For example, popular science like quantum mechanics is very different from the traditional popular science people have in mind. The purpose of traditional popular science is to make you “understand”; if you look at new physics popular science with this standard, then naturally you will feel that understanding it counts as success, while not understanding it counts as failure, and the more clearly the reader grasps it, the more gains there are. But it is not like that.
The traditional popular science we have in mind is typified by 100,000 Whys. From the title alone, you can tell the characteristics of this kind of popular science:
The characteristic of this kind of popular science is that it begins with “why.” People first read popular science with puzzled, bewildered questions in mind, such as “Why is there a rainbow? Why is the sky blue? What is this all about? Wow, what’s going on there?” Then the popular science book—often taking as its spokesperson the image of a bald, white-bearded old man in glasses and a white lab coat—reveals the mystery to us: “This is because of this, that is because of that, because this, therefore that, scientific principles…” and in the end the reader understands and says, “Oh, so that’s how it is!”—and then the popular science counts as a success.
But the situation with quantum popular science is just the reverse! At first we do not come to these books carrying any “why” at all. Most of the questions we can think of in life are sufficiently explained by classical mechanics. Who would think to ask questions about blackbody radiation and the like? When we first hear the concept of quantum mechanics, although we do not understand it, perhaps we still do not take it seriously—“So-called quanta just mean energy is discontinuous, that it comes in units, one unit after another? Nothing much.” But reading popular science on quantum mechanics is not a matter of becoming clearer and clearer as you read; rather, it is a matter of becoming more and more confused! After you finish this popular science book, you slam it down and say, “Good heavens! What on earth is all this chaotic mess?”—that means the book has done its job well!
The popular science of “100,000 Whys” aims to turn us from surprise and confusion into understanding; it is “de-enchanting,” “demystifying” popular science. After reading those books, even if there is still wonder, it is only admiration for the power of science. Such popular science is of course very necessary; it enables people to break away from ignorance and escape superstition. However, after too much exposure to this kind of 100,000 Whys popular science, one can easily develop the habit of thinking that all whys, whether there are 100,001 of them or a million of them, can be explained by science—that science can solve all problems—and thus easily become a believer in scientific superstition, a scientific omnipotent-ism advocate, a scientismist.
General popular science is meant to dispel mystery, whereas the popular science of quantum physics goes against the current; it hopes to present to readers the most profound and incomprehensible mysteries of the universe. It does not provide answers to mystery—or rather, it provides a whole bunch of answers; in any case, it is absolutely unlike ordinary popular science, which provides only one, scientific, correct answer. It helps people understand what exactly those scientists at the cutting edge of scientific exploration are doing!
Just a few days ago I finished writing a paper on the similarities between science and religion. When discussing the religious complex among great scientists, I quoted statements about religion from many great scientists such as Planck, Einstein, Bohr, Heisenberg, Schrödinger, Born, Feynman, Bohm, and so on. Although their views differed from one another, their attitudes were all tolerant, receptive, even admiring. And the whole string of names I listed happens, without exception, to be made up of major physicists who made outstanding contributions to the exploration of quantum physics! In fact, if you just add a few more names to that list—such as Dirac, Pauli, de Broglie, and so on—you more or less get the “dream team” of twentieth-century theoretical physicists. Besides their general friendliness toward religion, these top physicists are often all multi-talented. Einstein loved playing the violin, Planck, Heisenberg, and Born were skilled at the piano, and the scientific prankster Feynman goes without saying… Right, I originally wanted to recommend the Feynman Close-Up series. Recently Feynman has suddenly become very hot, it seems; biographies of Feynman, the Feynman Close-Up series, and the new edition of Feynman’s Lectures on Physics have all popped up. But it is right that he has become hot—Feynman is simply too interesting. Among the Feynman Close-Up books, I recommend Surely You’re Joking, Mr. Feynman! and The Pleasure of Finding Things Out. Gribbin’s biography of Feynman is called The Enchanting Science, and Feynman’s style is entirely different from the bald, white-bearded, bespectacled man in a white lab coat that we habitually picture, or from the scientist image typified by Chen Jingrun.
Oh yes, Schrödinger, whom I mentioned at the beginning, is very interesting. Philosophically, he not only loved Ancient Greece, but also held the Vedanta philosophy of India in high regard; and Bohr, for example, liked Kierkegaard. All of them have something of a mystical flavor. If Feynman is the old mischievous child Zhou Botong, then Schrödinger’s position is unquestionably Duan Zhengchun! On page 136 of this book there is a little after-dinner chat about Schrödinger’s girlfriend; everyone can take a look.
We know that physics can be called the purest of the natural sciences, and quantum physics is the most fundamental, the most “reductive,” and the most cutting-edge field. Yet why is it that the ones who seem most “off task” among scientists, the ones who most like to “talk metaphysics and expound the Way,” and the ones most accepting of the humanities, art, and religion are precisely that bunch who work on quantum physics? Although among theoretical physicists there are also many who resist and detest unscientific things like religion, compared with other scientists in fields such as biology and economics, it seems fair to say that quantum physicists are simply the least “scientistic” kind of scientist!
I believe this is by no means a coincidence. The exploration of quantum physics is the most fascinating, and quantum physicists are the closest to the mystery of nature; they are the most likely to experience the beauty and profundity of nature,
Feynman once said:
Poets always say that scientists don’t see the beauty of the stars—the stars are, in scientists’ eyes, merely a pile of gathered gas atoms. Nothing is “merely” anything. I can see the stars in the desert night sky, and I can feel them too. But do I see them less than others, or more? The vast sky arouses my imagination—staring at this revolving firmament, with my tiny eyes I can catch the light emitted a million years ago… Or I can observe these stars through the great eyes on Mount Palomar (the telescope), which can focus together the light emitted from the same source in large quantities. Perhaps those lights were originally together. What kind of picture is this, or what does it mean, or why is it like this? Knowing a little about the universe does not diminish the universe’s mystery. For the universe is far more wonderful than any artist before could imagine. Why don’t poets say this now?
The nature sung by poets is certainly beautiful, but the “nature” explored by scientists should likewise be beautiful, and these beauties should, by different routes, lead to the same destination. We are too familiar with the cold, mechanical picture of nature depicted by Newtonian mechanics. If we want to escape this chill, one approach is to forget science and reject science, and instead focus on the humanities; another is to rely on the pseudo-science of mysticism, to look at things like those “Complete Records of Unsolved Mysteries”; but a better approach is simply to take a look at quantum physics!
It should be noted that the “mystery” of nature revealed by quantum physics is entirely different from things like The Complete Book of Unsolved Mysteries, The Mysterious Crop Circles, or The Mysterious Bermuda Triangle. Those so-called popular science books are mostly just sensationalism and contrived obscurity. Of course, I also want to remind everyone that quantum physics should not be over-mystified. Science is certainly about seeking an understanding of nature; there can never be a science that studies the “supernatural.” Quantum mechanics does not mean that nature is incomprehensible; quantum physicists are all persistently pursuing an understanding of nature. But quantum physics is indeed incomprehensible in another sense, because it probably cannot be understood through everyday modes of thought, and perhaps there will be multiple different interpretations that are all “correct” at the same time.
Reading popular science on quantum physics is not merely a matter of “whether you understand it or not, it’s a gain”; rather, it is precisely “not understanding it that is the gain.” What I mean, of course, is not that you cannot understand the author’s written expression, but rather that after finishing the book you feel: “I don’t understand it!”—and thereby come to feel something of the depth of nature and the wonder of science, and that is enough. Bohr said: “Anyone who is not astonished by quantum theory has not understood it.” Feynman said: “If someone says he understands quantum mechanics, he is lying.” Pauli: “Beware, beware of reason and science. / The highest powers of humanity have formed a terrifying alliance. / You will be dazzled by the radiant products of witchcraft. / Again you will experience the seduction of the mysterious quantum realm.”
Second Story: How to Read Popular Science Books
Now that we have figured out that the goal of reading high-end popular science books is not to understand those scientific facts, how should we read such books?
As for this《Does God Play Dice》—it is a “history-telling” book, mainly written along historical lines. And according to Teacher Liu Bing’s account, the author has not received professional training in the history of science. Therefore, my understanding is that we might as well read this book as a kind of historical romancing or theatrical retelling, much like reading The Romance of the Three Kingdoms. Although the narrative in this book is not quite three parts truth and seven parts falsehood, many of the scientists’ dialogues and disputes are fictional, and it does indeed have a bit of the flavor of a romanced telling.
Whether it is official history, unofficial history, or romancing, when we read history books there is a method—unless we are doing professional historical research, in which case we need to read history books very thoroughly and analyze and understand all the details. But if we are reading history books as novels or recreational books, there is no need to be so serious. Many technical points can simply be skipped over. For example, we do not need to understand in detail what specific governance policies a certain person adopted; we only need to care about outcomes such as “under the rule of so-and-so, the people lived and worked in peace and contentment” or “popular resentment was boiling over.”
Reading a history of quantum theory is like watching martial arts or watching a chess match. Take, for example, the most famous dispute in the history of quantum physics, the argument between Einstein and Bohr: this dispute was unprecedented in the history of science, enough to shake heaven and move the spirits, and one simply cannot find a more splendid dispute than this! As we read their back-and-forth, it is as if we are watching two great masters of the martial world sparring, or two immortals playing chess. Clearly, we cannot have any very deep understanding of their moves; in fact, their attacks may be so dazzling that we cannot even see them clearly at all. But this still does not prevent us from appreciating the brilliance within. Of course, the more clearly we see and the more we understand, the more fully we can appreciate that brilliance; but even if our understanding of the moves is quite limited, we may still be intoxicated by that exceptionally splendid atmosphere.
Take another example: watching Detective Conan, say. Everyone has at least heard of that animated series, right? How does one appreciate Detective Conan? We know that every episode of Detective Conan contains a set of brilliant cases, with mechanisms, foreshadowings, deductions, and so on, all designed with extraordinary ingenuity. If your mind can keep up, and you can analyze and think together with Conan about the cleverness of the mechanisms, that is the most thrilling way to watch. But I think many people often cannot be bothered to watch it that way. In particular, many girls watch Conan more for the plot, right? For example, being obsessed with Haibara Ai and the like, or being Kaito Kid fans, or Ran fans, and so on. For these people, watching Detective Conan is no longer about understanding the logic of the cases. Moreover, even if they do not care about the plot at all, the exciting visuals, the tense and thrilling atmosphere, and its relaxed humor can all become reasons why Detective Conan is appealing. Watching this kind of high-level popular science book is similar. If I could deeply appreciate the subtlety of those mathematical formulas and understand the twists and turns of those ideas, then of course I would think that is the most splendid thing of all. But if I skip over those technical things and ignore them, and just watch the plot and savor the atmosphere, I can still read it with great relish.
Just as the Three Kingdoms period was in Chinese history, so too, in the whole history of science, the most stirring and hero-filled chapter is undoubtedly the history of the development of quantum mechanics! The history of quantum physics is the most vibrant and full of vitality, and this is by no means only because it is the newest frontier; in fact, quantum mechanics is jokingly called “boys’ physics,” because the shining stars in the history of quantum physics all came onto the scene very young—Einstein at 26, Bohr at 28, de Broglie at 31. When Heisenberg, at 24, made the crucial breakthrough that laid the foundations of quantum mechanics, his peers who also made major contributions included Pauli at 25, Dirac at 23, Goudsmit at 23, Jordan at 23; Schrödinger at 36, and Born at 43, were practically old men by comparison! There were no shortage of prodigies in earlier scientific history either, but there has never been another case where a whole new era was created by a group of young people. This alone is enough to show the surging passion of quantum mechanics.
Right, and what is it similar to? — Mathematics! In the history of mathematics, the breakthroughs were often made by genius youths in their twenties or thirties. Gauss, Galois, Abel, Ramanujan, and the like are all typical examples; who could think up a great mathematician who bloomed late? Anyway, there are very few. A mathematician who seems to have been called Adler once said: the professional life of a mathematician is extremely short; the golden period is between twenty-five and thirty. If by the end of that period one still has not achieved anything creative, one should give up the profession as early as possible, because no later change is likely to come. The model mathematician we came into contact with was Hua Luogeng, who taught us that genius is made through diligence. That is not wrong; genius does indeed require diligence. But the belief that diligence can produce genius has truly harmed quite a few people. Many people do not understand that everyone has their own strengths, and instead think that anyone can become Einstein; as a result, many pseudo-scientists were born. The most tragic thing is that the main ambitions of pseudo-scientists happen to be concentrated in the fields of the Goldbach conjecture, a mathematical problem, and the overthrow of Einstein, the field of new physics. You see, these two sciences are precisely the ones that require genius the most. If pseudo-scientists truly love science and really want to do something beneficial for the scientific cause, they might as well do natural history or astronomical observation; who knows, they might even make some earth-shaking new discoveries—at least there is more hope in that than in pondering the Goldbach conjecture into one’s seventies and eighties.
What does the similarity between quantum physicists and mathematicians on this point tell us? First, modern physics increasingly depends on mathematics; to do modern physics, one almost has to be highly proficient in mathematics. Another point is that the profundity of quantum mechanics can no longer be grasped by everyday language at all. Even Schrödinger, Bohm, and others who opposed the orthodox interpretation of quantum mechanics, believing that the quantum world is real and intelligible, nonetheless admitted that the quantum world is difficult to understand in current everyday language. What may be able to understand the quantum world is the language of mathematics; the best way for quantum physicists to ensure they do not become too crazy is to make greater use of abstract thinking.
Back to the point, let me speak of this book: Teacher Liu mainly recommends this book to science and engineering students, but I still insist on recommending it to everyone as well. Even if everyone reads these books and they do not serve the function of traditional popular science, even if one merely treats them as epics, novels, or books for amusement, I still think they are worth recommending.
However, reading these high-level popular science books brings up another problem—since I do not understand those sciences, what attitude should we take toward some of the conclusions in them?
Being somewhat skeptical about things one has not personally witnessed or personally tried is part of the scientific spirit, and this is true even for things one has seen with one’s own eyes; but one should not become dogmatic and go too far. Popular science in Ten Thousand Whys often gives us things we can verify. For example, when I once read that chewing rice turns starch into maltose, I took a mouthful of rice and chewed and chewed, and sure enough it became sweet. But, for example, new physics tells you that antimatter exists and that when antimatter and matter collide they annihilate each other… clearly we have no way to verify that. In fact, most scientists have no chance to verify such things either; doing that sort of thing requires reliance on huge cyclotrons, and some accelerators in the United States consume almost the electricity of an entire town when they operate. I think it is better to do less of that kind of verification. Although letting students verify things personally is a good way to cultivate their scientific spirit, it is obviously impossible to have every student in a physics department personally operate a particle collision. Just as biology students have to dissect many live rabbits, some scientific experiments seem to be done too often.
We cannot demand that things can only be believed when they can be personally verified by us. Scientists are not absolute authorities, but they are still comparatively reliable. The power of science is indeed formidable; believing scientists can be said to have become a good habit, just like the habit of causality. Accepting it without hesitation is certainly not rational, but rejecting it without reason is equally irrational. Our breaking the authority of science does not mean that science should not be respected.
I’m digressing. Actually, one benefit of reading popular science about quantum physics is precisely to break the traditional impression of science, isn’t it? One impression we get from quantum mechanics is that not only we ourselves, but even those scientists seem not to believe in the science they produced! For example, as the pioneer of quantum mechanics, Planck pulled the monster out of the lamp, but he himself was the first not to believe in quantum mechanics. If Planck’s behavior can still be seen as intellectually conservative, Einstein’s resistance to quantum mechanics was something entirely different. As one of the greatest and most insightful scientists, Einstein’s thinking was by no means conservative. Yet, as we see, the dispute between Einstein and Bohr was absolutely a scientific dispute, and by no means a dispute between science and pseudoscience, nor can it be said to be a struggle between truth and error. Of course, their dispute was not merely scientific, but also philosophical; and this was even more true in Bohm’s later work. Their disputes have always involved the most fundamental philosophical questions, such as realism and anti-realism, matter and spirit, subjectivity and objectivity, and so on; we will speak of these below. In short, we will see the close relationship between science and philosophy. Whether the so-called “metaphysical presuppositions” in scientific theory really exist, and what they are all about—we can feel a great deal of that from quantum mechanics.
Let me say again something about this book. It is very rare, because it was written by a Chinese person! I have never had much confidence in popular science books written by Chinese people, especially those in frontier fields. But this book is an exception; it is very well written.
Although I have been disappointed again and again, I still occasionally buy and read some popular science books written by Chinese people. For example, on the quantum world, there is a book called The Hazy Quantum World, edited by Jiang Xiangdong and Huang Yanhua. These two have translated many very good popular science books, but when it comes to writing one themselves, they really still fall short. On the one hand, the writing is not strong enough; it is not vivid and lively enough. On the other hand, the knowledge base may not be sufficient; it is neither deep enough nor accessible enough. But the most crucial problem is still the problem of the conception and direction of popular science. These books are still written from the attitude of imparting scientific knowledge from a position of superiority; this is a common problem in Chinese popular science. Most Chinese popular science writers are usually trying to popularize dead scientific knowledge; their pursuit is nothing more than how to convey those dead things in lively and plain language. But many excellent Western popular science writers are not like this. What they want to spread is itself alive, itself incomparably lively and vivid. What they are thinking about is how to share these lively, vivid impressions with more people, and how to preserve as much as possible of science’s own liveliness and vividness in a plain-language presentation, reducing loss, rather than trying by every possible means to add liveliness.
So, although it is a bit regrettable, from my experience of reading a whole shelf of popular science books, I suggest that if you want to read popular science, you should still start with excellent works written by foreigners. You can begin with branded series, for example the Philosopher’s Stone Series and the First Push Series are both quite good.
Of course, this book is an exception, and I recommend that everyone read it. Unfortunately, this does not mean that Chinese popular science can be compared with foreign masterpieces. This book is really hard to display on a refined shelf, because it was originally serialized on an Internet forum, and its lines are filled with Internet slang—things like “going crazy,” “I,” “boss,” and so on… But this counts as one of the book’s characteristics, I suppose: not rigorous enough, but more than sufficiently accessible. In fact, those popular science books written by foreigners are all very rigorous; even the most accessible books come with notes, bibliographies, indexes, and the like, treated in the same way as academic monographs! Chinese authors, by contrast, not only do not add notes and indexes, they even cut out all the indexes from translated books!
This book’s account of the development of quantum physics is indeed very interesting, and the relevant knowledge it covers is also very complete and very up to date. Add to that the absence of mistranslation problems, and for everyone this book is probably more worth recommending than Gribbin’s.
By the way, I must mention that the editorial standard of this book is truly appallingly poor! The “errata sheet” tucked into the book listed eight obvious errors. For example, errors like writing 10 to the 17th power as 1017—errors that can be spotted with a single glance—appeared many times, and in some places they simply left “???” in place!
Also, apparently for the sake of beauty, each page has in the top right corner a solar-system-style image of an electron orbiting an atom. Regardless of whether adding it is beautiful or ugly—and in fact it is ugly to an outrageous degree—what exactly does this image represent? It is precisely the classical image of the atom! Decorating a book on quantum mechanics with such an image feels a bit ironic…
Hehe, we have finally come to the matter of quantum mechanics! Let us now see just where the overthrow of classical mechanics by quantum mechanics lies.
Third Story: The Magical Quantum World
Even students who have never read a popular science book have probably heard something about the 20th-century physics revolution. In fact, the 20th century was a period when physics was transformed beyond recognition; roughly speaking, there were three areas that can be called physics revolutions: relativity, quantum mechanics, and chaos theory.
The one most familiar to everyone is probably the revolution of relativity, but in fact the status of relativity as a revolution is open to doubt! Strictly speaking, relativity was not a major revolution in thought. The change from Newtonian mechanics to relativity does not actually require Kuhn’s paradigm shift to explain. In reality, we also see that once Einstein’s relativity was proposed, it was immediately and generally accepted by the physics community—and not, as some exaggerated rumors claim, that at one point in time there were only thirteen people in the world who understood relativity—Einstein almost became famous overnight. Whether special relativity or general relativity, acceptance and recognition within physics came quite quickly—often it was the pseudo-scientists who could not accept it. Although there were some disagreements on specific issues, there were very few objections to the main line of the theoretical system of relativity!
Why is that? Actually, relativity is still a system built on the thought of classical Newtonian mechanics.
Classical mechanics has three conservation laws related to space-time—we can imagine several invariances related to space-time: one is time-translation invariance. Simply put, under the same other conditions, the results of doing an experiment today and doing an experiment yesterday should be the same. This invariance leads to the law of conservation of energy; the second is spatial translation invariance. Simply put, if you move the experimental apparatus and do the experiment, the result is still the same. This invariance leads to the law of conservation of momentum; the third is spatial rotational invariance, meaning that if you rotate the apparatus by an angle and do it, it is still the same. This leads to the law of conservation of angular momentum. Well, these three are all laws of Newtonian mechanics. But what did relativity take into account? It took into account the relativity of time and space, and thought more deeply about time translation and spatial translation. It introduced a new invariance—invariance under Lorentz transformations, simply put, invariance under uniform straight-line motion, plus the postulate that the speed of light is invariant. According to this invariance, new physics resulted; for example, the original law of conservation of energy was improved into the law of conservation of mass-energy…
Incidentally, among contemporary physicists, the conceptual foundation of relativity is almost unquestioned; only pseudo-scientists keep questioning its ideas. This is the same in China and in the West, and Western physicists are also very troubled by this.
I won’t go into details here. In short, relativity does not require a very great overturning of our way of thinking; it just thinks a little more carefully. The theoretical basis of relativity already existed long before Einstein. Einstein’s greatness is actually similar to Newton’s: his achievement lay in establishing a mature new system.
Of course, relativity can be called a physics revolution because its rewriting of the original theory, as well as the related experimental verification and applications, had an enormous impact. So relativity was a major revolution at both the theoretical and practical levels, but it was not a very obvious revolution in thought and conception.
As for chaos theory, even more people do not recognize it as a major revolution. I want to say that chaos theory was a revolution in thought and conception, but its theoretical and practical progress was very small. Chaos theory did not actually produce a whole complete theoretical system in physics, nor did it have much practical application—its applications in economics, biology, and the like have had some effect, but we are talking about a physics revolution. In chaos theory, only Prigogine got a Nobel Prize, and it was the chemistry prize!
In fact, relativity and chaos theory still belong to classical mechanics. That is also how we now use the term classical mechanics. If one were to speak of the 20th century’s truly all-around, overturning revolution in theory, practice, thought, and conception, it would be only quantum mechanics!
Quantum mechanics achieved quite enormous results in practice. In experiments, quantum mechanics, like relativity, is extremely precise. Feynman’s quantum electrodynamics has calculated the experimental precision of the magnetic moment of a single electron to 10 to the 11th power, and can be called the most precise physical theory since the beginning of time.
As for how severe the intellectual revolution of quantum mechanics was, how severe was it? It made old men like Planck and Lorentz dare not speak, made Einstein find it intolerable, and could even directly lead to mental collapse—this is not all a joke. There really was a quantum physicist who could not figure it out and committed suicide: (On September 25, 1935, Ehrenfest shot his intellectually disabled son in Leiden, the Netherlands, and then killed himself. In a letter left to his friends Einstein, Bohr, and others, he wrote: “In these years I have become increasingly unable to understand the rapid development of physics. I have tried hard, but I have become even more desperate and heart-rending. I have finally decided to give up everything; my life is extremely boring…” page 197)
So, what exactly was the revolution of quantum mechanics? We might as well begin with this image of atomic structure. (Note: I am not following the order of historical development.)
Anyone with some middle-school physics knowledge knows that the orbits in this solar-system-style atomic model are step-like, like walking up stairs rather than up a slope: an electron can only be on this orbit or that orbit, not in between. This is precisely the core concept of quantum mechanics—discontinuity.
Why must it be this way? Before Bohr proposed this step-like orbital theory, one of the major problems physics faced was this: if an electron orbits the nucleus, then it will radiate electromagnetic waves, thereby radiating energy. It is just like how we can use a circular electric current to make an electromagnet, and then use an electromagnet to make a crane—there is no free lunch in the world; since it can lift heavy objects, energy must always be consumed. And since the electron forms a ring of current by virtue of its motion, it will also continuously lose energy. And once energy is lost, the electron will no longer be able to maintain its motion on the original orbit; it will inevitably get closer and closer to the nucleus, and in the end, of course, it will irretrievably fall into the nucleus!
So Bohr proposed a way to save the electron, namely that the electron’s orbits are not arbitrary but step-like. The electron does not continuously release energy, but can only release it in discrete jumps—when the electron jumps from a higher energy level to a lower one, it radiates a corresponding amount of energy. But when the electron remains at a certain energy level, it does not radiate energy. In particular, at the lowest energy level, it is like going down all the stairs to the ground and being unable to jump downward any further, so it no longer radiates energy.
What I have just said is actually all material learned in middle school. How is it? Does this already seem sufficiently astonishing? Perhaps everyone has not yet felt it. Then let us continue along this line of thought. Remember, discontinuity is the starting point of quantum theory, the first step toward madness. What is called a quantum is a quantum of energy, doesn’t that mean energy comes in discontinuous pieces? Right now everyone may not feel that this is hard to accept, but let us look further down; in the end we will discover that in fact even this point of discontinuity itself is difficult for us to understand!
All right, the electron’s orbit is discontinuous, but what about the direction of its rotation? Bohr tells us that is discontinuous too! There are only two possible directions of electron spin—for example, clockwise and counterclockwise. Hold on! Isn’t the electron in three-dimensional space? Since it isn’t rotating on a plane, couldn’t it rotate in a plane inclined at 10 degrees, 20 degrees, 30 degrees, and so on, relative to the horizontal? No way! We can verify this with an experiment—because the electron’s rotation produces an electric current, and an electric current produces a magnetic field, a rotating electron is like a tiny magnet. If we let a hydrogen atom pass through a specially designed magnetic field (a Stern–Gerlach magnet, whose field is uneven in strength between the upper and lower parts), the atom will be deflected by magnetic force. If the directions of electron rotation were randomly distributed, then the deflections would also be distributed continuously from the maximum deflection to no deflection at all. But the actual result is this: particles passing through the magnetic field show only two behaviors—they are either deflected maximally upward or deflected maximally downward!
Fine, the electron’s direction of motion has only two possibilities! Either up or down! But isn’t up and down determined by how I arrange the magnetic field? What if we rotate the direction of the magnetic field by 10 degrees and look again? It’s all the same! However we observe it, the electron’s direction of motion always has only two possibilities!
Of course, perhaps you already thought of the answer—don’t rush, there are even more astonishing things ahead. Let’s continue.
Following the line of discontinuity, let us look at light. Everyone knows that light is both an electromagnetic wave and a particle—that’s middle-school knowledge, right? Has anyone ever doubted that? Actually, this is something very worth doubting! In fact, we will see that saying light is both a wave and a particle is simply incomprehensible. The fact that our schooling in middle school could make us so readily accept such a wildly absurd thing is astonishing!
But why must we speak of wave-particle duality? We won’t discuss that for the moment. Right now, just looking at light as a wave is already strange enough!
If light is a wave, then it is like me holding a rope, with the other end fixed, and I shake this rope. If the rope is long enough, everyone can imagine that a “wave” will appear in it—that is a wave. Light is more or less like that. So let us imagine. We can shake it horizontally, or vertically, or at any arbitrary angle—then the direction of the wave’s vibration will accordingly be different. Light is roughly the same, though with some differences, and this can be understood in this way; this is called polarization of light, and polarization has different directions. Let us imagine again that a grille has been placed across the middle of the rope in my hand. If the grille is vertical, then if I shake the rope horizontally, the wave will not pass beyond the grille; if it is horizontal, then vertical shaking will not get through. Light is roughly the same. We have something called a polarizing filter, and a vertical polarizing filter will not allow horizontally polarized light to pass through.
Then what about light polarized at 45 degrees? If we regard light as a wave, then a beam of 45-degree polarized light can be seen as a superposition of half vertical and half horizontal, and we can imagine that when a beam of 45-degree light passes through a horizontal or vertical polarizing filter, it will be blocked by half. In addition, ordinary natural light can be regarded as a mixture of light polarized in all directions, just as white light is a mixture of light of various wavelengths. Natural light passing through a polarizing filter will also be blocked by half. In fact, this principle is applied in everyday life; higher-grade sunglasses are essentially polarizing filters! The advantage of such sunglasses is that they can reduce the intensity of light by half without affecting its color. So there is a marvelous experiment that requires no expensive equipment, one that ordinary people can do. As long as you have three polarizing sunglass lenses (I don’t).
If we place two polarizing filters at the same angle, we will find that the light passing through both is about the same as when only one is used. But if we place the two polarizing filters perpendicular to each other, then no light at all will get through. Then, since the two filters already block all the light, what if we insert another one between them? Suppose we insert a 45-degree polarizing filter in the middle: we will find that half of the light gets through the first filter, and then half of that half gets through the second, and then half of that gets through the third. What we see is that one-eighth of the light passes through these three lenses!
Is this magical? Isn’t it magical? Perhaps you think it is very simple, because the light changes as it passes through the polarizing filters—the middle filter acts like a buffer, a transition, a lubricant. Fine, let us now write down our conclusion: magnetic fields and polarizing filters can “change” the state of electrons or photons. Of course, if we understand light as a particle at the same time, a big problem has already appeared here, but let us not do that for the moment. For now, we only know that electrons are particles and light is a wave; even with that alone, trouble is already about to begin. We do not need to accept wave-particle duality—just wait for the EPR paradox!
What does it mean that measuring devices affect the object? Let us turn back to electrons. When we observe electrons that have already passed through a Stern–Gerlach magnet once—for example, if we let those electrons that have already been deflected upward pass through the magnetic field again—we can imagine that they would all be deflected upward by another angle. But if we first let them pass through a horizontal Stern–Gerlach magnet, they will instead be split evenly into left and right, and then if these leftward or rightward electrons pass through a vertical magnet, their deflection will again be split half and half. What does this mean? — If we observe the horizontal component of the spin of a beam of electrons once, we will lose the information about their “original” vertical spin, and vice versa. In short, we can only measure either the horizontal aspect of the direction of rotation of a beam of electrons or the vertical aspect, but not both at the same time!
Well, this is called the uncertainty principle. When Heisenberg explained the uncertainty principle, he spoke of how one cannot precisely know both a particle’s momentum and position at the same time, because once a measurement is made, one must somehow “see” the particle. In the process of seeing it—for example, shining a beam of light on the particle—the light will affect the particle. The clearer you want to see it, the stronger the light you need, and the greater the disturbance to the particle, so that when you want to see its position clearly, its momentum becomes unclear.
The same is true whether we are measuring a particle’s momentum and position, the direction of an electron’s rotation, or the polarization of a light wave. The uncertainty principle is based on this line of thought: any observation will inevitably disturb the observed object!
Everything above is still thinking along the traditional lines of classical mechanics, but the shock brought by quantum mechanics is not merely this “uncertainty principle.” In fact, the Uncertainty Principle should more properly be called the “Indeterminacy Principle,” because quantum mechanics not only claims that we cannot “measure accurately” some thing; China’s earliest translators clearly did not grasp the deeper meaning of indeterminacy. What quantum mechanics further raises here is a sharp question: what was a particle like before it was observed? According to the traditional line of thought, an electron always has an objectively definite spin direction before being observed, one that is not subject to human will; it is only when it passes through the magnetic field we set up that its direction is forced to change, making the other direction unmeasurable. But quantum mechanics claims: before we perform an observation, it is meaningless to talk about the electron’s spin! “Indeterminacy” does not merely mean that the electron’s state cannot be determined by us experimenters; more fundamentally, it refers to a state inherent in nature itself—in advance of observation, the particle’s state is “indeterminate”! Wheeler: in the “real world of quantum physics, fundamental phenomena are not phenomena until recorded.”
That is to say, observation is not merely changing the electron’s direction of rotation; rather, observation creates the electron’s direction of rotation!
Things are getting more and more uncanny. Einstein could no longer sit still. When quantum mechanics was just rising, Einstein and Bohr and the others fought several rounds at the fifth and sixth Huashan sword duels—that is, the Fifth and Sixth Solvay Conferences—and all of them were brilliant and intense. In the mornings, Einstein would come up with one thought experiment after another refuting quantum mechanics, and in the evenings Bohr and the others would dissolve them. According to the description by Ehrenfest: “Einstein was like a spring toy, popping out of the box every morning with a new idea, while Bohr found tools in the mist-shrouded philosophy and smashed all of the other side’s arguments one by one.”
The two sides went back and forth. Although Einstein was the main attacker, he remained at a disadvantage throughout. I won’t go into the details here; everyone can learn them from books. What I want to talk about is the last decisive move Einstein devised by joining forces with his two colleagues—Podolsky and Rosen—the “EPR” paradox.
Part Four: EPR
Please note that my way of explaining quantum mechanics is different from the usual one. Take Gribbin, for example: he follows Feynman’s approach, starting right away with Young’s double-slit interference experiment. Feynman said that the whole mystery of quantum mechanics is concentrated in the double-slit experiment; when you encounter other strange things, you just need to think about the double-slit experiment—that is the same. If you can figure out the double-slit experiment, you have figured out at least half of quantum mechanics. The problem is that even these most basic mysteries are already impossible to make sense of.
The double-slit experiment is indeed the most direct shortcut into the mysterious quantum world, but I did not begin with it because it involves wave-particle duality. The double-slit experiment may already be at the high-school level, while middle-school physics may know less about wave properties. Besides, there are quite a few people who do not believe in wave-particle duality, aren’t there? So I plan to bypass wave-particle duality entirely and just look at what we generally take to be a particle—an electron. Without needing to consider that the electron is also a wave, we can already get some sense of the marvels of the quantum world. If there is time at the end, we will then talk about the double-slit experiment. For now, let us continue looking at the electron’s direction of rotation.
What made Einstein unable to accept quantum mechanics was the destruction of causality (actually determinism)—everything is decided by probability, and God plays dice! When a particle passes through a magnetic field, we can only say that there is a 50% chance it is deflected upward and a 50% chance it is deflected downward. What sort of thing is that? But what Einstein found even less tolerable was the destruction of “reality”! Fine, let’s say we are talking about dice. Whether it is God or me, once I shake the dice and put them there, before we open the box to look, the value has already been determined, hasn’t it? Quantum mechanics actually says that before we open the box and look, the state of the dice is some muddled “superposition state,” and only when we open the box does the state of the dice abruptly “collapse” into a definite value. What sort of thing is that? Has Bohr gone mad, or has God gone mad?
After suffering crushing defeats in the first two duels, Einstein came up with this EPR thought experiment, hoping to reveal the errors of quantum mechanics through the absurdity of this thought experiment. Yet, like the various other thought experiments expressing opposition, this one in turn was used by quantum mechanics to show quantum mechanics’ counterintuitive nature—aren’t the quantum world’s results just absurd? These thought experiments, far from overturning it, only keep interpreting its absurdity! What is special about EPR is that it would become a verdict, because this thought experiment could be realized!
I will introduce an improved version of the EPR experiment, still aimed at the earlier question of the electron’s direction of rotation. (The problem of the direction of revolution of an electron around the nucleus is similar to understanding the problem of electron spin.)
Let us imagine a particle with no spin. It will occasionally split into two electrons. According to the law of conservation of angular momentum, one of the most basic conservation laws in nature, we know that the directions of rotation of these two electrons must be opposite—that is, if one is up, the other must be down. We use a vertical magnetic field to measure electron A. If the result is upward, then if we also use a vertical magnetic field to measure electron B, the result must be downward! That is to say, even if we do not observe B, we can still know B’s state information! This violates the uncertainty principle!
Think about it again: if the electron’s direction of rotation is determined only by probability at the moment it is observed, then how can we explain why, whenever we measure the vertical spin of electron A and electron B at the same time, we always get opposite results? Suppose that A’s choosing the upward direction is a random choice made temporarily at the moment it is observed—then how could that choice instantaneously let B also “know”? At the time of observation the two electrons can be far apart, so is it possible that, because they lack communication, they might cooperate badly and both choose the upward direction? That would violate the law of conservation of angular momentum. Both theory and experiment tell us that the coordination between the two electrons is always so tacitly perfect. Therefore quantum mechanics is wrong—there is no uncertainty, no random choice! When the particle splits, the spin states of the two electrons are already definite. No matter how the measuring magnetic field is arranged, the direction in which the electron will be deflected is already determined at the moment of splitting.
Bohr’s reply this time was downright brutal. He pointed out that EPR is not a paradox at all; to think it is a paradox is precisely to use intuitive logic, and in the quantum world, talking about “reality” in the absence of observation is utterly meaningless. EPR precisely proves that intuitive logic fails in the quantum world!
The dispute over EPR did not end at the time. Bohr did not, as before, get Einstein to retract his thought experiment. Until Einstein’s death, Bohr still had not managed to convince him, and this was also one of Bohr’s great regrets.
Bohm and Bell were the key figures in finally resolving the EPR paradox. They proposed a set of experimental ideas sufficient to render a verdict. Ironically, both of them were opponents of the orthodox interpretation of quantum mechanics……
Bell proposed a famous “inequality.” This inequality is simply too magical and too important. In simple terms, it is like saying that the number of Chinese Han males plus the number of all Chinese women is greater than the number of Chinese Han. If everyone is willing to muster a bit of energy and follow along with a little mathematics, I will explain in detail.
My explanation is not exactly the same as the one in the book; I am following my own line of thought. Next we will need a little mathematics, probably no more than elementary-school level……
Let us consider measuring electron A. We can measure it with a magnetic field in direction A, or we can measure it with a magnetic field in direction B. Although each time we can choose only one method of measurement, according to the realist line of thought, even if we do not use B but use A to observe electron A, that electron also originally had a definite way of passing through the B magnetic field—at worst, the A magnetic field merely disturbed that initial state. Likewise, for electron B we can choose to measure with C or with D. Since each measurement of an electron will show only two possibilities, we denote them by 1 and -1 respectively; for example, if we say A=1, that means the result of electron A passing through A is upward, and so on. (By the way, are negative numbers elementary-school level? Probably learned in the upper grades of elementary school, right?)
Let us look at this expression: S＝A×C＋B×C＋A×D－B×D. That is, (A＋B)×C＋(A－B)×D. Here A, B, C, and D are all either +1 or -1. It is easy to see that between A+B and A-B, one is always 0 and the other is either +2 or -2, so the value of S is either +2 or -2.
Since each time we can only choose one observational method for electron A and one for electron B, that is to say, each time we can obtain only one of the values A×C, B×C, A×D, or B×D. But we can do the experiment repeatedly. We can imagine that after performing a number of experiments and taking the average, since S each time is either 2 or -2, the average after enough observations should be close to 0, right? At any rate, its average should always lie between 2 and -2, isn’t that simple?
However, according to the conclusions of quantum mechanics, by appropriately designing the directions of A, B, C, and D—we derived earlier that S lies between 2 and -2 completely independently of quantum mechanics, and even more so independently of any arrangement of directions; we merely used the simplest logical reasoning—we can make the final statistical result exceed 2! In short, quantum mechanics claims that Bell’s inequality may be violated!
How could that be possible? Bell thought this would become the fatal blow that overturned the orthodox interpretation of quantum mechanics, and all that would remain was to arrange the experiment. But he never imagined that what this verdict would shatter was actually the final judgment on the classical view of reality.
The setup may sound simple, but the experiment itself is not easy to perform. Although there do exist things like a π meson whose spin is zero and which occasionally splits spontaneously into two electrons, it is rather difficult to control and detect them well. So the final verdict was delayed until 1982, when it was delivered by Aspect. He used photons rather than electrons, and measured polarization rather than spin, but that is only a matter of detail. Aspect’s experiment was impeccable. In fact, many experiments had already been carried out, including measurements of the direction of electron revolution around protons and measurements of electron spin, and the results all clearly favored quantum mechanics. But Aspect’s experiment was so perfect that it became difficult for anyone in the physics community to doubt the result any longer. The EPR paradox turned into the EPR verdict. In any case, a classical world that is both realistic and local is gone for good.
Note that EPR still did not completely overturn the reality of the world, because if we assume that at the moment of observation there is instantaneous communication between the two electrons—even if they are at opposite ends of the universe—then reality might still be barely preserved. That is precisely what Bohm’s hidden-variable interpretation advocates! But this kind of “spooky action at a distance” is no easier to understand, and Bohm’s hidden-variable interpretation has some theoretical problems, so its persuasiveness is limited.
At the same time, EPR experiments and thought experiments such as Schrödinger’s cat have also shaken people’s confidence in the orthodox Copenhagen interpretation. In the second half of the twentieth century, many different approaches to quantum mechanics also emerged, but I won’t introduce them in detail here.
In 1997, a seminar on quantum mechanics was held at the University of Maryland, Baltimore County. A questionnaire was distributed among the participants, asking which interpretation of quantum theory they believed in. The results were as follows: 13 votes for the Copenhagen interpretation, 8 for the many-universe interpretation, 4 for hidden variables, 4 for decoherent histories, 1 for spontaneous localization theories (such as GRW), and 18 for other options or no idea yet; at a 1999 conference at the Newton Institute in Cambridge, a similar survey yielded 4 votes for Copenhagen, 4 for modified dynamics theories (such as GRW), 2 for Bohm, while many-worlds and many-histories together (the view that there is no collapse) got 30 votes, and another 50 votes came from people admitting they could not decide. Among cosmologists and experts in quantum gravity, many-worlds is especially popular; statistics show that 58% think many-worlds is correct, while only 18% think it is not.
The mathematical formalism of quantum mechanics is fixed: Heisenberg’s matrix mechanics and Schrödinger’s wave mechanics had long laid its foundation, and the two are completely equivalent mathematically. Later, Feynman proposed a path-integral interpretation, and he himself proved that it is a third formulation of quantum mechanics, completely equivalent to matrix mechanics and wave mechanics. Mathematical equivalence does not mean the disagreements can be resolved. The physical meanings of 2 plus 2 and 2 times 2 are obviously different. Even for the same variable, whether it stands for probability, a diffusing wave, or something hiding other variables—on these questions, physicists argue endlessly.
If physicists have all become philosophers, then what can philosophers do? I think we should be honest: the era when philosophers could often make profound insights into the natural sciences is long gone. The philosophers on the market today who shout about overthrowing Einstein and discovering some grand unified theory of the universe seem childish and ridiculous; while those philosophers who remain at the level of literal interpretation and then want to apply scientific conclusions wholesale to society and life are often quite obnoxious. No wonder Feynman was so sarcastic about those “cocktail-party philosophers” who bring up relativity at the drop of a hat. But this does not mean philosophers must give up and stay far away from science. Science and philosophy were originally different ways in which human beings seek knowledge; philosophy is the love of wisdom, and “love” does not mean the pursuit of utility, but rather represents a kind of emotion unique to human beings. Science certainly does not represent the whole of wisdom, but scientific knowledge is also an important part of human wisdom. Philosophers should care about science, just as philosophers should also care about history, art, religion, and so on. We cannot require every philosopher to do a great deal of scientific research or historical research, but basic popular works written for the public, such as these, are things students of philosophy should be even more proactive in coming into contact with. The biggest purpose of my lecture this time is precisely to “market” these miscellaneous books to everyone. I have a lot of books—there are probably close to a thousand books in my dorm room alone. Apart from almost no literary fiction, there are quite a lot of others, such as popular science books, psychology, religious studies, history books, and so on. In particular, in the popular science series, across all categories and all series, it can be said to have “everything you could want”! Anyone interested can borrow them from me, and can also listen to my recommendations. Some books I bought in duplicate, and I can give them away, if anyone is willing to write a few thousand characters of reading notes afterward.
Early morning of April 21, 2006
In Hai Ti Azhudan
Slightly revised at noon on April 21
Latest comments
- Gu
2006-04-21 23:46:11
I didn’t do a very good job explaining the quantum mechanics part. But the way I sidestepped wave-particle duality and directly derived the EPR argument should be pretty good. If I had a bit more time, I would have gone back to the double-slit interference experiment. The double-slit experiment and the delayed-choice experiment are also very revealing, and I didn’t have time to talk about either of them or about Schrödinger’s cat. I also didn’t get to the many-universe interpretation, which is a bit of a pity.
Translated from the Chinese original with AI assistance. The original text is authoritative.
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