Cosmologists

"I think that physics is about escaping the prison of the received thoughts and searching for novel ways of thinking the world, about trying to clear a bit the misty lake of insubstantial dreams, which reflect reality like the lake reflects the mountains."

"The landscape is magic, the trip is far from being over."

"... theoretical physics is less clean than the way it's usually solved. You can always change parameters and save yourself. ... it's very rare that theories are ruled out by just an experiment or a group of experiments. Theories usually come with flexibility. Theoreticians can add flexibility. And so new experiments — you can just patch up your theory."

"If we want to understand the past we must do so on its own terms, and disregard the future of that past, but if we want to understand the present we better not disregard the past steps that were essential for getting to the present. This is of importance especially for those of us engaged in trying to push ahead the scientific path of discovery today. We are not much interested in what scientists did wrong, there is too much of that. We are interested in what they did right, because we are trying to copy them in this, not in that."

"Hawking was one of the good physicists of his generation, not the universal genius the popular press has depicted. It is a pity, because this confusion fogs the memory of a remarkable man."

"In the 1930s Landau was already saying, "I am one of the few universal physicists"; after the death of Enrico Fermi, this became "I am the last of the universal physicists"."

"Once, lecturing in Moscow during his last visit to the USSR, Niels Bohr was asked how he had succeeded in creating such a famous and first-class school of theoretical physics. He answered: "Probably because I have never been ashamed of admitting to my students that I am a fool." Bohr's lecture was translated into Russian by Landau's closest collaborator, E. Lifshitz, who translated it: "Probably because I have never been ashamed to tell my students that they are fools." Lifshitz's mistranslation caused a lot of laughter among the listeners. Lifshitz became aware of his mistake, corrected himself, and apologized. Kapitza, who was present, remarked that this mistranslation had not been accidental at all: "Precisely here lies the difference between Bohr's and Landau's schools of theoretical physics.""

"In 1956 Shapiro had been very actively investigating the so-called $\tau-\theta$ problem, which had been puzzling physicists for a long time. Shapiro came to the conclusion that the only possible explanation could be the parity non-conservation in this decay of mesons... Landau, when Shapiro presented him the paper, laughed at such an idea -- without Landau's holy consent Shapiro's paper could not be published. It remained on his desk, where I saw it many months before Lee and Yang submitted their paper for publication. So, because of Landau, Soviet physics lost one Nobel prize. A similar case is reported by Landau's closest collaborator, A.A. Abrikosov. Landau's negative attitude to Abrikosov's theory had delayed the discovery of superconductivity II for about four years."

"It is Landau’s invention—as it may, I feel, be fairly called—of the order parameter that is so important but often underappreciated... Landau’s concept of the order parameter, indeed, brought light, clarity, and form to the general theory of phase transitions, leading eventually, to the characterization of multicritical points and the understanding of many characteristic features of ordered states. But in 1944 a bombshell struck! Lars Onsager, by a mathematical tour de force, deeply admired by Landau himself, computed exactly the partition function and thermodynamic properties of the simplest model of a ferromagnet or a fluid... the nature of the critical singularities disagreed profoundly—as I will explain below—with essentially all the detailed predictions of the Landau theory (and of all foregoing, more specific theories)."

"In 1958, Landau and certain other seminar participants were highly enthusiastic about the new Heisenberg theory in which all particles arise from a universal fermion field. (Others, however, took a highly skeptical view of this theory.) At one seminar Landau received a letter through Pontecorvo, supposedly from Pauli, and Landau read it aloud. In the brief letter, Pauli wrote that he liked Heisenberg's theory, that he'd found new arguments in its favor and found it highly plausible. Moreover, wrote Pauli, the latest experiments with Λ hyperons confirm Heisenberg's theory. No details were given about these experiments, though. There was great excitement: after all, Pauli was known as a person with a critical turn of mind, far from gullible. Different hypotheses were advanced; one young theorist even went up to the board and tried to imagine what the experiment could be that Pauli wrote of. Meanwhile, Migdal took the letter, read it carefully and said, "Something's strange here. If you read the first letters of all the lines from top to bottom, it spells the Russian word 'fools.' What could that mean?" The secret was simple: The letter was written by Migdal and Pontecorvo."

"BEWARE, HE BITES!"

"The idea seems to exist that there can be an absolutely continuous transition between the liquid and crystalline state (analogous to the transition liquid-gas), which would require the existence of a miraculous state which is neither isotropic nor anisotropic."

"People who hear of some extraordinary phenomenon start proposing to explain it with improbable hypotheses. First consider the simplest explanation: that it's all nonsense."

"A method is more important than a discovery, since the right method will lead to new and even more important discoveries."

"This work contains many things which are new and interesting. Unfortunately, everything that is new is not interesting, and everything which is interesting, is not new."

"Главное, делайте всё с увлечением, это страшно украшает жизнь."

"You know my favourite Dirac story: I go up to him once and I say, "Professor Dirac, I've just thought of a way of relating the formation of stars to cosmological things — not galaxies, stars — shall I tell you about it?" And he said, "No.""

"... I started thinking about gravitational theories and Mach's Principle and so on, I knew already then, very slightly, Hermann Bondi and Tommy Gold, and I talked to them a bit about these things, I remember I asked Bondi to tea one day and told him the thoughts I'd had and I said, "Are they rubbish? What should I do?" He said, "Why not go on thinking about them?" I think that was very good of him, because I'm quite sure in retrospect it was rubbish what I said, as I was very immature at that time ..."

"It is not surprising that it was the Greeks, with their profound understanding of geometrical principles, who were the first to devise methods of measuring the size of the earth and the distance to the sun and the moon. Indeed, their results were not superseded until the eighteenth century, when telescopes had been developed to the point where new methods could be introduced."

"The reader has by now probably become accustomed to the reversals of fortune so common in astronomy."

"It has now become clear that the exploration of the Universe, as conducted by physicists, astronomers and cosmologists, is one of the greatest intellectual adventures of the mid-twentieth century."

"A theorist can explain any correlation, and its inverse."

"Let us admit that no matter how small the chance it could happen, one molecule could be created by such astronomical odds of chance. However, one molecule is of no use. Hundreds of millions of identical ones are necessary. Thus we either admit the miracle or doubt the absolute truth of science."

"One example of these kinds of statistics comes from Evolution: Possible or Impossible by James F. Coppedge [who] cites an article by Ulric Jelinek … which claims that the odds are 1 in 10^243 against "two thousand atoms" (the size of one particular protein molecule) ending up in precisely that particular order "by accident." Where did Jelenik get that figure? From Pierre Lecompte du Nouy... who in turn got it from Charles-Eugene Guye, a physicist who died in 1942. Guye had merely calculated the odds of these atoms lining up by accident if "a volume" of atoms the size of the Earth were "shaken at the speed of light," failing to factor in laws of chemistry, which create preferences for the formation and behavior of molecules, and ignoring that there are millions if not billions of different possible proteins. This calculation comes to Coppedge third-hand, and is now outdated (it was calculated before 1942, even before the discovery of DNA)."

"The idea that elimination of coherence, in one way or another, implies the replacement of 'and' by 'or', is a very common one among solvers of the 'measurement problem'. It has always puzzled me."

"The first charge against 'measurement', in the fundamental axioms of quantum mechanics, is that it anchors there the shifty split of the world into 'system' and 'apparatus'. A second charge is that the word comes loaded with meaning from everyday life, meaning which is entirely inappropriate in the quantum context."

"Einstein said that it is theory which decides what is . I think he was right—'observation' is a complicated and theory-laden business. Then that notion should not appear in the formulation of fundamental theory. Information? Whose information? Information about what? On this list of bad words from good books, the worst of all is 'measurement'. It must have a section to itself."

"The concepts 'system', 'apparatus', 'environment', immediately imply an artificial division of the world, and an intention to neglect, or take only schematic account of, the interaction across the split. The notions of 'microscopic' and 'macroscopic' defy precise definition. So also do the notions of 'reversible' and 'irreversible'."

"I expect that mathematicians have classified such s. Certainly they have been much used by physicists. But is there not something to be said for the approach of Euclid? Even now that we know that is (in some sense) not quite true? Is it not good to know what follows from what, even if it is not necessarily FAPP? Suppose for example that quantum mechanics were found to resist precise formulation. Suppose that when formulation beyond FAPP was attempted, we find an unmovable finger obstinately pointing outside the subject, to the mind of the observer, to the Hindu scriptures, to God, or even only Gravitation? Would that not be very, very interesting?"

"I agree with them about that: ORDINARY QUANTUM MECHANICS (as far as I know) IS JUST FINE FOR ALL PRACTICAL PURPOSES. Even when I begin by insisting on this myself, and in capital letters, it is likely to be insisted on repeatedly in the course of the discussion. So it is convenient to have an abbreviation for the last phrase: FOR ALL PRACTICAL PURPOSES = FAPP."

"Surely, after 62 years, we should have an exact formulation of some serious part of quantum mechanics? By 'exact' I do not of course mean 'exactly true'. I mean only that the theory should be fully formulated in mathematical terms, with nothing left to the discretion of the theoretical physicist . . . until workable approximations are needed in applications. By 'serious' I mean that some substantial fragment of physics should be covered. Nonrelativistic 'particle' quantum mechanics, perhaps with the inclusion of the electromagnetic field and a cut-off interaction, is serious enough."

"In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that such a theory could not be Lorentz invariant. Of course, the situation is different if the quantum mechanical predictions are of limited validity. Conceivably they might apply only to experiments in which the settings of the instruments are made sufficiently in advance to allow them to reach some mutual rapport by exchange of signals with velocity less than or equal to that of light. In that connection, experiments of the type proposed by Bohm and Aharonov, in which the settings are changed during the flight of the particles, are crucial."

"1 + P(b, c) ≥ |P(a, b) － P(a, c)|"

"More generally, the hidden variable account of a given system becomes entirely different when we remember that it has undoubtedly interacted with numerous other systems in the past and that the total wave function will certainly not be factorable. The same effect complicates the hidden variable account of the theory of measurement, when it is desired to include part of the 'apparatus' in the system. Bohm of course was well aware of these features of his scheme, and has given them much attention. However, it must be stressed that, to the present writer's knowledge, there is no proof that any hidden variable account of quantum mechanics must have this extraordinary character. It would therefore be interesting, perhaps, to pursue some further 'impossibility proofs,' replacing the arbitrary axioms objected to above by some condition of locality, or of separability of distant systems."

"To know the quantum mechanical state of a system implies, in general, only statistical restrictions on the results of measurements. It seems interesting to ask if this statistical element be thought of as arising, as in classical statistical mechanics, because the states in question are averages over better defined states for which individually the results would be quite determined. These hypothetical 'dispersion free' states would be specified not only by the quantum mechanical state vector but also by additional 'hidden variables' - 'hidden' because if states with prescribed values of these variables could actually be prepared, quantum mechanics would be observably inadequate."

"Bohr was inconsistent, unclear, willfully obscure and right. Einstein was consistent, clear, down-to-earth and wrong."

"The discomfort that I feel is associated with the fact that the observed perfect s seem to demand something like the ‘genetic’ hypothesis [identical twins, carrying with them identical genes]. For me, it is so reasonable to assume that the photons in those experiments carry with them programs, which have been correlated in advance, telling them how to behave. This is so rational that I think that when Einstein saw that, and the others refused to see it, he was the rational man. The other people, although history has justified them, were burying their heads in the sand. I feel that Einstein’s intellectual superiority over Bohr, in this instance, was enormous; a vast gulf between the man who saw clearly what was needed, and the obscurantist. So for me, it is a pity that Einstein’s idea doesn’t work. The reasonable thing just doesn’t work."

"The theorem tells you that maybe there must be something happening faster than light, although it pains me even to say that much. The theorem certainly implies that Einstein's concept of space and time, neatly divided up into separate regions by light velocity, is not tenable. But then, to say that there's something going faster than light is to say more than I know."

"It can be argued that in trying to see behind the formal predictions of quantum theory we are just making trouble for ourselves. Was not precisely this the lesson that had to be learned before quantum mechanics could be constructed, that it is futile to try to see behind the observed phenomena?"

"While the founding fathers agonized over the question 'particle' or 'wave', de Broglie in 1925 proposed the obvious answer 'particle' and 'wave'. Is it not clear from the smallness of the scintillation on the screen that we have to do with a particle? And is it not clear, from the diffraction and interference patterns, that the motion of the particle is directed by a wave? De Broglie showed in detail how the motion of a particle, passing through just one of two holes in screen, could be influenced by waves propagating through both holes. And so influenced that the particle does not go where the waves cancel out, but is attracted to where they cooperate. This idea seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored."

"I am a Quantum Engineer, but on Sundays I Have Principles."

"A final moral concerns terminology. Why did such serious people take so seriously axioms which now seem so arbitrary? I suspect that they were misled by the pernicious misuse of the word ‘measurement’ in contemporary theory. This word very strongly suggests the ascertaining of some preexisting property of some thing, any instrument involved playing a purely passive role. Quantum experiments are just not like that, as we learned especially from Bohr. The results have to be regarded as the joint product of ‘system’ and ‘apparatus,’ the complete experimental set-up."

"Theoretical physicists live in a classical world, looking out into a quantum-mechanical world. The latter we describe only subjectively, in terms of procedures and results in our classical domain."

"The concept of 'measurement' becomes so fuzzy on reflection that it is quite surprising to have it appearing in physical theory at the most fundamental level... does not any analysis of measurement require concepts more fundamental than measurement? And should not the fundamental theory be about these more fundamental concepts?"

"John S. Bell (1928–1990, right) and I at in Bell’s office 10 years after the neutrino experiment. We were the quasi-official theorists of that experiment. We did not do very well, all things considered, because of inexperience and ignorance. After the experiment, in 1963, we both went to SLAC, where I wrote my computer program and he developed his famous inequalities. We also discussed other things, even wrote a paper together that was never published. He considered his work on the fundaments of quantum mechanics as a hobby, mainly to be done in the evening, at home. He told me that he intended to do away definitely with this nonsense of hidden variables, and so he did. Later he drifted more and more into this subject, and as I consider it as some sort of foolishness not good for anything having to do with the real world, I once asked him: “Why are you doing this? Does it make the slightest difference in the calculations such as I am doing?” To which he answered: “You are right, but are you not interested and curious about the interpretation?” He was right too, up to a point. While his work became very important, as it could be verified by experiment, often in this branch of physics the discussions are on the level of finding out how many angels can dance on the point of a needle. But even so: there are interesting things there."

"It was John Bell who investigated quantum theory in the greatest depth and established what the theory can tell us about the fundamental nature of the physical world. Moreover, by stimulating experimental tests of the deepest and most profound aspects of quantum theory, Bell's work led to the possibility of exploring seemingly philosophical questions, such as the nature of reality, directly through experiments. And this was just Bell's "hobby"."

"In my opinion, John Bell performed an extremely important role then, and also later, in generally supporting - thereby making respectable - the apparently "fringe" activities of such people as Karolyhazy, Bohm, [Philip M.] Pearle, Ghirardi, and many others (including myself) in suggesting schemes that go beyond standard quantum mechanics, in the intended direction of realism. No physicist could doubt the scientific credentials of John Bell. The fact that he was prepared to go out of his way to support research of this kind gave it a previously unaccustomed status."

"I told Wheeler that I had had a number of conversations with Bell about quantum theory. "He’s a wonderful fellow," Wheeler noted. "Did he say to you," Wheeler asked, laughing, "‘I’d rather be clear and wrong, than foggy and right’?" I told Wheeler that Bell had not used exactly those words, but that it certainly sounded like him. I also told Wheeler that from the time that Bell began to study the quantum theory, he had conceptual problems with it, and that I had asked Bell if, at that time, he thought that the theory might simply be wrong—to which Bell had answered, "I hesitated to think it might be wrong, but I knew that it was rotten." At this, Wheeler burst into a marvelous peal of laughter. The idea of the young Bell rebelling against the "rottenness" of the quantum theory struck Wheeler as incredibly funny."

"I had never met Bell, nor heard him lecture, but in my reading of his scientific papers I have developed a great admiration for him and his work. I have especially admired his attempts to dismantle the orthodox Copenhagen interpretation of quantum theory, written with such tremendous style and obvious enjoyment. Although in this book I have tried to present a balanced account - arguing one way and then another - I hope that I have done justice to Bell's superbly constructed criticisms. The debate over the meaning of quantum theory will certainly be poorer without him."

"We must thank John Bell for having shown us that philosophical questions about the nature of reality could be translated into problems for physicists, where naive experimentalists can contribute."