Academics From Northern Ireland

"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."

"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."

"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?"

"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."

"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"."

"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."

"A good man deliberating which of several actions proposed he shall choose, regards and compares the material goodness of them, and then is determined by his moral sense invariably preferring that which appears most conducive to the happiness and virtue of mankind."

"All our Ideas, or the materials of our reasoning or judging, are received by some immediate Powers of Perception internal or external, which we may call Senses … Reasoning or Intellect seems to raise no new Species of Ideas, but to discover or discern the Relations of those received."

"Kant in fact seems to have begun his reflections on moral theory as an adherent of Francis Hutcheson’s moral sense theory. Even after abandoning it, he persists in maintaining the importance of “moral feeling” and tries consistently to make a place for it within his moral psychology."

"Francis Hutcheson and David Hume were the two most prominent Scottish contributors to moral philosophy before Smith. They had criticized the view of rationalist philosophers, such as Samuel Clarke and William Wollaston, that the judgement and the motive of moral action are functions of reason, an understanding of necessary truth analogous to mathematical thinking. Hutcheson and Hume, in contrast, took the view that moral judgement is affective, rests on feeling, and that the motive for acting upon that judgement must likewise be affective, since reason alone does not have the power to stir bodily behaviour."

"Another valuable purpose of ridicule is with relation to smaller vices, which are often more effectually corrected by ridicule, than by grave admonition. Men have been laughed out of faults which a sermon could not reform; nay, there are many little indecencies which are improper to be mentioned in such solemn discourses. Now ridicule with contempt or ill-nature, is indeed always irritating and offensive; but we may, by testifying a just esteem for the good qualities of the person ridiculed, and our concern for his interests, let him see that our ridicule of his weakness flows from love to him, and then we may hope for a good effect. This then is another necessary rule, "That along with our ridicule of smaller faults we should always join evidences of good nature and esteem." As to jests upon imperfections, which one cannot amend, I cannot fee of what use they can be: men of sense cannot relish such jests; foolish trifling minds may by them be led to despise the truest merit, which is not exempted from the casual misfortunes of our mortal state."

"Wisdom denotes the pursuing of the best Ends by the best Means."

"That Action is best, which procures the greatest Happiness for the greatest Numbers; and that worst, which, in like manner, occasions Misery."

"Whence this secret Chain between each Person and Mankind? How is my Interest connected with the most distant Parts of it?"

"Whoever voluntarily undertakes the necessary office of rearing and educating, obtains the parental power without generation."

"The ultimate notion of right is that which tends to the universal good; and when one's acting in a certain manner has this tendency, he has a right thus to act."

"I need scarcely say that the beginning and maintenance of life on earth is absolutely and infinitely beyond the range of sound speculation in dynamical science."

"If the water flow down by a gradual natural channel, its potential energy is gradually converted into heat by fluid friction, according to an admirable discovery made by Mr Joule of Manchester above twelve years ago, which has led to the greatest reform that physical science has experienced since the days of Newton. From that discovery, it may be concluded with certainty that heat is not matter, but some kind of motion among the particles of matter; a conclusion established, it is true, by Sir Humphrey Davy and Count Rumford at the end of last century, but ignored by even the highest scientific men during a period of more than forty years."

"It is conceivable that animal life might have the attribute of using the heat of surrounding matter, at its natural temperature, as a source of energy for mechanical effect . . . .The influence of animal or vegetable life on matter is infinitely beyond the range of any scientific enquiry hitherto entered on. Its power of directing the motions of moving particles, in the demonstrated daily miracle of our human free-will, and in the growth of generation after generation of plants from a single seed, are infinitely different from any possible result of the fortuitous concurrence of atoms."

"Tesla has contributed more to electrical science than any man up to his time."

"To live among friends is the primary essential of happiness."

"Every boy... should be able by the age of 12 to write his own language with accuracy and some elegance; he should have a reading knowledge of French, and be able to translate Latin and easy Greek authors, and have some acquaintance with German. Having learned thus the meaning of words... a boy should study Logic, so as to be able to apply his words sensibly."

"Now I think hydrodynamics is to be the root of all physical science, and is at present second to none in the beauty of its mathematics."

"It is impossible by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects. [Footnote: ] If this axiom be denied for all temperatures, it would have to be admitted that a self-acting machine might be set to work and produce mechanical effect by cooling the sea or earth, with no limit but the total loss of heat from the earth and sea, or in reality, from the whole material world."

"1. There is at present in the material world a universal tendency to the dissipation of mechanical energy. 2. Any restoration of mechanical energy, without more than an equivalent of dissipation, is impossible in inanimate material processes, and is probably never effected by means of organized matter, either endowed with vegetable life or subjected to the will of an animated creature. 3. Within a finite period of time past, the earth must have been, and within a finite period of time to come the earth must again be, unfit for the habitation of man as at present constituted, unless operations have been, or are to be performed, which are impossible under the laws to which the known operations going on at present in the material world are subject."

"Thomson was a mathematical prodigy. At age 16, he mastered ’s ' and wrote and published a defense of it. Fourier’s theory allowed one to determine the distribution of heat in a body on the sole assumption that heat flow is proportional to temperature gradient. The approach was macroscopic, geometrical, and nonhypothetical, and Thomson took to it easily. During his undergraduate years at , he traveled to Paris and met the mathematical savants—in particular, mathematician Joseph Liouville and experimental physicist , who both considered Michael Faraday’s curved lines of force outré. At Liouville’s urging, Thomson produced for the ' a demonstration that the lines of force, whether electric or magnetic, followed from inverse square laws. The relevant mathematics was a near cousin to that for heat flow, but the insight was new and would be seminal in the thinking that led James Clerk Maxwell to electromagnetic field theory."

"If materialism cannot consistently escape the conclusion of a finite state, which William Thomson has traced out for it, then materialism is thereby refuted."

"According to Sir W. Thomson's theory of Vortex Atoms, the substance of which the molecule consists is a uniformly dense plenum, the properties of which are those of a perfect fluid, the molecule itself being nothing but a certain motion impressed on a portion of this fluid, and this motion is shewn, by a theorem due to Helmholtz, to be as indestructible as we believe a portion of matter to be."

"He was one of the few scientists to be knighted, and the only one in the nineteenth century to be raised to the peerage. These honors, however, were not in recognition of his scientific work but his genius as an engineer in solving the major technical problems of laying the first Atlantic cable and his entrepreneurial success as an instrument designer and manufacturer for the new electrical industries and the Navy. With his success with the Atlantic cable Kelvin became a symbol of science to the general public."

"The man of true Physical instincts, endowed with the great faculty of scientific imagination, possessed for example by Lord Kelvin in a very remarkable degree, is for ever imagining models which shall enable him by their working to represent and depict the course of actual physical processes. The possibility and consistency of such models require Mathematical Analysis for their investigation."

"There cannot be a greater mistake than that of looking superciliously upon the practical applications of science. The life and soul of science is its practical application; and just as the great advances in mathematics have been made through the desire of discovering the solution of problems which were of a highly practical kind in mathematical science, so in physical science many of the greatest advances that have been made from the beginning of the world to the present time have been made in earnest desire to turn the knowledge of the properties of matter to some purpose useful to mankind."

"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind; it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science, whatever the matter may be."

"There is nothing new to be discovered in physics now. All that remains is more and more precise measurement."

"The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds. I. The first came into existence with the undulatory theory of light, and was dealt with by Fresnel and Dr. Thomas Young; it involved the question, how could the earth move through an elastic solid, such as essentially is the luminiferous ether? II. The second is the Maxwell–Boltzmann doctrine regarding the partition of energy."

"Quaternions came from Hamilton after his really good work had been done, and though beautifully ingenious, have been an unmixed evil to those who have touched them in any way."