Physicists From England

"Could it be that some place out there in the computational universe, we might find our physical universe?"

"It's always seemed like a big mystery how nature, seemingly so effortlessly, manages to produce so much that seems to us so complex. Well, I think we found its secret. It's just sampling what's out there in the computational universe."

"I had a very selfish reason for building Mathematica. I wanted to use it myself, a bit like Galileo got to use his telescope four hundred years ago. But I wanted to look, not at the astronomical universe, but at the computational universe."

"It's clear that we can go further than the quantum mechanics that I've known for the last fifty years."

"It was the spring of 1978 and I was 18 years old. I’d been publishing papers on particle physics for a few years, and had gotten quite known around the international particle physics community (and, yes, it took decades to live down my teenage-particle-physicist persona). I was in England, but planned to soon go to graduate school in the US, and was choosing between Caltech and Princeton. And one weekend afternoon when I was about to go out, the phone rang. In those days, it was obvious if it was an international call. “This is Murray Gell-Mann”, the caller said, then launched into a monologue about why Caltech was the center of the universe for particle physics at the time."

"Problem 9. What is the correspondence between cellular automata and continuous systems? Cellular automatat are discrete in several respects. First, they consist of a discrete spatial lattice of sites. Second, they evolve in discrete steps. And finally, each site has only a finite discrete set of possible values. The first two forms of discreteness are addressed in the numerical analysis of approximate solutions to, say, differential equations. ... The third form of discreteness in cellular automata is not so familiar from numerical analysis. It is an extreme form of round-off, in which each "number" can have only a few possible values (rather than the usual 216 or 232)."

"Computational reducibility may well be the exception rather than the rule: Most physical questions may be answerable only through irreducible amounts of computation. Those that concern idealized limits of infinite time, volume, or numerical precision can require arbitrarily long computations, and so be formally undecidable."

"Cellular automata are discrete dynamical systems with simple construction but complex self-organizing behaviour. Evidence is presented that all one-dimensional cellular automata fall into four distinct universality classes. Characterizations of the structures generated in these classes are discussed. Three classes exhibit behaviour analogous to limit points, limit cycles and chaotic attractors. The fourth class is probably capable of universal computation, so that properties of its infinite time behaviour are undecidable."

"God didn't produce a ready-made world. The Creator has done something cleverer than this, making a world able to make itself."

"God is not a God of the edges, with a vested interest in beginnings. God is the God of the whole show."

"There is much cloudy unpredictable process throughout the whole of the physical world. It is a coherent possibility that God interacts with the history of creation by means of "information input" into its open physical process. The causal net of the universe is not drawn so tight as to exclude this possibility. Mere mechanism is dead, and a more subtle and supple universe is accessible to the providential interaction of the Creator."

"Let me end this chapter by suggesting that religion has done something for science. The latter came to full flower in its modern form in seventeenth-century Europe. Have you ever wondered why that's so? After all the ancient Greeks were pretty clever and the Chinese achieved a sophisticated culture well before we Europeans did, yet they did not hit on science as we now understand it. Quite a lot of people have thought that the missing ingredient was provided by the Christian religion. Of course, it's impossible to prove that so - we can't rerun history without Christianity and see what happens - but there's a respectable case worth considering. It runs like this. The way Christians think about creation (and the same is true for Jews and Muslims) has four significant consequences. The first is that we expect the world to be orderly because its Creator is rational and consistent, yet God is also free to create a universe whichever way God chooses. Therefore, we can't figure it out just by thinking what the order of nature ought to be; we'll have to take a look and see. In other words, observation and experiment are indispensable. That's the bit the Greeks missed. They thought you could do it all just by cogitating. Third, because the world is God's creation, it's worthy of study. That, perhaps, was a point that the Chinese missed as they concentrated their attention on the world of humanity at the expense of the world of nature. Fourth, because the creation is not itself divine, we can prod it and investigate it without impiety. Put all these features together, and you have the intellectual setting in which science can get going. It's certainly a historical fact that most of the pioneers of modern science were religious men. They may have had their difficulties with the Church (like Galileo) or been of an orthodox cast of mind (like Newton), but religion was important for them. They used to like to say that God had written two books for our instruction, the book of scripture and the book of nature. I think we need to try to decipher both books if we're to understand what's really happening."

"Quantum theory also tells us that the world is not simply objective; somehow it's something more subtle than that. In some sense it is veiled from us, but it has a structure that we can understand."

"Thomson and then his young men demolished a recurrent scientific myth—one that had surfaced again in the 1870's: that there was nothing left to be discovered, nothing new under the sun. Part of the immutable wisdom of the day, endorsed and believed long before the greatest of scientists, Isaac Newton, was a kind of billiard ball theory of the atom, which went back to the ancient Greeks. The word itself is from the Greek atomos, meaning "inidivisible.""

"Notes on Recent Researches in Electricity and Magnetism, published in 1883, had won him enough acclaim at the age of twenty-seven that he was named director of the [Cavendish] laboratory the next year."

"Thomson's work suggested an alternative version—the instability of matter—to that of the indivisible atom. It was revolutionary stuff."

"J. J. Thomson was about to make the most significant find of the late nineteenth century... Thomson had been investigating the nature of cathode rays. He was convinced that they were some kind of electrified particles and, to prove his theory, began testing their behavior in electric or magnetic fields. By measuring both the extent to which such fields deflected them and their electric charge, he discovered that cathode rays consisted of very small negatively charged particles whose mass was about eighteen hundred times smaller than the lightest known substance—the hydrogen atom. ...He initially named these tiny carriers of electricity "corpuscles." Later they would become known as "electrons." The corpuscles were, in fact, the first subatomic particles to be found..."

"His reluctance to pay for elaborate or expensive equipment, perhaps the result of an impoverished childhood, had established the legendary "sealing wax-and-string" tradition of the Cavendish, where everyday materials were ingeniously used to make and patch up experimental equipment, with sealing wax proving particularly useful for vacuum seals."

"Cathode Rays... he adheres to the hypothesis that the rays are due to the violent projection of the negatively charged particles from the cathode. In another abstract from presumably the same lecture, he states that in the cathode discharge the matter is in something beyond the ordinary state and that the carriers of the discharge in a cathode ray are not atoms but something very much smaller; his conclusions are that the particles carrying the charge must be in a much more finely divided state than the ordinary molecule and possibly may be the primordial element; the numerical ration of the mass of the particle to the charge carried is about 1,100 times less than that deduced electrolytically for the hydrogen ion, showing that either the charge must be very great or the particle very small, and it is the latter which he thinks is the case."

"The electron: may it never be of any use to anybody!"

"This example illustrates the differences in the effects which may be produced by research in pure or applied science. A research on the lines of applied science would doubtless have led to improvement and development of the older methods—the research in pure science has given us an entirely new and much more powerful method. In fact, research in applied science leads to reforms, research in pure science leads to revolutions, and revolutions, whether political or industrial, are exceedingly profitable things if you are on the winning side."

"I have described at some length the application of Positive Rays to chemical analysis; one of the main reasons for writing this book was the hope that it might induce others, and especially chemists, to try this method of analysis. I feel sure that there are many problems in chemistry, which could be solved with far greater ease by this than any other method. The method is surprisingly sensitive — more so than even that of spectrum analysis, requires an infinitesimal amount of material, and does not require this to be specially purified; the technique is not difficult if appliances for producing high vacua are available."

"We see from Lenard's table that a cathode ray can travel through air at atmospheric pressure a distance of about half a centimetre before the brightness of the phosphorescence falls to about half its original value. Now the mean free path of the molecules of air at this pressure is about 10-5 cm., and if a molecule of air were projected it would lose half its momentum in a space comparable with the mean free path. Even if we suppose that it is not the same molecule that is carried, the effect of the obliquity of the collisions would reduce the momentum to half in a short multiple of that path. Thus, from Lenard's experiments on the absorption of the rays outside the tube, it follows on the hypothesis that the cathode rays are charged particles moving with high velocities, that the size of the carriers must be small compared with the dimensions of ordinary atoms or molecules. The assumption of a state of matter more finely subdivided than the atom of an element is a somewhat startling one; but a hypothesis that would involve somewhat similar consequences—viz. that the so-called elements are compounds of some primordial element—has been put forward from time to time by various chemists."

"If, in the very intense electric field in the neighbourhood of the cathode, the molecules of the gas are dissociated and are split up, not into the ordinary chemical atoms, but into these primordial atoms, which we shall for brevity call corpuscles; and if these corpuscles are charged with electricity and projected from the cathode by the electric field, they would behave exactly like the cathode rays."

"The discovery by Monsieur and Madame Curie that a sample of radium gives out sufficient energy to melt half its weight of ice per hour has attracted attention to the question of the source from which the radium derives the energy necessary to maintain the radiation; this problem has been before us ever since the original discovery by Becquerel of the radiation from uranium."

"As the cathode rays carry a charge of negative electricity, are deflected by an electrostatic force as if they were negatively electrified, and are acted on by a magnetic force in just the way in which this force would act on a negatively electrified body moving along the path of these rays, I can see no escape from the conclusion that they are charges of negative electricity carried by particles of matter."

"The difficulties which would have to be overcome to make several of the preceding experiments conclusive are so great as to be almost insurmountable."

"Thomson's lecture drew from Fitz Gerald the suggestion that "we are dealing with free electrons in these cathode rays"—a remark the point of which will become more evident when we come to consider the direction in which the Maxwellian theory was being developed at this time."

"J. J. Thomson, by a rotating-mirror method, succeeded in measuring the velocity of the cathode rays, finding it to be 1.9 x 107 cm./sec.; a value so much smaller than that of the velocity of light that it was scarcely possible to conceive of the rays as vibrations of the aether."

"The fact that there simply is 5,000 times more sun power than our consumption needs makes me very optimistic. It's a fantastic resource. We have the ingenuity to send man to the moon, so we definitively have the ingenuity to tap the sun's resources."

"My starting point is as an academic who always thought nuclear was the answer, but who then looked at the figures and came to an inescapable conclusion that solar-hydrogen is the long-term future. I did not come at this as a green evangelist. I am a reluctant convert."

"My advice to prospective PhD students is to follow your passion and pick a topic that interests you — don't do a PhD topic that you hate, but you think will be lucrative. Because the big picture is that it is the fundamentals learned and problem solving skills gained from your PhD that will open the real career doors. Topics come in and out of fashion — it is the investment in yourself and the person you become through your PhD experience that really matters in the end. Of course, if you happen to love a topic that turns out lucrative then great — but this is hard to predict."

"My advice to all students is to question everything! You never know where a "silly question" may lead you."

"Efficiency is not the issue when you go solar. There is so much solar that all you have to do is invest in the non-recurring cost of more dishes to drive a solar-hydrogen economy at whatever efficiency it happens to sit at."

"The biggest challenge [for solar power] is escaping from the economic effects of vendor lock-in where large investments in nuclear and traditional energy sources keep us 'locked-in' to feeding monsters that will bring us down an economic black hole. It's rather like the play The Little Shop of Horrors where a man-eating plant is initially fed small amounts, but then its voracious appetite sends it into a downward spiral swallowing up anyone that gets in its way."

"One can justify solar-hydrogen simply on grounds of economic resource viability without any green agenda."

"Another conspicuous failure of classical mechanics was with one aspect of the problem of radiation. ...Imagine a crowd of steel balls rolling about on a steel floor. ...There must... be a steady leakage of energy from... causes, such as air resistance and the friction of the floor, so the balls will eventually lose energy, and, after no great length of time, will be found standing at rest on the floor. The energy of their motion seems to have been lost... most of it has been transformed into heat. The classical mechanics predicts that this must happen; it shows that all energy of motion, except possibly a minute fraction of the whole, must be transformed into heat whenever such a transformation is physically possible. It is because of this that perpetual-motion machines are a practical impossibility."

"Therefore the observer may well look to Jeans' theory for the thread of physical significance that shall vitalize a system of classification of non-galactic nebulae. In the scheme presently to be proposed, a conscious attempt was made to ignore the theory and to arrange the data purely from an observational point of view. The analogy however was so suggestive that at several points... there was no hesitation in accepting the one favored by Jeans' theory of spirals."

"Jeans was not a man of many friends, partly because of his temperamental shyness and reticence and partly because of his intolerance of what he deemed to be second-rate. With his own quick perception he lacked the patience which would have enabled him to understand and appreciate a slower-moving mind and consequently he missed those intimacies which he fundamentally desired."

"Two particular cross-sections, he claimed, were of special interest: first, a cross-section near the beginning of time (the creation of the world); secondly, a cross-section only slightly differing from the present. In the latter case, all those parts of the universe not in our immediate vicinity could be disregarded..."

"He then embarked on a criticism of causality, as expressed by Kant or Bertrand Russel. He says that there is no scientific justification for supposing that the happenings of the world can be divided into detached events, and 'strung in pairs, like a row of dominoes, each being the cause of the event which follows and at the same time the effect of that which precedes.' He warned... at the same time against the other extreme... it was not necessary for all previous events in the history of the world to be considered as separate causes. For one thing, the effects of the earlier of them were already taken into account in the later..."

"He pointed out that amongst the hindrances to a joint discussion by philosophers and physicists are differences of idiom, if not language. He stated that, whether one understands the meaning of a sentence in Newton or not, one knows at least the meaning of the words, whereas philosophy has no agreed terminology. He was right in pointing out that various old problems in philosophy owed their existence to imperfections of language... he argued that the philosopher thinks and speaks in the subjective, the scientist in objective, terms."

"What philosophical conclusions should we draw from the abstract style of the superstring theory? We might conclude, as Sir James Jeans concluded long ago, that the Great Architect of the Universe now begins to appear as a Pure Mathematician, and that if we work hard enough at mathematics we shall be able to read his mind. Or we might conclude that our pursuit of abstractions is leading us far away from those parts of the creation which are most interesting from a human point of view. It is too early yet to come to conclusions."

"To be historically accurate, Hubble failed to acknowledge two of his pivotal sources for those ideas which now bear his name: Reynolds and Jeans. As agreed by Allan Sandage, the graphical representation of the Hubble tuning fork [style diagram of the Hubble sequence] must be attributed to Sir James Jeans - a scientist who adored music, and who wrote the famous book Science and Music on that theme. In the Lowell Observatory archives, Hubble revealed to Slipher that he had "been trying to construct a classification of non-galactic nebulae analogous to Jeans' evolution sequence, but from purely observational material.""

"Any region of space-time that has no gravitating mass in its vicinity is uncurved, so that the geodesics here are straight lines, which means that particles move in straight courses at uniform speeds (Newton's first law). But the world-lines of planets, comets and terrestrial projectiles are geodesics in a region of space-time which is curved by the proximity of the sun or earth... No force of gravitation is... needed to impress curvature on world-lines; the curvature is inherent in the space..."

"Minkowski... supposed that this fourth dimension of time was not detached from and independent of the three dimensions of space. He introduced a new four-dimensional space to which ordinary space contributed three dimensions, and time one; we may call it 'space-time'. ...The succession of positions which a particle occupied in ordinary space at a succession of instants of time would be represented by a line in space-time; this he called the 'world-line' of the particle. ...Newton's absolute space and absolute time fell out of science, and they carried much with them in their fall. First to go was the concept of simultaneity. ...It now became necessary to find a way of treating gravitation which should not involve simultaneity. Einstein found through the medium of his 'Principle of Equivalence'."

"It can hardly be a matter for surprise that our race has not succeeded in solving any large part of its most difficult problems in the first millionth part of its existence. Perhaps life would be a duller affair if it had. For to many it is not knowledge but the quest for knowledge that gives the greater interest to thought - to travel hopefully is better than to arrive."

"Physics and philosophy are at most a few thousand years old, but probably have lives of thousands of millions of years stretching away in front of them. They are only just beginning to get under way..."

"When two hypotheses are possible, we provisionally choose that which our minds adjudge to be simpler, on the supposition that this is the more likely to lead in the direction of truth. It includes as a special case the principle of Occam's razor-entia non multiplicana praeter necessitatem."

"The complete closed world consists of three parts-substratum, phenomenal world, and observer. By our experiments we drag up activities from the substratum into the phenomenal world of space and time, but there is no clear line of demarcation between subject and object, and by performing observations on the world, we alter it, much as a fisherman dragging up fish from the depths of the seas disturbs the waters and also damages the fish."