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10 oeuvres 1,318 utilisateurs 20 critiques

A propos de l'auteur

David Lindley holds a Ph.D. in astrophysics. He began his career as a working scientist with stints at the Institute of Astronomy in Cambridge, England, and at the Fermi National Accelerator Laboratory in Batavia, Illinois, but soon turned his talents to writing about science. As the Quizmaster for afficher plus a phone-in segment of Sounds Like Science, a weekly radio science magazine hosted by Ira Flatow, he brought science to the public in a fun and engaging way. afficher moins
Crédit image: The Lindley Family History

Œuvres de David Lindley

Étiqueté

Partage des connaissances

Date de naissance
1956-12-04
Sexe
male
Nationalité
UK
Lieux de résidence
Alexandria, Virginia, USA
Études
Cambridge University (BA|theoretical physics|1978)
University of Sussex (PhD|astrophysics|1981)
Professions
Writer
astrophysicist (theoretical)
Organisations
Fermi National Accelerator Laboratory
Courte biographie
David Lindley, formerly a theoretical astrophysicist at Cambridge University in England and the Fermi National Accelerator Laboratory in Illinois, has been an editor of the journals Nature and Science and is currently Associate Editor of Science News, in Washington, D.C.

Membres

Critiques

I really liked this book. And therein lies a danger. Did I like it because it appeals to my prejudices? Well, yes...I guess. Or did I like it because of the line of argument developed? "Yes" again. Would I like it if it was very "pro" string theory? Probably not. So my liking of the book is probably not really an objective measure of its worth. How can one summarise such a series of complex and historical thoughts? Well I'll try. It seems to me that Lindley, who has a respectable background both as a scientist and an editor at "Nature" and "Science"....both the top world journals....has the credentials to write something like this. And overall, I thought it well balanced. He distinguishes between the understanding that Plato sought (epistome) with the kind of knowledge that Aristotle pursued (techné)....or practical knowledge. And he suggests that most of what scientists are doing today is basically engineering or techné. But physicists have attracted the "wrong sort" into their ranks who are employing esoteric forms of mathematics to both provide a "theory of everything" and a justification for a many worlds hypothesis. So they are not following where the experiments lead but are looking for exotic mathematics which supports their theories. And Lindley wishes its practitioners would take the trouble to ponder where they are going, and to what end.

For my own edification and as memory joggers I have extracted the following key quotes from the book.....which hopefully also captures the gist of his arguments:
Galileo found a place for the parabola in the real world. He had taken a commonplace worldly phenomenon-the flight of a cannonball —analyzed it in the light of his lifelong observing, theorizing, and testing of the rules of motion and had determined the mathematical form of the cannonball's trajectory. He had proved it was a parabola. He had used observational and experimental information to infer a reliable mathematical rule.....He had invented science.

The idea of putting the sun at the center of the universe was not entirely new. The Greek mathematician Aristarchus, active in the third century BCE, had suggested not only that the earth moves around the sun but also that the earth rotates on its own axis.

The “Little Commentary” laid out the essential problem Copernicus had set himself. Making the planets go around the sun was a simplifying stroke. Insisting that their orbits be circular made everything difficult again. To get his model to work, Copernicus resorted to epicyclets, or little epicycles. In effect, he got rid of the big epicycles of the Ptolemaic system and replaced the much derided equants with little epicycles,
But at the heart of the argument was a much larger question, whether truth was to be found in old books or instead established by investigation and reason. More than anything, what came between Galileo and Rome was an argument over how truth was to be known and who could be entrusted with it.

But Aristotelianism, as practiced in pre-renaissance Europe, was a highly refracted interpretation of Aristotle's principles and opinions, and embodied an intellectual dogmatism that was uncharacteristic of the man himself....... The upshot is that Aristotle created a planetary system with a total of fifty-six spheres (although some modifications could bring the number down to forty-nine or forty-seven) but, not being a mathematical sort, he provided no deep analysis of this model to show that it would work as desired.
To his credit, though, or perhaps in rueful recognition of the mess he had gotten himself into, Aristotle concluded his discussion of astronomical matters on a modest note: "If those who study this subject form an opinion contrary to what we have now stated, we must esteem both parties indeed, but follow the more accurate."

What characterizes the ancient attempts to map out the heavens is a form of idealism. Because the heavens are the perfect creation of an infallible creator, they must be ruled by the most rigorous of intellectual systems, namely mathematics. And only the best mathematics would do. Circles were perfect, while other curves, although well-known to the ancients, were not. The underlying belief, more-over, is that human thought alone, powered by logic and reason, is what it takes to comprehend the heavens. Observation of the motion of heavenly bodies is important, to be sure, but pure reasoning is what allows us to make sense of what we see. The idea that we can understand the cosmos best through the application of pure thought is a deep-seated one.

What attracted Averroës to Aristotelian thinking was the insistence that things happened for reasons, that nature conforms to laws written by God..... Al-Ghazali argued for what is called occasionalism, which says that all phenomena on earth and in the heavens happen strictly because of God's will—which means that there are no rational laws of nature, since God can make anything happen at any time, according to His Whim. This belief became a fundamental tenet of Islam...... Averroes wrote a rebuttal of al-Ghazali with the acerbic title “The Incoherence of the Incoherence”. His arguments were heresy, according to the precepts that held sway in the eastern part of the Islamic world,

The sine function originated in trigonometry as one of the basic properties of right-angled triangles, and the wave it generates can be seen as the variation in height of a triangle that rotates at constant speed within a circle, with one vertex at the center and another moving around the circumference. Hence the deep connection between sine waves and circular motion, which is why they turn up so often in physics.

The toolbox of nineteenth-century mathematical physics, like the workshop of a master watchmaker, was stuffed with ingenious gadgets. Legendre polynomials, Chebyshev polynomials, Hermite polynomials; Fourier and Laplace transforms; hyperbolic trig functions and elliptical integrals; and, most splendid of all in my recollection, the method of steepest descent. It doesn't matter what all these things are, except that they were invented by mathematicians or mathematically inclined physicists for the purpose of solving equations. There is no single universal method for solving differential equations. With experience, you learn tricks and techniques....... Understanding the mathematical properties of equations and their solutions allowed physicists to think that they understood how nature itself behaved.

There was a real feeling, I remember, that solving an equation with a computer wasn't really solving it. Sure, the computer could churn through the numbers and spit out answers, but how would you know what those answers really meant? If your answer, as in the old days, was a collection of sine waves or Bessel functions or the like, you could claim to have a mental picture of the solution, because you had some familiarity with how sines and Bessel functions behaved. But a long list of numbers zapped out by a computer? For a time, no-one quite knew what to make of such "solutions."

Today, a solution is a complex computer-generated image. What hasn't changed, though, is Galileos dictum that mathematics is the language of the universe. Fluency in that language is what allows insight into natural behavior.
But—and I want to stress the point again —it is indeed a language, a means of translating the workings of nature into symbols or numbers or graphs or computer-made movies. These mathematical tools portray the universe; they don't create it. It's the underlying laws of nature that do that.

As physicists became accustomed to dealing with the new theory, the electromagnetic field inevitably took on a certain kind of reality in their minds. They knew how it behaved, they understood what it did, and in time those mathematically fueled insights took on the nature of intuitions.... In this way, the field attained a certain kind of understood reality, at least in the minds of physicists, even though they were no wiser as to its fundamental nature.

the notion of a universe completely captured in a set of mathematical rules derived from mechanically based physical models was always a dream rather than a reality. The theory of heat showed how the model was supposed to work, a previously enigmatic substance satisfyingly explained as the Newtonian mechanics of molecules in motion. But the theory of electromagnetism had a huge unknown at its heart: the electromagnetic field was, in mathematical terms, plainly defined, but in physical terms utterly mysterious.

But if, as with quantum wave functions, you can't visualize theoretical models in the old-fashioned, intuitive way, how do you proceed? Dirac's answer was that you must rely on mathematics to point you in the right direction. This, indeed, is how he arrived at his prediction of a new particle. A few years earlier, in 1928, Dirac had made his defining contribution to quantum physics: he devised an equation for the electron.

This was Dirac's point of departure in his 1931 paper [predicting the anti-electron]. If you can't envisage the physics by means of appealing mental imagery, you have to lean all the more on mathematics...... To put it shortly, a theoretical physicist predicted the existence of a new particle, and in due course an experimental physicist [Anderson] found it.

Maxwell began by imagining space filled with rotors and idler wheels that transmitted magnetic influences, and thereby developed a mathematical theory that also delivered a new concept, the electromagnetic field. The nature of the field wasn't so easy to grasp, but still, it was a definite thing that, with growing familiarity, came to seem like a respectable and visualizable part of the physical world.

Turning the logic around, a collection of experimental outcomes does not, in general, point to a specific wave function; it can only ascribe probabilities to a variety of wave functions that are consistent with those outcomes.

Dirac's invention of antimatter, at the time of its invention, explained no puzzling experimental results. It cleared up no confusions or discrepancies in the data. But it added to our understanding of the physical world, and it came out of mathematics, pure and simple.

The old word "particle" prevailed, out of habit and convenience, but the underlying concepts were very different. A particle, in the modern sense, was not a little solid ball, but exactly what it was, was hard to say. Nevertheless, the mathematics of wave functions, as Dirac had foretold, proved a reliable guide, and as physicists learned to handle the complexities of particle physics with increasing ease, they were entitled to think that they understood what these new particles did, if not precisely what they were.

Other mathematical innovations proved helpful, in particular the mathematics of symmetries and groups. To take a simple example, a cube has certain obvious symmetries. It can be rotated about its center through various combinations of right angles and will still look like the same cube...... if a certain particle and its mirror image, for example, were known to be related in a certain way, then their wave functions must embody the same relationship. What made this result—it became known as Wigner's theorem-powerful was that it applied to any kind of symmetry, including not simply rotations and reflections in real space............The utility of symmetry and group theory in physics in the twentieth century was not so easily accounted for. These devices recommended themselves initially as organizational tools capable of taming the chaos of elementary particles, but in the quark model, which posited the existence of new fundamental particles corresponding to the mathematical structure of the group SU(3), the mathematics of symmetry seemed to take on the role of a fundamental principle of nature.

In May 1959, Wigner delivered a lecture at New York University with the memorable title "The Unreasonable Effectiveness of Mathematics in the Natural Sciences." The title summarized the question that nagged at him: How come so many tools of mathematics find their way into the physicist's description of the inanimate world?.......Wigner says that for the physicist, it is in essence an article of faith that physics can be couched in mathematical laws-it's pretty much a definition of physics that it is the search for such laws, and, so far, faith in that principle has been amply rewarded..... But no amount of practical success can prove, to a logician's satisfaction anyway, that the principle is a priori correct.

It may well seem that whatever beauty resides in the more compact version of Dirac's equation has been added through sleight of hand redefining symbols and inventing new ones to sweep all the awkwardness under the carpet..... To put this another way, the Dirac equation, no matter how it is written, is not something that a pure mathematician would necessarily prize as an expression of delightful mathematical beauty. Whatever beauty it has comes from its ability to encapsulate physical meaning in a terse mathematical statemen......Dirac acknowledged that the beauty of mathematics is recognized only by those in the know, but suggests that all who know math will agree on what is beautiful. This is a questionable proposition........ A theme running through [G H Hardy’s ] book is his insistence that true mathematics, the best and most pure kind of mathematics, is marked by its uselessness........But even Dirac was not infallible. In his 1931 paper arguing for the positive electron, Dirac offered a companion argument for the existence of something called the magnetic monopole...... So Dirac's prized sense of mathematical elegance led to the successful prediction of the positive electron but also the unfulfilled prediction of the magnetic monopole. It's worth quoting an apt remark of Niels Bohr, made in passing judgment on a very clever but ultimately unsuccessful theoretical proposal in the 1930s. "I cannot understand what it means to call a theory beautiful" he said, "if it is not true".

In the ancient world, techne was the province of craftspeople and artisans, while episteme was the stuff of philosophy, and there was little connection between the two........ My contention, however, is that in recent decades the greatest portion of scientific activity has drifted closer to techne, in the sense that the theoretical foundations are secure and the crucial matter is putting them to use or understanding their implications in ever greater detail...... But fundamental physics has become a thing apart, a form, perhaps, of ancient philosophy in modern clothes.

Declarations that unification per se is the basic task of fundamental physics began to appear only in the twentieth century. Perhaps Kaluza's attempted theory marks the onset of such ambitions, although his particular theory wasn't a success....... Although the original Kaluza-Klein theory quickly faded from view, one legacy of it is still with us —the possibility that there are more dimensions to space and time than meet our eyes...... A key element in this new attempt at unification was the introduction of broken symmetries. Symmetry itself helped make sense of the proliferation of particles by showing that they could be arranged in groups or families with related properties. Symmetry breaking proposed that, at very high energies, the three elementary forces are the same, and that differences emerge only as the typical energy of particles falls.

Unification of the weak and electromagnetic forces was the first step.
The idea was that in particle collisions at very high energies, the W and Z particles have no mass, just as the photon has no mass. Under these conditions, the weak and electromagnetic forces behave in very similar ways, and can easily be seen as different aspects of a single electroweak interaction. But at lower energies, the electroweak incarnation of the Higgs mechanism springs into action. The Higgs boson goes from being massless to acquiring a mass, and in the process it gives the W and Z particles masses, too. This is symmetry breaking—a state of affairs that was formerly equal, with photon, W, and Z all massless, changes into a new state where only the photon remains massless...... There was a certain downside to this achievement, however. The Higgs mechanism is no one's idea of beautiful mathematics. It is ingenious, but it is a trick, a gadget, a kludge, as computer programmers say of a piece of code that is tacked on to a piece of software to perform some necessary but overlooked task....... But its widespread adoption suggests that theorists' fondness for mathematical elegance is somewhat opportunistic: if an aesthetically unpleasing piece of theory does a valuable job and gains empirical support, then by all means use it; only when theory pushes into realms beyond the easy reach of experimentation does beauty take on a more significant role.

Only if these theories lived in ten dimensions did the superstring theory generate the array of particles and forces that we know, so six of the dimensions had to be wrapped up somehow to create tiny compact spaces, far below our ability to detect them.... But it quickly turned out that five superstring theories offered themselves up as equally plausible candidates....... it's also the case, at least in my jaundiced opin-ion, that the basic hope of superstring theory has not substantially advanced in that time, [since 1999] and that we are no closer to a true theory of everything than we were at the end of the twentieth century....... Whatever splendid uniqueness string theory might possess in its pristine habitat is utterly lost by the time we come down to our universe. Brian Greene, in The Hidden Reality, says that the number of possible universes that can spring from a single version of string theory is around 10 to power 50. For comparison, our planet earth weighs somewhat less than 10 to power 28 grams; it contains about 10 to power 50 atoms..... Any fleeting hope that a string-based theory of everything would tell us how the universe must be or, in the words of Stephen Hawking, let us "know the mind of God" has long since departed.'.... What string theory offers is the potential for such a theory [unification of quantum mechanics and gravity] to exist, assuming all the details can eventually be worked out in a satisfactory way. But there is no proof that such a theory exists.

Smolin makes an acute point toward the end of The Trouble with Physics: string theory attracts the wrong kind of people..... from increasingly recondite areas of mathematics......In short, the spirit of Plato is abroad in the world again..... When it comes to fundamental physics and the science of the universe as a whole, mathematics has moved steadily to center stage.........No one has taken this idea further than Max Tegmark, an MIT professor...... What we perceive as physical reality is, according to Tegmark, pure mathematics alone. I will say upfront that I'm not convinced, but Tegmark's arguments are by no means outlandish —or at least, they start out reasonably enough but creep stealthily into strange and unfamiliar territory.

The arena I call fundamental physics has seen the entrance of grandiose ambitions. Or, more accurately, the revival of ancient but similarly expansive hopes. The philosopher's task, according to Plato and his disciples, was to use the power of reason to discern the very structure of the cosmos. Everyday phenomena were beneath them, too picayune for their consideration. Aristotle, contrary to accepted wisdom, had a more modern scientific instinct........ Long after [Dirac’s] days of scientific glory were past, he began to wax lyrical about the glories and beauties of mathematics in the search for cosmic truth. And Dirac was far from the only one to succumb to delusions of grandeur. Albert Einstein was supposed to have wondered whether God had any choice in the creation of the universe.

It is certainly true that the existence of a universe like ours is consistent with the multiverse idea, but that hardly amounts to vindication... Granted, the multiverse hypothesis is consistent with the existence of our universe. But does it make any specific predictions beyond that? Does it point to any measurable or observable datum that scientists cannot explain in any other way? Not at all.

We've looked at the search for a final theory uniting quantum mechanics and gravity, and we've now veered into a discussion of the multiverse. These are related but clearly distinct notions...... A difficult question arises: If the final theory of fundamental physics and the multiverse hypothesis are complementary, how much explanatory power should we ask of each one?.......It's widely believed that three dimensions of space and one of time are just right..... A universe with two distinct dimensions of time is mathematically imaginable but it would be zany, to say the least— again, it's hard to see how it would allow stable, lasting structures....... In short, if you want a universe that allows long-lasting material objects and rational laws of cause and effect, our present situation is just the ticket. Superstring theories, as we have learned, are based on ten or eleven dimensions, but the extra ones are rolled up tight so we don't notice them.

We are faced with a real question that we cannot resist asking: How did our universe, in the form we perceive, come to be? We can't not ask the question. But science cannot answer it.
That makes most of the questions about why our universe is as it is either unanswerable (it happens to be thus, but need not be) or self-evident (it has to be thus, or we wouldn't be here making inquiries). Either way, we do not reach a satisfying conclusion.
This is why I classify fundamental physics today as a kind of philosophy. The questions it asks are basic and important; they cannot easily be set aside. But the answers it posits are less about a strictly rational understanding of the universe and more about finding a scenario that we deem intellectually respectable.

Researchers in fundamental physics, knowingly or not, have .........declared in advance what they are looking for and are toiling to create a theory that matches their expectations. They do this, arguably, out of necessity. Observation, experiment, and fact-finding are no longer able to guide them, so they must set their path by other means, and they have decided that pure rationality and mathematical reasoning, along with a refined aesthetic sense, will do the job.
As an intellectual exercise, fundamental physics retains a powerful fascination, at least for those few who are fully able to appreciate it. But it is not science. It's not that I think such research should cease altogether. But I wish its practitioners would take the trouble to ponder where they are going, and to what end.
As I said. I really like the book and think he makes some very sound arguments that string theory has a long way to go before becoming respectable. Five stars from me.
… (plus d'informations)
 
Signalé
booktsunami | 2 autres critiques | Feb 17, 2024 |
I enjoyed reading this book, although I’m not sure I fully -trust- the book. The ideal writer of this book would have a good knowledge of physics, a good background in the history of science and western history in general, and a good background in the philosophy of science and western philosophy in general. I trust that Lindley knows physics - not at a Nobel-prize level, but a broad knowledge (PhD in astrophysics) and also I believe he knows (and admits) whatever his limitations are in that in that area. BUT in the other things I mentioned, history of science? Philosophy of science? Those I’m not sure he’s expert about. Surely he knows tons more than me! But does he really know those fields well enough to put things in proper context? Like I said, I’m just not sure I trust his writing on that level. But again, I -enjoyed- reading this book, it’s very nicely written, and it’s not like I’m basing my life on it, so if I have a tiny bit of suspicion about some of his assertions about philosophy and history, does it really matter?

Good thing I’m going to be reading a book about epistemology soon, I think I must be in the right mood...
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Signalé
steve02476 | 2 autres critiques | Jan 3, 2023 |
A cogent and articulate addition to the mini-genre of books -- such as ones by Jim Baggott and Sabine Hossenfelder and Lindley's own _The End of Physics_ (1993) -- contending that fundamental physics research has gone off the rails in recent times by losing contact with experiment (e.g. string theory, multiverse theories) or being overly governed by mathematics and "beauty". "[It] has become a thing apart [from most of modern science], a form, perhaps, of ancient philosophy in modern clothes," Lindley says. An insightful history of the subject from Galileo onwards emerges from his way of formulating the argument.… (plus d'informations)
 
Signalé
fpagan | 2 autres critiques | Aug 28, 2020 |
Only read half of this, tell you nothing about Uncertainty, it's just about some of the personalites involved. Avoid Lindley's books.
 
Signalé
Baku-X | 8 autres critiques | Jan 10, 2017 |

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Œuvres
10
Membres
1,318
Popularité
#19,502
Évaluation
½ 3.6
Critiques
20
ISBN
73
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