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 Why Road to Reality Disappoints Me 
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Joined: 29 Mar 2009, 18:16
Posts: 15
Post Why Road to Reality Disappoints Me
I have two basic criticisms of The Road to Reality, hereinafter RTR. First, it does not do justice to particle physics. Second, it is far more technical than Penrose's previous books for general readers, so much so that it can be grasped only by someone who has done serious postgraduate coursework in either maths or physics, preferably both. I even submit that parts of RTR would prove hard going for a quite a few less than highbrow physicists. Thus it cannot serve as an introduction to the beauty of contemporary math and physics for educated lay people, or even for any but the very brightest undergraduates.

RTR is a vast exploration of Penrose’s fascination with mathematical Platonism. Bear with me as I now digress on the history and philosophy of mathematics. Mathematical Platonism says that maths exists independently of human thought, in a realm that humans are free to explore. Thus humans “discover” math. Chpt. 34 of RTR restates Penrose’s Platonist stance of long standing. I no longer agree with Platonism, but find myself constantly lapsing into it by virtue of bad habits of very long standing! I prefer to think that mathematics is a formal symbolic language invented by humans to help us reason about life, the universe, and everything, and to communicate to other humans (a select few, sadly) the results of our reasoning. My position here is pretty much that of Lakoff and Nunez, the authors of http://en.wikipedia.org/wiki/Where_Math ... Comes_From.

Penrose believes that the first steps on the road to reality were taken 2500 years ago, when the Pythagoreans made their discoveries about number theory and Euclidian geometry. After a few centuries, this work culminated in the work of Archimedes and Diophantus. But mathematics then lapsed into more than 1000 years of arrested development, until Arabic numerals and the associated arithmetical algorithms became generally known in Europe, circa 1500, and until the invention of algebraic notation, 1550-1620. (On the history of algebra, see John Derbyshire’s 2006 Unknown Quantity.) With arithmetic and algebra in hand, natural science soon emerged. In the late 18th century, technology and commerce, drawing on math and science, began to grow rapidly, hand in hand. Consequently, I consider the invention of algebra the fundamental precondition for the work that led to RTR, and thus the most consequential human invention since agriculture enabled us to cease being hunter-gatherers.

RTR disappoints me by its silence or off-hand attitude re much of fundamental physics, starting with the four interactions, and the dimensionless coupling constants. Penrose rightly devotes a lot of attention to the Lagrangian and Hamiltonian formulations of physical theory, but seldom mentions the beautiful Principle of Least Action (http://en.wikipedia.org/wiki/Least_action). RTR mentions the fine-structure constant but once. It is wholly proper for elder statesmen like Penrose to linger over historically important work. RTR rightly says a good deal about group theory and symmetry, but barely mentions Nöther's discovery of the deep relation between symmetry and conservation laws. Just how much justice does RTR do to Weyl's insights that are the starting point of gauge theories? To the oft-cited 1954 paper by Yang and Mills that founded non-abelian gauge theory?

Even though I am more comfortable with cosmology than particle physics, I still agree that any claimed “Road to Reality” must touch on many concepts from particle physics. RTR simply does not do justice to the particles and how they interact. While most of chpt. 25 is devoted to the Standard Model, the index is silent about that fact. (It is imperative that a book as long and as complex as RTR be equipped with a thorough and accurate index.) Where in RTR does one get a clear sense of the operational meaning of "generation" in particle physics, and where are set out the good theoretical and empirical reasons for believing that there are exactly three generations? Where is it clearly said in one place that the Standard Model (ignoring chirality) features a total of 60 elementary particles, broken down as follows?
• 24 fermions, each with a corresponding antifermion, broken down into 6 flavours of quarks, with each flavour having 3 colours, and 6 flavours of leptons;
• 12 gauge bosons, with each boson being its antiparticle (except that W+ and W- are each other’s antiparticle). 12 is also the sum of the generators in each Lie group the Standard model associates with each interaction other than gravity. This count omits the Higgs boson and graviton, about which we all live and hope... As for an introduction to particle physics, I recommend Frank Close's The New Cosmic Onion.

Martin Rees's Just Six Numbers is a vastly more superficial book than RTR, but I would still expect RTR to address more formally much of what Rees touched on informally. But if RTR has done so, I cannot find where. A case in point: perhaps no aspect of everyday macroscopic reality is more fundamental than its having 3 spatial and 1 temporal dimensions. And indeed, 3 spatial dimensions is one of Rees’s six numbers. There are good mathematical and physical reasons, mostly grounded in the theory of partial differential equations, for why this is the case. (I owe my awareness of those reasons to Barrow & Tipler 1986, and to Tegmark 1998.) But as best as I can determine, Penrose does not mention those reasons. His otherwise very ample bibliography does not include Ehrenfest (1917) or Whitrow (1955).

I share Penrose's scepticism re string theory (as expressed in chpt. 34 of RTR), but only because I have read Woit and Smolin. I have no opinion on the merits of his twistor research programme, although I like the way twistors, unlike strings, happily reside in Minkowski spacetime. I incline to agree with him that theoretical physics and pure maths are fated to grow closer in the future, but it is the more provocative writings of Max Tegmark that convinced me of that. I have an open mind re his claim that our received understanding of quantum theory misses something essential. But I doubt that Penrose’s reservations about quantum theory will convince a fellow theorist or a philosopher of science. And while we’re on the philosophy of science, just how much can we learn about http://en.wikipedia.or/wiki/Philosophy_of_physics by reading RTR? Not a great deal, I'm afraid, and if I am right, the title of Penrose's book misleads somewhat. The book is more of a guided tour through Penrose's remarkable and undervalued mind.

What would I recommend in place of RTR?

Icke, Vincent (1995) The Force of Symmetry. Cambridge Univ. Press.

Icke deliberately dowplays gravity in favour of the particles, the ways in which they interact, and the rudiments of quantum field theory. He also has a wonderful sense of humour. His book is far more concise than RTR, and its the level of difficulty is just right. Too bad it will soon be out of date.


Last edited by roger desmoulins on 12 Jan 2010, 01:25, edited 13 times in total.

08 Apr 2009, 02:39
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Post Re: Why Road to Reality Disappoints Me
Roger
Have you actually read "The Road to Reality"? I am hoping to read the whole book - at the moment I've read about 20%. You give the impression of having searched through the index looking for things to back up your pre-conceived ideas.
In your post you say:
Quote:
RTR simply does not do justice to the fundamental importance of the particles and how they interact. The book does not even have an index entry for the Standard Model.

The truth of the matter is that there is a whole chapter on the standard model - Chapter 25 - "The Standard Model of Particle Physics" and there is a reference to the standard model if you give the index more than a cursory glance. In the index you will find the following:

particle physics 100-2
    beyond the standard model 651-3
    ...
    ....
    origin of standard model 627-8 [Chapter 25]


On the second page of Chapter 25 Penrose writes:
Quote:
As we embark on the 21st century, a much more complete picture is to hand, known as the standard model of particle physics. This model appears to accommodate almost all of observed behaviour concerning the vast array of particles that are now known.


These are hardly the words of someone who dismisses the standard model out of hand.

I have not looked at your other 'disappointments' with the book. I may be able to devote some time to these in the future.

Vasco


08 Apr 2009, 08:54

Joined: 29 Mar 2009, 18:16
Posts: 15
Post Re: Why Road to Reality Disappoints Me
Peter Woit's blog, "Not Even Wrong," says that Frank Wilczek concluded in his 2005 Science review of RTR that its treatment of particle physics was inadequate.


16 Apr 2009, 09:27

Joined: 13 May 2009, 13:10
Posts: 4
Post Re: Why Road to Reality Disappoints Me
roger desmoulins wrote:
Peter Woit's blog, "Not Even Wrong," says that Frank Wilczek concluded in his 2005 Science review of RTR that its treatment of particle physics was inadequate.

For whatever it's worth, Penrose has addressed that specific criticism here (jump to "Corrections/criticisms by reviewers"). I have only started reading the book, so I'm in no position to give a comprehensive review of the book. However, the way I see the issues you've raised is that given the wide scope and complexity of the issues involved it would perhaps be a little too much to ask that everything should be perfect to the letter, especially in the 1st edition.

Errors, omissions and vague formulations seem to be attended to on a continuous basis in the reprints, and wherever he himself falls short there is a community of readers available for help, for instance when it comes to exercise solutions on this and other websites, etc. He also seems to make an effort to point out where he's introducing personal bias in the book and either way I think readers should be aware that they are not reading a physics bible but just one (very bright) man's presentation of cutting-edge physics with all its uncertainties.

If you're able to grasp the essence of his arguments outlined in the book, however, you should also be able to grasp possible counter-examples based on roughly the same level of knowledge with more ease than without this book. So, at least theoretically this book should equip you with the tools to understand both the arguments that he puts forward in the book as well as counter-arguments not included in his book. That's at least my current understanding of the book, which I view as a tool for building the necessary foundations knowledge-wise and that can be a useful reference to go back to even after having read it. Not necessarily that it will be the only source of information you'll ever need, despite the somewhat pretentious name of the book.

In fact, I'm pretty sure that you could compile your own "complete physics guide" using a collection of books and articles which combined could not only rival but surpass the quality of the presentations given in this book. However, there is a certain advantage in having everything presented in one single book in one uniform manner rather than relying on a collection of loose references. Still, nothing prevents you from looking at other sources if you get stuck on a specific topic and return to the book when that issue is resolved...


18 May 2009, 03:10

Joined: 29 Mar 2009, 18:16
Posts: 15
Post Re: Why Road to Reality Disappoints Me
I admire the recent critiques of string theory by Peter Woit and Lee Smolin, and the fact that Penrose is immune to the seductions of string theory. Hence I wish to note here that Woit thanks Penrose warmly for having urged a London firm to publish Woit's book Not Even Wrong. Woit was unable to find an university press willing to risk taking flack for publishing it. I am deeply grateful to Penrose for having facilitated the publication of Woit's controversial but very worthy book.


22 May 2009, 20:41

Joined: 29 Mar 2009, 18:16
Posts: 15
Post Re: Why Road to Reality Disappoints Me
bgd wrote:
roger desmoulins wrote:
Peter Woit's blog, "Not Even Wrong," says that Frank Wilczek concluded in his 2005 Science review of RTR that its treatment of particle physics was inadequate.

For whatever it's worth, Penrose has addressed that specific criticism here (jump to "Corrections/criticisms by reviewers").

ME. That URL contains Penrose's admission of a few errors of technical fact, not all the sort of thing I had in mind. My criticisms are not addressed at errors that are very easy to correct in future printings. Addressing my point (I have not read Wilczek's review) would require rewriting chpt. 25 of RTR, and adding at least 1 chapter to an already huge book.


I have only started reading the book, so I'm in no position to give a comprehensive review of the book. However, the way I see the issues you've raised is that given the wide scope and complexity of the issues involved it would perhaps be a little too much to ask that everything should be perfect to the letter, especially in the 1st edition.

ME. Again, the errors Penrose has admitted to are inconsequential and not at all a worry to me. My concerns lie elsewhere.


Errors, omissions and vague formulations seem to be attended to on a continuous basis in the reprints, and wherever he himself falls short there is a community of readers available for help, for instance when it comes to exercise solutions on this and other websites, etc. He also seems to make an effort to point out where he's introducing personal bias in the book and either way I think readers should be aware that they are not reading a physics bible but just one (very bright) man's presentation of cutting-edge physics with all its uncertainties.

ME. But much of present-day "cutting edge" physics, and its "uncertainties," lie in particle physics. And I insist that a thorough understanding of the particles, and how they interact and decay, are a fundamental part of any "road to reality."


If you're able to grasp the essence of his arguments outlined in the book, however, you should also be able to grasp possible counter-examples based on roughly the same level of knowledge with more ease than without this book. So, at least theoretically this book should equip you with the tools to understand both the arguments that he puts forward in the book as well as counter-arguments not included in his book. That's at least my current understanding of the book, which I view as a tool for building the necessary foundations knowledge-wise and that can be a useful reference to go back to even after having read it. Not necessarily that it will be the only source of information you'll ever need, despite the somewhat pretentious name of the book.

ME. RTR is a fascinating tour through Penrose's remarkable mind. But it is not a reliable reference book, not because what is says is wrong, but because of what it omits and the way it presents what it includes.


In fact, I'm pretty sure that you could compile your own "complete physics guide" using a collection of books and articles which combined could not only rival but surpass the quality of the presentations given in this book. However, there is a certain advantage in having everything presented in one single book in one uniform manner rather than relying on a collection of loose references.

ME. That's why RTR's limiting its discussion of the canonical Standard Model to 23.7 and 25.3-7 sharply disappoints me. (In fact, chpt. 25 devotes all of 19pp to what I see as the Standard Model.) RTR does not even include the now-standard tabular description of the fermions: items on a given row all have the same charge; all items in a given column belong to the same generation. The index does not mention lepton and baryon numbers, and how these are conserved. For these reasons, RTR fails as a single book intro to contemporary physics.


Still, nothing prevents you from looking at other sources if you get stuck on a specific topic and return to the book when that issue is resolved...


Last edited by roger desmoulins on 07 Oct 2009, 00:22, edited 3 times in total.

23 May 2009, 08:53

Joined: 29 Mar 2009, 18:16
Posts: 15
Post Re: Why Road to Reality Disappoints Me
Good news. I have just discovered Anthony Zee, a fine author on some of the topics to which RTR does not do justice: particle physics, quantum field theory, and symmetry as an organising principle in physical theory. I am reading Zee's book for general readers, Fearful Symmetry, which Princeton U Press has just put out in a second edition. Princeton also published his Quantum Field Theory in a Nutshell, which Penrose cites repeatedly. This text is long and difficult, but Zee is the most engaging writer on advanced physics I have ever encountered, John Wheeler excepted.

Zee does a good job of convincing the reader that the essence of contemporary physical theory is Noether's theorem, non-Abelian gauge theory (quantum field theory a la Yang-Mills), and Lie groups. About the only way Zee and I differ is that he is not as critical of string theory as Penrose (and I) are.


22 Jul 2009, 22:43

Joined: 29 Mar 2009, 18:16
Posts: 15
Post Re: Why Road to Reality Disappoints Me
I admit that, in this thread, I have been hard on Penrose.

Yet he definitely has his virtues. And they go beyond his brave and unconventional views about reality in the small. He has a literary gift. The opening pages of RTR are a case in point, describing the reaction of a middle class Egyptian craftsman to witnessing the volcanic eruption of Thera in the Greek islands. It is possible that that eruption is the historical basis for the nightmarish events of the first Passover, the escape of the early Hebrews from Egypt.

Another case in point is the following passage from pp. 888-89 in RTR:

"Imagine a tourist trying to locate a specific building in a vast and completely unfamiliar city. There are no street names…, no maps and no indication from the totally overcast sky as to which directions are north, south or whatever. Every so often there is a fork in the road. Should the tourist turn right or left, or perhaps try that attractive little passageway hidden over to one side? The turns are often not right angles, and the roads are hardly ever straight. Occasinally the road is a dead-end street, so steps must be retraced… There is no one around to ask the way; in any case the local language is unfamiliar. At least the tourist knows that the building that is sought has a particular sublime elegance… That, after all, is one of the main reasons for looking for it. And some of the streets that the tourist chooses have a more obvious aesthetic appeal than the others…, which sometimes, upon close examination [that appeal] turns out to be plastic...

“Perhaps, for a better analogy, let us suppose that you are the tourist, but you are part of a group, led by a tour guide of impressive intelligence, knowledge, and sensitivity – the only trouble being that… the guide has no prior knowledge of the city or of the local language… Each successive choice of turn is a gamble, and on frequent occasions you may perhaps feel that a different one held more promise than the one that the guide had actually chosen… “ (Thanks to Richard Dawid, who cited this passage in a 2009 paper on the controversies stirred up by string theory.)

Penrose’s moral: “If there are too many of these [choices], the chance of guessing right each time may become exceedingly small.” (RTR, p. 890)

This passage is a fable, and its setting is eerily familiar: Franz Kafka. Except that Penrose's moral is cheerier and has a clear sense of destination: let us turn our backs on the seductions of string theory.


06 Oct 2009, 05:33

Joined: 29 Mar 2009, 18:16
Posts: 15
Post Re: Why Road to Reality Disappoints Me
The bedrock of the Road of Reality should be the:
* 3 interactions: gravity, electroweak, strong;
* 12 known gauge bosons, or force carriers, mediating all interactions but gravity;
* 12 fermions, consisting of 3 generations and 4 flavours per generation.

This picture omits the unconfirmed graviton and Higgs boson.

I would like to share with readers of this forum the titles of some books on these topics I have discovered of late. They were all written by professional physicists for sophisticated lay people. I list these titles below in order of increasing difficulty as I see it:

Ford, Kenneth W. (2005) The Quantum World. Harvard Univ. Press. Ignore the title; this is really an intro to particle physics, written as a supplementary text for brighter high school students.

Zee, Anthony (2007) Fearful Symmetry, 2nd ed. Princeton Univ. Press.

Oerter, Robert (2006) The Theory of Almost Everything: The Standard Model, the Unsung Triumph of Modern Physics. Plume. Professor at the Univ. of Maryland.

Allday, Jonathan (2001) Quarks, Leptons, and the Big Bang, 2nd ed. Taylor & Francis. The curious British community college text that first got me hooked on particle physics. The author has a Ph.D. and teaches in a private high school.

Schumm, Bruce A. (2004) Deep Down Things: The Breathtaking Beauty of Particle Physics. John Hopkins Univ. Press. A valiant attempt to explain to lay readers the Standard Model other than QCD and symmetry breaking. Professor at UC-Santa Cruz.

The following are more technical:

Close, Frank (2006) The New Cosmic Onion, 2nd ed. London: Taylor & Francis.

Coughlan, G. D., J. E. Dodd, and B. M. Gripaios (2006) The Ideas of Particle Physics: An Introduction for Scientists, 3rd ed. Cambridge Univ. Press. Written for undergrad science majors who are not particle physicists.

Robinson, Matthew B., Karen R. Bland, Gerald Cleaver, and J. R. Dittman (2008) “A Simple Introduction to Particle Physics: Part 1,"
http://arxiv.org/PS_cache/arxiv/pdf/081 ... 3328v1.pdf . Baylor University Dept. of Physics. The level of difficulty here is roughly that of RTR.


07 Oct 2009, 00:44

Joined: 07 Mar 2010, 08:02
Posts: 1
Post Re: Why Road to Reality Disappoints Me
Re: Mathematical Platonism:

I'm no particular fan of Plato. The guessing game in the Meno dialogue
is not a convincing argument for innate knowledge. However, does not
the particular sequence of the prime numbers imply something inhering in the
initial conditions of the universe? i.e. certain mathematical entities do appear
to have an identity independent of human formulations, do they not?


07 Mar 2010, 08:08
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