Friday, June 26, 2009

Tales of Two Theories

I finished reading two very different books about two theories in physics, The Age of Entanglement: When Quantum Physics Was Reborn by Louisa Gilder and “Gina Says,” Adventures in the Blogsphere String War "selected and edited" by Gil Kalai. While vastly different in style they both feature scientists happy to talk about and defend their own points of view in controversy theories but rarely willing to reconsider those views.

Louisa Gilder's book takes a detailed look at the early years of quantum theory using an interesting technique: Creating imagined conversations between the leading scientists of the time based on their writings. These conversations make the development of the theory an exciting story when greats like Einstein, Bohr and Heisenberg struggle over the right ways to handle the seemingly paradoxical nature of quantum effects. As Bohr gets quoted in the book during a Copenhagen trolley ride with Einstein and Sommerfeld, "I suppose that during a stage in science where everything is in ferment, it cannot be expected that everybody has the same view about everything". 

Gilder's book gives a detailed year by year development through the 1935 Einstein-Poldolsky-Rosen paper but then moves much quicker through David Bohm's theories from his exile in Brazil (due to McCarthyism), the Bell inequalities and related experiments, and the development of quantum cryptography and computing. The computer science aspects are particularily short with only a brief mention of "the reclusive Peter Shor and the witty Luv Grover". She doesn't ignore the political backdrops of the times but thankfully she doesn't overly emphasize it either.

You won't learn more than the broad strokes of quantum physics with this book but you get to relive the development of a discipline as brilliant minds argue the right way to model a new phenomenon. 

Gil Kalai's book is a quick read from the viewpoint of "Gina" a non-expert who comments on the blogs of mostly string theory skeptics. It certainly was a fun read but I finished not sure of the purpose of the book. Seemed to focus more on the role of bloggers and commentors than the philosophical questions of developing a complicated theory that seemingly can't be tested. Where's Occam's Razor when you need it? Kalai had some interesting digressions to areas like Godel's incompleteness theorem and Bayesian learning but those just added to the disjointness of the book. Kalai's book does have the big advantage of being a free download.

So I'd recommend Gilder's book if you want a detailed almost novel-like development of a field and Kalai's book if you want a quick fun free read on how some skeptics defend their skepticism. 

Both books remind us that theoretical research must go beyond just doing the math, in finding the simplest models that best capture the concepts we study. Lessons that hold as much in computer science as they do in physics.


  1. Gosh ... three days and no comments ... perhaps this "dog not barking in the night" is in itself worthy of a comment.

    Very early on, Gil Kalai's book proposes the following answer to the question "What is string theory?"

    "String theory is a very ambitious (yet incomplete) answer to the problem, prevalent on the minds of physicists for almost a century, of bringing together quantum theory and Einstein's theory of gravitation."

    Let's regard this statement as Great Truth in the sense that its opposite is a Great Truth too.

    If string theory is not about unifying quantum theory with gravity, then what is it about? The following three paragraphs will take the point of view that string theory (and more broadly, quantum theory in general) can be viewed (with equal justification) as being all about (1) education, (2) enterprises, and (3) jobs.

    Here's why: (1) The case for string theory being all about education starts with Patricia Schwarz' fine "graduate mathematics guide" that is hosted on (a Google search will find it). Patricia describes her guide as being for "people who want to learn advanced topics in theoretical physics". But isn't this needlessly narrow? Doesn't Patricia's guide serve (equally well) a broader educational base of "people who want to understand complex systems?"

    (2) The case for string theory being all about enterprise starts from the premise that the class of "people who want to understand complex systems" now includes pretty much every engineering student, including (for example) students in electrical engineering, computer science, bioinformatics, financial engineering, and (my own interest) quantum systems engineering. Nowadays the state-spaces of all these engineering disciplines are regarded as having, not a vector space structure, but a more general manifold structure (and/or graph structure). For example, Patricia Schwarz' reading list serves our first-year graduate students in quantum system engineering just as well as it serves graduate students in math and physics who intend to study string theory. The point is, that nowadays the mathematics of Schwarz' guide are at the foundations of every large-scale enterprise ... including string theory but by no means limited to it (and this is good news for every mathematics and physics department).

    (3) The case for string theory being all about job creation starts when we reflect on the sobering reality that our planet is presently in urgent need of one billion jobs (meaning family-supporting jobs). These jobs need to be created not "someday" ... after some diffusely specified future "breakthroughs" ... but jobs created as rapidly as feasible. Job-creation on this planetary scale requires mathematical engagement with complex systems ... and this thoroughly entangles job-creating enterprise with complex systems engineering and with mathematics education. Earlier generations of mathematicians, scientists, and engineers did not shrink from contemplating planetary-scale enterprises, and our generation should shrink from it either.

    From this point of view, when we read existing accounts of string theory (like Gilder, Woit, Kalai, Smolin, etc.), we are struck more by the similarity of these authors' writings than by their differences. These writings all embrace the strict-constructionist view that string theory it is "all about" gravity and quantum theory, and in consequence, discussions of "education", "enterprise", "engineering", and "jobs" are absent from all of these works. This restriction makes the story easy to tell ... but isn't it needlessly narrow?

    Even more fun is to be had (IMHO) by viewing research in gravity and quantum theory as being at the forefront of our century's larger adventure in planetary-scale education, enterprise, and job creation.

  2. Thanks, Lance
    Let me just add that I put 1/3 of the book on my blog so there is more to come. The second part takes place on n Category Cafe and has no relations to string theory. I am not sure if "the purpose" of the book will become clearer though.

  3. Gil, what will be the focus of the "third third" of the book? Is this third part written yet?

  4. John, most of the third part deals with Lee Smolin's book at takes place on "Asymptotia". Among the discussed issues: "how to debate beauty".

  5. LOL ... Gil, I seldom debate "beauty" ... because (as feminist thought correctly emphasizes) it is "a truth universally acknowledged" that standards of beauty within a community are intimately bound to that community's practices of social ranking and access to resources.

    Surely, this is no less true in mathematics than in fashion, art, and politics?

    For me, the essence of beauty resides in simplicity, utility, and cheerfulness: a beautiful person has a cheerful smile and embraces good works; beautiful mathematics can be put to cheerful purpose and encourages further enterprise.

    Philosophically, this standard of beauty is Spinozist ... because it was Spinoza who first argued for cheerfulness as the highest human virtue. Good on `ya, Spinoza! :)

    Thus, as the cheerful simplicity and practical utility of string theory mathematics becomes more apparent, it becomes (to me) more beautiful.

  6. cheerfullness is the highst human virture... interesting John, but are you objective?

  7. LOL! Yes, for centuries bow-tie-wearers have been secret secret members of the Cheerful Illuminati ... the bow-tie is a signifier.

    Another secret is that women of the Cheerful Illuminati wear pony-tails for exactly the same reason ... Jane Goodall is their ring-leader!