Physics Wor ld June 2012 19

physicswor ld.com Comment: Rober t P Crease

Critical Point Quantum guidebooks

If you listened to the most recent Physics World books podcast, you will know that I have been collecting new tomes about quantum mechanics and the quantum world – and stacking them in a pile on my desk. The pile rises monthly, and is now more than two dozen high. But such popu-larizations of quantum mechanics are by no means new – they began in earnest way back in 1927, when Arthur Eddington delivered a series of popular lectures on “The nature of the physical world” just as the revolution that produced quantum mechanics was culminating with the formulation of the uncertainty principle.

Eddington’s lecture series, published in 1928, was followed by many others writ-ten by scientists attempting to explain the dramatic events and their meaning to the public. These authors, who included James Jeans and Bertrand Russell, were insightful people and excellent writers. Although they were writing at a time of fast-paced devel-opments – and they occasionally made mis-takes – even today I am often astounded by the clarity and inventiveness of their prose and images.

Quantum immigrantsYet these books, evidently, did not slake our curiosity about the subject, which has only grown with time. Richard Feynman was being typically provocative when he quipped “nobody understands quantum mechanics”, but his comment underscores the famous difficulty and utterly counter-intuitive nature of the subject. Why, then, do people keep writing – and buying – books that try to help people understand it? A century on, we very much remain immi-grants in quantumland – still behaving like newcomers seeking ways to make this quirky and mind-bending world familiar.

Guides to quantumland, as to anywhere, come in different genres depending on the nature and expectations of the audience. Is the guide aimed at tourists, who wish to visit and then depart, or for potential or existing settlers? Does the audience want

to learn about the subject’s history, people, institutions or atmosphere – and in what detail? Let me take you on an opinionated tour of the books in my stack – a guide to the guides, if you will. What is clear is that they vary greatly in their coverage of his-tory, mathematics and personalities, and in their originality and freshness.

Handbooks and anthologiesI’m fond of quick, no-frills handbooks. The best recent one is Lev Okun’s ABC of Physics: a Very Brief Guide (2012). Our current picture of the world, Okun writes, has a “solid quantum and relativistic foun-dation” that is easier to grasp in outline than many people think, and that should be made accessible even to those who will not become physicists. Okun aims his book at dedicated readers equipped with high-school mathematics. Barely more than 100 pages, it uses virtually no metaphors and consists of short, paragraph-long sec-tions on key topics (“matrices”, “action”,

“the Lamb shift” and the like) that will be helpful review material even for those in the field. It is like using Google Earth to zoom in on the complex metropolis that is quantum theory, providing a delightful and often surprising overview.

Another genre I like consists of anthol-ogies of seminal articles – scientific versions of the Federalist Papers, the col-lection of 85 articles by the US’s Found-ing Fathers written in 1787 and 1788 that spelled out the logic of the US Constitu-tion in an attempt to persuade New York State voters to accept it. One excellent anthology for quantumland is Sources of Quantum Mechanics (1968, reprinted 2007), edited by B L van der Waerden. The book includes 17 key papers from an early phase of quantum history, beginning with Einstein’s 1916 paper “Zur Quantentheorie der Strahlung”, which introduced a prob-ability factor into the theory for the first time. Other key articles by Bohr, Heisen-berg, Born, Jordan and Pauli follow, end-ing with Dirac’s seminal paper of January 1926, “Quantum mechanics and a prelimi-nary investigation of the hydrogen atom”. Unfortunately, the book stops there, and does not include Schrödinger’s famous papers published later that year – although they can be found in Collected Papers on Wave Mechanics (1978).

The most disappointing book in my pile is Stephen Hawking’s The Dreams that Stuff is Made of: the Most Astounding Papers of Quantum Physics and How they Shook the Scientific World (2011). In his meagre three-page introduction, Hawking claims that the volume “employs original texts to trace the development of the revolutionary new concepts required to explain nature at and below the scale of atoms”. But some of its 33 entries are complete while others are extracts, and range from original docu-ments with advanced mathematics to popu-larizations of questionable interest.

One terrible omission is the famous BKS (Bohr–Kramers–Slater) article of 1924 – a titanic, last-ditch effort of the “old” quan-tum theory to make sense of things that became one of the most influential “wrong” papers in the history science. (It is, though, in Van der Waerden’s collection.) Even worse, Hawking’s book devotes 137 pages to four of Schrödinger’s original papers on wave mechanics with all their difficult mathematics, while, bizarrely, only one page of his 1935 essay, “The present situ-ation in quantum mechanics”, is reprinted – the two famous paragraphs outlining his over-the-top “cat” image.

That’s exasperating. To excerpt only that

Pile 'em high What makes a good guide to the quantum world?

Fresh from his appearance on the latest Physics World podcast, which examined the enduring popularity of books about quantum mechanics, Robert P Crease surveys the many tour guides to the quantum world

iSto

ckph

oto.

com

/Eln

ur A

mik

ishi

yev

A century on, we are still behaving like newcomers seeking ways to make this quirky, mind-bending world familiar

20 Physics Wor ld June 2012

physicswor ld.comComment: Rober t P Crease

image from the essay is like a guide to Paris that includes only a drawing – and no other information – about the Eiffel Tower. In the essay’s far more interesting preceding parts, for instance, Schrödinger insight-fully contrasts classical and quantum model-building. Hawking’s book is also sloppily assembled. Tomonaga’s name is misspelt in the table of contents and in the byline of the supposedly reprinted article.

Quantum biographiesI include biographies in my pile, for a founder’s life can provide a coherent narra-tive focus for telling a country’s story. Solid biographies already exist for almost all the quantum founders, but several excellent new ones have appeared. In The Strangest Man (2009), Graham Farmelo focuses on Dirac’s life, fleshing out the portrait Helge Kragh provided two decades ago in Dirac: a Scientific Biography. John Gribbin’s book Erwin Schrödinger and the Quantum Revolution (2012) highlights Schrödinger’s intellectual and social influences more than Walter J Moore’s 2003 book A Life of Erwin Schrödinger.

Lawrence Krauss’s scientifically ori-ented biography, Quantum Man: Richard Feynman’s Life in Science, which was named the Physics World Book of the Year 2011, complements James Gleick’s two-decades-old Genius: the Life and Science of Richard Feynman. My least favourite new biogra-phy is The Many Worlds of Hugh Everett III: Multiple Universes, Mutual Assured Destruction, and the Meltdown of a Nuclear Family (2010). Written by the investigative reporter Peter Byrne, it champions its bio-graphical subject and his nutty idea (multi-ple universes), and is uncharitable to many other quantum founders and their ideas.

I tend not to like collective portraits, which tend to be sketchier the more peo-ple they include. In 2008 Manjit Kumar limited himself to two in Quantum: Einstein, Bohr, and the Great Debate About the Nature of Reality, which does a tolerable job of centre-staging the philosophical debate between these two strong person-alities. Gino Segre’s Faust in Copenhagen: a Struggle for the Soul of Physics outlines the lives and contributions of seven physi-cists – Bohr, Delbrück, Dirac, Heisenberg, Meitner, Pauli and Ehrenfest – all but one of whom appeared at a gathering in Copenhagen in 1932. Sheilla Jones’s 2008 book The Quantum Ten: a Story of Passion, Tragedy, Ambition, and Science – the least satisfying group biography in my pile – pro-files the lives of 10 leading physicists, all but one of whom were at the famous 1927 Solvay Conference.

Meeting it head-onI’m fond of tour guides that confront the mysteries of the quantum world head-on, explaining the science without gimmicks

or metaphors. The most ambitious is by the late John H Marburger – George W Bush’s former presidential science adviser – enti-tled Constructing Reality: Quantum Theory and Particle Physics (2011). Marburger, who once said that he thought about quantum mechanics almost every day of his adult life, had a deep and insightful appreciation for the quantum world, writing that “my over-riding objective is to disclose the intercon-nectedness and internal logic” of quantum theories. “I have tried very hard to avoid saying what these theories are like, but rather to say what they are,” he says.

Brian Cox and Jeff Forshaw’s 2011 book The Quantum Universe: Everything That Can Happen Does Happen is easier to read but less satisfying, as the authors overextend themselves in trying to paint a sweeping panorama from the discovery of radioactivity and the atomic nucleus to the creation of the Standard Model and the idea of the Higgs boson.

The most serious history is by Guido Bac-ciagaluppi and Antony Valentini, Quantum Theory at the Crossroads: Reconsidering the 1927 Solvay Conference (2009), an exhaus-tive and detailed study of this key event in the development of quantum mechanics and the events leading up to it. Quantum Leaps by Jeremy Bernstein (2009) is a kind of travelogue; imagine the reminiscences of a seasoned observer whose tone is that of an imperious guide who is sure that anything he doesn’t show you isn’t worth seeing.

Gimmicks and twistsThe most original approach of any book in my pile is taken in How to Teach Quantum Physics to Your Dog (2010), by Chad Orzel. Using man’s best and most patient friend as a foil allows the author to concoct crea-tive explanations of difficult material with-out sounding patronizing. Louisa Gilder adopts another clever approach in The Age of Entanglement: When Quantum Physics Was Reborn (2008), highlighting the idea of entanglement through imagined con-versations between key scientists. Anton

Zeilinger, in Dance of the Photons: From Einstein to Quantum Teleportation (2010), addresses entanglement via the story of the fictional Dr Quantinger, who sets two students (Alice and Bob) to figure it out for themselves.

Jim Baggott, in The Quantum Story: a History in 40 Moments (2011), tells its tale through 40 “significant moments of truth or turning points in the theory’s develop-ment” – but breaking the story down this way doesn’t improve its digestibility much. Nor does 101 Quantum Questions: What You Need to Know About the World You Can’t See, by Kenneth Ford, which organ-izes explanations as responses to questions. The Amazing Story of Quantum Mechanics: a Math-Free Exploration of the Science that Made our World (2010), by James Kaka-lios, opts to leaven the diet with mate-rial from science-fiction magazines and comic books.

The critical pointWith so many creative strategies to choose from, why do we still feel like quantum immigrants, a century on? One possible answer is that we cannot go native. We were evolutionarily adapted to the classical world as a species, we matured in it as indi-viduals, and we are conceptually moored in it by how our minds process experi-ence. This was Bohr’s Kantian approach. According to it, an unbridgeable difference separates the classical and quantum worlds, so we will always find the latter exotic and incomprehensible. The pleasure in learn-ing about the quantum world is like that of a magic show, where we delight in, but accept, the mismatch between what we expect and what happens. The thrill will never wear off.

But there is another possibility: that the weirdness stems, not from the quan-tum world, but from us. Things are weird only in contrast with the familiar. If what we thought was familiar turned out to be a fantasy and to contain false assumptions – if our world is odder than we thought – the quantum world to which we contrast it would not seem so freakish. This suggests that our quest to learn about the quantum world might eventually have some sort of upside-down Wizard of Oz ending, in which we suddenly realize that what we thought was home was really only a dream, and our world was always a little Oz-like.

Then we’ll be natives.

● The Physics World podcast on quantum books is available to listen, download or subscribe via physicsworld.com (http://ow.ly/ad8n9)

Robert P Crease is chair of the Department of Philosophy, Stony Brook University, and historian at the Brookhaven National Laboratory, US, e-mail rcrease@notes.cc.sunysb.edu

Quantum questions Some authors struggle to explain the mysteries of quantum phenomena.

Vic

Le B

illon