The physics of mass -- A dialogue with nature

The physics of mass
A dialogue with nature

Sep 4th 2008
From The Economist print edition
AFP It's a patchwork of quantum fields

NATURE abhors a vacuum; physicists are none too keen on it either. However, conceptual attempts to fill it up, most famously with ether as a hypothetical medium, have regularly created more problems than they solved. This is because whatever occupies empty space would have to be somehow different from the tangible stuff the world is made of. Now, in a fascinating twist, modern physics challenges the ancient dichotomy between substance and void. What is perceived as empty space turns out to be a new kind of ether, a patchwork of quantum fields teeming with spontaneous activity, and the fundamental building block of nature. Subject to random disturbances, this “grid”, as Frank Wilczek names it, creates stable packets of energy which, by dint of Einstein’s most famous discovery, expressed in the equation E=mc2, account for the mass of ordinary matter.

Hence “The Lightness of Being”, the title of Mr Wilczek’s new book. In it the renowned physicist from the Massachusetts Institute of Technology engages in a riveting dialogue with nature, using experiments and hypotheses as questions. He draws on recent developments in the special theory of relativity, quantum field theory and quantum chromodynamics (which accounts for the behaviour of quarks and which won Mr Wilczek the Nobel prize in 2004) to arrive at a satisfactory answer about the origin of mass. In the process, he broaches some probing questions about the ultimate structure of physical reality, and about the prospects for a unified theory that would account for all its seemingly disparate aspects.
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The book offers not just some striking answers, but also a peek at the creative process that produces them. At its heart lies the continual tension between new consequences derived from existing mathematical formulae, their novel physical interpretations and the search for their discernible manifestations. The most recent monument to this quest is the Large Hadron Collider, a $9 billion machine due to be fired up on September 10th at CERN, the European particle physics laboratory near Geneva. There, Mr Wilczek’s own theories will be among the first to be tested.

The book is not without flaws. Mr Wilczek seems undecided as to his intended audience. True, he minimises the use of equations and has dreamt up some imaginative metaphors to help make complex notions more accessible. But this is still not a book for the novice. Those who cannot decipher Feynman diagrams or have never heard of gauge fields (undefined even in the glossary), are advised to bone up beforehand. In chapter seven, and in the index, colour charge (a property of fundamental particles similar to electric charge) is said to come in three hues—red, white and blue. But in chapter 17, Mr Wilczek suddenly talks of a green and purple charge, leaving the reader scratching his head. What is more, the conceptual shortcuts that pose as explanations will baffle most beginners.

“The Lightness of Being” began as a series of public lectures given by the author at different institutions. They needed to be better edited to work as a book. A quotation from a 19th-century German physicist, Heinrich Hertz, for instance, appears twice, while the notion of a coupling constant (in effect, the measure of a fundamental force’s strength) is explained only some 100 pages after it is first mentioned. The numerous extended comments in brackets are also a bit of an eyesore. Most would be better as footnotes, or dispensed with altogether.

Ultimately, however, these imperfections do not stop the book being a thrilling read. In an endnote Mr Wilczek warns that the nitty gritty of quantum field theory is not for sissies. Nor is this book. But readers who are both doughty and patient will be rewarded with a glimpse of physics at its quirkiest and most illuminating.