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Thursday, March 12, 2009

Reading List: The Lightness of Being

Wilczek, Frank. The Lightness of Being. New York: Basic Books, 2008. ISBN 978-0-465-00321-1.
For much of its history as a science, physics has been about mass and how it behaves in response to various forces, but until very recently physics had little to say about the origin of mass: it was simply a given. Some Greek natural philosophers explained it as being made up of identical atoms, but then just assumed that the atoms somehow had their own intrinsic mass. Newton endowed all matter with mass, but considered its origin beyond the scope of observation and experiment and thus outside the purview of science. As the structure of the atom was patiently worked out in the twentieth century, it became clear that the overwhelming majority of the mass of atoms resides in a nucleus which makes up a minuscule fraction of its volume, later that the nucleus is composed of protons and neutrons, and still later that those particles were made up of quarks and gluons, but still physicists were left with no explanation for why these particles had the masses they did or, for that matter, any mass at all.

In this compelling book, Nobel Physics laureate and extraordinarily gifted writer Frank Wilczek describes how one of the greatest intellectual edifices ever created by the human mind: the drably named “standard model” of particle physics, combined with what is almost certainly the largest scientific computation ever performed to date (teraflop massively parallel computers running for several months on a single problem), has finally produced a highly plausible explanation for the origin of the mass of normal matter (ourselves and everything we have observed in the universe), or at least about 95% of it—these matters, and matter itself, always seems to have some more complexity to tease out.

And what's the answer? Well, the origin of mass is the vacuum, and its interaction with fields which fill all of the space in the universe. The quantum vacuum is a highly dynamic medium, seething with fluctuations and ephemeral virtual particles which come and go in instants which make even the speed of present-day computers look like geological time. The interaction of this vacuum with massless quarks produces, through processes explained so lucidly here, around 95% of the mass of the nucleus of atoms, and hence what you see when stepping on the bathroom scale. Hey, if you aren't happy with that number, just remember that 95% of it is just due to the boiling of the quantum vacuum. Or, you could go on a diet.

This spectacular success of the standard model, along with its record over the last three decades in withstanding every experimental test to which it has been put, inspires confidence that, as far as it goes, it's on the right track. But just as the standard model was consolidating this triumph, astronomers produced powerful evidence that everything it explains: atoms, ourselves, planets, stars, and galaxies—everything we observe and the basis of all sciences from antiquity to the present—makes up less than 5% of the total mass of the universe. This discovery, and the conundrum of how the standard model can be reconciled with the equally-tested yet entirely mathematically incompatible theory of gravitation, general relativity, leads the author into speculation on what may lie ahead, how what we presently know (or think we know) may be a piece in a larger puzzle, and how experimental tests expected within the next decade may provide clues and open the door to these larger theories. All such speculation is clearly labeled, but it is proffered in keeping with what he calls the Jesuit Credo, “It is more blessed to ask forgiveness than permission.”

This is a book for the intelligent layman, and a superb twenty page glossary is provided for terms used in the text with which the reader may be unfamiliar. In fact, the glossary is worth reading in its own right, as it expands on many subjects and provides technical details absent in the main text. The end notes are also excellent and shouldn't be missed. One of the best things about this book, in my estimation, is what is missing from it. Unlike so many physicists writing for a popular audience, Wilczek feels no need whatsoever to recap the foundations of twentieth century science. He assumes, and I believe wisely, that somebody who picks up a book on the origin of mass by a Nobel Prize winner probably already knows the basics of special relativity and quantum theory and doesn't need to endure a hundred pages recounting them for the five hundredth time before getting to the interesting stuff. For the reader who has wandered in without this background knowledge, the glossary will help, and also direct the reader to introductory popular books and texts on the various topics.

Posted at March 12, 2009 02:36