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Physics 'Rule Books' for Reality

Newspaper article International New York Times

Physics 'Rule Books' for Reality

Article excerpt

Two new books about physics address the science's competing "rule books" for reality.

The Universe in Your Hand. A Journey Through Space, Time and Beyond. By Christophe Galfard. 386 pages. Flatiron Books. $27.99.

Seven Brief Lessons on Physics. By Carlo Rovelli. Translated by Simon Carnell and Erica Segre. Illustrated. 86 pages. Riverhead Books. $18.

Have you heard the joke about the elderly rabbi who tries to settle a bitter dispute between two men? The rabbi listens to one man's case and pronounces him right. Then he hears the second man's case, and concludes the second man is right. At this point his eavesdropping wife steps in and points out that both men can't possibly be right. To which the rabbi replies, "And you are right as well!"

That conundrum lies at the heart of two new books: Christophe Galfard's "The Universe in Your Hand," and Carlo Rovelli's "Seven Brief Lessons on Physics." Mr. Rovelli uses the case of the indecisive rabbi to illustrate the dilemma faced by theoretical physicists in the 21st century, except in this case what is under dispute are two competing "rule books" for reality: Einstein's general theory of relativity, and quantum mechanics. Each functions perfectly well within its specific realm: Quantum mechanics governs the subatomic world of the very small, while general relativity describes how the world works at very large scales. But neither offers a complete description of how the world works.

Mr. Galfard is a protege of Stephen Hawking, co-authoring a young adult book with Mr. Hawking and his daughter, Lucy, in 2007 ("George's Secret Key to the Universe"). Those Y.A. roots show in "The Universe in Your Hand." There's a lot to be said in defense of plain, simple language, but in this case it proves a mixed bag. The earlier chapters read more like draft scripts for the television series "Cosmos," covering very familiar ground (the sun, the moon, our solar system, stars and galaxies) without doing much to make the material seem fresh.

More problematic is Mr. Galfard's frequent use of the second person -- no doubt to provide a stronger sense of immediacy for the reader -- which wears thin rather quickly and adds a whiff of condescension to the overall tone. He also tends to repeat himself a great deal; for Mr. Galfard, if a point is worth making, it's worth restating at least twice more. The book could easily be trimmed by a third by eliminating some of those redundancies.

That chatty plain-spoken approach pays off, however, once Mr. Galfard digs into the headier realms of special relativity, quantum mechanics, black hole physics and string theory. As befits a Hawking protege, he's quite skilled at clever analogies. For instance, the excitation of atoms is "a bit like children being offered sweets at a party," and the sweets that the children prefer are analogous to which kinds of light an atom will absorb, seen in the absorption lines of atomic spectra. And he deftly sums up why distances must contract and time must dilate under the rules of relativity: Something has to give in order for the speed of light to remain constant regardless of the viewpoint of the observer.

Where Mr. Galfard really shines is in his crystal-clear explanation of quantum field theory -- a welcome inclusion for a popular physics book. Most stick with the intuitive description of matter being made of atoms, and atoms being made of elementary particles, with those particles being composed of quarks. But in reality, the world is made up of fields. Particles are just what we see as a manifestation of those fields. Case in point: The electromagnetic field is "a sea of force out of which virtual particles of light can pop at any moment."

Mr. Galfard even dares to venture where many popular science writers fear to tread with a careful breakdown of how physicists deal with infinities. If we wish to calculate the probability of two electrons bouncing off each other, for example, we can use a classical equation describing how billiard balls scatter as a first approximation. …

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