Monday, 2 August 2010

'Leaping into the history of quantum theory'

A review from the Providence journal in the US:

'Something deeply hidden had to be behind things,” Albert Einstein thought as a child, thereby expressing the human need and compulsion to see through, behind and beyond the world that we inhabit in order to discover religious truths, scientific laws or cosmic visions.

In this clearly written and understandable analysis of quantum theory, the major discovery of 20th-century physics, Manjit Kumar, who has degrees in both philosophy and physics and is the author of “Science and the Retreat from Reason,” tackles an epic task and interweaves his chronological saga with biographies and backgrounds of all the major physicists who were involved — from Einstein, the “Pope,” to Niels Bohr, the Danish “King,” from Paul Dirac’s silences to Wolfgang Pauli’s sarcastic asides, from French princes to German professors, laboratories and “thought experiments” to the quantum leaps of physicists from the major universities and institutes in Munich, Gottingen, Copenhagen and Berlin.

When Max Planck in 1900 discovered the quantum, “the indivisible packet of energy,” as well as matter, he was unaware that he had destroyed centuries of Newton’s mechanical, deterministic and materialistic vision of the cosmos, undermining notions of gravity and clearly defined orbits.

In 1905, Einstein discovered that light was a particle, made up of quanta, and thus upended the century-long belief in light as a wave, though Newton had thought in terms of particles of light as well. Einstein went on to conjure up relativity, in which matter and energy, forever separate before 1905, became interchangeable, limited only, as in all things, by the speed of light.

Kumar makes the fifth Solvay conference in Brussels in October 1927 the centerpiece of this fascinating, intriguing tale of speculations made and shattered, friendships formed and strained, lavish correspondences that exploded and collapsed, and the heady rush to publish papers in leading journals in order to stake out the latest possible theory and reveal yourself on the cutting edge of the new, confounding vision of the subatomic world.

Politics also intervenes, with the Nazis condemning “Jewish physics” and the flight into exile of many German scientists. At that conference, Einstein and Bohr squared off in terms of what all the quantum mechanics, matrices and wave equations meant, wrestling with one another’s theories in terms not of animosity but of camaraderie.

Bohr had decided that everything was both a particle and a wave — the central conundrum of quantum theory — mutually exclusive but necessary. However, one could measure the radioactive traces of electrons and photons on photographic screens only as particles or waves, never simultaneously. Because he believed that the act of measurement always interferes with and disturbs what we are seeing, we can only see snapshots of the quantum realm. “An unobserved electron does not exist,” he declared. Uncertainty, discontinuity, chance and accident govern all things. Only statistical probabilities worked.
Einstein, on the other hand, believed that the subatomic realm exists independent of human observation. Quantum theory had proved itself, but it was incomplete, and that possibility of incompleteness has dominated the study of physics ever since. How does measurement interfere? Is there a border between the quantum realm and our own?

Kumar has done a splendid job of explaining complex theories and describing the people involved with discovering them, mired in cultural and historical upheavals that haunted all of them. This is a necessary, mesmerizing and meticulous volume.'

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