Uncertainty primarily concerns the development of quantum physics and more specifically of the uncertainty principle. This principle made clear the true nature of the quantum world and its distinctiveness from the world of Newtonian physics. Newtonian physics holds that the universe must function according to strict laws and principles that enable scientists to predict with precision the movements and behaviors of objects as small as atoms and as large as planets, stars, and galaxies. Quantum physics, informed by the uncertainty principle, views the universe as subject at a subatomic level to a certain unpredictability. The behavior of subatomic particles becomes a matter of statistical probability, not of exact behavior and measurement. Certain seemingly impossible and paradoxical principles come into play. For instance, science can measure the velocity of a photon but not its exact location. Or, science can measure the location of a photon but not its velocity. Newtonian physics would argue that it should be possible to measure both, while quantum physics argues that it is impossible to measure both. There are other aspects of unpredictability: for instance, science can explain the process of radioactivity, how an atom splits and emits particles that are detected as radiation. However, it cannot predict when a particular atom will split or why it splits at a particular moment. This apparent randomness and unpredictability are characteristics of the quantum world.
Some predicted that science would end when Heisenberg and others defined a principle that described the limitations of science's ability to measure and define precisely certain basic phenomena. Einstein in particular was deeply bothered and could never accept uncertainty, though he could see the sense of it. One of the purposes of this book is to show how the Heisenberg principle did not bring an end to science at all.
Uncertainty also discusses the lives and contributions of a number of mainly German scientists in the first three decades of the 20th century. Lindley is especially interested in these men as individuals, often very different individuals, of various political and religious and cultural persuasions, who argued over and ultimately contributed to the discovery of the Heisenberg principle. The three main players according to Lindley were Neils Bohr (not a German but a Dane), Albert Einstein, and Werner Heisenberg, from southern Germany. (Lindley discusses many others as well). Einstein was renowned as the genius whose special and general theories of relativity changed modern concepts of the universe, and whose theory that light could be described as tiny packets of energy (quanta) was crucial to the development of quantum theory. Even so, Einstein in this book becomes the conservative elder doubter who believes that classical physics—its ability to predict with utter precision how the world must operate—must not be undermined by a theory holding that at a certain level there is no precision or certainty. Neils Bohr is the elder pontifical theorist, the philosophizing egoist, who eschews mathematical calculations for insights and enigmatic pronouncements couched in such difficult and obtuse language that few really understand them. Heisenberg is the quiet genius whom many are suspicious of but whose insights and mathematical skills allow him to discover and understand the uncertainty principle. Bohr and Heisenberg argue over the meaning and nature of uncertainty, and it is Bohr who finally provides the vocabulary through which the world has come to understand the principle. But it is Heisenberg who emerges from the book as the great genius and visionary. Lindley describes the scientists in his narrative with great effect—he presents them as characters in a fascinating story, as human personalities, and the result is a deeper appreciation of the interests and issues that engaged them than discussions of the physical concepts alone would have allowed.
The great drama of this book comes in the description of the "insight" that leads Heisenberg to the understanding of uncertainty, and the months-long arguments and debates that he and Bohr held about the principle, debates that began in friendship but ended with a personal distance that never closed. Moreover, Einstein made a number of attempts in the 1920s and 1930s to refute the uncertainty principle, but never succeeded. To the end of his life he refused to accept it and increasingly spoke of it in terms that seemed almost theological. He could not believe that "God" or "the Old One" would create a universe that was not entirely predictable. It is ironic that one of the great revolutionary thinkers of the 20th century is left an increasingly irrelevant bystander in the development of quantum theory, whose validity experiments and observations continue to confirm to this day. Great genius that he was, Einstein had his limitations.
Lindley presents all of these men as flawed, human, diverse, and interesting—some are conservative, some verge on Marxism, many left Germany when Hitler came to power (Heisenberg did not), some were womanizers, others were conservative, upright men, some were outspoken and others were reticent. All were participants in one of the great periods of scientific discovery in modern history.
In later chapters, Lindley explains the significance of the uncertainty principle to modern science—scientists use it routinely in their research, even if they don't wholly understand it. Science, that is, did not end as a result of uncertainty, as some feared. He also argues that the popularity of modern cultural, philosophical, and literary theories that depend on the notion of uncertainty, randomness, and unpredictability really have no real connection to Heisenberg's principle, other than the fact that it helped popularize the notion of uncertainty in the 20th century. Heisenberg provided a metaphor for these theorists, nothing more. (I especially enjoyed Lindley's discussion of British novelist's D. H. Lawrence's reaction to uncertainty and to modern science in general). Lindley also refutes the argument that the willingness of German scientists to accept a theory of uncertainty was their unconscious reaction to the unsettlement and change rampant in the Weimar Republic of the 1920s. Uncertainty was a principle developed as a result of mathematics, scientific inquiry, and thought, not as the result of cultural influences.
David Lindley's Uncertainty provides a clear, accessible, and highly readable account of how quantum physics developed, of the uncertainty principle, and of the various scientists who were part of its discovery.
Originally published at Blogcritics, http://blogcritics.org/archives/2007/05/16/014806.php
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