Two Tours de Force of Physics and Man
Monday, December 31, 2007 
The Ultimate Force
Gravity - Creator of Worlds
By Louis Girifalco
Oxford, 320 pp. $39.95
Faust in Copenhagen
A Strugle for the Soul of Physics
By Gino Segrè
Viking. 384 pp. $29.95
Reviewed by Richard Di Dio
Philadelphia Inquirer - Monday, Dec 31, 2007
You think you can hear it, but you can't. A jumble of solid matter and hot gases, infused with cosmic radiation, swirls around the sun. With no atmosphere to carry sound, there is only a silent whoosh as the debris that forms the building blocks of the solar system accretes into wispy proto-planets, which soon collapse under their own weight into solid chunks of elliptically orbiting ice and rock.
Gravity, the force that is always with us, tugging our bones whenever we take a step, is the silent choreographer of this dance. What this all-powerful force can assemble, however, can just as easily be obliterated by the forces of personality and history.
In a unique publishing feat, two physicists from the University of Pennsylvania have written equally remarkable stories of physics and physicists in which all of those forces play starring roles. Both The Universal Force: Gravity - Creator of Worlds, by Louis Girifalco, and Faust in Copenhagen: A Struggle for the Soul of Physics, by Gino Segrè, combine science, history and culture in rich narratives of the very human quest to understand the nature of the physical world.
The Universal Force begins with a cosmic tour that stretches from early Ptolemaic cosmology to warped space-time and black holes. Ever-changing views of the universe from Aristotle to Einstein are driven by, and drive, the development of different theories of gravity.
The Universal Force does not just refer to gravity, however. Here, universal alludes to the scope of physical principles postulated to be valid for all space and time. For Girifalco, relativity is the paramount example of such a principle. Because of its theoretical and philosophical foundations, "relativity is unparalleled. The stark simplicity of its assumptions, its striking mathematical structure, its universality . . . make it unlike any other scientific theory."
The principles of relativity led to Einstein's stunning reimagining of gravity as a property of curved space-time. Using relativity as a defining concept, Girifalco then turns to fundamental questions that are themselves universal: What is time? What is space? What is truth?
Girifalco's conversational style and excellent explanations belie the difficulty of these topics, resulting in a deep, yet understandable, explanation of all the "weird" facts about the universe that relativity implies, none more so than the true nature of gravity.
Faust in Copenhagen is Segrè's dramatic, very literary account of the scientific lives and events that define the Miracle Year of Experimental Physics - 1932. The experimental discovery of the positron and the neutron, and the observation of the first artificially induced nuclear reaction were breakthrough successes, but that year also marked a divide in the history of physics, and ultimately, the world. For, the year that ushered in the era of nuclear physics was also the last year of a genuine scientific camaraderie that transcended nationalities and was defined by the pursuit of fundamental knowledge. In 1933, Hitler came to power, and scientists soon dispersed - some seeking neutrality, others choosing sides.
The title refers to a remarkable evening at the Niels Bohr Institute in Copenhagen. The institute was the nexus of quantum theory, a place to apprentice with Bohr, who, next to Einstein, was the world's most revered physicist. Conferences were held every summer, with a week of serious talks often concluding with a lighthearted evening of entertainment. That year, 1932, marked both the 10th anniversary of the institute and the 100th anniversary of the death of Goethe, whose work was immensely influential among Western scientists. Perhaps it was inevitable, then, that the physicists decided to parody Faust for this special event.
The satire was quite clever, with the main characters and story rewritten to represent the participating physicists and their discoveries. The Lord was modeled on Bohr, while Mephisto was based on the prickly but brilliant Wolfgang Pauli. Faust, searching for the truth about the physical universe, was clearly Paul Ehrenfest - a brilliant but troubled physicist. (In an ending more tragic than that of Goethe's play, Ehrenfest killed his son and himself the next year - some claim because of his feelings of inadequacy when compared with his colleagues.)
The mixture of laughter and seriousness of the scientists is rendered with great tenderness by Segrè, whose tale is a painting of the old Europe of his ancestors, and of his own beginnings as a scientist. Along with excellent descriptions of the important physics developed by each of the characters, Segrè masterfully sets his stage in the context of the nationalistic tensions that would soon lead to world war and the ultimate Faustian bargain - the secrets of the nucleus in exchange for atomic weapons.
In their books, Girifalco and Segrè convincingly demonstrate that the unity of the physical world is discoverable by the inhabitants of this planet, which, thanks to the action of gravity, emerged out of that cloud of swirling debris so many years ago.
Richard Di Dio teaches physics and mathematics at La Salle University. He writes on chaos and culture at FractaLog Blog (www.fractalog.com)
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R.A. DiDio
Recent letters of Ehrenfest have been discovered that presage his suicide by a year:
"And so it is that most likely in the coming school year, to finally free up my position in Leiden, the only way out left to me is to kill myself."
The Austrian-born theoretical physicist Paul Ehrenfest wrote that to some of his former PhD students on 15 August 1932, about a year before his suicide at age 53. In the letter, he tells them that "each of you has been, during some stretch of your life, something like my own child" and "I have you much more to thank than you realize. Your affection, your consistent wish to give me confidence in myself made it possible until just recently for me to maintain my enthusiasm. Forgive me that it is now over."
See the Physics Today article describing the letters, and more info about Ehrenfest's evident despair.
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The mixture of laughter and seriousness of the scientists is rendered with great tenderness by Segrè, whose tale is a painting of the old Europe of his ancestors,