Extraordinary advances in science in the twentieth century profoundly changed the way we perceive the world. New discoveries restored mystery to the universe, revealing a system of symmetry and chaos. In this book, world-renowned astrophysicist Trinh Xuan Thuan reignites the excitement of these discoveries while considering their philosophical and theological implications. He describes the process through which constraining and sterile determinism was challenged, transformed, and swept aside by contingency, which took a prominent place in fields as diverse as cosmology, astrophysics, geology, biology, and genetics. He traces the view of reality as dependent not only on natural laws, but also on a series of historical and contingent events. Originally published in France where it became a bestseller, this is the first paperback English-language edition. Trinh Xuan Thuan has been a professor of astronomy at the University of Virginia since 1976. He currently teaches a course in astronomy for non-scientists. His primary research involves studying very young dwarf galaxies in the local universe; he recently co-authored a study that identifies what is possibly the youngest known galaxy within this universe. He has written many articles on galaxy formation and evolution, and he is the author of several books for the general public. Chaos and Harmony Perspectives on Scientific Revolutions of the Twentieth Century By Trinh Xuan Thuan Templeton Foundation Press Copyright © 2006 Trinh Xuan Thuan All right reserved. ISBN: 9781932031973 Chapter One Truth and Beauty A MAN AND A WOMAN It is a beautiful spring day in Paris. At a sidewalk café, a man is enjoying aglass of beer while reading a newspaper. At the next table, a woman is sippingcoffee while watching passersby. They haven't noticed each other yet.Suddenly, the man turns his head and his gaze meets the woman's. At thatinstant, a remarkable series of events is set in motion. The golden light ofthe sun reflects off the woman's slender body and penetrates the man's eyes.Traveling at a speed of 300,000 kilometers per second, 10,000 billion particlesof light (called photons) rush in through his pupils. First they traversean oval-shaped body called the lens, then a transparent and gelatinous substance,before they strike the retina. THE DANCE IN THE RETINA In the retina, more than 100 million rod- and cone-shaped cells go to work.Covering the retina like darts bristling out of a dartboard, some of theserods receive large amounts of light from the bright areas of the woman'sbody, such as her moist lips highlighted by vivid red lipstick. Others receiveless light, because it comes from more subdued parts of the woman, such asher discreetly made-up cheeks. While rods are sensitive to very dim light,cones require brighter light. Both rods and cones contain light-sensitivepigments that respond differently to different levels of light coming fromthe woman's body. All rods have the same type of pigment. Cones, however,come in three types, each containing a different visual pigment. One typeabsorbs best in the blue, another in the green-yellow, and the third in theorange-red. Visual pigment molecules are each composed of 20 carbonatoms, 28 hydrogen atoms, and 1 oxygen atom. They respond to light byengaging in a kind of strange ballet. When at rest, in the absence of light,each such molecule is attached to a protein and is all crumpled up. But assoon as light strikes it (the light reflected by the woman hits 30 million billionmolecules in the man's eye every second), the molecule in the retinaseparates from the protein and straightens out. After a while, it crumplesback up until the next photon arrives. NEURONS SPRING INTO ACTION All these events took less than 1/1,000 of a second since the moment the man'sgaze met the woman's. But the man is still not "conscious" of the woman'spresence, because the information carried by the particles of light has yet toreach his brain. The frenetic dance of the molecules in his retina must fireup neurons, first in his eyes and then in his brain. Molecules on the surfaceof neurons also change shape, blocking the flow of sodium ions (particleswith a positive electrical charge) in the surrounding liquid, which triggersan electrical current propagating from neuron to neuron, from the eye allthe way to the brain. In the cerebral cortex, each neuron processes theinformation transmitted by thousands of neurons before relaying it in turnto thousands of other neurons farther up the chain. A great many of thehundreds of billions of neurons in the man's brain, interconnected in anincredibly complex network, participate in relaying the information. Theflow of potassium and sodium stops depending on whether or not it isblocked by neurons. Electrical currents race furiously through neural networks,exciting swarms of neurons relaying signals that go on to excite yetmore neurons. Current crackles everywhere. After a few thousand