During the past 40 years, study after study has addressed why more women do not become scientists. The question is most apt for physics. Advanced physics degrees awarded to women have always lagged, hitting a nadir at under 5 percent from the 1950s to the 1970s. Progress has been made since; in 2003, 193 women (17.9 percent) received a Ph.D. in physics, according to the National Science Foundation. But physics still trails the other sciences. The flip side of the question is: Why and how did those few prominent female physicists succeed? Historian Judith P. Zinsser's La Dame d'Esprit and the profiles of women physicists in Out of the Shadows unveil the scintillating lives of women who overcame discrimination and made major contributions that went largely unacknowledged. Zinsser debunks legends about the life and loves of the vivacious and unorthodox 18th-century French noblewoman Marquise du Châtelet and analyzes her contribution to physics. Du Châtelet (1706-49) gained notoriety as Voltaire's lover. When government censors deemed his literature subversive, she offered him shelter at her château in Cirey. There they collaborated and commented on each other's manuscripts. Du Châtelet transformed a room into a laboratory for experimenting in the "natural sciences," as physics was then called, and built a small theater for Voltaire's plays. Du Châtelet's next major project was translating Newton's Principia Mathematica from Latin into French; she was the first person to undertake this task, and hers remains the definitive text. On its publication, an anonymous editor praised her commentary for being clearer than the original. In it, she walks us through Newton's three proofs of attraction, which incorporate his theory of fluids, the shape of the earth, its relation to the moon and sun, and the parabolic orbits of comets. Along the way, she updates Newton with new data from the first expedition to Lapland and Daniel Bernoulli's study of tides. Several society women never forgave du Châtelet for winning Voltaire's devotion and described her as crude and ungainly. They ridiculed her when she fell madly in love with a younger poet and became pregnant at the age of 43. She died in 1749 shortly after giving birth. Despite her turbulent personal trials, du Châtelet had managed to find great joy in her lifetime and even wrote an essay on her search for happiness. In it, she explained that she sought fame as a man would but accepted having to find it in other ways, recommending cultivation of "mind and understanding." Out of the Shadows celebrates the achievements of 40 femmes d'esprit, women physicists who worked in the 20th century. Editors Nina Byers and Gary Williams selected them from 200 nominations received after they posted a call on the Web. The book is filled with unexpected gems. Herta Ayrton stopped streetlamps from sputtering by perfecting the electric arc. Her patents transferred that technology to film projectors, and movies were called "flicks" because of the flickering arc. Dorothy Crowfoot Hodgkin persisted in solving the structure of insulin for 30 years, finally succeeding in 1970, when computers could perform the needed calculations. One surprise is Freeman Dyson's essay on Mary L. Cartwright, a pure mathematician whom he credits with the foundations of chaos theory. He corrects the record as James Gleick tells it in Chaos: Making a New Science, which begins with the discoveries of Edward Lorenz in the 1960s. It "barely mentions the earlier discoveries of Cartwright and Littlewood (her collaborator)," Dyson writes, although he is careful to praise the book as an excellent popular account. One hopes that professors will bring these female physicists' discoveries to light in their lectures, thereby demonstrating role models to female students. Perhaps all those attending--men and women--will perfect their "minds and understanding" so that none remain in the shadows. Editors' note: A recent report from the American Psycho璴og璱cal Association, Why Aren't More Women in Science? edited by Stephen J. Ceci and Wendy M. Williams, looks in depth at barriers to women in science. Passionate Minds: The Great Love Affair of the En璴ight-enment, by David Bodanis (Crown Publishers, 2006), recounts the personal rather than the scientific aspects of the Marquise du Châtelet's story. The Marquise du Châtelet on Women's Education "I feel the full weight of the prejudice which so universally excludes us from the sciences; it is one of the contradictions in life that has always amazed me, seeing that the law allows us to determine the fate of great nations, but that there is no place where we are trained to think.... Let the reader ponder why, at no time in the course of so many centuries, a good tragedy, a good poem, a respected tale, a fine painting, a good book on physics has ever been produced by women. Why these creatures whose understanding appears in every way similar to that of men, seem to be stopped by some irresistible force, this side of a barrier. Let the people give a reason, but until they do, women will have reason to protest against their education.... If I were king ... I would redress an abuse which cuts back, as it were, one half of human kind. I would have women participate in all human rights, especially those of the mind.... The new education would greatly benefit the human race. Women would be worth more and men would gain something new to emulate.... I am convinced that either many women are unaware of their talents by reason of the fault in their education or that they bury them on account of prejudice for want of intellectual courage. My own experience confirms this. Chance made me acquainted with men of letters who extended the hand of friendship to me.... I then began to believe that I was a being with a mind." SOURCE: The Marquise du Châtelet, from the preface (written about 1735) to her translation of Bernard Mandeville's The Fable of the Bees. According to Zinsser, du Châtelet's mother recognized her daughter's prodigious curiosity and fostered it by permitting her to question elders even though that was considered impolite. Other biographers report that du Châtelet's father considered her too plain for marriage, so he educated her with the best teachers. Image: RICHARD HUTCHINGS Corbis Du Châtelet was in her 20s when she and Voltaire became lovers in 1733, and several biographers have highlighted their affair at the expense of the marquise's accomplishments. To trace her development as a mathematician and physicist, Zinsser plumbed archives all over Europe and the U.S. Voltaire did introduce du Châtelet to the ideas of Descartes, Leibniz and Newton, which were being debated at the French Academy of Sciences, from which women were barred. When the academy held a competition for best essay on the nature of fire, the interpretations of the lovers differed, and both entered the contest--she under an assumed name. Leonhard Euler won, but the academy considered Euler's, Voltaire's and du Châtelet's essays so outstanding that it published all three. The couple then collaborated on The Elements of the Philosophy of Newton, introducing Newton's theories to readers with no background in higher mathematics. As Zinsser interprets it, du Châtelet and Voltaire's relationship faltered as her scientific expertise exceeded his, as it did in her next book, Institutions of Physics. Not merely explaining the metaphysical theories of Descartes, Leibniz and Newton, du Châtelet synthesized them, Zinsser says, whereas academy members, including one of her mentors, only spoke of doing so. She explored a broad sweep of concerns, from "how one can know anything, to the origins of the universe and the role of the divine." Du Châtelet also devoted a chapter to the scientific method, explaining hypotheses as "probable propositions" that could be rejected because of one contradiction. One confirmation, however, was insufficient to prove a hypothesis. Rather "each non-contradictory result would add to the probability of the hypothesis and ultimately ... we would arrive at a point where its 'certitude' and even its 'truth,' was so probable that we could not refuse our assent." If antievolutionists today understood the scientific method as well as this woman of the Enlightenment did, perhaps they wouldn't glibly say, "It's only a theory."