My friend the physicist often insists that science is a part of culture. What he means is that there are "sentimental" fruits of science as well as practical fruits; that the invention of new scientific ideas can alter our ways of thinking, our points of view. Science can give us insights on which to base our theories, and perspectives on which to build our beliefs.

This becomes immediately evident, for example, the moment one stops to look at the sky. Understanding that an ordinary star and not our Earth is the center of the solar system makes us reevaluate our place in the sun. Calculating how high the sky is (about the relative thickness of your condensed breath on a marble) makes us ponder the thin skin that seals our planet, the nakedness of life on Earth. Acknowledging a million years of evolution gives us an appreciation for the care that has gone into fashioning our fellow woman and man.

My favorite fruit of scientific thinking is the notion of complementarity. Complementarity pervades science because nature is full of unresolved -- unresolvable -- paradoxes. Light, for example, is both a particle of matter and a wave of energy. In fact, every particle of matter is also a wave of energy. The two definitions seem and are completely contradictory, mutually exclusive. And yet, both are necessary for an accurate understanding of light.

Complementarity has helped me to become more relaxed about the uncertainties that blur the most important issues in my life, that eat away at the edges of my confidence and make it hard for me to grasp a point of view. At times, it seems that my small family is the pivot of the universe; nothing matters quite as much as my son's school or my husband's job or a good night's sleep. And yet, if I stop to contemplate the history of the cosmos or the extinction of humanity be a future nuclear way, my family seems pathetically insignificant and small.

"It is one of the special beauties of science," wrote physicist Emilio Segre, "that points of view which seem diametrically opposed turn out later, in a broader perspective, to be both right."

Once you begin to think about things this way, examples abound. It explains how I can be a mother opposed to the abuses of abortion, but still adamant to preserve the right. It explains how I can want to keep my old-fashioned femininity and my newfangled feminism at the same time. It helps to explain how a concern for human rights and a priority on national interest can be part of the same foreign policy. It helps us to understand the inate complementarity of what's legal and what's right.

Complementarity arose to explain one of the most prickly paradoxes of science -- the theory of quantum mechanics. Quantum mechanics (which gives a description of the peculiar behavior of things on a microcosmic level) demonstrates that on the scale of the very, very small, things do not happen continuously, but in a series of small quantum leaps. Spin and magnetism and gravity and even a property called "charm" come in indivisible units or bits. But if you try to measure the exact position or size of the quantum, it completely disappears. Founder of quantum mechanics Niels Bohr must have been a skier, for he resolved the paradox this way: "When you try to analyze a christiana turn into all its detailed movements, it will evanesce and become an ordinary stem turn, just as the quantum state turns into classical motion when analyzed by a sharp observation."

MIT physicist Victor Weiskopf compares it with Beethoven: "We cannot at the same time experience the artistic content of a Beethoven sonata and also worry about the neurophysiological processes in our brains.But we can shift from one to the other."

I've come to think that the complementarity of quantum mechanics is a key to resolving some of our most profound practical and ethical problems -- if only because most of those problems contain profound practical and ethical paradoxes. Our view of the world is strangely quantized: We are unnecessarily committed to a strong defense or peace, to handgun control or crime control, to women's rights or "family" rights, to social welfare or free enterprise, to strength or compassion.

Weisskopf says, "Whenever in this history of human thought one way of thinking has developed with force, other ways of thinking become unduly neglected and subjugated to an overriding philosophy claiming to encompass all human experience."

Weisskopf continues, "This situation has its root in a strong human desire for clear-cut, universally valid principles containing the answers to every question. However, the nature of human problems is such that universally valid answers do not exist, because there is more than one aspect to each of these problems." The point is not to choose sides between waves and particles. The point is not to choose which viewpoint is "right" or "wrong". It is rather to decide when each point of view is appropriate.