As I've yet to complete my unified theory of the universe, he did not include me in his survey. If he had, I'd have answered: Just about everything.

As I reported in last week's column, Brockman's respondents were forward-looking, describing cutting-edge research that will help combat global warming and other looming problems. My optimism is anchored in the past.

By almost any measure -- greater wealth, better health, diminishing levels of violence -- the world is good and getting better. My only regret is that I am alive today because tomorrow will be even brighter.

Where to start with the good news? How about with the Big Kahuna: During the 20th century, life spans for the average American rose from 44 years to 77 as we tamed age-old scourges such as smallpox, malaria, polio and plague.

Most of us are passing those gifted years in historic comfort. Imagine your life without light bulbs, air conditioning, automobiles, airplanes and 17 types of lettuce at the Harris Teeter. Such was the fate of our great-great-grandparents, whose days were summed up by Hobbes' observation that life was "solitary, poor, nasty, brutish, and short." But not ours.

We hear much today about the growing gap between rich and poor, but the thrust of 20th-century history was the elimination of this disparity. As Gregg Easterbrook observed in "The Progress Paradox," the rich lived longer than the poor and middle class at the start of the 20th century. They ate better food, received better medical care and could travel to far-flung places. They were even taller. Now, most everyone "live[s] about the same way," Easterbrook wrote, "have about the same education, drive on the same roads, visit the same hospitals, and, for good or ill, share the same cultural experiences, namely television and the movies." I'd rather be rich, but Americans are no longer divided between the haves and have-nots but the haves and have-mores.

In recent years, these benefits have spread. The World Bank reports that the poverty rate in Asia has declined 50 percent during the last 10 years and may decline an additional 90 percent during the next decade. Even the abjectly poor region of sub-Saharan Africa enjoyed 5 percent economic growth last year.

This emerging prosperity should also attenuate the dangers posed by overpopulation. Economists have long subscribed to Thomas Malthus' 19th-century observation that a little wealth leads to a lot of children, who place impossible demands on the world's resources. Geoffrey Carr, the science editor of the Economist magazine, notes that this is now false.

"On the face of things," he writes, "better conditions should lead to larger families, not smaller ones. However, it is impossible to argue with the facts, and the facts are that the rate of population increase is dropping, and that the drop is correlated with increases in personal economic well-being."

As the world becomes richer, it is also becoming more just. It may be fashionable to complain that civil liberties are under siege in modern America, but the recent expansion of rights for women, homosexuals, blacks and other minorities is without precedent.

Harvard psychologist and author Steven Pinker argues that the spread of compassion is a worldwide phenomenon. "Cruelty as popular entertainment, human sacrifice to indulge superstition, slavery as a labor-saving device, genocide for convenience, torture and mutilation as routine forms of punishment, execution for trivial crimes and misdemeanors, assassination as a means of political succession, pogroms as an outlet for frustration, and homicide as the major means of conflict resolution -- all were unexceptionable features of life for most of human history," he writes. "Yet today they are statistically rare in the West, less common elsewhere than they used to be, and widely condemned when they do occur."

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