A year ago he brain-teased: "What do you believe is true even though you cannot prove it?" And this time: "What is your dangerous idea?"

Brockman's challenge is noteworthy because his buddies include many of the world's greatest scientists: Freeman Dyson, David Gelertner, J. Craig Venter, Jared Diamond, Brian Greene. Yet their ideas, delineated in brief and engaging essays, are not just for tech-heads. The 119 responses Brockman received to the most recent question -- posted at www.edge.org -- are dangerous precisely because they so often stray from the land of test tubes and chalkboards into the realms of morality, religion and philosophy.

Some dangerous ideas based on recent research:

* It is better to let parents design their children -- using genetics to influence their sex, height, hair color and intelligence -- than to halt research that makes us queasy.

* Parents have no power (other than genetic) to shape a child's personality, intelligence or the way he or she behaves outside the home.

* People have adapted so thoroughly to the world of computers that the difference between the real and the virtual is becoming meaningless.

* The universe has no purpose. The only meaning that exists comes from the myths we create to fill the existential void.

* The criminal justice system must be reformed in light of mounting evidence that people are just souped-up machines. "When a computer malfunctions, we do not punish it," writes the evolutionary biologist Richard Dawkins. "We track down the problem and fix it. ... Why do we not react in the same way to a defective man: a murderer, say, or rapist?"

Brockman's survey -- which he started in 1998 and calls "The Edge Annual Question" -- is particularly pertinent in light of the ongoing struggle between advocates of Darwinism and Intelligent Design.

Several respondents approach this conflict with a flamethrower, arguing that scientists have lacked the courage to debunk ideas contradicted by their work.

"Our fear of provoking religious hatred has rendered us incapable of criticizing ideas that are now patently absurd and increasingly maladaptive," writes Sam Harris, author of "The End of the Faith." "It has also obliged us to lie to ourselves -- repeatedly and at the highest levels -- about the compatibility between religious faith and scientific rationality. ... Iron Age beliefs -- about God, the soul, sin, free will, etc. -- continue to impede medical research and distort public policy. The possibility that we could elect a U.S. President who takes biblical prophesy seriously is real and terrifying; the likelihood that we will one day confront Islamists armed with nuclear or biological weapons is also terrifying, and growing more probable by the day. We are doing very little, at the level of our intellectual discourse, to prevent such possibilities."

Other respondents floated the dangerous idea that science's fundamental understandings about time and space may be wrong.

Consider the Big Clock, which holds that the universe was created about 14 billion years ago in a Big Bang. According to Paul Steinhardt of Princeton University, that watch might be off by oh, let's see, trillions and trillions of years.

Steinhardt reports that cosmologists have begun exploring the idea that "the evolution of the universe is cyclic. The Big Bang is not the beginning of space and time but, rather, a sudden creation of hot matter and radiation that marks the transition from one period of expansion and cooling to the next cycle of evolution. Each cycle might last a trillion years, say. Fourteen billion years marks the time since the last infusion of matter and radiation, but this is brief compared to the total age of the universe. Each cycle lasts about a trillion years and the number of cycles in the past may have been ten to the googol power or more!"

Meanwhile, physicists are increasingly attracted to the idea that there is no single universe, governed by a single set of physical law. Instead there might be millions or billions of "multiverses" with their own physical realities. If true, science's long quest for a unified theory has been a fool's errand.

These dangerous ideas -- that the universe is far older, larger and more varied than we have imagined -- lead to another dangerous idea, articulated by the writer Karl Sabbagh: "Our brains may never be well-enough equipped to understand the universe and we are fooling ourselves if we think they will. ... While human brains are complex and capable of many amazing things, there is not necessarily any match between the complexity of the universe and the complexity of our brains, any more than a dog's brain is capable of understanding every detail of the world of cats and bones, or the dynamics of stick trajectories when thrown."

And so we are left with our final dangerous idea: Science's long journey down the corridors of knowledge has led us back to the realms of mystery and wonder. A method of inquiry that promised us mastery may ultimately remind us of our limits.

A final question: What's your dangerous idea?

Get $150+ in coupons in every Sunday N&O. Click here for convenient home delivery.