But at a party some years later in her native New Mexico, she bumped into Rip Anderson, a scientist at Sandia National Laboratories, with "curly, receding gray hair, a full mustache, blue eyes," a wiry build, a flannel shirt, and an "international reputation in the fields of probabilistic risk assessment, environmental health, and nuclear safety." His manner of speaking, "courteous and laconic, with the occasional archaic word thrown in, reminded me of the Old West." Their conversation sparked this book, Power to Save the World , which the author calls "an unexpected journey through the nuclear world with Rip as my Virgil." Cravens, as Dante, begins each section with a fluttering set of questions: Isn't radiation dangerous? Can't the terrorists turn these things into bombs? What will we do with the waste? And the unflappable Anderson takes her on a suitable field trip -- to a reactor control room or a mine or a waste storage site. In each case she sees that things are not as she has feared, and Anderson seals the deal with some anecdotes about radiation as a small sprin-kling of salt on a plate of hash browns or why the physics of "ground effect" would make it extremely difficult to crash a speeding jet into a relatively squat reactor.

This strategy works well to convey copious amounts of fairly dry information about the risks of a nuclear accident. The only problem is that Anderson is the truest of true believers -- he ends the book with a little sermon about how God sent "the brainiest guys in human history" to crack the atom "and enough uranium and thorium to last for thousands of years." And while Cravens is diligent in following him through the vast nuclear archipelago, she's less diligent in tracking down the opponents of nuclear power to hear their metaphors and statistics. She quotes a couple of former opponents, there's one throwaway sentence apiece from Greenpeace and the Sierra Club, and she scolds Barbra Streisand and "former supermodel" Christie Brinkley for being environmental hypocrites. But other than that, she mostly just lets it Rip.

Which is a shame, because this is an issue that needs as much clear thinking as possible. Cravens performs a real service by doing something too few people have done: comparing the risks of a nuclear reactor with those of its most common competitor, the coal-fired power plant. We know that nuclear power represents some risk; even Anderson says so. But we also know by now that a new conventional coal plant offers a flat-out guarantee of environmental destruction -- even if nothing goes wrong. If everything operates exactly as it's supposed to, a conventional coal plant hastens the greatest environmental cataclysm, with the highest risk to our health, in human history. Environmentalists need to understand that times and circumstances change, and they need to rethink priorities. It's not enough for greens to say that nuclear power is risky and comes with consequences; everything comes with consequences.

The trouble, however, is that Cravens does a less credible job of asking another, even more important, question: whether nuclear reactors represent the wisest possible alternative to fossil fuels. She's so captivated by her protagonist that she doesn't bring him into conflict with others who have different ideas: She doesn't use, say, the brilliant device that John McPhee employed when he floated down the Colorado with David Brower and his arch-nemesis, the dam-builder Floyd Dominy. If she'd driven north for a day from New Mexico, for instance, she could have spent some time with Amory Lovins, director of the Rocky Mountain Institute and longtime advocate of a different energy path. As charismatic in his way as Anderson is (though not as laconic), Lovins has been working with myriad Fortune 500 companies (and the Department of Defense) in recent years to plot a very different energy future. Instead of promoting the massive and centralized power system represented by nuclear energy, Lovins imagines a much more supple, decentralized electricity grid -- "distributed power," he calls it -- taking advantage of everything from solar and wind to cogeneration and small-scale natural gas. And he's been doing more than imagine it. He's been watching it grow, much faster than nuclear power is growing.

Lovins is a gospel preacher, too. He's been harping on energy conservation for two decades, and with increasing success (big companies like DuPont have managed to trim their energy budgets radically; Lovins's own house high in the Rockies uses essentially no energy in the course of a year). While private capital is financing the growth in micropower, "only huge subsidies have kept the nuclear power industry alive," Lovins says. Reactors, he notes, "are bought only by central planners."

For their part, Anderson and Cravens would probably argue that smaller-scale solutions like renewables and distributed energy are too unreliable and intermittent to supply uninterrupted "baseload" power around the clock. Lovins would come back with recent data showing that as networks of wind, solar, and tide power start to grow in Europe, they actually complement one other much better than previously imagined. (A study released in July, for instance, shows that onshore winds on the hottest summer days mean that the new windmills planned for Cape Cod will coincide perfectly with peak air-conditioning demand.)

And it's not just Lovins. Cravens could have talked to swashbucklers like the venture capitalist Travis Bradford, whose Solar Revolution , published last year by MIT Press, made the case that technological advances were dramatically accelerating the integration of photovoltaic panels into our energy economy.

The real risk of the moment is not, in other words, from radiation or nuclear accident. The real risk is that we'll squander opportunity and resources on the wrong solutions. Given that a new nuclear plant costs $3 billion, is there a way of spending that sum that would reduce carbon emissions more quickly? Would we be better off building co-generation plants to make use of the waste heat disappearing up smokestacks? Should we invest more in energy conservation? The danger of wasting money and time in the fight against global warming is the nightmare that haunts me the most, because this wave is breaking over our heads, and we'd better choose right the first time.

Cravens, unfortunately, does little to bolster our confidence in her conclusions on this score. Her treatment of wind power, for instance, is perfunctory -- she gives exactly the same kind of blind credence to the arguments of opponents that she criticizes in people who fear nuclear power. After dismissing the problems of nuclear waste storage, it seems strange to seriously engage the idea that lubricants leaking from off-shore windmills will devastate the oceans.

Cravens has written an impassioned brief for the nuclear industry. Too impassioned, perhaps, but that's not the problem. What we need right now is fewer passionate briefs and more work to understand which emerging technologies provide the cheapest, quickest, and most transformative solutions. The closest such attempt so far is the report last May from Working Group III of the Intergovernmental Panel on Climate Change. Its team of economists did not turn their backs on nuclear energy, but they didn't say it would save the world, either. Their assessment was that by 2030 it should pro-vide 18 percent of the planet's electricity, up from 16 percent at the moment.

There are no silver bullets in the fight against climate change, only silver buckshot. Some of the pellets may be radioactive, but not all that many.