Struggling to make this messy world more manageable, physicists sometimes create cartoonishly simple, two-dimensional versions of it called "toy models." I have a toy model, called "Futureworld," in which humanity has overcome poverty, famine, disease, war and environmental degradation, and robots do all the chores.

The point of Futureworld is to pose the question: What would we do if we could do anything? Because I've never come up with a satisfactory answer, I opened "Year Million," a collection of essays edited by Australian science writer Damien Broderick, with a feeling of pleasurable expectation. Fourteen writers with backgrounds in economics, physics, medicine, mathematics, computer science and science fiction imagine the world not just a century or millennium but a million years hence. Surely that's enough time for Futureworld to arrive!

The tone of the essays ranges from giddy to gloomy. Indeed, some spoilsports warn that our survival is by no means assured. We may be wiped out by an asteroid, the blast from a nearby supernova or our own creations: nukes, hyper-lethal viruses or "nanobots" that turn all matter into "grey goo." If humanity vanishes, science writer Dougal Dixon predicts, the world may be ruled by "rats, rabbits, moles, crows and seagulls -- animals we regard as pests." For those who prefer crows to people -- my wife is one of them -- there may be something comforting in this vision.

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