Would someone please tell Robert Hazen there are only 24 hours in a day?

As a research scientist at the Carnegie Institution's Geophysical Laboratory, Hazen routinely worries about such weighty topics as mineral physics and superconductivity. He teaches earth science at George Mason University. He is finishing his eighth book, this one with a co-author, James Trefil (Science Matters: Achieving Scientific Literacy, due soon from Doubleday). And he and Trefil are working with the Carnegie Institution on a science literacy campaign.

But when his brain rests, his fingers begin to work.

Hazen, 41, a man with bachelor's and master's degrees from MIT and a PhD from Harvard (in "mineralogy and crystalology, a cross between solid-state physics and earth sciences," he says matter-of-factly, as if that explains everything), makes music in his spare time. A lot of music.

"I kind of slid into being a professional trumpeter," says Hazen, whose credits include the National Gallery Orchestra, the National Chamber Orchestra, the Smithsonian Chamber Orchestra, the Handel Festival Orchestra and the Filene Center Orchestra. He also does "extra work with the Kennedy Center Orchestra and a lot of pickup things."

Now that his book is almost finished, Hazen has picked up a new hobby: He's learning to play the cello -- "just for fun because I always wanted to play in a string quartet."

But don't think all that music is Hazen's creative release.

"I have to play what the conductor says. That's just doing what someone tells you to do, and doing it as precisely as you can," he says. "There's a technical skill involved, but the actual playing of the music is about as uncreative as anything you can imagine in the arts because it has to conform precisely with someone else's wishes.

"Most scientists think learning and research is a very creative act because nature has secrets and she doesn't give them up all that willingly," he says. "Scientists are constantly thinking of the idea of 'Eureka!' The idea of not being able to solve a problem and then suddenly in the shower" -- he snaps his fingers -- "it comes to you! That's a creative process. That's a process of problem solving of the most elegant kind."