This fall will mark the thirtieth anniversary of an important milestone in my education. It was then, inspired by a great teacher, David R. Wones, that I declared Course XII, earth science, as my undergraduate major at MIT. To his students, Professor Wones seemed to possess an encyclopedic knowledge of rocks, minerals, geomorphology, and plate tectonics. He demanded much of us, with lengthy lab exercises and exhausting field trips in the New England rain. But his enthusiasm for scientific discovery-his passion to learn the things that we don't know but might someday find out-was infectious. He rekindled in me the deep curiosity that everyone feels as a child, and he focused that untutored, youthful instinct into an exacting experimental rigor. How shocking and sad, then , to read that I may be one of the last of a breed, for science, we are told, has entered its twilight, the victim of its own success. An eager pack of science watchers, led by science journalist John Horgan, author of The End of Science: Facing the Limits of Knowledge in the Twilight of the Scientific Age (Addison-Wesley, 1996) would have us believe that the end of science is at hand (see "The Twilight of Science" by John Horgan, TR July 1996). We are nearing the time, these observers contend, when we will have deduced all the great laws of nature and learned everything of significance about the natural world that can be learned. There are only so many things to find out, Horgan says, and each discovery brings us closer to closure. J. J. Thompson discovered the electron, so check that off the list. Evolution by natural selection, nuclear reactions, electromagnetic radiation, DNA-soon we'll know it all.

What rubbish! Such facile claims ignore the nature of the scientific process and the character of the questions it attempts to answer. Horgan is at least honest enough to warn unsuspecting readers that his college studies of literary criticism taught him to write analysis that is not "the final word" but rather "more clever, more interesting than the rest." Horgan is a clever writer, and he has managed to say something interesting, if exceptionally misleading.

But Horgan's smoke and mirrors is more than harmless literary legerdemain. By using stylish prose to cast doubt about the future vitality of science, he runs the risk of creating a self-fulfilling prophecy. Why should the public support basic research if nothing of interest is left to discover?

William Harvey, the seventeenth-century English physician who discovered the nature of blood's circulation, spoke for today's researchers when he said, "All that we know is still infinitely less than all that remains unknown." The key to understanding why science is an endless frontier lies not in cataloging what we know but rather in recognizing the vast amount of what remains unknown-the unanswered questions. These questions, which drive basic scientific research, fall logically into three broad categories of inquiry-questions about what exists, how it came to be, and how nature works. As the following summary of today's leading research demonstrates, those questions are inherently unlimited in scope, and the chain of discovery-and human curiosity that drives the quest for knowledge-shows not the slightest sign of ending.