Sixteen miles from Grand Canyon's south rim, a cone-shaped butte rises like a lone sentinel 1,000 feet above the Coconino Plateau floor. Thousands of tourists rush past on Arizona Highway 64 without giving it another thought, yet this humble little hill testifies to a remarkable past.

"Glittering generalities"--a phrase describing grand, panoramic scenarios that sweep difficulties under the rug--appropriately describes theories of planetary evolution. They're not as simple as "add dust, stir, and wait." I remember a planetary science professor years ago admitting that planetary evolution models usually hit a snag where a miracle is needed to continue.