Yosemite Valley, California — The day starts with the song birds conversing over the distant pounding of Bridal Veil Falls, amidst the deep flat-bottomed valley. Slowly the sky above evolves into a dawn blue. With little warning, the sun breaks above the eastern ridge alongside Half Dome. Its rays walk down the northern slope, warming up the sheer rock walls of El Capitan and occasionally prying loose a thawed rock. Pine bows bounce in the wind. We feel time passing on a geological scale. Often called "the incomparable valley," Yosemite's dramatic waterfalls, rounded domes and massive monoliths have inspired painters, poets and photographers for ages.