Since the beginning, artists have yearned to stop time, or at least to examine their nagging awareness that it's unstoppable. But only San Rafael native Christian Marclay has so successfully managed to turn the anxious sport of clock-watching into a weird and highly mediated form of transcendental meditation. He calls it The Clock, and it's simple: just a day-long movie made up entirely of clock shots from other movies, or shots of someone saying what time it is, synchronized to whatever time it really is. All this practical yet decorative timepiece required was three years for Marclay and six assistants to build, and the entirety of cinema history to build on. Newly installed at SFMOMA as of today, The Clock already has drawn rave reviews and long lines of viewers from all over the world, provoking such existential questions as, "Does he use Bill Murray waking up in Groundhog Day for 6 a.m.?" and "It's driving me crazy, what the hell is that shot from?" and "When you really think about it, what is time, anyway?" Marclay knows this: It's ticking away.