There are places in Silicon Valley where you can stand along the edge of San Francisco Bay and look back at the Coastal Range, and during the summer you can watch as the fog from the Pacific Ocean spills over the low points in the ridge line. On the other side of the Coastal Range, an ocean current hits the shore line, and deep cold water comes to the surface where it meets warmer air, and condenses into fog. The fog will build up until it’s five hundred or a thousand feet high, high enough to spill over the low points in the ridge. You can watch the fog working its way down through the distant woodlands some miles away and hundreds of feet higher than where you stand, down at sea level, in the warm bright sunshine of Silicon Valley.