Medieval philosophers once wondered how many angels could dance on the head of a pin. Gordon Moore, who with his liking for pad, pencil and a quiet, solitary desk often looked philosophical, wondered how many transistors could be etched on one silicon wafer to make an integrated circuit. The first transistors he had ever encountered, in 1954 at a lecture by the man who had co-invented them, William Shockley, were as big as peanuts. But they were shrinking fast. The more you could pack together, the more these tiny marvels could do, until they could probably change the world.