In 1776, writer Adam Smith came up with a theory: when lots of buyers and lots of sellers get together, the resulting "market price" that emerges through all that buying and selling is in fact the work of an "invisible hand." He meant god. We think he really meant "emergence." This segment, we go looking for invisible hands in a variety of places: at an ox-guessing contest in Plymoth, England, in the roiling mass of traders in the "pit" of the New York Securities and Exchange, and also in the secret recipe that makes Google such a great search engine. Author Steven Johnson explains the art of Google-bombing. Producer Ben Rubin presents the bottom-up organization of stock trading in sound.