Years ago I was a part of a group that gathered weekly to discuss WNYC’s Radio Lab podcast episodes. In that group we hashed out the morality of pre-viable births and driverless cars, the science of eyeballs and bat guano, and the mystery of chromosomes and pharmaceuticals. It was, without question, one of the best small groups I’ve ever been a part of and we all had a hard time not talking about it in conversation with others. The more people we spoke to about it, the more people wanted to join (including my future husband—before I knew him of course). But the group had decided that much of the value we found in the discussions would be lost if we added more people to the room. Ten was the decisive number.