1. A system for discovering important elements that drive an online discussion of a topic, the system comprising: one or more processors and a non-transitory memory having instructions encoded thereon such that when the instructions are executed, the one or more processors perform operations of: receiving, as input, a message from an online discussion related to a topic; analyzing the message for information related to the message; generating a graph comprising a plurality of nodes, wherein each of the plurality of nodes represents an entity, resulting in a plurality of entities; updating the graph over time as additional messages from the online discussion are received, such that additional nodes are generated and linked with at least one of the plurality of nodes by paths having path lengths; determining a closeness value for each node based on the path lengths, resulting in a plurality of closeness values; ranking the plurality of entities based on the plurality of closeness values, thereby providing a ranking of the plurality of entities by level of importance in the online discussion; and outputting the ranking of the plurality of entities to a user.