The ripple diagram shows this post spreading as users share it on Google+. Arrows indicate the direction of resharing. (Only public posts show up.) Circles within circles represent a resharing sequence, so large circles indicate heavy resharing.
At the moment it is not possible to find Hangouts on Google+ Search. But there are some sites which let you create a Hangout and make it available for everyone. Just go to one of this pages and search for a Hangout you want to join.