Michela Del Vicarioa, Alessandro Bessib, Fabiana Zolloa, Fabio Petronic, Antonio Scalaa,d, Guido Caldarellia,d, H. Eugene Stanleye, and
 Walter Quattrociocchia,

The wide availability of user-provided content in online social media facilitates the aggregation of people around common interests, worldviews, and narratives. However, the World Wide Web is a fruitful environment for the massive diffusion of unverified rumors. In this work, using a massive quantitative analysis of Facebook, we show that information related to distinct narratives––conspiracy theories and scientific news––generates homogeneous and polarized communities (i.e., echo chambers) having similar information consumption patterns. Then, we derive a data-driven percolation model of rumor spreading that demonstrates that homogeneity and polarization are the main determinants for predicting cascades’ size.