Recent social movements demonstrate an important role of social media information diffusion in promoting social changes. Transnational information diffusion may be influenced by spatial proximity between the origin nation and other parts of the world. Proximity implies more than just physical distance. This paper develops a mathematical spatiotemporal diffusion model based on partial differential equations, called "diffusion-advection" model. The model is applied to four sets of global spatial arrangements, respectively based on geographical, ideological, economic and diaspora perspective on proximity. Twitter data on Egyptian Revolution 2011 is used for the model validation. The developed model shows an acceptable accuracy rate. Among the different definition of proximity, ideology-based arrangement (i.e., democracy) explained most effectively the spatial diffusion process over the course of the revolution, showing that different types of messages are diffused at a different pace.