Abstract : As science communication goes beyond the traditional borders of academia, new science dissemination genres emerge. This paper presents a multimodal analysis of two online science videos uploaded to YouTube: a recorded TEDx talk and a PBS Space Time video. We have determined the existence of two layers of modes in online science videos: embodied and filmic modes. The former are deployed by the speaker, while the latter are added to the ensemble during postproduction and editing. Our analysis sheds light on three main aspects of this multimodal orchestration: modal density, modal coherence, and genre definition. Our findings show that online science videos are more modally dense as a result of the incorporation of more filmic modes into the ensemble. In addition, we also find that the use of filmic modes requires some degree of expertise and know-how in order to keep the coherence of the multimodal ensemble. In short, the PBS Space Time video shows a higher degree of density and coherence. We conclude that the two genres are at different stages of development as digital genres.
