Research in Ambient Intelligence and Ubiquitous Computing has put computational devices into many social settings while leaving intact much of the "task support and information access" model from traditional HCI. Recently, researchers have proposed novel approaches that support systems designed for engagement, enjoyment, enchantment, and wonder. Since the objectives for these systems differ, the design approach, development decisions, and evaluation questions shift in turn. Tableau Machine is an instance of an ambient intelligence and ubiquitous computing system designed for extended experience. It is an example of an Alien Presence, in that viewers interact with the system both as an autonomous agent, ascribing some intentionality to it, and as an alien reflection, a strange mirror of social life. We present Tableau Machine, a non-human social actor for the home that intends to open a space for contemplation and conversation among members of a home environment. Author Keywo...