Temporal Contraptions are hybrid interactive installations/objects that create multi-directional feedback loops between the physical world, computational systems, and past states of both. In these pieces, an artist-written computer program creates projected visual output in response to people's presence and movements. The output is projected onto sculpted, dimensional, and mobile surfaces. The surfaces can be manipulated by participants to change the state of the system, and in turn affect the response of the projections. Some contraptions can also move mechanically on their own in reaction to what is happening in the projections. The rules of each system are constructed so that visual and mechanical responses are based on moments that have occurred in the past as well as the present. By storing and responding to encoded information about past and current movement - of participants, projected information, and the physical projection surfaces - the state of each system represents intersections and extrapolations between different moments in time.