This paper investigates rationality and its relationship to trust in science in the context of three proposed spaces of science education: the formal, informal and casual. It begins with the place of science as a trusted institution and its role in formal and informal education across the world. Through educational systems, we have come to trust that students are being educated about science and its trustworthiness. However, formal and informal education spaces are not the only spaces in which individuals and society seek science understanding. While the science education literature has long concerned itself with science education in these spaces, this paper proposes a third space, the casual space. The casual space is decentralised and provides access to a range of norms and explanations about the world. We investigate how each of the formal, informal and casual spaces privileges particular forms of rationality as a means for understanding trust in science in each of these spaces. This paper considers the implications for education's response to the challenge of equipping students to make rational judgements about science.