In this project, we will develop new models and tools for on-line education that will demonstrate how to effectively implement evidence-based instructional strategies and assessments into on-line learning environments, while bridging the gap between formal university-based learning and informal lifelong learning. The rapidly increasing capability of the Internet for the delivery of educational content has caused the number of students taking on-line classes to dramatically increase from two million in 2002 to ten million. Many face-to-face courses are also incorporating on-line elements. For example, "flipped" or "hybrid" courses use the Internet to deliver content that would otherwise be presented in class, freeing up class time for more complex and collaborative activities. The migration of education to the Internet has led to the emergence of MOOCs, massively open on-line classes. The classic MOOC is free, open to everyone, and does not result in college credit. However, Coursera, one of the leading providers of MOOCs, is pioneering the delivery of on-line courses for transferrable college credit, through a process approved by the American Council of Education. Meanwhile there is criticism of MOOCs for relying primarily on ineffective lecture-centered instructional strategies, and for using assessments that probe students' understandings at superficial levels. The challenge of implementing evidence-based, active engagement pedagogy without face-to-face contact or real-time interactions is a problem that remains to be solved. This project is one of the first attempts to arrive at a solution. We will develop two new mutually-reinforcing, multi-tiered introductory astronomy courses - one a flipped course, one a MOOC - in which we will study how to maximize student learning and engagement, and also how to develop, scale, adapt, and implement evidence-based instructional strategies into an on-line environment. These strategies and lessons learned will be disseminated broadly in the science education and research communities.