This project explores the effectiveness of learner-centered education (LCE) principles and practices on student learning and attitudes in an online interactive introductory astronomy course for non-science majors by comparing a high-quality Internet-delivered course with a high-quality on-campus course, both of which are based on the principles of LCE. To date, there have been numerous comparisons of conventional lecture courses with distance-learning courses described in the literature, which show little significant difference between the two learning environments. A careful review suggests that these are often noninteractive lecture courses, compared with traditional reading and correspondence courses in which assignments are submitted via e-mail. In contrast, this study compares an interactive Internet-delivered course with a learner-centered on-campus course, both of which use highly interactive teaching techniques characteristic of LCE. To do this, we created a hypermedia learning experience for introductory astronomy that matches Internet technology with how people learn. This course weaves multimedia visualizations into a structured learning environment by breaking down complex concepts into bite-sized pieces. Each cognitive piece contains hyperlinks that explain all terms. Illustrations consist of high-resolution images, animations, and videos that students manipulate to answer questions. Each module helps students engage in the pursuit of learning astronomy by providing activities in which students use astronomical data. Learners are required to answer premodule questions--not as multiple-choice questions, but as written narratives--about the concept under study to make their knowledge explicit. At the conclusion stage, students compare new ideas with their initial answers and evaluate various alternative explanations. We find that although this innovative course accomplishes its goals and students achieve an acceptable level of achievement, the high-quality on-campus course experience yields significantly higher achievement gains. (Contains 1 table and 1 figure.)