This paper deals with the features and design of explanations in public physics lectures. It presents the findings from a comparative study of three exemplary public physics lectures, given by practicing physicists who are acknowledged as excellent public lecturers. The study uses three different perspectives: the lecture, the lecturer, and the audience (high school physics teachers and students). It concludes with a grounded theory explanatory framework for public physics lectures. The framework demonstrates that a "Translated Scientific Explanation" (TSE) draws upon four clusters of explanatory categories: analogical approach, story, knowledge organization, and content. The framework suggests how the lecturer fits the content of the presentation to the audience's knowledge throughout the lecture, taking into account the listeners' lack of necessary prior knowledge. (Contains 2 figures and 5 tables.)