Dark stars were predicted ìn 1783 using Newtonian gravity. Black holes are something similar but wildly different predicted by general relativity.
Assumed Preparation: This lesson assumes that the students have already gone through the activities and questions of General Relativity: Curving Spacetime. It also assume that students have made a thorough study of Newtonian gravity and its application to orbital motion and escape velocity.
Subversive Physics: General relativity is not an explicit part of any high school curriculum, so how can you justify spending time on the curved spacetime and black holes? Newtonian gravity is an explicit part of the curriuiculm and we would be doing our students a disservice if we left them thinking that Newtonian gravity was the last word on the subject. Furthermore, all students have heard of black holes and they are interested in hearing more. However, Newtonian gravity is incapable of dealing with these bizarre objects. This lesson has students compare the predictions of these two theories and making comparisons is a powerful learning tool. That means that teaching about general relativity can strengthen their understanding of Newtonian gravity.
The Activity: The students will explore the predicitons of the the two theories of gravity through concept questions, diagrams and small group discussions. You will need the student worksheet and the teacher`s answers. The PowerPoint slides have lots of pretty pictures - but is not essential. You will need about 60 minutes to go through the whole lesson.
Further Information:
The best site for information about relativity is Einstein Online. http://www.einstein-online.info/elementary/generalRT.
The Perimeter Institute has a one-minute cartoon that looks at thee effect of black holes on time. "Can we travel through time?" http://www.perimeterinstitute.ca/en/Outreach/Alice_and_Bob_in_Wonderland/Alice_and_Bob_in_Wonderland/