© Reprinted with permission from Nova Science Publishers, Inc. from: Sabine Hossenfelder, "What Black Holes Can Teach Us," in Focus on Black Hole Research, ed. Paul V. Kreitler (New York: Nova Publishers Inc., 2006), 121-58.
Black holes are objects so massive that gravity prevents matter from escaping them. But black holes are warm or even hot, and we will see in Unit 5 that hot bodies radiate. How is it possible for anything to escape a black hole? The answer, as Stephen Hawking insightfully showed, is quantum mechanics. Black holes can emit photons and other particles, now known as "Hawking radiation," through a quantum process that general relativity cannot explain. (Unit: 4)