On 2nd November 2011, Fay Dowker, Professor of Theoretical Physics, gave a Perimeter Institute Public Lecture; Black holes are hot! This discovery, made by Stephen Hawking, ties together gravity, space-time, quantum matter and thermal systems into the science of “Black Hole Thermodynamics.” The excitement arises because it tells us that there is something lacking in our understanding of space-time. In this talk, Professor Dowker describes black hole thermodynamics.