From two of the world's great physicists-Stephen Hawking and Nobel laureate Roger Penrose-a lively debate about the nature of space and timeEinstein said that the most incomprehensible thing about the universe is that it is comprehensible. But was he right? Can the quantum theory of fields and Einstein's general theory of relativity, the two most accurate and successful theories in all of physics, be united into a single quantum theory of gravity? Can quantum and cosmos ever be combined? In The Nature of Space and Time, two of the world's most famous physicists-Stephen Hawking (A Brief History of Time) and Roger Penrose (The Road to Reality)-debate these questions.The authors outline how their positions have further diverged on a number of key issues, including the spatial geometry of the universe, inflationary versus cyclic theories of the cosmos, and the black-hole information-loss paradox. Though much progress has been made, Hawking and Penrose stress that physicists still have further to go in their quest for a quantum theory of gravity.

Foreword by Michael Atiyah vii
Acknowledgments ix
CHAPTER ONE Classical Theory, Stephen Hawking 3
CHAPTER TWO Structure of Spacetime Singularities, Roger Penrose 27
CHAPTER THREE Quantum Black Holes, Stephen Hawking 37
CHAPTER FOUR Quantum Theory and Spacetime, Roger Penrose 61
CHAPTER FIVE Quantum Cosmololgy, Stephen Hawking 75
CHAPTER SIX The Twistor View of Spacetime, Roger Penrose 105
CHAPTER SEVEN The Debate, Stephen Hawking and Roger Penrose 121
AFTERWORD TO THE 2010 EDITION The Debate Continues, Stephen Hawking and Roger Penrose 139
References 143