Reinventing Gravity: A Physicist Goes Beyond Einstein

REINVENTING GRAVITY A PHYSICIST GOES BEYOND EINSTEIN John W. Moffat To Patricia whose dedication and help made this book possible Contents Introduction: A N E W G R A V I T Y T H E O R Y v Prologue: T H E E L U S I V E P L A N E T V U L C A N , A P A R A B L E 1 P A R T 1: D I S C O V E R I N G A N D R E I N V E N T I N G G R A V I T Y 1: T H E G R E E K S T O N E W T O N 2: E I N S T E I N PA R T 2: T H E S TA N D A R D M O D E L O F G R AV I T Y 7 9 25 49 3: T H E B E G I N N I N G S O F M O D E R N C O S M O L O G Y 51 4: D A R K M A T T E R 69 5: C O N V E N T I O N A L B L A C K H O L E S 78 PA R T 3: U P D AT I N G T H E S TA N D A R D M O D E L 6: I N F L A T I O N A N D V A R I A B L E S P E E D O F L I G H T ( V S L ) 7: N E W C O S M O L O G I C A L D A T A PA R T 4: S E A R C H I N G F O R A N E W G R AV I T Y T H E O R Y 89 91 110 125 8: S T R I N G S A N D Q U A N T U M G R A V I T Y 127 9: O T H E R A L T E R N A T I V E G R A V I T Y T H E O R I E S 14 3 10: M O D I F I E D G R A V I T Y ( M O G ) 15 3 iv CONTENTS PA R T 5: EN V ISIONING A ND T ES T ING THE MOG UNIVERSE 171 11: T H E P I O N E E R A N O M A LY 173 12: M O G A S A P R E D I C T I V E T H E O R Y 181 13: C O S M O L O G Y W I T H O U T D A R K M A T T E R 19 3 14: D O B L A C K H O L E S E X I S T I N N A T U R E ? 200 15: D A R K E N E R G Y A N D T H E A C C E L E R A T I N G U N I V E R S E 205 16: T H E E T E R N A L U N I V E R S E 212 Epilogue 221 Notes 225 Glossary 24 6 Bibliography 257 Acknowledgments 26 0 Index 261 About the Author Credits Cover Copyright About the Publisher Introduction A N E W G R AV I T Y T H E O R Y n 1916, Einstein published his new theory of gravity called general relativity. In 1919, the theory was validated by the observation of the bending of light during a solar eclipse, as the sun’s gravitational pull warped spacetime. Since then, there has been much speculation as to whether Einstein’s theory of gravity is perfect and unchangeable, much like Michelangelo’s David. Why would we want to modify Einstein’s outstanding intellectual achievement? Until recently, most physicists have considered Einstein’s general relativity theory to be in perfect agreement with observational data. However, this is not necessarily true. Neither have the attempts succeeded to unify Einstein’s gravitational theory with quantum mechanics, despite much effort: Many physicists consider the search for a successful quantum gravity theory the holy grail of modern physics. Moreover, there are some fundamentally unsatisfactory features of Einstein’s theory, such as those related to the beginning of the universe and the collapse of stars under their own gravitational forces. Finally, since the early 1980s, a growing amount of observational data has been accumulating that shows that Newtonian and Einstein gravity cannot describe the motion of the outermost stars and gas in galaxies correctly if only their visible mass is accounted for in the gravitational field equations.* There are much stronger gravitational forces being observed—causing the peripheral orbiting stars and gas to move faster—than are predicted by Newton’s and Einstein’s theories. There is now overwhelming evidence for stron- I * Einstein’s gravity theory reduces to Newton’s theory for weak gravitational fields and slowly moving bodies. vi I N T R O D U C T I O