BLACK HOLES, WORMHOLES, AND TIME MACHINES
C O N T E N T S SPACE T H E 4 T H D I M E N S I O N TO DO WITH SHAPES WHAT IS SPACE? 2DWORLD AND 2D’ERS CURVED SPACE IS THERE REALLY A FOURTH DIMENSION? M AT T E R S O F S O M E G R AV I T Y 2 APPLES AND MOONS EINSTEIN’S GRAVITY FREE FALL RUBBER SPACE TWINKLE, TWINKLE COOKING THE ELEMENTS CHAMPAGNE SUPERNOVAE IN THE SKY T H E U N I V E R S E 3 THE NIGHT SKY HOW BIG IS THE UNIVERSE? THE EXPANDING UNIVERSE HUBBLE, BUBBLE SPACE IS STRETCHING DID THE BIG BANG REALLY HAPPEN? THE EDGE OF SPACE A CLOSED UNIVERSE ANOPENUNIVERSE WHATSHAPEISTHEUNIVERSETHEN? INVISIBLE MATTER 1998: A BIG YEAR IN COSMOLOGY IS THE UNIVERSE IN?NITE? WHY IS IT DARK AT NIGHT? BEFORE THE BIG BANG? SUMMARY B L A C K H O L E S 7 MORE TO LIGHT THAN MEETS THE EYE! INVISIBLE STARS BEYOND THE HORIZON A HOLE THAT CAN NEVER BE ?LLED SPINNING BLACK HOLES FALLING INTO A BLACK HOLE TO SEE A BLACK HOLE NOT SO BLACK AFTER ALL WHITE HOLES TIME T I M E S A R E C H A N G I N G 1 0 WHAT IS TIME? WHO INVENTED TIME? THE ?RST MOMENT DOES TIME ?OW? SOMETHING CALLED ENTROPY ARROWS OF TIME STEPHEN HAWKING GETS IT WRONG A POSSIBLE SOLUTION E I N S T E I N ’ S T I M E 1 3 WHAT IS SO SPECIAL ABOUT SPECIAL RELATIVITY? THE TWO FACES OF LIGHT THOUGHT EXPERIMENTS AND BRAIN TEASERS SLOWING DOWN TIME SHRINKING DISTANCES LIGHT—THE WORLD SPEED RECORD WHEN TIME RUNS BACKWARDS LITTLE GREEN MEN FAST FORWARD TO THE FUTURE SPACETIME—THE FUTURE IS OUT THERE GRAVITATIONAL TIMES T I M E T R AV E L PA R A D O X E S 1 6 THE TERMINATOR PARADOX TRYING TO SAVE THE DINOSAURS MONA LISA’S SISTER NO WAY OUT? PARALLEL UNIVERSES WHERE ARE ALL THE TIME TRAVELLERS? TIME MACHINES W O R M H O L E S 1 8 A BRIDGE TO ANOTHER WORLD ALICE THROUGH THE LOOKING GLASS WHEN SCIENCE FACT MET SCIENCE ?CTION WORMHOLES—KEEPING THE STAR GATE OPEN VISITING A PARALLEL UNIVERSE H O W T O B U I L D A T I M E M A C H I N E 2 0 TIME LOOPS THE TIPLER TIME MACHINE COSMIC STRING TIME MACHINES A RECIPE FOR A WORMHOLE TIME MACHINE INSURMOUNTABLE PROBLEMS? 10 W H AT D O W E K N O W ? 2 3