XVMI
PREFACE
exhilarating to work on a "final theory" that may ultimately answer
some of the most difficult "impossible" questions in science today, such
as whether time travel is possible, what lies at the center of a black
hole, or what happened before the big bang. I still daydream about my
lifelong love affair with the impossible, and wonder when and if some
of these impossibilities might enter the ranks of the everyday.