Nothing expands the mind like the expanding universe. The music of the spheres is a nursery rhyme, a jingle to set against the majestic chords of the Symphonie Galactica. Changing the metaphor and the dimension, the dusts of centuries, the mists of what we presume to call “ancient” history, are soon blown off by the steady, eroding winds of geological ages. Even the age of the universe, accurate—so Lawrence Krauss assures us—to the fourth signi!cant !gure at 13.72 billion years, is dwarfed by the trillennia that are to come.
But Krauss’s vision of the cosmology of the remote future is paradoxical and frightening. Scienti!c progress is likely to go into reverse. We naturally think that, if there are cosmologists in the year 2 trillion “#, their vision of the universe will be expanded over ours. Not so—and this is one of the many shattering conclusions I take away on closing this book. Give or take a few billion years, ours is a very propitious time to be a cosmologist. Two trillion years hence, the universe will have expanded so far that all galaxies but the cosmologist’s own (whichever one it happens to be) will have receded behind an Einsteinian horizon so absolute, so inviolable, that they are not only invisible but beyond all possibility of leaving a trace, however indirect. They might as well never have existed. Every trace of the Big Bang will most likely have gone, forever and beyond recovery. The cosmologists of the future will be cut off from their past, and from their situation, in a way that we are not.