Pale Blue Dot - Carl Sagan [19]
Moreover, we have no access to any of those putative alternative universes. We have no experimental method by which anthropic hypotheses may be tested. Even if the existence of such universes were to follow firmly from well-established theories—of quantum mechanics or gravitation, say—we could not be sure that there weren’t better theories that predict no alternative universes. Until that time comes, if it ever does, it seems to me premature to put faith in the Anthropic Principle as an argument for human centrality or uniqueness.
Finally, even if the Universe were intentionally created to allow for the emergence of life or intelligence, other beings may exist on countless worlds. If so, it would be cold comfort to anthropocentrists that we inhabit one of the few universes that allow life and intelligence.
There is something stunningly narrow about how the Anthropic Principle is phrased. Yes, only certain laws and constants of nature are consistent with our kind of life. But essentially the same laws and constants are required to make a rock. So why not talk about a Universe designed so rocks could one day come to be, and strong and weak Lithic Principles? If stones could philosophize, I imagine Lithic Principles would be at the intellectual frontiers.
There are cosmological models being formulated today in which even the entire Universe is nothing special. Andrei Linde, formerly of the Lebedev Physical Institute in Moscow and now at Stanford University, has incorporated current understanding of the strong and weak nuclear forces and quantum physics into a new cosmological model. Linde envisions a vast Cosmos, much larger than our Universe—perhaps extending to infinity both in space and time—not the paltry 15 billion light-years or so in radius and 15 billion years in age which are the usual understanding. In this Cosmos there is, as here, a kind of quantum fluff in which tiny structures much smaller than an electron are everywhere forming, reshaping, and dissipating; in which, as here, fluctuations in absolutely empty space create pairs of elementary particles—an electron and a positron, for example. In the froth of quantum bubbles, the vast majority remain submicroscopic. But a tiny fraction inflate, grow, and achieve respectable universehood. They are so far away from us, though—much farther than the 15 billion light-years that is the conventional scale of our universe—that, if they exist, they appear to be wholly inaccessible and undetectable.
Most of these other universes reach a maximum size and then collapse, contract to a point, and disappear forever. Others may oscillate. Still others may expand without limit. In different universes there will be different laws of nature. We live, Linde argues, in one such universe—one in which the physics is congenial for growth, inflation, expansion, galaxies, stars, worlds, life. We imagine our universe to be unique, but it is one of an immense number—perhaps an infinite number—of equally valid, equally independent, equally isolated universes. There will be life in some, and not in others. In this view the observable Universe is just a newly formed backwater of a much vaster, infinitely old, and wholly unobservable Cosmos. If something like this is right, even our residual pride, pallid as it must be, of living in the only universe is denied to us.*
Maybe someday, despite current evidence, a means will be devised to peer into adjacent universes, sporting very different laws of nature, and we will see what else is possible. Or perhaps inhabitants of adjacent universes can peer into ours. Of course,