In response to:
WAP, SAP, PAP, & FAP from the May 8, 1986 issue
To the Editors:
Martin Gardner, in his review of The Anthropic Cosmological Principle by myself and J.D. Barrow [NYR, May 8, 1986], unfortunately seems to have relied mainly on obsolete and quite inaccurate popular articles for his knowledge of the Anthropic Principle.
Gardner errs in saying the Many-Worlds Interpretation (MWI) requires measurements to split the entire universe. We emphasized in chapter 7 of our book that it is far more appropriate to regard the observer (or observing apparatus) as splitting rather than the universe. As Einstein said, it is silly to think a mouse’s glance could drastically change the universe. In the MWI, only an observer is changed by an observation. The “worlds” created by the observer are to be regarded as different aspects of itself.
Gardner errs in saying there can be no communication between worlds. We humans indeed cannot interact with the other versions of ourselves, but this is due to Weak Anthropic Principle (WAP) selection: our brains store information irreversibly, hence humans must split permanently. But D. Deutsch of Oxford University has shown that a computer can be built with a reversible memory: such a machine could communicate (in a sense) with the various versions of itself: it could split, come together again, and yet remember it had split. See chapter 7 for references to Deutsch.
Since quantum mechanics doesn’t allow a wave function to be concentrated along a single trajectory, the MWI does imply there must be other universes in the usual sense of “universe,” though these are not created by observation. But this doesn’t mean all possible universes exist. If the Strong Anthropic Principle (SAP) holds, then only those universes which allow us to evolve will exist, whereas if our existence is only a WAP selection effect, then probably all possible universes exist. We show in chapter 7 that these two differences between WAP and SAP can be expressed mathematically as boundary conditions on the universal wave function, leading to different evolutionary histories for the universe we actually live in. The evolution of our universe is affected by the presence or absence of the parallel universes; the parallel worlds are truly real. (The WAP boundary condition solves the cosmological Flatness Problem without the inflation mechanism.)
Gardner asserts WAP is trivial and incapable of making testable predictions. Even if the latter were true, WAP would still be essential in evaluating data: some approximate equalities, e.g., the universe’s age and our sun’s lifetime, are due to self-selection, and do not require new physics for explanation, as many thought. But it is not true. Both we in our introduction and Wheeler in his preface gave great emphasis to Carter’s inequality, which predicts the probable length of time the Earth will remain as a habitable planet from the number of improbable steps that occurred in the evolution of intelligent life on Earth. Clearly, a relation between these numbers is neither obvious nor trivial. Yet Carter’s inequality is a consequence of WAP: self-selection from our nature as carbon-based organisms which evolved on a G-type star’s planet. We give a derivation of Carter’s inequality in chapter 8.
One of the assumptions which goes into Carter’s inequality is the improbability of the evolution of intelligent life: we are probably the only intelligent life to ever evolve in our galaxy. We discuss in chapter 8 one piece of evidence for this conclusion: the approximate equality between the solar lifetime, and the time needed to evolve intelligence on Earth. More evidence for the absence of extraterrestrial intelligent life [ETI] is the evolution argument, detailed in chapter 3. Gardner’s claim that I have misunderstood this argument is false, as the great evolutionists G.G. Simpson and E. Mayr have assured me in personal letters.
The third piece of evidence for the absence of ETI in the galaxy is the local absence of ETI. The work of Klass and Menzel (see chapter 9 for references) has established that ETI spaceships are not now and probably never have been on Earth. Hence, ETIs are probably not in our solar system. As we emphasize on page 590 of our book, this absence of ETI in our solar system is a fact which obviously provides us with information about ETI. Gardner’s slogan “absence of evidence is not evidence of absence” falsely claims we have no information on ETI.
I interpret the absence of ETI in our solar system to mean they have never existed in our galaxy. My argument is based on the astro-physical fact that if our evolutionary history is typical, then many civilizations must have reached our level of technology billions of years ago. An interpretation of any ET experiment, even radio searches, must estimate what technology ETs this far ahead of us would have, and how they would use it.
I have argued that such a civilization would explore or colonize the galaxy. The calculations of both Sagan and myself agree: if such a civilization begins such a program, then the entire galaxy would be explored/colonized in less than a billion years, a period short in comparison to the age of these civilizations. Since they are not here, they don’t exist.
Anyone can think of ways of apparently avoiding this conclusion. Perhaps technical civilizations destroy themselves before beginning to explore/colonize. Perhaps a civilization so advanced doesn’t need to colonize: it can do anything it pleases using its own solar system’s resources. Sagan avoids the conclusion of his own calculations by invoking the latter possibility. Reasons for disbelieving both these and other suggested possibilities are given in chapter 9.
I think an advanced civilization would conduct exploration/colonization via self-reproducing intelligent machines. Gardner considers intelligent machines to be a fantasy, but judging from the current rate of computer development, I think we shall have the capacity to construct intelligent machines in the near future. A civilization billions of years ahead of us should thus have this technology too. Sagan thinks that an advanced civilization would stop intelligent machines from expanding through the galaxy. Gardner apparently views intelligent machines similarly: even if possible, their reproduction must be controlled; they can be restricted as humans see fit.
But we ourselves are just a special type of intelligent machine: one made of organic molecules. Thus an intelligent machine made of metal would a person. A person whose skin is metallic can no more have its reproduction restricted than a black-skinned person. Regarding life as a form of machinery and intelligent machines as people without our environmental limitations is essential in understanding FAP, the Final Anthropic Principle, which deals with evolution in the far future. Gardner seems to think evolution ended with Homo sapiens; his world-view is static.
We call FAP “quite speculative,” but it must not be thought more speculative than it is. FAP merely hypothesizes that the laws of physics are benign and permit for all future time the continued existence of (machine) intelligent life. It is possible to study and test FAP using the second law of thermodynamics, information/computer theory, particle physics, and relativistic cosmology. We conclude the known laws of physics allow the continued existence of machine life, but organic life is doomed either by proton decay and great cold (in open universes), or by high temperatures (in closed universes).
However, although the known laws of physics seem to allow machine life to survive, the large-scale structure of the universe and high energy particle physics (which are unknown) may not. Thus FAP can make testable predictions about these. For example, FAP implies the particle mass spectrum must obey a certain power law.
Another prediction is that the universe must be closed, with its final singularity being a single point in Penrose’s c-boundary topology. To relativists, such a c-boundary is very counter-intuitive: one would expect a more complex structure. (In the standard closed universe model the final c-boundary is a 3-sphere.) Since the final c-boundary point is both the end of time and of life, it is natural to borrow Teilhard’s term: the Omega Point. In contrast to Teilhard’s Omega Point, ours has a precise definition and its properties can be studied mathematically.
Three of these properties provoked Gardner’s derision: omnipotence, omniscience, and omnipresence. The terms merely mean that at the end of time, life has engulfed the entire universe (omnipresence), has gained control over all that can be controlled (omnipotence), and knows everything that can be known (omniscience). Aren’t these terms the natural ones to apply to these properties? What else could these words mean?
The Omega Point has a fourth property. Mathematically, the c-boundary is a completion of spacetime: it is not actually in spacetime, but rather just “outside” it, forming its “boundary.” From the c-boundary definition, a single c-boundary point would be formally equivalent to the entire collection of spacetime points, and yet from another point of view, be outside spacetime altogether. In natural terminology, the Omega Point is “both transcendent to and immanent in” all of spacetime. Significantly, these four properties follow from the mathematical analysis of FAP; they are not put in from the beginning.
Gardner calls this theory “metaphysics and fantasy.” In The Whys of a Philosophical Scrivener, he calls himself a fideist: a believer in a static personal God, but one unable to justify this belief, or say what is meant by “God.” It is fideism which is metaphysics and fantasy. Worse, fideism requires religion to be divorced forever from science. Gardner’s real objection to our Omega Point theory is that it threatens to end the divorce. But the domain of science is ultimately all existence; the post-Darwinian divorce is strictly temporary.
Frank J. Tipler
New Orleans, Louisiana
Martin Gardner replies:
December 4, 1986