The Goldilocks Enigma: Why Is the Universe Just Right for Life?

by Paul C.W. Davies

Let me repeat my warning. Just because we can’t explain how life began doesn’t make it a miracle.

Figure 26: Existence in a nutshell. A schematic depiction of the set of all that can in principle exist. A distinction is made between what actually exists and what could exist but doesn’t. Included within the former set is a smaller subset, consisting of all that can in principle be observed. Left out of this subset are other things that exist but are unobservable (for example, universes that do not permit life). Anthropic reasoning may be applied to boundary A,

to explain why we observe a life-friendly universe, but not to boundary B (to determine the rule that separates what can exist from what does exist).

Figure 27: What if there is just one universe? Like Figure 26, this diagram also depicts all that can in principle exist. Some physicists hope that there is only one possible universe consistent with a final, mathematically unified supertheory (for example, M theory) and that what we observe is it. (It would have to be!) If they are right, then what gets observed is all there is. (We may not be able observe it all at any one time, but what we don’t observe right now would be the same sort of thing as what we do observe.) However, this mathematically unique theory of everything would still not explain why this universe is the one that exists, as opposed to all other logically possible universes that don’t “have fire breathed into them,” for example, universes described by other unified theories that do not fit the observational facts of our universe, depicted here by the dark region on the other side of boundary B.

Figure 28: Tegmark’s “anything goes” multiverse. According to Max Tegmark, everything that can exist does exist: that is, all logically possible universes described by all possible mathematical structures are really out there somewhere. Anthropic reasoning may be used to define the (tiny!) subset of universes that can be observed (the lightly shaded region). The rest, located on the other side of boundary A, is the set of all possible things that can—and do—exist and that go unobserved.

Figure 30: Super-turtle! To avoid an infinite regress (the bottomless tower of turtles in Figure 29), one might consider a levitating super-turtle, which is self-explaining and self-supporting. Theologians call this “a necessary being,” and some have tried to prove that such a being exists. Some scientists have argued for the necessary existence of a unique super-unified theory. Many People Think the Universe Absurd The root of the turtle trouble can be traced to the orthodox nature of reasoned argument. The entire scientific enterprise is predicated on the assumption that there are reasons for why things are as they are. A scientific explanation of a phenomenon is a rational argument that links the phenomenon to something deeper and simpler. That, in turn, may be linked to something yet deeper, and so on.

Key Points This chapter contains more of the author’s personal opinions than the earlier chapters. In some respects, such as its strange fitness for life, the universe appears designed. Some people suggest that it is. Invoking a supernatural designer, however, opens up its own as-yet-unsolved philosophical issues about the designer’s nature, origin, uniqueness, necessity, and relationship to time. It is important to distinguish between design in the laws of physics and design in objects or in systems

such as biological organisms. The appearance of design in organisms has a testable scientific explanation based on Darwin’s theory of evolution. The appearance of design in the laws might be explained by hypothesizing a multiverse with “anthropic” selection. However, a multiverse is not a complete explanation of existence because it still requires some unexplained physical laws. Some scientists pin their hopes on a complete “theory of everything” that would explain the universe without invoking observer selection effects. If such a theory were correct, the bio-friendliness of the universe would be a lucky coincidence. However, the existence of a unique final theory is very doubtful. Unless everything that can exist does exist, something still unexplained must separate what exists from what doesn’t. To avoid an infinite regress (a tower of turtles), something must be accepted on faith, even in scientific accounts, but that something should be as simple as possible. We are not finished yet!

The question before us, then, is whether living organisms may legitimately be regarded as in some sense fundamental—and therefore significant—or incidental and insignificant side effects of the main game.

Today we know that there is no life force. Living organisms are machines, and

they derive their extraordinary qualities from their great complexity.

The primary job of genes is to code for the manufacture of proteins. Most DNA in complex organisms such as human beings is in fact “noncoding”—it is not genetic information and is often referred to as “junk DNA.”11

without introducing an observer, we have a dead universe, which does not evolve in time”16 and “We are together, the universe and us. The moment you say that the universe exists without any observers, I cannot

make any sense out of that. I cannot imagine a consistent theory of everything that ignores consciousness . . . In the absence of observers, our universe is dead.”17 And observers will exist, obviously, only in those “Goldilocks” universes in which the laws and conditions are such as to permit them to emerge.

minds (human minds, at least) are much more than mere observers. We do more than just watch the show that nature stages. Human beings have come to understand the world, at least in part, through the processes of reasoning and science.

Any sort of life principle or cosmic imperative reintroduces into science the dreaded t-word: teleology. The word derives from the Greek telos, meaning “end” or “outcome,” and it goes to the heart of what scientists mean when they use the word cause.

there is no justification for invoking mathematical operations to describe physical laws if those operations cannot actually be carried out, even in principle, in the real universe, subject as it is to various physical limitations. In other words: Laws of physics that appeal to physically impossible operations must be rejected as inapplicable.

mathematics is a product of the human intellect.

So our universe possesses laws and states that not only permit self-simulation, they also permit self-comprehension. The cosmic rule book, in being fit for life and in facilitating the eventual emergence of consciousness, has not only ensured that the universe has constructed its own awareness: the cosmic scheme has also constructed an understanding of the cosmic scheme.

The universe clearly cannot be self-explanatory without containing the ability to explain itself!67 If there is to be a complete explanation for the universe as a loop, the universe has to know and understand the laws it is responsible for in order to bring those laws into being. How could it be otherwise?

Key Points

Conventional explanations run into a tower-of-turtles problem. Some scientists and philosophers have suggested self-consistent explanatory loops instead. Some scientists reject the orthodox, Platonic view of physical laws (idealized, infinitely precise mathematical relationships that transcend the physical universe). The laws of physics may not operate with infinite precision because the universe has finite computational power. Teleology, or final causation, is taboo in orthodox science. The concept of a universe destined to bring forth life and observers is clearly teleological. Backward causation could provide a quasi-respectable scientific route to teleology. Wheeler’s delayed-choice experiment describes a way in which observers today help shape the nature of reality in the past without being able to send information backward in time. If the universe is self-explanatory, then it must evolve beings able to explain it.

It seems to me that there is a genuine scheme of things—the universe is “about” something.

I do not believe Homo sapiens to be more than an accidental by-product of haphazard natural processes. Yet I do believe that life and mind are etched deeply into the fabric of the cosmos, perhaps through a shadowy, half-glimpsed life principle,

There is also a sizable group of scientists who, perhaps in reaction to the homocentrism of traditional religion or motivated by dismay at humanity’s brutality and destruction of the environment, wish to diminish or even besmirch human significance, and with it the significance of human qualities such as intelligence and understanding.