Fine-tuning, the multiverse and God
-Geraint Lewis and Luke Barnes explore cosmological fine-tuning in their new book The Fortunate Universe
How is the universe like a babelfish? No, that's not a riddle from a Douglas Adams-Lewis Carroll mashup. It's a question that came to mind after reading Lewis and Barnes' A Fortunate Universe: Life in a Finely Tuned Cosmos. In Adams' classic works of science-fiction/geek humor, the babelfish is a tiny leech-like organism which, when placed into the ear of a hapless space traveler, ingests the sound waves of alien languages and instantly translates them into the language of the host. The narrator drily remarks that some thinkers chose to see such a wildly improbable, extraordinarily useful coincidence as proof that God does not exist, since God would never undermine the faith of believers with such brazen and impudent evidence of His existence.
The allegation that we are living in a fine-tuned universe must strike many people in the same way. A large number of physicists, including Lewis and Barnes, believe that the fundamental constants of physics, its laws, and its initial conditions are narrowly tuned for the existence of life. In the book's opening chapter, the authors ask us to imagine tuning in to a particular station on an old-fashioned radio. If we nudge the dial even a small amount, the station we're listening to will dissolve into static. According to our current understanding of physics, 'tuning in' to life in the universe is many times harder than 'tuning in' to a radio station. There is not just one dial, but dozens. And many of them need to be jiggled only a fraction of a percent to make life in the universe impossible. To put it another way, bacteria, petunias, frogs, dolphins and human beings can only exist because multiple dials are set to very, very, very precise values.
This claim sounds ridiculous, but the authors spend five chapters unpacking the various components of modern physics that support fine-tuning. From the masses of elementary particles like quarks and electrons, to the strength of the fundamental forces like the strong force and electromagnetism, to the ability of stars to produce heavy elements, to the low entropy state of the early universe, fiddling with physics even a little can render the universe sterile. For example, the cosmological constant, which controls the acceleration of the universe's expansion, needs to be fine-tuned to one part in 10^120, or one part in one trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion, trillion, in order for life to exist. And not just the carbon-based life that we're fammiliar with. Tinkering with physics doesn't merely lead to Earth-like planets with slightly less oxygen or slightly higher temperatures. Changing these fundamental parameters and constants leads to universes that collapse into giant black-holes within a second of the Big Bang, or universes composed of nothing but hydrogen atoms hurtling through a nearly endless void, or universes in which the periodic table of elements does not exist (chemistry-haters of the world, rejoice!) No matter how generous we are in our definition of 'life' and how optimistic we are about the ability of life to thrive in harsh conditions, it strains credulity to insist that we can make 'life' out of nothing but hydrogen in a universe with no stars which pops into existence for five seconds before collapsing into a black hole.
Throughout the book, the authors emphasize that the problem of 'fine-tuning' is not the invention of religious apologists eager to find evidence for the divine. Instead, it is an active area of research spanning decades and involving the work of dozens of eminent physicists writing in mainstream scientific journals. Commenting on the findings of over 200 papers related to the subject of fine-tuning, the authors write that "[On] balance, the fine-tuning of the Universe for life has stood up well under the scrutiny of physicists... Only a handful of peer-reviewed papers have challenged the fine-tuning cases we've discussed in this book and none defend the contention that most values of the constants and initial conditions of nature will permit the existence of life" (p. 242-243). So how should we react to claims of fine-tuning?
The penultimate chapter of the book entitled "A Dozen (or so) Reactions to Fine Tuning" provides a dozen (or so) options. The authors begin by observing that their professional talks on fine-tuning are remarkable for the strong, passionate responses they evoke. "A forty-minute talk [is] followed by an hour and a half of questions... this never happens. In a typical seminar, astronomers become anxious to leave after three or four questions, and for good reason. It's lunchtime" (p. 237). The authors spend fifty pages answering some of the most common reactions to fine-tuning from physicists and non-physicists alike, considering everything from "It's Just A Coincidence" to "Fine-Tuning Has Been Disproved by (Insert Name Here)" to "Life Chauvanism - Why Think That Life is Special?" But after all these alternative explanations have been considered and dismissed, do any remain? The final chapter addresses this question in a very helpful way, as Barnes and Lewis engage in a dialogue in which both present their preferred explanation for fine-tuning.
Lewis appeals to the idea of a 'multiverse', the hypothesis that our own universe is one of many other universes, perhaps an infinite number of universes. In each parallel universe within the multiverse, the fundamental constants are slightly different. For the reasons given in the book, Lewis agrees that almost all of these other universes are devoid of life. But our universe was the one that won the universe lottery, so to speak, and began with just that set of parameters and initial conditions which allowed for the existence of life.
Lewis agrees that this explanation has its problems: how do we know that such an undetectable multiverse exists? How do we know that, if it exists, the fundamental constants of physics really do vary within the multiverse ensemble? What exactly is the mechanism that generates members of the multiverse? Most bizarrely problematic is the worry that the multiverse, if it exists, might predict that we are disembodied 'Boltzmann brains' brought into existence by a random quantum fluctuation and implanted with false memories of our lives on Earth. This, Lewis concedes, is a real worry and one that proponents of the multiverse need to grapple with. But if the multiverse sounds too much like a bad plot device from a discarded episode of Futurama, what is left?
According to Barnes, we have to start talking about 'The G Word' - the idea that God created the universe with the life-permitting properties we observe precisely because He intended to populate it with embodied moral agents like us. Interestingly, the discussion at this point turns to philosophy rather than science. Is it ever reasonable to invoke a supernatural explanation for natural phenomena when so many previous supernatural explanations have proven to be false? While God may explain the fine-tuning of the universe, doesn't God himself need an explanation? If God created the universe, then why didn't he create a universe with less evil in it? In a relatively short space, Barnes does a good job answering these questions. But, to my mind, he does an even greater service in reminding the reader that the kinds of answers he's giving have been around for thousands of years, are supported by robust argumentation, and will not "wither at the touch of a first-year philosophy student" (p. 328).
So is the universe like a babelfish? In other words, does fine-tuning provide such irrefutable evidence for God that it renders faith unnecessary and any faith-based religion false? That depends on whether we think the multiverse is a plausible explanation. But it also depends on what we mean by 'faith.' If faith is 'belief without evidence', as New Atheist authors like Richard Dawkins and Sam Harris insist, then evidence does seem to undermine faith. But what if 'faith' refers to 'trust'? Believing in God is different than trusting in God. Anyone who has stood at the edge of a high dive, who has boarded a plane or who has exchanged marriage vows knows that intellectual belief is not enough. At some point, we need to commit ourselves personally to what we believe intellectually to be true. Ultimately, cosmological fine-tuning might convince us that there is a God. But how we choose to relate to Him is up to us.
- Why Should We Believe that Christianity is True?
- Science and religion: is it either/or or both/and?
- Three Paradoxes of Atheism
If anyone reading this essay has questions about it or Christianity, feel free to e-mail me at Neil -AT- Shenvi.org. I also highly recommend the book The Reason for God by Tim Keller. It is phenomenal. Free sermons treating many of the topics covered by this book can be found here.