A friend recently emailed me to ask about multiverse theory. His question was whether there is anything to it at all or if it is simply an attempt to escape the clear theological implications of the 20th century recognition that the universe came into being a recent time ago and is amazingly designed to make possible life on Earth. Here's my response...
The answer to your question is actually a bit complex, and getting it right involves identifying several aspects of the issue. As you are well aware, the discoveries in astrophysics and cosmology of the past several decades have provided stunning support for the claims of the Bible and of Judeo-Christianity. General relativity has become the most rigorously tested—and verified—idea in all of physics, which leads to the almost universal acceptance among scientists of so-called big bang cosmology and the space/time theorem, the recognition that the universe began, and powerful scientific support for the cosmological argument for God’s existence. Moreover, the teleological (design) argument for God’s existence has likewise found a great ally in modern science, with the development of the anthropic principle, the recognition that the universe is extremely fine-tuned for human life on Earth.
The astronomer or physicist today who would remain an atheist needs to explain away, then, in naturalistic terms, three things—the beginning of the universe, the fundamental fine-tuning of the universe (that is, the hundreds of characteristics of the universe itself that demonstrate design for life), and the environmental fine-tuning (the far greater number of identified characteristics of our more local environment—galaxy, solar system, and such).
Appealing to some form of multiverse theory is the claim of choice for many scientists who seek to deny the Creator. And (as you suggest) some forms of multiverse theory are completely speculative (and even absurd), with no evidential or theoretical support, beyond the possibility of testing, and likely offered only in hopes of denying the theological implications of the available evidence from the actual universe. Into this category are those bizarre theories referred to (by Max Tegmark, a physicist at MIT) as Level III and Level IV multiverse models. There is really no need to describe or discuss these.
But the same cannot be said of Level I and Level II models. Both sets enjoy at least some theoretical support, and some form of Level I multiverse is almost certainly true. While some advocates of these models may be motivated by a desire to explain away the beginning and design of the universe, the models themselves are worth describing, so that we can discuss their actual theological implications.
It is somewhat of a misnomer to call Level I models ‘multiverse’ models. What is meant by a Level I multiverse is just a single huge universe, one much larger than the portion of it that is observable from our position in it. It is pretty well accepted among astrophysicists that there is more to the universe than what we can see. This is because all of the available evidence indicates that there was a brief period of hyper-inflation early in the universe’s history. (To put it another way, the evidence has led scientists to focus their research on a very narrow suite of big-bang models that remain viable, and these are all inflationary models.) Inflation solves three problems of more basic big bang models (the flatness problem, the horizon problem, and the monopole problem.)
It is important to point out that a Level I multiverse does not explain away the beginning of the universe—its origin is still the big bang singularity of 13.7 billion years ago. Likewise, it does not explain away the fundamental fine-tuning of the universe, as the same laws of physics would apply to all corners of such a multiverse. Moreover, the environmental fine-tuning would be explained away only if the Level I multiverse were nearly infinitely large. All of the available evidence (relating to the ‘geometry’ of the universe) argues against such an infinitely large multiverse. For all these reasons (and others), the existence of a Level I multiverse does not offer any hope for the person intent on denying God’s existence.
Level II models involve the existence of a vast number of ‘bubble’ universes, each with different laws of physics. In most such models, inflation occurs before the forming of our (or any other) universe. The theoretical support for some form of Level II multiverse comes from certain very specific variations of string theory, but there is almost no actual evidence supporting these models. Indeed, the available evidence supports inflation’s occurring within (not prior to) our universe. While the existence—against all evidence—of an infinite number of other bubble universes would help explain away the fundamental fine-tuning of our universe, it would not do away with the problem of the environmental fine-tuning.
Nor would it explain away the beginning of our universe or undermine the cosmological argument for God’s existence. This is the direct conclusion from the relatively-recent BVG theorem. (This proof was developed by Arvind Borde, Alexander Vilenkin, and Alan Guth, and takes its name from the first letter of their last names.) According to the BVG, any universe that expands on average—as does an inflationary multiverse—must have a beginning in the finite past. In other words, rather than undermining the cosmological argument, Level II multiverse models make this argument more robust.
I’m all for continued research in these areas, which will undoubtedly result in a better understanding of the creation in which we live. The scientists involved likely have a variety of motives, some of them good and some of them less so. Those seeking to find intellectual support for their denial of God are more to be pitied than censored, though, since the universe in which we all live really is the one accurately described by the Bible, the exquisitely-designed creation of an all-powerful, loving Creator.
Thanks for the question.