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Such is the advice from Bernard Carr in grappling with the fascinating discovery that the physics of the universe had to be fine-tuned if it were to support life. Carr views the only viable options as being either God or a multiverse (the theory that there are a vast number of other universes). Stanford physicist Leonard Susskind also calls our attention to these relatively recent discoveries: “Science may be undergoing a huge course correction, a paradigm shift. A titanic controversy has erupted over the strange anthropic pattern that nature seems to exhibit – the pattern of extraordinary unexplained coincidences that are necessary for our own existence.[1]” I will discuss these fine-tuning discoveries and their implications in a series of blogs as part of my ongoing series on scientific evidence for God.

If You Don’t Want God, You Better Have a Multiverse!

Here are my previous blogs in this series prior to the recent hiatus:


Can Science Disprove God?
What Counts as Evidence for God from Science?

Evidence for God from the Origin of the Universe:

Origin of the Universe

Doesn’t Quantum Mechanics Violate the Causal Principle?

Much Ado About Nothing

Philosophical Arguments that the Universe had a Beginning

 Before presenting the actual fine-tuning scientific data, I want to explore the philosophical basis of the argument. We can then examine the scientific data relative to some reasonable evaluation criteria.

What is Fine-Tuning?

Fine-tuning is not a synonym for design but is rather a technical term in physics that refers to a narrow range for suitable values among possibilities. All else being equal, if theory A requires fine-tuning and theory B doesn’t, then theory B is deemed to be more likely to be true because it doesn’t rely on assumptions for narrow constraints for the values of one or more parameters. There are other contexts where fine-tuning is discussed with respect to various hypotheses having nothing to do with life, but I defend this fine-tuning claim:

“In the set of possible physical laws, parameters and initial conditions, the subset that permits rational conscious life is very small.”

The universe is said to be finely-tuned for life if most possible ways for setting up physics would have resulted in no intelligent life anywhere in the universe. My claim is close to that defined by Luke Barnes[2] in his important review article. I use the term “rational conscious life” rather than “the evolution of intelligent life” because the fine-tuning claim can be evaluated independently of biological evolution. My wording also reflects Christian expectations that God wanted creatures in His image – rational, conscious creatures with whom He could have a relationship.

It’s important to note that my fine-tuning claim deals with the fundamental physics of the universe required before any biological evolution could get started. I personally happen to be skeptical of the all-encompassing claims about naturalistic macroevolution but even if it explains the full diversity of life that is irrelevant to my fine-tuning claim. For example, a universe without one type of fine-tuning would have lasted only a few hours and never cooled below 9000K. Thus, it is unreasonable to expect such a universe to have contained life – much less intelligent life. Physicists writing fine-tuning articles routinely make claims about life being impossible without certain finely-tuned parameters or initial conditions. Craig Hogan, for example, is very explicit, stating that “changing the quark masses even a small amount has drastic consequences [for] which no amount of Darwinian selection can compensate.” Alan Lightman of MIT clarifies the nature of the fine-tuning: “if these fundamental parameters were much different from what they are, it is not only human beings that would not exist but no life of any kind would exist.” No biological evolution can start until you have the first living cell and the vast majority of ways to setup the physics never allow life to get started.

My future blogs will detail some of the evidence supporting my fine-tuning claim but here is a foretaste from atheist physicist Stephen Hawking’s best-selling book, A Brief History of Time (on p. 125):

“The remarkable fact is that the values of these numbers [i.e. the constants of physics] seem to have been very finely adjusted to make possible the development of life. For example, if the electric charge of the electron had been only slightly different, stars would have been unable to burn hydrogen and helium, or else they would not have exploded. It seems clear that there are relatively few ranges of values for the numbers [i.e. the constants of nature] that would allow for development of any form of intelligent life.”

How widespread is the acceptance of fine-tuning among physicists?

In a word – very! In my years of researching this topic, I’m amazed at how few scientists who have studied the fine-tuning details disagree with this core claim that the subset of life-permitting physics is a tiny fraction among possibilities. Since Luke Barnes is a top researcher on this topic, consider his input on the level of acceptance of the fine-tuning claim: “I’ve published a review of the scientific literature, 200+ papers, and I can only think of a handful that oppose this conclusion, and piles and piles that support it.[3]

Of course, any topic with potentially significant philosophical or even spiritual implications is likely to encounter some opposition. Many physicists who accept the fine-tuning data do not, of course, embrace the design implications. Some readers might be wondering how the skeptics interpret this evidence. The most common response among skeptical physicists is an appeal to the multiverse as alluded to in the introduction.


Image: Courtesy Kevin Hainline

Is the multiverse a satisfying explanation of the fine-tuning?

If we have an enormous number of other universes and if they have widely varying laws, then perhaps sufficient probabilistic resources exist for life to emerge in some universe. We need to carefully evaluate how well the multiverse serves as a potential explanation for fine-tuning. Here are some potential challenges to a multiverse explanation of the fine-tuning:

– No empirical evidence exists for any universe other than our own

– We need vast numbers of other universes to overcome horrendous odds against a life-permitting universe – probably more than 10100 (which is more than the number of subatomic particles in our observable universe)

– A universe generating mechanism might itself require fine-tuning to generate so many universes o This is certainly true for the most popular multiverse theory – eternal inflation.

♦ Sean Carroll admits[4] that “inflation only occurs in a negligibly small fraction of cosmological histories, less than 10-66,000,000.”

o Also, other assumptions are required for eternal inflation – as Vilenkin admits: “The most likely thing to pop out of the [quantum vacuum] is a tiny Planck-sized universe, which would not tunnel, but would instantly recollapse and disappear. Tunneling to a larger size has a small probability and therefore requires a large number of trials. It appears to be consistent only with the Everett interpretation.” This Everett or many-worlds interpretation of quantum physics is one of a dozen or so interpretations and many physicists are skeptical of this interpretation because it entails that parallel universes are spawned at every quantum event.

–  The new universes would need to have different physical constants

o There are many theoretical reasons for thinking constants might vary but we have no clear evidence that fundamental constants have ever been more than trivially different in different parts of our observable universe. Without new physics in each universe, our odds for life wouldn’t be helped – it’d be like buying a million lottery tickets with the same set of numbers for each ticket!

–  The constants would need to vary extremely widely

o The degree of variety in possible values for the constants may not be sufficient unless a particular version of string theory is true. Some string theorists think that perhaps there are as many as 10500 different possible values for the constants. This variance would be more than sufficient. Polchinski, however, is one of many string theorists who disagree with this proposal – “there is no reason to expect … a large number of variations in the constants of physics.[5]”

♦ A significant minority segment of the physics community is highly skeptical of any version of String Theory because it thus far has no clear empirical confirmation and a history of failed predictions.

– It is fallacious to view the fine-tuning itself as evidence for a multiverse since the existence of other universes doesn’t make it any more likely that our universe supports life. We need independent evidence for the multiverse hypothesis before it becomes a viable candidate explanation of the fine-tuning. MIT philosopher of science Roger White shows this using Bayesian logic and summarizes: “the fact that our universe is fine-tuned gives us no further reason to suppose that there are universes other than ours.”

– Is the multiverse theory even scientific?

o Personally I’m not too concerned about this question – we just want to follow the evidence wherever it leads even if that is beyond the realm of direct empirical confirmation. It should be pointed out though that the most popular multiverse theories, such as eternal inflation, postulate other universes that could not have interacted with our universe, even in principle. About the only way to affirm such multiverse theories is to examine how well our universe conforms to multiverse predictions after applying a selection effect due to the constraint that observers can only observe a life-permitting universe. This selection effect is known as the anthropic principle although it really deals with any type of observer whereas ‘anthropic’ is derived from the Greek word ‘anthropos,’ which means human.

o Thus, our universe should be typical among life-permitting universes. If our universe appears “overly” fine-tuned it would still look more like the product of design than a random member of an ensemble of life-permitting universes. For further information about this widely accepted principle among multiverse advocates, see this excellent book of essays by prominent physicists entitled Universe or Multiverse?

♦ Many scientists are highly critical of this approach of trying to indirectly affirm the multiverse. However, some skeptical scientists seem willing to accept this approach because it seems to be the only way to avoid the design implications of the fine-tuning. Polchinski, a leading string theorist, acknowledges that “anthropic reasoning runs so much against the historic goals of theoretical physics that I resisted it long after realizing its likely necessity. But now I have come out.”[6] Susskind claims that “the stakes are to accept the [string] landscape and the dilution in the scientific method it implies or give up science altogether and accept intelligent design (ID) as the explanation for the choices of parameters of the standard model.”[7]

As we’re examining the fine-tuning evidence in future blogs, I’ll point out cases where parameters are significantly more fine-tuned than is necessary since this counts against the multiverse as a solution to the fine-tuning problem. As a preview consider that many physicists such as Lee Smolin have pointed out problems in this arena such as proton decay rates being many orders of magnitude smaller than the life permitting region. Also, Oxford physicist Roger Penrose says that the multiverse is “worse than useless” as explanation of the finely-tuned initial conditions because the multiverse predicts hyper-exponentially more tiny universes than large ones like ours.

Some physicists have rightly pointed out that a multiverse by itself is not necessarily a violation of Occam’s razor since it could arise from a simple law-like mechanism for generating universes. The key issue though is that for the multiverse to be an adequate explanation for the fine-tuning it requires the conjunction of several hypotheses for which we lack any empirical evidence:

  1. A universe-generating mechanism that generates a plethora of universes
  2. That this mechanism doesn’t itself require fine-tuning
  3. The many-worlds interpretation of quantum physics
  4. The ability to widely vary constants in those universes. If you think that it’s a foregone conclusion that String Theory/M-Theory[8] will come to the rescue in this area, you should watch this video clip by Oxford physicist Roger Penrose where he exclaims that “it’s not even a theory … it’s a collection of hopes”.

Occam’s razor therefore does seem to favor design over the multiverse. When one accounts for the extensive problems in affirming premise 2 and how these multiverse theories make predictions incompatible with our universe, the hypothesis that God designed the physics of the universe to bring about life is more plausible. That so many physicists appeal to the multiverse to explain away the design implications of fine-tuning testifies to the power of this argument!


[1] Susskind, The Cosmic Landscape: String Theory and the Illusion of Intelligent Design. The Chattahoochee Review Podcast. (near about the 6th minute)

[2] I highly recommend Barnes’ excellent blogs correcting various people on both sides of the debate when they make mistakes in their analysis of the math, physics, or philosophy. I hope I can get more people to read his blogs. I recommend his blogs more than my own – I’m just trying to be a popularizer of the excellent scholarly work that is out there!

[3] To support the claim that Barnes is a top researcher/thinker on fine-tuning consider that he was invited to speak at last summer’s Philosophy of Cosmology conference. Here is his blog article from which I obtained his quote:

[4] Carroll, Tam. Unitary Evolution and Cosmological Fine-Tuning.

[5] Polchinski, String Theory. (1998, Vol. 2, pp. 372-73).

[6] Lee Smolin. The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next. (New York: Houghton Mifflin Co., 2006), 169.

[7] Ibid., 197.

[8] M-Theory is simply a more generalized version of String Theory

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