Wintery Knight

…integrating Christian faith and knowledge in the public square

What are Boltzmann brains, and what challenge do they post to the multiverse hypothesis?

I thought I would turn to the atheist theoretical physicist Sean Carroll, who has previously debated William Lane Craig, to explain to us what a Boltzmann brain is, and what threat it posts to the multiverse hypothesis.

Here is Sean Caroll, quoted by

Ludwig Boltzmann was one of the founders of the field of thermodynamics in the nineteenth century. One of the key concepts was the second law of thermodynamics, which says that the entropy of a closed system always increases. Since the universe is a closed system, we would expect the entropy to decrease over time. This means that, given enough time, the most likely state of the universe is one where everything is the in thermodynamic equilibrium … but we clearly don’t exist in a universe of this type since, after all, there is order all around us in various forms, not the least of which is the fact that we exist.

With this in mind, we can apply the anthropic principle to inform our reasoning by taking into account that we do, in fact, exist. Here the logic gets a little confusing, so I’m going to borrow the words from a couple of more detailed looks at the situation. As described by cosmologist Sean Carroll in From Eternity to Here:

Boltzmann invoked the anthropic principle (although he didn’t call it that) to explain why we wouldn’t find ourselves in one of the very common equilibrium phases: In equilibrium, life cannot exist. Clearly, what we want to do is find the most common conditions within such a universe that are hospitable to life. Or, if we want to be more careful, perhaps we should look for conditions that are not only hospitable to life, but hospitable to the particular kind of intelligent and self-aware life that we like to think we are….

We can take this logic to its ultimate conclusion. If what we want is a single planet, we certainly don’t need a hundred billion galaxies with a hundred billion stars each. And if what we want is a single person, we certainly don’t need an entire planet. But if in fact what we want is a single intelligence, able to think about the world, we don’t even need an entire person–we just need his or her brain.

So the reductio ad absurdum of this scenario is that the overwhelming majority of intelligences in this multiverse will be lonely, disembodied brains, who fluctuate gradually out of the surrounding chaos and then gradually dissolve back into it. Such sad creatures have been dubbed “Boltzmann brains” by Andreas Albrecht and Lorenzo Sorbo….

In a 2004 paper, Albrecht and Sorbo discussed “Boltzmann brains” in their essay:

A century ago Boltzmann considered a “cosmology” where the observed universe should be regarded as a rare fluctuation out of some equilibrium state. The prediction of this point of view, quite generically, is that we live in a universe which maximizes the total entropy of the system consistent with existing observations. Other universes simply occur as much more rare fluctuations. This means as much as possible of the system should be found in equilibrium as often as possible.

From this point of view, it is very surprising that we find the universe around us in such a low entropy state. In fact, the logical conclusion of this line of reasoning is utterly solipsistic. The most likely fluctuation consistent with everything you know is simply your brain (complete with “memories” of the Hubble Deep fields, WMAP data, etc) fluctuating briefly out of chaos and then immediately equilibrating back into chaos again. This is sometimes called the “Boltzmann’s Brain” paradox.

[...]Now that you understand Boltzmann brains as a concept, though, you have to proceed a bit to understanding the “Boltzmann brain paradox” that is caused by applying this thinking to this absurd degree. Again, as formulated by Carroll:

Why do we find ourselves in a universe evolving gradually from a state of incredibly low entropy, rather than being isolated creatures that recently fluctuated from the surrounding chaos?

Unfortunately, there is no clear explanation to resolve this … thus why it’s still classified as a paradox.

Naturalists like to propose the multiverse as a way of explaining away the fine-tuning that we see, and explaining why complex, embodied intelligent beings like ourselves exist. But even if the multiverse hypothesis were true, we still would not expect to observe stars, planets, and conscious embodied intelligent beings. It is far more likely on a multiverse scenario that any observers we had would be “Boltzmann” brains in an empty universe. The multiverse hypothesis doesn’t explain the universe we have, which contains “a hundred billion galaxies with a hundred billion stars each” – not to mention our bodies which are composed of heavy elements, all of which require fine-tuning piled on fine-tuning piled on fine-tuning.

William Lane Craig answered a question about Boltzmann brains a while back, so let’s look at his answer since we saw what his debate opponent said above.

He writes:

Incredible as it may sound, today the principal–almost the only–alternative to a Cosmic Designer to explain the incomprehensibly precise fine tuning of nature’s constants and fundamental quantities is the postulate of a World Ensemble of (a preferably infinite number of) randomly ordered universes. By thus multiplying one’s probabilistic resources, one ensures that by chance alone somewhere in this infinite ensemble finely tuned universes like ours will appear.

Now comes the key move: since observers can exist only in worlds fine-tuned for their existence, OF COURSE we observe our world to be fine-tuned! The worlds which aren’t finely tuned have no observers in them and so cannot be observed! Hence, our observing the universe to be fine-tuned for our existence is no surprise: if it weren’t, we wouldn’t be here to be surprised. So this explanation of fine tuning relies on (i) the hypothesis of a World Ensemble and (ii) an observer self-selection effect.

Now apart from objections to (i) of a direct sort, this alternative faces a very formidable objection to (ii), namely, if we were just a random member of a World Ensemble, then we ought to be observing a very different universe. Roger Penrose has calculated that the odds of our solar system’s forming instantaneously through the random collision of particles is incomprehensibly more probable that the universe’s being fine-tuned, as it is. So if we were a random member of a World Ensemble, we should be observing a patch of order no larger than our solar system in a sea of chaos. Worlds like that are simply incomprehensibly more plentiful in the World Ensemble than worlds like ours and so ought to be observed by us if we were but a random member of such an ensemble.

Here’s where the Boltzmann Brains come into the picture. In order to be observable the patch of order needn’t be even as large as the solar system. The most probable observable world would be one in which a single brain fluctuates into existence out of the quantum vacuum and observes its otherwise empty world. The idea isn’t that the brain is the whole universe, but just a patch of order in the midst of disorder. Don’t worry that the brain couldn’t persist long: it just has to exist long enough to have an observation, and the improbability of the quantum fluctuations necessary for it to exist that long will be trivial in comparison to the improbability of fine tuning.

In other words, the observer self-selection effect is explanatorily vacuous. It does not suffice to show that only finely tuned worlds are observable. As Robin Collins has noted, what needs to be explained is not just intelligent life, but embodied, interactive, intelligent agents like ourselves. Appeal to an observer self-selection effect accomplishes nothing because there is no reason whatever to think that most observable worlds are worlds in which that kind of observer exists. Indeed, the opposite appears to be true: most observable worlds will be Boltzmann Brain worlds.

Allen Hainline explained some of the OTHER problems with the multiverse in a post on Cross Examined’s blog. I recommend taking a look at those as well, because I feel funny even talking about Boltzmann brains. I would rather just say that there is no experimental evidence for the multiverse hypothesis, as I blogged before, and leave it at that. But if the person you are talking to fights you on it, you can disprove the multiverse with the Boltzmann brains.

Filed under: Polemics, , , , , , ,

Robin Collins lectures on the fine-tuning argument at Pepperdine University


Dr. Robin Collins is a Professor of Philosophy and Chair of the Department of Philosophy at Messiah College. Collins is the foremost defender of what is known as the teleological argument for the existence of God. He has a background in both physics and philosophy and will be discussing how the specific physical constants and conditions in the universe are finely-tuned for intelligent life and how this “fine-tuning” gives us reason to believe in a Creator.

Here is the video:


  • the constants and quantities set at the origin of the universe is fine-tuned for conscious, embodied intelligences like us
  • three kinds of fine-tuning: 1) laws of nature, 2) constants, 3) quantities
  • examples of 1): gravity, electromagnetism, strong force, quantization, Pauli exclusion principle
  • examples of 2): gravitational constant, cosmological constant,
  • examples of 3):  initial distribution of mass-energy
  • in addition to fine-tuning for life, there is also fine-tuning for discoverability
  • Naturalistic response to the evidence: the multiverse hypothesis
  • problems with the multiverse hypothesis
  • additional topics

I put the ones I am ready to speak on in bold. I recommend you learn those as well in order to illustrate the fine-tuning with evidence when you present it. The evidence is important because I’ve never found a single atheist who I discussed this with who could properly state the argument or understand the evidence. They talk about it without really understanding it, which is why we need to be ready to explain it to them.

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Dr. Walter Bradley explains the requirements for life of any imaginable kind

I was talking to a friend of mine earlier this week about my experiences as an undergraduate in college, and it turns out that both of us relied on the same web site to get us through our late teens and early 20s. The web site is Leadership University, and it features articles on many different topics from Christian professors.

Here’s an article by famous mechanical engineering professor Walter Bradley to explain what it takes for a universe that supports complex, embodied life.


We teach mechanical engineering students to begin the design process by specifying as clearly as possible the “needs statement” for their project. Then, the assignment for the semester is to develop a design solution that accomplishes the “need(s)” specified for the project. In similar fashion, the minimal needs to be satisfied for a universe to be capable of supporting life of any imaginable type, not just life as we know it, must be identified. Like our automobile illustration, many of the specifications will necessarily be interrelated to make a functional universe. From this essential “needs statement” we can then see how these needs (or design requirements) are met in our universe. We are essentially doing reverse engineering, constructing the blueprint backwards from the product (like an illicit manufacturing company copying a competitor’s product). Only then will we be ready to entertain Dawkins’ question, “Are there many ways in which these requirements could be satisfied within nature?” Or are the conditions so unique and interrelated that their collective satisfaction by accident would be a “miracle” in its own right? Let us then begin by drafting a “needs statement” for a habitable universe. Then we shall see how these requirements are satisfied in our universe.

Needs Statement for a Suitable Universe

An abbreviated list of requirements for a universe suitable to support life of any imaginable type must include the following items:

  • Order to provide the stable environment that is conducive to the development of life, but with just enough chaotic behavior to provide a driving force for change.
  • Sufficient chemical stability and elemental diversity to build the complex molecules necessary for essential life functions: processing energy, storing information, and replicating. A universe of just hydrogen and helium will not “work.”
  • Predictability in chemical reactions, allowing compounds to form from the various elements.
  • A “universal connector,” an element that is essential for the molecules of life. It must have the chemical property that permits it to react readily with almost all other elements, forming bonds that are stable, but not too stable, so disassembly is also possible. Carbon is the only element in our periodic chart that satisfies this requirement.
  • A “universal solvent” in which the chemistry of life can unfold. Since chemical reactions are too slow in the solid state, and complex life would not likely be sustained as a gas, there is a need for a liquid element or compound that readily dissolves both the reactants and the reaction products essential to living systems: namely, a liquid with the properties of water.
  • A stable source of energy to sustain living systems in which there must be photons from the sun with sufficient energy to drive organic, chemical reactions, but not so energetic as to destroy organic molecules (as in the case of highly energetic ultraviolet radiation).
  • A means of transporting the energy from the source (like our sun) to the place where chemical reactions occur in the solvent (like water on Earth) must be available. In the process, there must be minimal losses in transmission if the energy is to be utilized efficiently.

Unless ALL of these conditions and many more not included in this list are met, we would have a universe that would preclude the possibility of conscious, complex life forms. However, it is possible to meet all of these conditions for the universe and still not necessarily find a suitable habitat in the universe for complex, conscious life. Therefore, we might say that the above requirements for our universe are necessary, but not by themselves sufficient, conditions for a habitat suitable for complex human life. Next we try to identify the additional conditions within such a suitable universe that would provide a place of habitation for conscious, complex life.

Needs Statement for a Habitat Place in the Suitable Universe for Complex, Conscious Life

An abbreviated, but illustrative, list of additional requirements must be specified for a place of habitation in this universe. First, we need a star that is located in a relatively “quiet” region of the universe (e.g., not too many neighbors that are producing high intensity, sterilizing radiation). This star needs to have its highest intensity of radiation in the range that is suitable to drive the chemical reactions essential to life without destroying the products of these reactions. Furthermore, this star needs to have a very special satellite within its solar system. A partial list of the requirements this satellite must meet include:

  • a planet or moon that is terrestrial–or, solid rather than gaseous;
  • a temperature range suitable to maintain the universal solvent as a liquid rather than a solid or gas;
  • just the right concentration of heavy (radioactive) elements to heat the core of the planet and provide the necessary energy to drive plate tectonics, to build up land mass in what would otherwise be a smooth, round planet completely covered with solvent;
  • just the right amount of solvent (carefully coupled to the plate tectonics activity) to provide a planet with similar proportions of its surfaces as oceans and land mass;
  • just the right protection from the destructive forces in nature such as radiation and asteroids over a reasonable amount of time; and
  • just the right stabilized axis tilt and angular velocity to give moderate, regular, and predictable seasons and moderate temperature fluctuations from day to night.

While one is temped to think that these requirements are easily met, given the large number of stars, it should be noted that there are few places in the universe sufficiently free of sterilizing radiation to provide a suitable solar system. The number of candidate “neighborhoods” is further reduced by the requirements of a sun with the right amount of mass to give the right electromagnetic radiation spectrum. Furthermore, the occurrence of a suitable satellite in conjunction with such a star is even more problematic. Only the earth in our solar system of sixty-two satellites meets the above requirements for a “home” (earth) in safe “neighborhood” like our sun and solar system, which are well placed in a quiet place in a suitable universe as described above.

In the next sections, we will see how these universal and local “needs” (or design requirements) are met by: the specific mathematical form encoded in nature, the exact values of the universal constants in our universe, and the remarkable “coincidence” that initial (or boundary) conditions are exactly what they must be. We will also see that the “evolutional” or developmental path that our universe navigated is consistently remarkable, making the origin of our “Garden of Eden” all the more wondrous and enigmatic.

If you want to see the next sections of his article, you can click here to read the rest.

Why is this important? It’s important because a lot of people on the other side want to dismiss the fine-tuning argument by saying that if the fundamental constants and quantities specified in the Big Bang had been different, then the results would be a universe that permits life of some other kind. That’s false. If you vary the constants and quantities, you lose things that are required for any conceivable kind of complex life. You can’t form stable, metal-rich stars. The universe recollapses into a hot fireball. You have only hydrogen. You have NO hydrogen. It’s not just that people have some ridges on their noses or maybe an extra pair of arms. It’s that there is no life, period.

This is important. There are minimum requirements for life of any conceivable kind, and messing with the fine-tuning of the universe destroys the ability of the universe to provide those minimal requirements. Naturalists can smirk and shrug this off, but this is the science that we have today and we have to deal with it.

Filed under: Polemics, , , , , , , , , , ,

Do most cosmologists accept the reality of the cosmic fine-tuning?

I don’t know how I missed this, but apparently Dr. Richard Carrier, a historian, wrote a critique of the fine-tuning argument a while back, and Dr. Luke Barnes, a cosmologist responded to him.

Much of what is said by both of them in their contributions is beyond me, but I did want to quote one part from a blog post by Luke Barnes about whether most scientists accept that our universe is finely-tuned for complex embodied life.

First, Dr. Carrier writes this:

[Dr. William Lane Craig] claims “the fundamental constants and quantities of nature must fall into an incomprehensibly narrow life-permitting range,” but that claim has been refuted–by scientists–again and again. We actually do not know that there is only a narrow life-permitting range of possible configurations of the universe. As has been pointed out to Craig by several theoretical physicists (from Krauss to Stenger), he can only get his “narrow range” by varying one single constant and holding all the others fixed, which is simply not how a universe would be randomly selected. When you allow all the constants to vary freely, the number of configurations that are life permitting actually ends up respectably high (between 1 in 8 and 1 in 4: see Victor Stenger’s The Fallacy of Fine-Tuning).

And Dr. Barnes replies (in part): (links removed)

I’ve said an awful lot in response to that paragraph, so let’s just run through the highlights.

  • “Refuted by scientists again and again”. What, in the peer-reviewed scientific literature? 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. Here are some quotes from non-theist scientists. For example, Andrei Linde says: “The existence of an amazingly strong correlation between our own properties and the values of many parameters of our world, such as the masses and charges of electron and proton, the value of the gravitational constant, the amplitude of spontaneous symmetry breaking in the electroweak theory, the value of the vacuum energy, and the dimensionality of our world, is an experimental fact requiring an explanation.” [emphasis added.]

  • “By several theoretical physicists (from Krauss to Stenger)”. I’ve replied to Stenger. I had a chance to talk to Krauss briefly about fine-tuning but I’m still not sure what he thinks. His published work on anthropic matters doesn’t address the more general fine-tuning claim. Also, by saying “from” and “to”, Carrier is trying to give the impression that a great multitude stands with his claim. I’m not even sure if Krauss is with him. I’ve read loads on this subject and only Stenger defends Carrier’s point, and in a popular (ish) level book. On the other hand, Craig can cite Barrow, Carr, Carter, Davies, Deutsch, Ellis, Greene, Guth, Harrison, Hawking, Linde, Page, Penrose, Polkinghorne, Rees, Sandage, Smolin, Susskind, Tegmark, Tipler, Vilenkin, Weinberg, Wheeler, and Wilczek. (See here). With regards to the claim that “the fundamental constants and quantities of nature must fall into an incomprehensibly narrow life-permitting range”, the weight of the peer-reviewed scientific literature is overwhelmingly with Craig. (If you disagree, start citing papers).

There’s more, too.

I wish I understood cosmology enough to understand everything Dr. Barnes says, but it seems to me that this much is clear. If you’re an atheist and you’re reading stuff by these very far-out atheists, then you need to be very careful. Dr. Stenger and Dr. Carrier are both highly-intelligent and have great credentials, but it’s probably better for all of us to be interacting with the other side when we form our worldviews.

I noticed that respected atheist Jeff Lowder has a post up where he looks at both sides and comes down more with Barnes than with Carrier.

Filed under: Polemics, , , , , , , ,

MIT physicist explains the challenge of cosmic fine-tuning for naturalism

Here’s the article from Harper’s magazine.

The MIT physicist says that the fine-tuning is real, and is best explained by positing the existence of an infinite number of universes that are not fine-tuned – the so-called multiverse.


While challenging the Platonic dream of theoretical physicists, the multiverse idea does explain one aspect of our universe that has unsettled some scientists for years: according to various calculations, if the values of some of the fundamental parameters of our universe were a little larger or a little smaller, life could not have arisen. For example, if the nuclear force were a few percentage points stronger than it actually is, then all the hydrogen atoms in the infant universe would have fused with other hydrogen atoms to make helium, and there would be no hydrogen left. No hydrogen means no water. Although we are far from certain about what conditions are necessary for life, most biologists believe that water is necessary. On the other hand, if the nuclear force were substantially weaker than what it actually is, then the complex atoms needed for biology could not hold together. As another example, if the relationship between the strengths of the gravitational force and the electromagnetic force were not close to what it is, then the cosmos would not harbor any stars that explode and spew out life-supporting chemical elements into space or any other stars that form planets. Both kinds of stars are required for the emergence of life. The strengths of the basic forces and certain other fundamental parameters in our universe appear to be “fine-tuned” to allow the existence of life. The recognition of this fine-­tuning led British physicist Brandon Carter to articulate what he called the anthropic principle, which states that the universe must have the parameters it does because we are here to observe it. Actually, the word anthropic, from the Greek for “man,” is a misnomer: if these fundamental parameters were much different from what they are, it is not only human beings who would not exist. No life of any kind would exist.

If such conclusions are correct, the great question, of course, is why these fundamental parameters happen to lie within the range needed for life. Does the universe care about life? Intelligent design is one answer. Indeed, a fair number of theologians, philosophers, and even some scientists have used fine-tuning and the anthropic principle as evidence of the existence of God. For example, at the 2011 Christian Scholars’ Conference at Pepperdine University, Francis Collins, a leading geneticist and director of the National Institutes of Health, said, “To get our universe, with all of its potential for complexities or any kind of potential for any kind of life-form, everything has to be precisely defined on this knife edge of improbability…. [Y]ou have to see the hands of a creator who set the parameters to be just so because the creator was interested in something a little more complicated than random particles.”

Intelligent design, however, is an answer to fine-tuning that does not appeal to most scientists. The multiverse offers another explanation. If there are countless different universes with different properties—for example, some with nuclear forces much stronger than in our universe and some with nuclear forces much weaker—then some of those universes will allow the emergence of life and some will not. Some of those universes will be dead, lifeless hulks of matter and energy, and others will permit the emergence of cells, plants and animals, minds. From the huge range of possible universes predicted by the theories, the fraction of universes with life is undoubtedly small. But that doesn’t matter. We live in one of the universes that permits life because otherwise we wouldn’t be here to ask the question.

I thought I was going to have to go outside this article to refute the multiverse, but Lightman is honest enough to refute it himself:

The… conjecture that there are many other worlds… [T]here is no way they can prove this conjecture. That same uncertainty disturbs many physicists who are adjusting to the idea of the multiverse. Not only must we accept that basic properties of our universe are accidental and uncalculable. In addition, we must believe in the existence of many other universes. But we have no conceivable way of observing these other universes and cannot prove their existence. Thus, to explain what we see in the world and in our mental deductions, we must believe in what we cannot prove.

Sound familiar? Theologians are accustomed to taking some beliefs on faith. Scientists are not. All we can do is hope that the same theories that predict the multiverse also produce many other predictions that we can test here in our own universe. But the other universes themselves will almost certainly remain a conjecture.

The multiverse is not pure nonsense, it is theoretically possible. The problem is that the multiverse generator itself would require fine-tuning, so the multiverse doesn’t get rid of the problem. And, as Lightman indicates, we have no independent experimental evidence for the existence of the multiverse in any case. Atheists just have to take it on faith, and hope that their speculations will be proved right. Meanwhile, the fine-tuning is just as easily explained by postulating God, and we have independent evidence for God’s existence, like the the origin of biological information, the sudden appearance of animal body plans, the argument from consciousness, and so on. Even if the naturalists could explain the fine-tuning, they would still have a lot of explaining to do. Theism (intelligent causation) is the simplest explanation for all of the things we learn from the progress of science.

We need to be frank about atheists and their objections to the progress of science. Within the last 100 years, we have discovered that the physical universe came into being out of nothing 15 billion years ago, and we have discovered that this one universe is fine-tuned for intelligent life. I don’t think it’s like that the last 100 years of scientific progress on the origins question are going to be overturned so that science once again affirms what atheists believe about the universe. Things are going the wrong way for atheists – at least with respect to science.

See it in action

To see these arguments examined in a debate with a famous atheist, simply watch the debate between William Lane Craig and Christopher Hitchens, and judge which debater is willing to form his beliefs on scientific progress, and which debater is forming his beliefs against the science we have today, and hoping that the good science we have today based on experiments will be overturned by speculative theories at some point in the future. When you watch that debate, it becomes very clear that Christian theists are interested in conforming their beliefs to science, and atheists are very interested in speculating against what science has shown in order to maintain their current pre-scientific view. That’s not what rational people ought to do when confronted with evidence.

Positive arguments for Christian theism

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