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, , , , , , ,

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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Pew survey: evangelical Christians least likely to believe superstitious nonsense

The Pew Research survey is here.

They are trying to see which groups believe in superstitions and new age mysticism.

Here are the parts that I found interesting:

Click for full image.

Click for full image.

Notice the numbers for Republicans vs Democrats, conservatives vs. liberals, and church-attending vs non church-attending. The least superstitious people are conservative evangelical Republicans, while the most superstitious people are Democrat liberals who don’t attend church. I think there is something to be learned from that. It’s consistent with the results of a Gallup survey that showed that evangelical Christians are the most rational people on the planet.

Here’s the Wall Street Journal article about the Gallup survey entitled “Look Who’s Irrational Now“.


The reality is that the New Atheist campaign, by discouraging religion, won’t create a new group of intelligent, skeptical, enlightened beings. Far from it: It might actually encourage new levels of mass superstition. And that’s not a conclusion to take on faith — it’s what the empirical data tell us.

“What Americans Really Believe,” a comprehensive new study released by Baylor University yesterday, shows that traditional Christian religion greatly decreases belief in everything from the efficacy of palm readers to the usefulness of astrology. It also shows that the irreligious and the members of more liberal Protestant denominations, far from being resistant to superstition, tend to be much more likely to believe in the paranormal and in pseudoscience than evangelical Christians.

The Gallup Organization, under contract to Baylor’s Institute for Studies of Religion, asked American adults a series of questions to gauge credulity.

[...]The answers were added up to create an index of belief in occult and the paranormal. While 31% of people who never worship expressed strong belief in these things, only 8% of people who attend a house of worship more than once a week did.

Even among Christians, there were disparities. While 36% of those belonging to the United Church of Christ, Sen. Barack Obama’s former denomination, expressed strong beliefs in the paranormal, only 14% of those belonging to the Assemblies of God, Sarah Palin’s former denomination, did. In fact, the more traditional and evangelical the respondent, the less likely he was to believe in, for instance, the possibility of communicating with people who are dead.

When I think of the “weird” things that evangelical Christians believe, I think of the origin of the universe, the cosmic fine-tuning, the origin of life and the sudden origin of animal body plans in the Cambrian. All of this is superstition to an atheist, and yet all of it is rooted in mainstream science. Not just that, but they’ve grown stronger as science has progressed. I can accept the fact that an atheist may be ignorant of the science that defeats his atheism, but that’s something that has to be remedied with more studying of the evidence, not less. If you generate a worldview by 1) your desire to dispense with moral judgment and/or 2) your desire to prefer Star Trek and Star Wars to mainstream science, then of course you are going to have an irrational worldview. I’m not saying that all atheists do this, surely someone like Peter Millican does not. But for rank-and-file Dawkins acolytes, I think this is pretty accurate, and it’s why we get the survey results that we do.

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Physicist George Ellis interviewed by science writer John Horgan in Scientific American

I’m mentioned George Ellis on this blog before, specifically on his doubts about the speculative multiverse cosmology.

Here he is interviewed in Scientific American. (H/T Think Apologetics)


Biologist Rupert Sheldrake, whom I interviewed in my last post, wasn’t the only fascinating scientist I hung out with recently at Howthelightgetsin, a festival hosted by the Institute of Arts & Ideas. I also befriended George F. R. Ellis, the physicist-mathematician-cosmologist, an authority on the Big Bang and other cosmic mysteries. Ellis and I hit it off initially because we share some—how shall I put it?—concerns about the direction of physics, but I soon discovered that his interests range far beyond physics. He has published papers and books not only on physics and cosmology (including the 1973 classic The Large-Scale Structure of Space-Time, co-authored with Stephen Hawking) but also on philosophy, complexity theory, neuroscience, education and even low-income housing. (See his website, and his terrific 2011 critique of multiverse theories in Scientific American.) A native of South Africa, Ellis is professor emeritus at the University of Cape Town, where he taught for decades, and has also held positions at Cambridge, the University of Texas, the Fermi Institute and other institutions around the globe.


Horgan: Lawrence Krauss, in A Universe from Nothing, claims that physics has basically solved the mystery of why there is something rather than nothing. Do you agree?

Ellis: Certainly not.  He is presenting untested speculative theories of how things came into existence out of a pre-existing complex of entities, including variational principles, quantum field theory, specific symmetry groups, a bubbling vacuum, all the components of the standard model of particle physics, and so on. He does not explain in what way these entities could have pre-existed the coming into being of the universe, why they should have existed at all, or why they should have had the form they did.  And he gives no experimental or observational process whereby we could test these vivid speculations of the supposed universe-generation mechanism. How indeed can you test what existed before the universe existed? You can’t.

Thus what he is presenting is not tested science. It’s a philosophical speculation, which he apparently believes is so compelling he does not have to give any specification of evidence that would confirm it is true. Well, you can’t get any evidence about what existed before space and time came into being.  Above all he believes that these mathematically based speculations solve thousand year old philosophical conundrums, without seriously engaging those philosophical issues. The belief that all of reality can be fully comprehended in terms of physics and the equations of physics is a fantasy. As pointed out so well by Eddington in his Gifford lectures, they are partial and incomplete representations of physical, biological, psychological, and social reality.

And above all Krauss does not address why the laws of physics exist, why they have the form they have, or in what kind of manifestation they existed before the universe existed  (which he must believe if he believes they brought the universe into existence). Who or what dreamt up symmetry principles, Lagrangians, specific symmetry groups, gauge theories, and so on? He does not begin to answer these questions.

It’s very ironic when he says philosophy is bunk and then himself engages in this kind of attempt at philosophy. It seems that science education should include some basic modules on Plato, Aristotle, Kant, Hume, and the other great philosophers, as well as writings of more recent philosophers such as Tim Maudlin and David Albert.

He likes fine-tuning, but not multiverse and string theory:

Horgan: Are you a fan of multiverse theories? String theory? The anthropic principle?

No (may be true but unproveable, much too much untestable speculation about existence of infinities of entities, ill defined and untestable probability measures), no (too much speculative introduction of very complex unseeable entities, treats gravity just like any other force), yes (however one responds to it, it’s a real question that deserves consideration).  Fine tuning of fundamental physics parameters is required in order that we can exist. Examining this issue has led to many very interesting studies.

Horgan: Physicist Sean Carroll has argued that falsifiability is overrated as a criterion for judging whether theories should be taken seriously. Do you agree?

Ellis: This is a major step backwards to before the evidence-based scientific revolution initiated by Galileo and Newton.  The basic idea is that our speculative theories, extrapolating into the unknown and into untestable areas from well-tested areas of physics, are so good they have to be true. History proves that is the path to delusion: just because you have a good theory does not prove it is true. The other defence is that there is no other game in town. But there may not be any such game.

Scientists should strongly resist such an attack on the very foundations of its own success. Luckily it is a very small subset of scientists who are making this proposal.

Free will is real:

Horgan: In some of your writings, you warn against excessive determinism in physics, and science. Could you summarize your concerns?

Many scientists are strong reductionists who believe that physics alone determines outcomes in the real world, This is demonstrably untrue – for example the computer on which I am writing this could not possibly have come into being through the agency of physics alone.

The issue is that these scientists are focusing on some strands in the web of causation that actually exist, and ignoring others that are demonstrably there – such as ideas in our minds, or algorithms embodied in computer programs. These demonstrably act in a top-down way to cause physical effects in the real world. All these processes and actual outcomes are contextually dependent, and this allows the effectiveness of processes such as adaptive selection that are the key to the emergence of genuine complexity.

As I stated above, mathematical equations only represent part of reality, and should not be confused with reality.  A specific related issue: there is a group of people out there writing papers based on the idea that physics is a computational process.  But a physical law is not an algorithm. So who chooses the computational strategy and the algorithms that realise a specific physical law? (Finite elements perhaps?) What language is it written in? (Does Nature use Java or C++? What machine code is used?) Where is the CPU? What is used for memory, and in what way are read and write commands executed? Additionally if it’s a computation, how does Nature avoid the halting problem? It’s all a very bad analogy that does not work.

Horgan: Einstein, in the following quote, seemed to doubt free will: “If the moon, in the act of completing its eternal way around the Earth, were gifted with self-consciousness, it would feel thoroughly convinced that it was traveling its way of its own accord…. So would a Being, endowed with higher insight and more perfect intelligence, watching man and his doings, smile about man’s illusion that he was acting according to his own free will.” Do you believe in free will?

Ellis: Yes. Einstein is perpetuating the belief that all causation is bottom up. This simply is not the case, as I can demonstrate with many examples from sociology, neuroscience, physiology, epigenetics, engineering, and physics.  Furthermore if Einstein did not have free will in some meaningful sense, then he could not have been responsible for the theory of relativity – it would have been a product of lower level processes but not of an intelligent mind choosing between possible options.

I find it very hard to believe this to be the case – indeed it does not seem to make any sense. Physicists should pay attention to Aristotle’s four forms of causation – if they have the free will to decide what they are doing. If they don’t, then why waste time talking to them? They are then not responsible for what they say.

Sometimes, you have to just point out that a speculation is a speculation, and that we do not prefer speculations over experimental results. The data we have is consistent with an origin of the universe out of nothing, and the best explanation of this effect is a supernatural cause. Period.

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William Lane Craig and atheist Daniel Dennett discuss cosmology and fine-tuning

This audio records a part of the Greer-Heard debate in 2007, between prominent atheist Daniel Dennett and lame theistic evolutionist Alister McGrath. Craig was one of the respondents, and this was the best part of the event. It is a little bit advanced, but I have found that if you listen to things like this over and over with your friends and family, and then try to explain it to non-Christians, you’ll get it.

By the way, this is mostly original material from Craig, dated 2007, and he delivers the speech perfectly, so it’s entertaining to listen to.

Craig presents three arguments for a Creator and Designer of the universe:

  • the contingency argument
  • the kalam cosmological argument
  • the teleological argument

He also discusses Dennett’s published responses to these arguments.

Dennett’s response to Craig’s paper

Here is my snarky paraphrase of Dennett’s reponse: (this is very snarky, because Dennett was just awful)

  • Craig’s three arguments are bulletproof, the premises are plausible, and grounded by the best cutting edge science we know today.
  • I cannot find anything wrong with his arguments right now, but maybe later when I go home it will come to me what’s wrong with them.
  • But atheism is true even if all the evidence is against it today. I know it’s true by my blind faith.
  • The world is so mysterious, and all the science of today will be overturned tomorrow so that atheism will be rational again. I have blind faith that this new evidence will be discovered any minute.
  • Just because the cause of the beginning of time is eternal and the cause of the beginning of space is non-physical, the cause doesn’t have to be God.
  • “Maybe the cause of the universe is the idea of an apple, or the square root of 7″. (HE LITERALLY SAID THAT!)
  • The principle of triangulation might have brought the entire physical universe into being out of nothing.
  • I don’t understand anything about non-physical causation, even though I cannot even speak meaningful sentences unless I have a non-physical mind that is causing my body to emit the meaningful sentences in a non-determined manner.
  • Alexander Vilenkin is much smarter than Craig and if he were here he would beat him up good with phantom arguments.
  • Alan Guth is much smarter than Craig and if he were here he would beat him up good with phantom arguments.
  • This science stuff is so complicated to me – so Craig can’t be right about it even though he’s published about it and debated it all with the best atheists on the planet.
  • If God is outside of time, then this is just deism, not theism. (This part is correct, but Craig believes that God enters into time at the moment of creation – so that it is not a deistic God)
  • If deism is true, then I can still be an atheist, because a Creator and Designer of the universe is compatible with atheism.
  • I’m pretty sure that Craig doesn’t have any good arguments that can argue for Christianity – certainly not an historical argument for the resurrection of Jesus based on minimal facts, that he’s defended against the most prominent historians on the planet in public debates and in prestigous books and research journals.

This is a very careful treatment of the arguments that Dr. Craig goes over briefly during his debates. Recommended.

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