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The New Philosophy of Cosmology

March 19, 2012     Time: 00:26:55
The New Philosophy of Cosmology

Summary

Dr. Craig interacts with an article on Tim Maudlin of NYU on the developments in the philosophy of cosmology. What are the top questions this field must address?

Transcript The New Philosophy of Cosmology

 

Kevin Harris: Welcome to the podcast. It's Kevin Harris with Dr. William Lane Craig at Reasonable Faith. Bill, it's so funny that so many things that we talk about here on the podcast are also in the news. I wonder if we're having some impact on the media? [laughter] We're looking at this The Atlantic article “What Happened Before the Big Bang? The New Philosophy of Cosmology.” [1] Ross Anderson wrote this piece and he did it by interviewing Tim Maudlin, who was recently hired by New York University, the top ranked philosophy department in the English speaking world. Maudlin is a philosopher of physics whose interests range from the foundations of physics to topics more firmly within the domain of philosophy, like metaphysics and logic. Tim Maudlin—you're familiar with him.

Dr. Craig: Yes, brilliant, brilliant philosopher of science. His work has been very helpful to me in my own study of special and general relativity theory and trying to integrate that with an understanding of divine eternity. Maudlin was at Rutgers University for many years and is the author of really outstanding work in philosophy of time.

Kevin Harris: To be hired by New York University and their philosophy department is a real achievement. Now, he really gets some attention here by saying Stephen Hawking is brilliant but he's wrong about philosophy. Again, this is because, as you and I have discussed, Stephen Hawking has basically said philosophy is dead. What's Tim Maudlin's answer to that?

Dr. Craig: Well, Maudlin is not very impressed with Hawking's declaration of the death of philosophy. He says,

Hawking is a brilliant man, but he's not an expert in what's going on in philosophy, evidently. Over the past thirty years the philosophy of physics has become seamlessly integrated with the foundations of physics work done by actual physicists, so the situation is actually the exact opposite of what he describes. I think he just doesn't know what he's talking about. . . . I think he's just . . . uninformed.

He says Hawking is a brilliant man but he's not an expert in what's going on in philosophy. So what Maudlin is saying there is that over the last thirty years there is a discipline that's called the philosophy of physics and it tends to coincide with a discipline called foundations of physics which is pursued by the physicists themselves, and these two fields have become seamlessly integrated so that those who are working on the deep questions in the foundation of physics, the underpinnings of this field, are both philosophers and physicists who are collaboratively pursuing these important philosophical questions that lie at the very root of physics. And in particular this article focuses on the field of physics called cosmology, which is the study of the large scale structure of the universe. And Maudlin identifies a philosophy of cosmology as an area of specialization.

Kevin Harris: How about that. Lawrence Krauss is not going to like that very much. [laughter] As you noted in an earlier podcast he thinks that that's ridiculous and a waste of time.

Dr. Craig: Yes, exactly, and what Maudlin shows, I think, through these examples is that those who deprecate philosophical work in these fields simply don't know what they're talking about it.

Kevin Harris: He was asked in this interview what were the outstanding conceptual problems at the foundation of cosmology? And the central goal of the philosophy of cosmology is to identify those. Maudlin says,

I guess I would divide that into two classes. There are foundational problems and interpretational problems in physics, generally --say, in quantum theory, or in space-time theory, or in trying to come up with a quantum theory of gravity-- that people will worry about even if they're not doing what you would call the philosophy of cosmology.

Dr. Craig: Right, so you have these general philosophical questions that he says can be of two types. One would be the foundational problems: what is time, for example? What is space? And then in addition to that there are interpretational questions. When a theory like quantum mechanics gives descriptions by equations and makes predictions what is the correct physical interpretation of those equations? The mathematics works but how do you understand it physically? And in the case of quantum mechanics, that subatomic physics, there are around ten different competing physical interpretations of quantum theory, and no one knows which one is correct. So there are both these foundational questions and then there are these interpretational questions that are explored in philosophy of physics as well as in more specific questions to the philosophy of cosmology. [2]

Kevin Harris: Yes, jumping ahead in the article, he says exactly that. He says,

The problem is that quantum mechanics was developed as a mathematical tool. Physicists understood how to use it as a tool for making predictions, but without an agreement or understanding about what it was telling us about the physical world. And that's very clear when you look at any of the foundational discussions.

Well, in particular to quantum mechanics, the reason that that's important is because people are always saying, well, quantum mechanics answers that.

Dr. Craig: Quantum theory or quantum mechanics becomes a sort of black box that uninformed people can appeal to to explain away almost anything. And I love what Maudlin says here in this interview. He says,

Quantum mechanics was merely a calculational technique that was not well understood as a physical theory. Bohr and Heisenberg tried to argue that asking for a clear physical theory was something you shouldn't do anymore.

That's so typical, you see, of the positivist era in which they were raised. For the positivists all that mattered were the empirical predictions and the results. And physical interpretations that were empirically equivalent, they were regarded as the same theory even though they postulated vastly different physical interpretations of what was going on. And so Maudlin says,

And they were wrong, Bohr and Heisenberg were wrong about that. But the effect of it was to shut down perfectly legitimate physics questions within the physics community for about half a century. And now we're coming out of that, fortunately.

So this pall that positivism cast over physics suppressed certain questions about the correct physical interpretation of the theories or the equations that we're using. And now in a post-positivist era we're fortunately coming out of that and beginning to explore these metaphysical questions again about what exactly do these theories really postulate in terms of the structures of space and time and the subatomic word that they're about.

Kevin Harris: Bill, what is this that I'm seeing, that I observe, that mathematical tools like this take on a life of their own and become something that they're not when it comes to quantum mechanics or the idea that a particle will take all possible routes and all that. And some have said, see there, that's counter-intuitive and that's impossible, how could it take all the possible routes at the same time? But that's just like real numbers and things like that. These are mathematical tools.

Dr. Craig: Exactly.

Kevin Harris: And they get out of their boundaries somehow.

Dr. Craig: That's right. They take mathematical calculational devices, or as they’re sometimes called “tricks” (not in the pejorative sense but in the sense that this is a way of solving the equations, solving the problems, getting rid of messy infinities, for example), and they take those and interpret them as if they were literal physical descriptions of reality, and in many cases the interpretation is absurd. It's nonsensical to talk about the particle taking all possible paths from A to B, and yet this is appealed to by people to answer deep metaphysical questions about creation and God and the origin of the universe, as though these physical interpretations are just to be read off the sleeves, so to speak, of these theories, which is simply not true.

Kevin Harris: Everybody hold your breath because Maudlin here says this is the number one question that we want to answer in this field:

This question of accounting for what we call the "big bang state" -- the search for a physical explanation of it -- is probably the most important question within the philosophy of cosmology, and there are a couple different lines of thought about it. One that's becoming more and more prevalent in the physics community is the idea that the big bang state itself arose out of some previous condition, and that therefore there might be an explanation of it in terms of the previously existing dynamics by which it came about. There are other ideas, for instance that maybe there might be special sorts of laws, or special sorts of explanatory principles, that would apply uniquely to the initial state of the universe.

Dr. Craig: Right, those two alternatives would be on the one hand multiverse theories where our universe is simply a bubble in a sea of false vacuum that is expanding and there are other bubbles, other universes like ours. That would explain the initial Big Bang state on the basis of broader conditions. [3] Or someone like Roger Penrose prefers the second alternative, that there's special sorts of laws that would require that an initial singularity out of which our universe was spawned would be characterized by very low entropy, as the Big Bang state is, and that's the mystery, is why this highly ordered improbable low entropy state should mark the beginning of the universe. And, of course, another special sort of explanatory principle would be to say that God created the universe with a highly ordered low entropy state. This has the advantage of being in accord with the scientific evidence that the universe has not always existed, that the universe did in fact have an absolute beginning.

Kevin Harris: He talks about bubble universes and then goes on. This is the second time recently that this has come up – it came up with Krauss in our podcast – the anthropic principle. And he's not saying that he necessarily holds to this.

Dr. Craig: No.

Kevin Harris: But he says there's a line of thought that says, “Well now, if that's the case, we as living beings will certainly find ourselves in one of those bubbles that happens to support living beings.”

Dr. Craig: Right. The idea is that if you have many of these bubbles of true vacuum in this sea of expanding false vacuum, and if these are randomly ordered in their constants and quantities, their initial conditions, then by chance alone in some of these bubbles intelligent life like ourselves would emerge and that therefore we shouldn’t really be surprised at the incredible fine-tuning of the universe for our existence. In a multiverse of randomly ordered universes somewhere in the multiverse such finely-tuned universes will appear by chance alone. That's the hypothesis.

Kevin Harris: He also says that,

This is a branch of the philosophy of physics, in which you happen to be treating the entire universe --which is one huge physical object-- as a subject of study, rather than say studying just electrons by themselves, or studying only the solar system. There are particular physical problems, problems of explanation, which arise in thinking about the entire universe, which don't arise when you consider only its smaller systems.

He says he would like to go on and try “to articulate what those particular problems are, and the avenues for solving them.” Well, I observe that, too, Bill. Studying the universe as a whole is different from studying the parts of it. And people will point out that what applies to the parts doesn't necessarily apply to the whole.

Dr. Craig: Sure.

Kevin Harris: It seems to me they're trying to get past the contingency problem or the contingency argument by saying – the composition fallacy – by saying, well, look, we're talking about the whole universe, we're not just talking about one piece of matter within the universe.

Dr. Craig: Right, and that's correct. You couldn't reason that the entire universe is contingent just because the various things in the universe are contingent. It could be that matter and energy themselves are necessarily existent and then the configurations that matter and energy assume in this world are contingent. But I don't think anybody believes that, Kevin. I don't know anyone who thinks that the matter and energy in the universe is metaphysically necessary. Think of it: according to the standard model of particle physics, on the subatomic level matter is made up of fundamental particles – things like quarks and electrons. These aren't composed of anything smaller than that on the standard model. These are the basic units of matter. So to say that matter exists necessarily would be to say that every quark in the universe is a metaphysically necessary being, which just seems fantastic. Does every quark in the universe exist with metaphysical necessity? Couldn't the universe have had, say, three less quarks than it does? Surely that's true. In fact, couldn't the universe have been composed of an entirely different set of quarks than the quarks of which it's made. It seems obvious that these quarks are not necessary in their being. Indeed, if there were a different model, different laws of nature, you might not have quarks at all. You might have some other fundamental entities like strings that would be the fundamental units of energy or matter. So given that the quarks and the fundamental particles don't exist necessarily it would follow, I think, that neither does the universe exist necessarily, Think of it then in this way: imagine, say, this table at which we're seated. Could this table, this very table, could it have been made of ice? Well, I think not. [4]  You could certainly have an ice table in place of this table, but it wouldn't be this table. Now, if that's true a universe composed of a different collection of quarks wouldn't be the same universe. It would be a different universe. So it would show that if the quarks are contingent, the universe is also contingent.

Kevin Harris: If all the tiles on the roof are brown, the roof is brown.

Dr. Craig: Well, in that case, yes. So in that case you would not have this problem that you have just expressed where people would try to say “Well, things in the universe are contingent, but the universe itself exists necessarily.” That would require us to say, I think, that every single quark in the universe is a metaphysically necessary being, which seems absurd.

Kevin Harris: Bill, off the top of your head, what do you think are some of the problems there are that would need to be looked at and solved as far as treating the universe as a whole, as opposed to treating it in its parts?

Dr. Craig: Well, one would be the question of, I think, the existence of time, and what is the nature of time, and is there a sort of worldwide time that measures the duration of the universe? Is temporal becoming real or illusory? These are questions that arise in this discipline, and are things about which he has some good things to say.

Kevin Harris: Yeah. Don't you agree that the contingency of the universe as a whole is a major field of study?

Dr. Craig: Yes, I think philosophically that would be a deep metaphysical question. Why does the universe exist at all? Why is there any contingent reality at all?

Kevin Harris: Here's Maudlin's comment on how things in cosmology apply both to the physical realm and also the philosophical realm. He says, you know, gravity was

a physical discovery of momentous importance, as important as anything you could ever imagine because it knit together the terrestrial realm and the celestial realm into one common physical picture. It was also a philosophical discovery in the sense that philosophy is interested in the fundamental natures of things.

What a beautiful example of how philosophy and the physical sciences work together and are as legitimate as one another.

Dr. Craig: Yes, this is a good example of this issue of foundational questions that arise in physics that are profound philosophical questions as well as scientific questions. He says later in the interview,

The basic philosophical question, going back to Plato, is "What is x?" [And you fill in the blank there for the x.] What is virtue? What is justice? What is matter? What is time? You can ask that about dark energy [in the universe that propels the acceleration of the universe] – what is it? And it's a perfectly good question.

So these are some of these deep foundational questions about the nature of the universe.

Kevin Harris: Krauss says just the opposite. In an interview we listened to he says, “It's not why, it's how. The why question doesn't matter. The how question is what matters.”

Dr. Craig: Yeah, and you can't even answer, really, the how question unless you know what you're talking about, and that's this fundamental question “What is x?” that Plato posed.

Kevin Harris: Finally, he does say a lot of attention has been given to the fine-tuning argument. The interviewer says,

One example of philosophy of cosmology that seems to have trickled out to the layman is the idea of fine tuning – the notion that in the set of all possible physics, the subset that permits the evolution of life is very small, and that from this it is possible to conclude that the universe is either one of a large number of universes, a multiverse, or that perhaps some agent has fine tuned the universe with the expectation that it generate life. Do you expect that idea to have staying power, and if not what are some of the compelling arguments against it?

Well, Maudlin agrees with the statement of it. He says that is,

. . . a perfectly correct statement of [the fine-tuning argument], depends upon making judgments about the likelihood, or probability of something. Like, "how likely is it that the mass of the electron would be related to the mass of the proton in a certain way?" Now, one can first be a little puzzled by what you mean by "how likely" or "probable" something like that is. You can ask how likely it is that I'll roll double sixes when I throw dice, but we understand the way you get a handle on the use of probabilities in that instance. It's not as clear how you even make judgments like that about the likelihood of the various constants of nature (an so on) that are usually referred to in the fine tuning argument.

Dr. Craig: Robin Collins in his forthcoming book A Well Tempered Universe has a long discussion of the application of probability theory to the fine-tuning argument, [5] and argues that it's using a standard probability measure that is normal in physics and that we are making judgments of epistemic probability. We're saying how likely is it given that there is a single universe and no divine designer that the constants and quantities would have the values they do? And he argues it is extremely incomprehensibly low. One way to visualize this is to imagine – and this illustration comes from John Barrow – a piece of paper with a red dot in the middle of it representing our universe. Now, he says, alter the constants and quantities slightly and that describes a new universe. If it's a life-permitting universe make it a red dot. If it’s a life-prohibiting universe make it a blue dot. Now, do it again, do it again, do it again, do it again, until the sheet of paper is filled with dots. And, he says, what you will have at the end is a sea of blue with only a few pin-points of red. And that's what it means to say that our fine-tuned universe is enormously, unfathomably improbable. The range of possibilities for the values of the constants and quantities is so vast and the vast, vast majority of them are life-prohibiting that it becomes highly, highly improbable that a randomly thrown dart would strike a life-permitting universe.

Kevin Harris: He says here that the physicists that he talks to about fine-tuning seem to say that if you have enough worlds eventually you are going to come up with the particular fine-tuning elements that we see. So in other words if there is a multiverse or bubble universes this is no problem. Eventually something is going to come up—right?

Dr. Craig: Well, it depends on whether or not the constants and quantities vary across these universes. There's two problems. First, you got to generate the many worlds; you've got to have some mechanism that produces them. Secondly, you have to have some sort of mechanism for explaining why they would be randomly ordered in their constants and quantities. If they’re not randomly ordered then there's no guarantee at all that a life-permitting universe will appear anywhere in the ensemble of universes. And so physicists are trying to marry string theory with inflationary theory to develop a mechanism for doing this. But so far it remains wildly speculative, and moreover it's not clear that even that theory will be free of fine-tuning. If that theory exhibits fine-tuning then you haven't solved the problem, you've just kicked the can down the road, and you have to face it all over again on this higher level.

Kevin Harris: He says,

If we give up on [this whole multiverse idea], and it turns out there aren't these many worlds, that physics is unable to generate them, then it's not that the only option is that there was some intelligent designer. It would be a terrible mistake to think that those are the only two ways things could go. You would have to again think hard about what you mean by probability, and about what sorts of explanations there might be. Part of the problem is that right now there are just way too many freely adjustable parameters in physics. Everybody agrees about that. There seem to be many things we call constants of nature that you could imagine setting at different values, and most physicists think there shouldn't be that many, that many of them are related to one another.

Dr. Craig: Right. What he's saying here is that if you can get rid of the fine-tuning by showing that many of these constants and quantities are inter-related to one another then you really don't have as many examples of fine-tuning as you thought. If you turn one dial maybe it will affect the other dials as well. But the problem is there is just no physical evidence for this, Kevin. All the evidence we have suggests that the fine-tuning is here to stay. Every effort that we've had to suppress the fine-tuning at one point is like an ugly bump in the carpet – it pops up somewhere else. And so I think, given both the multiplicity and the variety of the examples of fine-tuning, it's highly unlikely that this is going to go away with any sort of future physics. So we probably are left with the choice between an intelligent designer or agent and this multiverse hypothesis.

In my published work I've tried to explain why this multiverse hypothesis in the end really is a failure at explaining the fine-tuning. Roger Penrose of Oxford University has been a determined critic of these world ensemble or many world hypotheses to explain away fine-tuning. What they try to do is explain our existence on the basis of a selection effect, [6] namely, it's only fine-tuned universe that can have observers in them – right? – like us, so why should we be surprised at observing the fine-tuning of our universe? What this fails to reckon with is that it is not true that all observable universes have to be fine-tuned. The most probable universe that is observable would be one in which a single brain fluctuates into existence out of the quantum vacuum with the illusion of seeing an external world around us. This is called a Boltzmann Brain after Ludwig Boltzmann, the great nineteenth century German physicist. So the vast majority of observable worlds in the multiverse would be Boltzmann Brain worlds; they would be worlds in which there is only a single brain that exists, not a finely-tuned universe. So what that means is you can't explain away fine-tuning as a result of an observer selection effect because the most probable observable universes will be universes having Boltzmann Brains in them. So the fact that we observe a universe with intelligent, interactive, embodied agents is unfathomably improbable and still cries out for explanation. So it turns out this world ensemble multiverse hypothesis doesn't do anything to explain away the fine-tuning of the universe after all.

Kevin Harris: We're out of time on this podcast but there are two more questions that Maudlin brings up in this article that we'll look at in the next podcast dealing with time and also the probabilities and the problems of the evolution of intelligent life. We'll talk to you next time on Reasonable Faith. [7]