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The Big Bang

April 13, 2008     Time: 00:22:30
The Big Bang


Conversation with William Lane Craig

Transcript The Big Bang


Kevin Harris: Dr. Craig, we’ve been discussing Big Bang cosmology and right off the bat some people of faith and some Christians find this as a threat to their faith in God or to Christianity, that somehow the Big Bang would supplant God. Is that a warranted fear?

Dr. Craig: I don’t think so at all, Kevin. The Big Bang doesn’t explain why the universe came into being. It is simply a description of the expansion of the universe from its original point before which nothing existed. So it doesn’t itself explain why the universe exists or where it came from. You still need to have a cause of the Big Bang.

Kevin Harris: In the third edition of your book Reasonable Faith, you expand a little bit into some of the latest theories in Big Bang cosmology. Some of those things that are coming down the pike right now, the theories that are being thought over, involve multiple universes. Perhaps we are not the only universe, there may be much more. Is that the multiverse theory?

Dr. Craig: Right, sometimes this is called the multiverse. “Uni” means “one” as in “unicycle” - that would be just a one wheeled thing. Universe would be one world. So a multiverse would be a sort of collection of universes. Or sometimes our universe is called a pocket universe, sort of a little section of a much bigger universe. So this has become quite the rage in contemporary cosmological discussion. The notion that we may live in a multiverse and our universe is just one bubble or part of this wider reality.

Kevin Harris: It is getting into popular literature and novels and movies as well. The book from Michael Crichton Timeline postulated that we do live in a multiverse, there are multiple universes, and we can’t travel back in time in the one we are in but they find a way to step over into the next one which is very similar to this one. So similar in fact that you really can’t even tell the difference and you can go back in time in that one! So you find a way to step over into the other one. It has gotten into popular literature as well. Is there anything to these multiverse theories?

Dr. Craig: Well, yeah, I think you have to say there is something to them though it is important to understand that the motivation behind the multiverse, I think, for many scientists is to try to find an explanation for the incredible fine-tuning of the universe for intelligent life. The universe is so incomprehensibly fine-tuned for the existence of life that this cannot be simply dismissed as an accident, as due to chance. It cries out for some sort of an explanation. If cosmologists are to avoid the “G” word what they are going to do is to appeal to a world ensemble or multiverse of worlds in which all of the constants and quantities of nature vary randomly. If there is an infinite number of these universes within the world ensemble then by chance alone finely tuned universes will appear somewhere in the ensemble and the observers that exist within them will look out and see a finely tuned universe for their existence and think, gosh, there must be a designer when in fact it is all just due to chance. So the multiverse hypothesis for many scientists is really an attempt to multiply your probabilistic resources so as to reduce the improbability of getting a finely tuned universe by chance. It is like saying there is not just one spin of one roulette wheel, but there are billions of roulette wheels spinning so somewhere in the system your number is going to come up.

Kevin Harris: You mentioned the fact that if the universe had not allowed intelligent life then we wouldn’t be here to observe it. We discussed that in other programs and you’ve written on that, Dr. Craig, but it brings up the anthropic principle and the weak anthropic principle. What is the difference between the two? [1]

Dr. Craig: I really don’t think that there is a difference between the two. I think the differentiation between strong and weak versions of the anthropic principle is unhelpful. What the anthropic principle basically says is that our own existence acts as a kind of selection effect upon what we can observe. Namely, we can’t observe universes that are incompatible with our existence because if it were, say, too hot or too dense or expanding too rapidly, those conditions would not be conducive to life and so we couldn’t exist to observe them. So by its very nature our existence acts as a kind of selecting factor on what universes we can observe. We can only observe universes which are appropriately fine-tuned for our existence. The anthropic principle can be used in conjunction with a world ensemble to say that in the world ensemble of randomly ordered universes by chance alone finely-tuned universes will appear, and of course only those universes can be observed by observers because in all the other ones there aren’t any observers. There isn’t any life. So by its very nature the observers will observe finely-tuned universes. So we shouldn’t really be surprised when we look out and see our universe fine-tuned for our existence. It doesn’t cry out for a creator or a designer. Rather, it is just by chance and we couldn’t observe anything else.

Kevin Harris: Our observing the universe as a sort of selection process is not the same as saying “We create the universe by our observation.”

Dr. Craig: Right, that is absolutely correct. That would be a misunderstanding. The idea is not that our existence somehow makes the universe fine-tuned for our existence. Or that our existence somehow explains why the universe is fine-tuned for our existence. That is why the anthropic principle only works if you have a multiverse or world ensemble. You’ve got to have the multiverse of randomly ordered worlds that is big enough so that by chance alone somewhere in the ensemble a life permitting universe will arise by chance. Then you can use the anthropic principle to tell those observers, look, you couldn’t observe anything else so why are you surprised? It is just by chance. So the anthropic principle alone won’t do the job. It’s got to be the anthropic principle plus the world ensemble or multiverse together. That is what current theorists who want to avoid the “G” word are appealing in order to explain the fine-tuning of the universe.

Kevin Harris: Let’s go to John Leslie’s firing squad illustration. I think we can tie some of this together. Why did he give this analogy of the firing squad? How does it relate and what is it?

Dr. Craig: He gave this analogy because early on people were trying to use the anthropic principle on its own to get rid of design. They were trying to just say you ought not be surprised at the fine-tuning of the universe for life because after all if it weren’t fine-tuned you wouldn’t be here to be surprised about it. So it is no big deal. Well, Leslie said [2] that it is like being dragged in front of a firing squad of one hundred trained marksmen all with rifles aimed at your heart at point blank range and you hear the command given - “ready, aim, fire!” And then you hear the roar of the guns. And then you observe that you are still alive! All of the one hundred marksmen missed. Now Leslie says what would you conclude in this case? You wouldn’t be surprised that you don’t observe that you are dead because if you were dead you couldn’t observe it. So that is right. There is no surprise that you don’t observe that you are dead. But you should still be surprised that you do observe that you are alive in view of the improbability of all of these marksmen missing. Given the improbability that they would all miss, you should be very surprised that you observe that you are alive even though you are not surprised that you don’t observe that you are dead. In fact, you would probably conclude that they all missed on purpose; that it was the result of some kind of a setup engineered by someone for some reason.

So what Leslie is pointing out is that in the absence of a world ensemble where all possibilities are actualized you can’t use the anthropic principle to explain away our surprise at seeing the fine-tuning of the universe. [3] You still have to have some explanation for why those marksmen all missed. It is not enough just to say, well, if they hadn’t all missed you wouldn’t be there to be surprised about it.

Kevin Harris: One guy tried to get around Leslie’s analogy by saying that the guy who was about to be shot, after he heard the roar of the guns and he was still alive, he took off his blindfold and there were one hundred other condemned criminals but one of them was shot.

Dr. Craig: Yeah, see what he is trying to do is a world ensemble.

Kevin Harris: Multiple.

Dr. Craig: Exactly. And that would be right. He is right. If you posit enough firing squads shooting at people that the incredibly infinitesimal possibility that they would all miss would somewhere be actualized then, yeah, the guy shouldn’t be surprised that they all missed because somewhere in the ensemble of firing squads and victims one of them by chance alone would have missed. But that just illustrates my point that the anthropic principle without the world ensemble won’t do the trick. You’ve got to have the multiverse to generate all of those other possibilities. As I say, multiply your probabilistic resources so that somewhere this infinitesimally improbable event is going to happen.

Kevin Harris: People who discuss this topic often refer to the work of Barrow and Tipler. Can you summarize some of the things that they said?

Dr. Craig: Barrow and Tipler wrote a book called The Cosmological Anthropic Principle in 1985 which is just a masterpiece of compiling all of the evidence for fine-tuning in the universe. They show how incredibly fine-tuned the universe is for our existence. Then they enunciate a couple of versions of the anthropic principle as you say and attempt to defend it. I think that their own view does succumb to the criticism that I've just lodged – the anthropic principle is invalid or impotent in the absence of this world ensemble. So the real question that is facing us today and this whole question of fine-tuning and how is it to be explained, is the question: which is the better explanation? An intelligent designer of the universe or a multiverse or world ensemble of universes, of a randomly ordered infinite number of worlds. Which is the better explanation of those two?

Kevin Harris: In your new edition of Reasonable Faith, the book, you expand the chapter dealing with this. What are some of the things that you put in?

Dr. Craig: What I point out is a couple of criticisms of the world ensemble hypothesis that I think make it less preferable to the design hypothesis. One of these is fairly obvious; namely, if the world ensemble itself is to be a plausible scientific alternative to design, you've got to have some sort of a mechanism for generating the many worlds. You can't just say they are out there. You need some sort of a theory that would generate this world ensemble of an infinite number of randomly ordered universes. Well, the best shot at this would be inflationary theory. If the early universe were configured just right then as the universe expands there would appear bubbles within it of lower energy vacuum and these bubbles could each then constitute a separate universe. These would be your little universes within the multiverse that spawns the bubbles. If there were enough of these and they were randomly ordered then you'd get your world ensemble. Now, the question is: what about the mechanism that produces these bubble universes? Is it fine-tuned or not? If it is fine-tuned then obviously the problem hasn't been solved. The world ensemble gets rid of the cosmic designer only if there is no fine-tuning required for the world ensemble. That is far from obvious. For example, the cosmological constant, which drives inflation, has to be fine-tuned to one part out of 10120 and there is no explanation of that. Also, in the best theory that we have of a kind of theory of everything today – M-Theory, or Super String theory – the theory only works if there are exactly 11 dimensions. But the theory itself doesn't explain why the world should have 11 dimensions rather than any other number. So you have a kind of geometrical fine-tuning in this case in the number of dimensions. So it is not at all obvious that the world ensemble hypothesis has eliminated the need for fine-tuning. That is one problem. [4]

Here's another problem. As I mentioned earlier, the theorem developed by Borde, Guth, and Vilenkin has shown that the multiverse itself cannot be extended into the infinite past. There had to be a beginning to this multiverse and ever since its beginning it has been chugging away producing these bubble universes. Now think what that implies, Kevin. If it had a beginning, then that means that there can only be as many universes in the ensemble as have been generated since the multiverse began. But in that case it is going to be a finite number, not an infinite number, and therefore given the incomprehensible improbability of the fine-tuning, there is no guarantee whatsoever that finely tuned universes will have appeared yet in the world ensemble of bubble universes. So you don't have an infinite number of randomly ordered worlds in the way that the multiverse hypothesis requires to explain away fine-tuning.

So that is just a couple of problems. But perhaps the most damaging objection is the third one which has been developed by theorists like Roger Penrose, mathematical physicist at Oxford University. What Penrose points out is that if we are just a random member of a world ensemble of randomly ordered worlds then it is highly, highly probable that we ought to be observing a very different universe than the one we observe. For example, Penrose calculates that the odds of the universe having its exact thermodynamic characteristics is one chance out of 1010(123) – just an incomprehensible number. So the odds that the universe would be fine-tuned in the way that we observe it to be are just incomprehensibly small. By contrast to that, what are the odds that the solar system would just pop into existence suddenly by the random collision of particles? Just particles jostling around would suddenly – boom! - fall into the configuration of our solar system. Penrose figures this out. He says it is about 1 chance out of 1010(60). Now that is an incomprehensibly large number but it is infinitesimally small compared to 1 chance out of 1010(123). In fact, Penrose says it is “utter chicken feed” by comparison. [5] What does that imply? That implies that if we are just one random member of a world ensemble then as we look out at the universe what we ought to be observing in all probability would be a universe no larger than our solar system because that kind of world is vastly more probable than a finely tuned universe like ours. Therefore, our observations disconfirm the world ensemble hypothesis. It makes it very, very improbable that we are just a random member in a world ensemble.

In fact, the current wrinkle in cosmology today has been to calculate what would be the smallest observable universe there could be. In fact, it would be smaller than the solar system. The smallest observable universe and therefore the most probable observable universe to just pop into being from a random collision of particles would be a universe which consists of a single brain which has the illusion of an external universe around it, that appears to see an external universe when in fact all that exists is just a single brain. These are called Boltzmann Brains after the German 19th century physicist Ludwig Boltzmann. Therefore, if that is true then in all probability, if we are just a member of a random world ensemble, each one of us ought to conclude that he is in fact a Boltzmann Brain and that your hands, your head, the world around you, the trees, the cars, other people, all of these are just illusions of your consciousness' projections of your brain and all that really exists is just you, your single Boltzmann Brain. If you don't think that you are a Boltzmann Brain, if you think you are a respectable ordinary observer in an external world, then you should conclude that therefore a world ensemble does not in all probability exist.

Kevin Harris: Our question of the day, Dr. Craig. This is kind of a rough one. Are we to understand hell as being a place of fire and bodies being burned alive and so forth? [6]

Dr. Craig: I'm not sure what to make of these images in the Scriptures of hell that describe it as flames and others describe it as outer darkness. There is the resurrection of the body that does take place. So it could be that this would involve a kind of corporal punishment. On the other hand, it seems that the real essence of hell is not in corporal punishment but is spiritual separation from God, a kind of abandonment left apart from all that is good and lovely and true and worthwhile and being abandoned to one's own self and one's own wicked nature. So Paul says in Thessalonians that those who reject Christ will suffer the punishment of eternal exclusion from the presence of the Lord. I think that is the real essence of hell. Whether or not it will involve corporal punishment or whether these are just dramatic metaphorical images to depict how awful the suffering of this abandonment is, I have an open mind.

Kevin Harris: It surely may not be the kind of fire, chemical combustion that we are familiar with on planet earth.

Dr. Craig: Right, that would require oxygen to burn and fuel and things of that sort.

Kevin Harris: For eternity.

Dr. Craig: Right, that wouldn't seem to make sense.

Kevin Harris: Biblical descriptions describe hell as torment and not torture – torture being from with out – the corporal punishment. Torment being more of an internal conscience aspect.

Dr. Craig: My only reservation about that is I do think that the Scriptures teach the resurrection of the body and not just for the saved but I think that the unsaved also will be raised and then judged. So that makes one wonder, well, maybe there will be a kind of corporal torment as well as the anguish of being separated from the presence of the Lord. In any case, these images certainly mean to convey to us that this is awful, that it is unspeakably painful, and therefore we ought to do everything to avoid it.

Kevin Harris: Don't go there.

Dr. Craig: Yeah, don't go there. [7]