A Tribute to Stephen Hawking

KEVIN HARRIS: Dr. Craig, the famed physicist Stephen Hawking has died at age 76. He said – one of his famous quotes – My goal is simple. It is a complete understanding of the universe. Why it is, as it is, and why it exists at all. He has been the subject of your study. You have been familiar with him for quite some time.

DR. CRAIG: Yes, his work in cosmology and the origin of the universe has been very significant and of interest to me. He has become probably the best known scientist in the world today because of his courageous struggle with Lou Gehrig's disease. He was diagnosed with this disease as a young man, and against all expectation lived to an extraordinary age. Normally someone with Lou Gehrig's disease would not live more than a few years, and yet he managed to live until he was 76 years old and bore this terrible debilitating illness with great courage.

KEVIN HARRIS: Virtually his entire adult life.

DR. CRAIG: Yes. That’s right. One can only take hats off to someone who has born such infirmity bravely and with such a good spirit.

KEVIN HARRIS: What would you say would be the importance of his contribution?

DR. CRAIG: There are two things that stand out. One would be his development with Roger Penrose in the early 70s of the Hawking-Penrose singularity theorems. Prior to that time the singularity that marked the beginning of the universe in the standard Big Bang model was thought to be perhaps merely a mathematical artifice, perhaps a feature of only a very idealized universe that had ideal homogeneity and what is called isotropy – being the same in all directions. But what the Hawking-Penrose singularity theorem showed was that any sort of universe which is governed by the equations of the general theory of relativity when extrapolated in the past will inevitably shrink down to a singularity – to a point of infinite spacetime curvature, temperature, density, and so on, and therefore would mark the beginning not only of all matter and energy but of physical space and time themselves. They helped to show that this prediction of the standard model was not some unrealistic prediction of an ideal model but would in fact characterize the real universe insofar as it is governed by the equations of Einstein’s general theory. Interestingly enough, Hawking helped to put in place some of the strongest evidence for the truth of the second premise of the kalam cosmological argument, namely that the universe began to exist. That is why his work became of such interest to me as a young philosopher working on this particular cosmological argument for God’s existence. I find it ironic that even though Hawking himself was not a theist – indeed he was fairly vociferous in his opposition to theism – nevertheless his work on the singularity theorems helped to provide some of the strongest evidence for the fact of the beginning of the universe.

The other discovery for which he is remembered is so-called Hawking radiation. The time-reversed expansion of the universe is like a sort of black hole. As the universe goes back in time it shrinks down to the singularity. Similarly there are in the universe today these sort of gravitational sinks of collapsed objects which suck in to themselves everything within a certain distance.[1] These are called black holes. It was thought that nothing would come out of a black hole once it came within the horizon or the perimeter of one of these things. But Hawking discovered that these black holes actually radiate radiation. These black holes at their perimeters suck in certain particles and then emit a different particle which lies outside this horizon. This radiation is actually detectable. This suggests that in fact eventually black holes themselves will radiate away and will evaporate and will disappear. So it doesn’t represent the final state of matter. In the far, far distant future even the black holes will evaporate into particles that continue to expand throughout the universe. The discovery of this Hawking radiation, contrary to expectation, was one of his most significant contributions to astrophysics.

KEVIN HARRIS: In one of his interviews he said, All the evidence seems to indicate the universe has not existed forever, but it had a beginning about 15 billion years ago. He went on to say, There must have been a beginning, otherwise the universe would be in a state of complete disorder by now and everything would be the same temperature.

DR. CRAIG: That would be the argument from entropy that Penrose has defended so forcefully. His colleague Roger Penrose has pointed out that the universe began in an extraordinarily, unimaginably improbable low entropy condition, and that it is now increasing in entropy as time goes on. Entropy is a measure of the usable energy in a system. As the universe expands, its usable energy declines. That is to say, it’s entropy increases. But at its beginning it was in an extraordinarily low entropy state that is enormously improbable. This is one of the key factors in the famous fine-tuning argument for God’s existence. It seems that the fact that we do not now exist in the highest entropy state or in a state in which the universe is dark, cold, dilute, and dead is best explained by the fact that the universe has not always existed and so hasn’t run its course into this high entropy condition. It began a finite time ago with an initial low entropy condition that was just put in inexplicably as an initial condition of creation. This is one of the indications of the beginning of the universe as well as one of the parameters of the universe that must be incomprehensibly fine-tuned in order for the universe that we observe to exist. This discovery supports both the kalam cosmological argument for the beginning of the universe as well as the fine-tuning argument for a cosmic designer. That is a different consideration than the singularity theorems which show that an object which is under gravitational self-collapse cannot shrink down to a minimum size but will go all the way down to this infinitely dense state which therefore forms a boundary to the universe – a past boundary at which space and time began. People need to understand that if this prediction is correct, it means that there wasn’t anything prior to the Big Bang. There was nothing prior to the singularity because this is the origin of time and space as well as of all matter and energy in the universe.

KEVIN HARRIS: We have to kind of parse through some of the popular articles because the article that we have in front of us that was so widespread – the title is “Stephen Hawking says he knows what happened before the dawn of time.” Then it goes on to talk about Stephen Hawking who says there is no time before time began but that time was always there, it was just different. It then tries to explain I guess the boundary condition.

DR. CRAIG: This is very misleading.[2] The article makes it sound as though Professor Hawking had made some new discovery that was now being trumpeted in the media just a few weeks ago when in fact when you read the article what this is about is about the Hartle-Hawking model of the origin of the universe which Hawking developed back in 1983 with James Hartle of the University of California Santa Barbara and which was popularized in Hawking’s 1988 book, A Brief History of Time. So, in fact, there is nothing new here. This is just a rehearsal of the same Hartle-Hawking model that was developed decades ago. But it is being sort of repackaged here in the popular media as though this were some new discovery.

The statement that he knows what happened before the dawn of time is simply a self-contradiction. I think most listeners to Reasonable Faith will realize that the word “before,” like the word “after,” is a temporal word. It is a temporal relation. So it is simply a self-contradiction to talk about what there was before the beginning of time. This is a misrepresentation therefore of Hawking’s view. His view is that time itself had a beginning. In the Hartle-Hawking model the contribution here is to be able to describe the beginning of the universe in such a way that you don’t have an initial singularity. Instead, the beginning of the universe is rounded off as it were rather like a badminton birdie where instead of going back to a sharp point it goes back to a kind of southern hemisphere and is rounded off. It is still finite. Time still begins to exist. But it doesn’t begin to exist at a singularity. His model, if true, would make an advance over the standard model in that physics would not break down at the beginning of the universe. It would apply all the way back to the south pole. Although in A Brief History of Time Hawking, I think, makes the fallacious inference that a universe which doesn’t have a singular beginning doesn’t have a beginning, he corrects that in the book with Leonard Mlodinow, The Grand Design, where they do recognize that in order to begin to exist time doesn’t have to begin at a singular point. It can begin, for example, at the south pole of the southern hemisphere. In The Grand Design they treat that south pole as the beginning of time and the beginning of the universe. So the Hartle-Hawking model is tremendously supportive of the doctrine of creation and of the kalam cosmological argument by giving us a theory of the beginning of the universe and of time which doesn't involve a breakdown of physics.

KEVIN HARRIS: It is as if he seems to say, We hit a wall in physics when it comes to the Big Bang, when we come to the beginning. He says,

Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them.[3]

DR. CRAIG: This statement, I think, tends to reflect Hawking’s verificationism and positivism. He has made it clear in a number of places that he is a kind of verificationist. If these events have no observational consequences you just cut them out and pretend they don’t exist. That is obviously, I think, fallacious. Just because something may not have an observational consequence doesn’t mean that they don’t exist, and it doesn’t mean that they don’t have causal consequences. This early period of the universe was causally prior, if not temporally prior, to the expansion of the universe as we know it and therefore relevant. The Hartle-Hawking model is itself an attempt to provide a physical description of the universe all the way back to its very beginning.

KEVIN HARRIS: It is almost a tacit admission that this leads to metaphysics – we are now in the metaphysical realm when we get to a certain point.[4]

DR. CRAIG: Alexander Vilenkin, who is one of the most prominent contemporary cosmologists, has described what he does as metaphysical cosmology. It does, I think, lapse over or spill over into metaphysics when we ask questions about the nature of time and the beginning of the universe and what would bring the universe into being. Although Hawking, in A Brief History of Time, made some, I think, very incautious statements about eliminating the need for a Creator because on the Hartle-Hawking model there isn’t a beginning point. His colleague James Hartle certainly didn’t take that perspective. I sat down with Hartle in his office as UCSB and had a good conversation with him about the model. When I said, Does it eliminate the need for a Creator? Does it explain how the universe came into being from nothing? He said, Of course not! It doesn’t aspire to that sort of thing. Hartle wouldn’t try to draw the sort of metaphysical implications from a physical theory. The fact is that the model pushes you back to the beginning of time even if that beginning is not a singular point. The error that is made in A Brief History of Time is a philosophical mistake, namely thinking that having a beginning entails having a beginning point. That is simply not true. Something begins to exist if it has existed for only a finite amount of time. In fact, time begins to exist if and only if for any finite interval of time that you pick (say, a second or a minute or an hour) there have been only a finite number of equal intervals prior to that selected interval. That provides the necessary and sufficient conditions for beginning to exist, and it doesn’t entail that there was a singular point at which the universe or time began to exist.

KEVIN HARRIS: By the way, Stephen gave an interview to New Scientist magazine not long ago. He says there is still one puzzle left for him. Asked what he thought about most during the day, Hawking replied, “Women. They are a complete mystery.” [laughter] As we wrap up our podcast today, what is going to happen now is that a lot of people who just have a cursory knowledge of Stephen Hawking, know the name, know that he is a scientist, because of his death what typically happens is they will begin to look into what he is saying. People who otherwise wouldn’t bother with his books, they will buy his books now and begin to read. It seems to me that there are opportunities for you, for Reasonable Faith, for all of us to be conversant on some of the issues that are going to emerge because of the interest that will generate because of his death.

DR. CRAIG: Absolutely. I’ve interacted with Hawking’s work philosophically over the years and would commend to folks some of the articles that I’ve written on him. For example, the article “Has Hawking Eliminated the Need for a Creator?”[5] Or my article on The Grand Design.[6] Or, finally, the talk that I’ve given on “Cosmology – A Religion for Atheists?”[7] which is the way he defines cosmology in the movie, A Theory of Everything, when his wife-to-be, Jane, asks him what is cosmology. What I want to emphasize is that as a philosopher I wouldn’t think to criticize Stephen Hawking’s physics. That would be absurd. But when Hawking steps over into my discipline and begins to draw philosophical implications – and particularly theological implications – then he is in my field and he needs to be patient of correction and criticism as well. I think that we do have a great deal to learn from his work about the nature of the universe, particularly its beginning, but also I think it causes us to think critically about the philosophical and theological assumptions and implications of his work.[8]