Alex Vilenkin on the Beginning of the Universe, Part 3

In the current series of posts I have been discussing Alex Vilenkin's book, Many Worlds in One: The Search for Other Universes (New York: Hill and Wang, 2006). In particular I've talked about the theorem he developed with Arvind Borde and Alan Guth which shows that the universe had a beginning. I will be interested to see if that theorem has been challenged or overturned in the past couple of decades—I don't believe it has, but I might do another post on that topic if I find anything interesting. In the meantime, I want to continue this discussion by sharing some very brief thoughts about Vilenkin's own explanation for where the universe came from. I think I might also do one more post briefly responding to Vilenkin's comments about why God would not make sense as the cause of the universe.

Intuitively, I think most people understand that if the universe had a beginning, then there needs to be some kind of explanation for where it came from. What caused it to come into being? To deny that there needs to be any explanation would seem to undercut scientific investigation and philosophical reasoning, and we tend to explain things by their causes. This is what makes the Kalam cosmological argument so formidable. Remember the formulation of that argument:

1. Everything that begins to exist has a cause.
2. The universe began to exist.
3. Therefore, the universe has a cause.

Before we get to Vilenkin's view, I want to make a few comments about the KCA. Let's take Vilenkin's theorem (the Borde-Guth-Vilenkin theorem) as given. In that case, the second premise of the argument is established. But what about the first premise?

There is a common-sense quality to the first premise, but that doesn't mean that there's nothing more to be said about it (which is good because common sense can obviously be wrong). In fact, there are several reasons to think that the first premise is true, and I will mention two. First, it follows from a fundamental metaphysical principle that "out of nothing, nothing comes." In other words, you cannot get something from nothing.

There seems to be a fair amount of confusion about this, which stems (I think) from the way that so many people speak about "nothing" in a misleading way. Some physicists seem to equate nothing with empty space, or a vacuum, which is a mistake. Vilenkin identifies this problem himself:

A quantum fluctuation of the vacuum assumes that there was a vacuum of some pre-existing space. And we now know that "vacuum" is very different from "nothing." Vacuum, or empty space, has energy and tension, it can bend and wrap, so it is unquestionably something. (p. 185, italics in original)

If you get something from a vacuum, you are getting something from something. By contrast, "nothing" is the complete absence of anything, including vacuums and empty spaces. If I may editorialize just a little, when critics of the KCA dance around the first premise of the argument by changing the meaning of the word "nothing," it is hard not to think that they are not taking the issue seriously enough.

The point is, you can't get something from nothing because nothing has no properties or potentialities. Or, to word it more carefully, if nothing existed, there wouldn't be anything that had properties, and there wouldn't be any potential for bringing anything into existence. So to say that something could just pop into being from nothing would be a matter of blind faith in an impossibility.

Second, if things could pop into being from nothing, then it is fair to wonder why we don't see this happening all the time. I think the significance of this point is often lost on critics of the KCA. We will encounter this problem in Vilenkin's own theory. People who deny the first premise of the argument often do so because they think that the universe is, in some way, an exception. On their view, a universe beginning to exist without a cause is somehow different from, say, a person who suddenly begins to exist without a cause. But once you realize that we're talking about something coming into being from a literal state of absolute nothingness (again, no empty space, no vacuums, etc.), then it doesn't really make any sense to treat these cases differently. And it raises the question of why, if some things can pop into existence uncaused out of nothing, we don't see this happening all the time. After all, there can't be any physical constraints on nothingness.

At the very least, I think it's okay to say that the first premise of the KCA is plausible. Personally, I would have a very hard time believing that anything could just come into existence from nothing for no reason. It is part of why I find the KCA to be so persuasive. If the first premise turns out to be false, then the evidence for its negation would need to be very strong indeed.

Now, Vilenkin's own view is that the universe "tunneled" into existence from nothing, and that this was uncaused. Here are some quotes:

If there was nothing before the universe popped out, then what could have caused the tunneling? Remarkably, the answer is that no cause is required. In classical physics, causality dictates what happens from one moment to the next, but in quantum mechanics the behavior of physical objects is inherently unpredictable and some quantum processes have no cause at all. (p. 181)

Most of our concepts are rooted in space and time, and it is not easy to create a mental picture of a universe popping out of nothing. (p. 181)

This theory seems vulnerable to several important criticisms. To begin with, Vilenkin seems to reveal that he is not really talking about "nothing":

The initial state prior to the tunneling is a universe of vanishing radius, that is, no radius at all. There is no matter and no space in this very peculiar state. Also, there is no time. . . . In the absence of space and matter, time is impossible to define. (pp. 180–1)

I am not sure what the phrase "vanishing radius" is supposed to mean, and I think it's crucially important to keep the language here very clear. I would think that there is a difference between saying that the universe has a radius of zero and saying that the universe does not have a radius at all. Maybe I am wrong about that. If you have no radius, no matter, no space, and no time, it sounds like you have no physical universe at all. But notice what Vilenkin says next:

And yet, the state of "nothing" cannot be identified with absolute nothingness. The tunneling is described by the laws of quantum mechanics, and thus "nothing" should be subjected to these laws. The laws of physics must have existed, even though there was no universe. (p. 181, italics in original)

This seems to be confused on a couple of levels. First, it makes no sense to distinguish between nothing and "absolute nothingness." There can't be different tiers of nothing, as if you could have one state that is absolute nothingness and another state that is only 85% nothingness. Nothingness is, well, an all-or-nothing affair. So it sounds like Vilenkin is describing a universe arising from some kind of something. Second, since the initial state of the universe is not absolute nothingness, this seems to contradict Vilenkin's own theorem, since he himself is claiming that cosmologists cannot avoid a cosmic beginning for the universe. At least, he seems to be equivocating a bit.

Vilenkin makes another statement that reveals he is either not really talking about a universe coming from nothing, or he does not fully understand what it means for something to come from nothing:

If the Copenhagen interpretation [of quantum probabilities] is adopted, then the creation was a one-shot event, with a single universe popping out of nothing. This, however, leads to a problem. The most likely thing to pop out of nothing is a tiny Planck-sized universe. (p. 187)

Vilenkin is using this to explain why he adopts the Everett interpretation, but never mind that. Notice his comment about how the most likely thing to pop out of nothing is a tiny universe. If he is talking about absolute nothingness, then this statement is just a non sequitur. If you have a state of nothingness, then there is no sense in talking about probabilities at all, and the size of different objects makes no difference. It's no more likely for a small universe to pop into being out of nothing than it is for a gigantic megaverse to pop into being out of nothing.

I suspect that, based on his earlier comment about distinguishing between nothing and "absolute nothingness," Vilenkin is equivocating here with the word nothing. If he is not, then his theory is simply incoherent. But if he thinks the universe tunneled into existence from an earlier initial state, my own question would be about how the initial state came into existence. Vilenkin doesn't seem to answer that question, or if he has, then perhaps I've just not understood what he is saying.

In any case, I wouldn't say that Vilenkin has successfully overturned the first premise of the KCA. To say that the universe popped into being, uncaused, out of "nothing" is, for me, no better than believing something just because the Bible says it. In both cases, we seem to be dealing with statements that have to be accepted on blind faith. Of course, if Vilenkin's "nothing" is actually supposed to be a kind of something, then I am left wondering why the BGV theorem doesn't rule it out. I suspect that it's because, on Vilenkin's view, time has no meaning once you get to the initial state of the universe, but in that case I think I just have a philosophical disagreement with him about the nature of time.

The last issue I want to mention here is Vilenkin's comment that the laws of physics must have existed in the absence of a physical universe, and so it can't be true that the universe came from a state of absolute nothingness. Vilenkin talks more about this later in the book, and his comments are a bit confusing. I should mention that he speaks of a "Creator" writing the mathematical equations which underlie physical reality:

Earlier cosmological models suggested a Creator meticulously designing and fine-tuning the universe. . . . The new worldview evokes a different image of the Creator. After some thought, he comes up with a set of equations for the fundamental theory of nature. This initiates the process of runaway creation. No further instructions are needed: the theory describes quantum nucleation of universes from nothing, the process of eternal inflation, and the creation of regions with every possible type of particle physics, ad infinitum. (p. 200)

This makes Vilenkin sound like a theist, but I think he is speaking metaphorically. What I am more confused about is the idea that the equations for the fundamental theory of nature could somehow "initiate" the process of runaway creation. Equations are not causes, and I personally doubt it even makes sense to speak of equations having some kind of existence, unless Vilenkin really does mean to suggest that they exist somehow in the mind of God. And then, of course, there is the lingering puzzle of what Vilenkin means by "nothing" since equations about nature would not have any bearing on which things could arise spontaneously from a state of nothingness.

Vilenkin seems to put quite a lot of stock in the existence of infinite universes—the "many worlds" from his book title. I may want to come back to that idea in future posts, especially since I am hoping to eventually learn more about multiverse theories and try to form a stronger opinion about them. For now I'm happy to leave that to the side, although I remain very skeptical of there being an infinity of other worlds, but for reasons I've not discussed here.