Some time ago a very active discussion of the causes of the existence of the Universe began among cosmologists and philosophers of science. Yes, we are not doing this nonsense.
First, Lawrence Krauss released a new book, "The
Universe from Nothing. Why God Doesn't Need to Create the Universe from Void " [
A Universe from Nothing: Rather than Nothing ] (based, in particular, on a popular lecture
available on YouTube ) covering this issue from the point of view of a modern cosmologist. Then David Albert, a modern philosopher of science, compiled a
devastating book
review for the New York Times. This discussion has continued since then: an interview with
Jerry Coyne (on Albert’s side), Rutgers’s
Cosmology Philosophy blog, an
extensive interview with Krauss in The Atlantic, comments by
Massimo Piglucci , another Krauss
answer on Scientific American.
For personal and scientific reasons, I was also going to insert my opinion. The origin of the universe is one of the themes of
my work , and Lawrence and David are my friends and blog partners.
Content
The article will be large, so I will give a brief summary. Roughly speaking, there are two kinds of questions around the “why does something exist?” Problem. One type, based on the platform of physical laws, flexible enough to allow the existence of "something" or "nothing" (and time and space can also be included in the concept of "something"), sounds like: why is there any manifestation of reality? Another type of questions is related to why we have this particular platform of physical laws, or something at all called “physical laws”?
Lawrence, to put it simply, addresses the first type of questions, and David is interested in the second, and both parties spend a lot of energy insisting that their question is more correct, instead of recognizing that these questions are different. Nothing in modern physics explains why we have such laws, and not others, although physicists sometimes talk about it - and they could have avoided this error if they took philosophers more seriously.
Then the discussion quickly slips into accusations and arguments not about that, but a pity, because these people are smart and agree about 95% of interesting problems, and the chances of a productive dialogue are constantly diminishing.
How does the universe work
Let's talk about how physics really works, according to our concepts. Since the time of Newton, the paradigm of fundamental physics has not changed; it consists of three parts. The first is the “state space”: in fact, a list of all possible configurations in which the universe can be. The second is a definite state representing the Universe at some point in time, usually the current one. The third is a certain rule according to which the Universe develops in time. Give me the Universe for today, and the laws of physics will tell you what will happen to it in the future. This way of thinking is no less true for quantum mechanics or GTR or quantum field theory, than for Newtonian mechanics or Maxwellian electrodynamics.
Quantum mechanics, in particular, is a special, but very versatile implementation of this scheme. (Quantum field theory is just a specific example of quantum mechanics, not a new way of thinking). States are “wave functions”, and the set of all possible wave functions of a particular system is called “
Hilbert space ”. Its advantage is that it greatly limits the range of possibilities (because it is a vector space: a remark for experts). As soon as you tell me its size (number of dimensions), you will fully determine your Hilbert space. This is fundamentally different from classical mechanics, in which the state space can become extremely complex. And then there is the machine - "
Hamiltonian " - indicating how to develop from one state to another over time. I repeat that there are not so many varieties of Hamiltonians; it is enough to write down a certain list of quantities (eigenvalues of energy - a refinement for you, annoying experts).
It is necessary to have an unbiased approach to what form the final laws of physics will take, but almost all modern attempts to deduce them take quantum mechanics to be true. This is true for string theory and for other approaches to quantum gravity - they may differ very much in their views on what space-time or matter consists of, but very rarely carelessly address the fundamentals of quantum mechanics. This clearly applies to all options that Lawrence considers in his book. On this platform, the definition of the "laws of physics" is a matter of choosing a Hilbert space (for which, in turn, you only need to determine its size) and the Hamiltonian. One of the wonderful properties of quantum mechanics is how restrictive it is; We do not have much freedom of choice from the types of laws of physics It seems that there is a lot of room for creativity, since the Hilbert space can be very large, and the simple essence of the Hamiltonian can be hidden by our complicated interaction with the outside world, but the basic recipe remains unchanged.
Therefore, what do “universe out of nothing” conversations mean within this platform? We still need to choose one of two possibilities, but at least this list of two points is exhaustive.
Possibility one: time is fundamental
The first possibility is that the quantum state of the Universe really changes over time - that is, the Hamiltonian is not zero, and it really pushes the state forward in time. This case seems to be general (there are more ways to differ from zero than to be zero), and it is on its study that we spend time on introductory courses, for the first time imposing quantum mechanics on fearless students. The miraculous and underestimated corollary of quantum mechanics is that if this possibility turns out to be true (the universe truly evolves), time cannot begin or end — it goes on forever. It is not at all like the classical mechanics, in which the trajectory of the Universe in the state space can push it with the singularity, in which time, as it is supposed, stops flowing. In quantum mechanics, every state is no worse than any other, and evolution will happily go on.
So how does this relate to the “something against nothing” question? In the process of evolution of the quantum state of the Universe, it can pass through phases in which it is very similar to nothing in the generally accepted sense - that is, as empty space, or as a strange non-geometric phase, in which we would not recognize space at all. Later, through the relentless influence of the Hamiltonian, it can evolve into something that is very similar to “something”, even very similar to the universe that we see today. Therefore, if for you “nothing” is “emptiness” or “lack of space”, then the laws of quantum mechanics provide a convenient way to understand how nothing can turn into a wonderful something within which we discover ourselves. This is interesting, and important, and worthy of writing a book, and this is one of the possibilities that Lawrence discusses.
Possibility two: time is secondary / approximately
The second possibility is that the Universe does not evolve at all - the Hamiltonian is zero, the space of possible states exists, but we just sit in it motionless, without a fundamental “flow of time”. You may decide that this possibility is logical, but not believable; don't we see how everything around us changes all the time? But it is precisely in this opportunity that you will immediately be buried if you simply take classical GTR and try to quantize it (that is, invent a quantum theory converging to GTR in the classical limit). We do not know whether this is right -
Tom Banks, for example, believes that it does not - but this possibility exists, so we need to think about what this could mean if it turned out to be true.
Of course, we believe that we feel the passage of time, but maybe time is secondary, not fundamental (I do not think the use of the word “illusory” is correct in this context, but others are not so careful). That is, perhaps, there is an alternative description of this one fixed point of Hilbert space - a description approximately similar to “The Universe evolves in time”, at least for a while. Imagine a metal bar on a hot surface, not evolving in time, but with a temperature gradient distributed from top to bottom. It is conceptually possible to divide this bar into layers of equal temperature, and then write an equation showing how the state of the bar changes from layer to layer and find that the resulting mathematical formalism is similar to "evolution over time." In this case, unlike the previous one, time may run out (or begin), since it was originally a useful approximation, valid under certain conditions.
Such a variant is meant by such quantum cosmologists, as James Hartl, Stephen Hawking, Alex Vilenkin, Andrei Linde and others, speaking about "the creation of the Universe out of nothing." In this view, in the history of the Universe there literally exists a moment before which other moments did not exist. There is a time boundary (presumably, before the Big Bang), before which there was nothing. Neither matter nor quantum wave function; there was nothing previous, since the concept of "pre-" does not make sense. This is also interesting, important, and it is worth writing a book about this, and this is another of the possibilities that Lawrence is talking about.
Why does the universe even exist?
So, modern physics has given us these two ideas, rather interesting, and responding to our informal idea of how “something comes from nothing”. One of them speaks of evolution from empty space (or non-space) into the Universe, full of everyone, and the other speaks of time, as an exemplary concept that ends at some boundary in the abstract space of possibilities.
So what should we complain about? If you think, then such reasoning, if you accept some specific definition of the concept of "nothing", can explain how the Universe can arise out of nothing. But they do not explain, and do not even try to explain, why something exists — why this evolution of the wave function, or why even this whole system of “wave functions” and “Hamiltonians” will be the right way to talk about the Universe. And maybe you are not interested in these questions, and no one has the right to take away from you the right not to be interested in them; but if the subtitle of your book says “why there is something, and not just nothing,” you, in essence, give up the right not to be interested in it.
Does the development of modern physics and cosmology help us to address these questions about why there is something called the “universe” at all, why there are such things as the “laws of physics”, why these laws take the form of quantum mechanics, why such a wave function and Hamiltonian? In short, no. It is not clear to me how they could do this.
Sometimes physicists pretend to answer these questions, which is very bad, because they are just lazy and do not try to think carefully about this problem. You, for example, can hear statements that our laws of physics can be the only kind of conceivable laws or the simplest possible one. But this is clearly not the case. Within the framework of the platform of quantum mechanics, there is an infinite number of possible Hilbert spaces and an infinite number of possible Hamiltonians, each of which defines a completely admissible set of laws of physics. And only one of them can be correct, therefore it is absurd to say that our laws can be the only possible ones.
Calls for simplicity do not help here either. The universe could be the only point that does not change over time. Or a single oscillator, endlessly oscillating here and there. It would be very simple. Somehow there may be some definition of simplicity, according to which our laws will be the simplest, but there will always be others, according to which they are not. In any case, we could then ask the question, why should laws be simple? In the same way, the statement “perhaps all physical laws are real somewhere” does not answer our question. Why are all physical laws real?
And sometimes, on the other hand, modern cosmologists talk about other laws of physics in the context of the multiverse, and suggest that we see one set of laws, and not another, for fundamentally
anthropic reasons. But this, again, is a simple inaccuracy. We are talking about the low-energy manifestation of the basic laws, but these basic laws are the same throughout the multiverse. We still have the question of the existence of these deep laws, creating a multiverse.
End of explanation
All these questions are interesting to ask, and not one of them is not answered by modern physics or cosmology. Or, at least, it is interesting to raise them, but from my point of view, the best answer would be to quickly lower them back. To this point, note, we have already come to a purely philosophical, not scientific, problem.
The why questions do not exist in the void; they make sense in some explanatory context. If we ask “why did the chicken cross the road?” [Popular topic of short anecdotes / approx. transl.], we understand that there are such things as roads, they have special properties, and things called "hens" have different goals and motivations, and there are things that exist on the other side of the road or other advantages of its transition. Only in this context can we offer a meaningful answer to the question "why." But the Universe and the laws of physics are not built into some larger context. This is the largest of the existing contexts, as far as we know. There is nothing wrong with admitting that the sequence of explanations ends somewhere, and the only explanation that remains is “it’s just like that”.
Well, or not. We must be good empiricists and be open to the possibility that what we consider to be the Universe exists in some larger context. But then we will probably redefine it as a universe, and remain with the same questions. As long as you acknowledge that the Universe has more than one conceivable way to exist, the chain of explanations will always have an end. I may be wrong, but insist that “the universe must explain itself” is rather unfounded.
Sounds and Furies
This is what I can say about these interesting questions, but I do not have enough strength to resist a couple of comments on procedural points.
First, I think that Lawrence’s book makes a lot more sense as part of the popular atheism versus theism controversy, and not as just a thorough philosophical study of an old problem. The afterword to the book was written by
Richard Dawkins , and initially Lawrence asked for this service from
Christopher Hitchens , while he was not seriously ill yet - and both of these people, although very smart, are neither cosmologists nor philosophers. If you set out to reject statements about the need for the existence (or usefulness) of the Creator within the framework of the cosmological scheme, then the above reasoning about the “creation out of nothing” really comes to a place. The physical universe may beautifully be self-sufficient; she does not need anything and no one outside to launch it, even if she had a “beginning”. This does not answer the classical question of Leibniz, but there is little doubt that this fact is a remarkable property of modern physics and has interesting implications for fundamental cosmology.
Secondly, after the release of the review from David, Lawrence unsuccessfully attacked the “idiotic philosophers” and the whole philosophy as a whole, instead of continuing to lead a meaningful discussion on the issues of interest. Like most scientists, Lawrence gets little from the philosophy of science. But the goal of philosophy is not to be useful to science, no more than mycology is to be useful to mushrooms. Philosophers of science are not trying to do science, they are trying to understand how science works, and how it should work, choose the logic and standards underlying scientific argumentation, place scientific knowledge within a broader epistemological context, and do a lot of interesting things, not pretending to be science. And if you are not interested, well, okay. But one should not try to undermine the legitimacy of the existence of a region with attacks on its side - this is stupid and not intellectually, and represents just the very unwillingness to argue respectfully with researchers from another field, which we regret when it comes to science. It is a pity that smart people who agree on most of the important things cannot but agree on everything else without exchanging insults. We should try to be above it.