Don Page - Physics of What Happens

Don, we're here at this FQXI conference in Banford, the Beautiful Art Museum. One of the points of this conference is the nature of events, what that means in quantum physics and in general relativity. How can an understanding of events help us with some of the deeper issues that we have to face? Well, in basic quantum mechanics, we have a state space and a quantum state, but they're both very abstract. So, of course, we'd like to relate it to things that happen or things that we observe. And I'm not really sure what basic things there are other than sentient experiences or conscious perceptions. So, for me, a lot of times when people talk about events, the events that I think really do occur are sentient experiences, what a conscious observer is aware of, all at once including your visual sensations and what you can taste and hear and feel and smell and memories and the qualia of the particular nature of what red, blue, and green look like and your memories and so on. Isn't that something like an accident of evolution and there's one isolated planet and one isolated system and one galaxy? I mean, how could that be that important? Well, I think it's very rare on a per-planet basis, but in some sense, I think it's a little bit of the point of it all because that's the stage at which we and other conscious beings actually become aware of things and we can actually have an experience and experiences can be positive or negative or neutral. I mean, I'm having a happy experience in conversation with you now and, of course, other times we have a headache, it's a negative experience. So, in some sense, I think it's kind of a little bit of the point to it. I think it's one of the main reasons that God created the universe so there can be sentient beings that can experience happiness and joy and even for advanced beings like us, have a fellowship with God and other things that we experience and that, I think, requires consciousness. Okay, that's fine and believe in God or not believe in God, that would affect human beings, but it can't affect the quantum systems of other parts of the universe that are inhabited or before human beings ever came into existence, there was still quantum stuff happening. Well, there was certainly quantum stuff. Now, exactly what's happening in the quantum state is a little bit ambiguous to me. I mean, it depends. You can certainly make ways of defining things in which you can say things happen, but in some sense, the most basic description of the quantum theory is in terms of the quantum state. And then there are things called operators which could change the state and there's also the property of theory that a quantum state gives what we call expectation values to operators. It means for every operator, there's a complex number associated with it. But that's all very mathematical and that by itself doesn't seem to have any obvious physical interpretation. So it's not clear to me what's going on until you add some extra structure. And I mean, one structure that I do believe is there is consciousness and conscious perceptions. Of course, there may be other preferred structures too. I mean, maybe in some sense, atoms are fundamental, but I don't know. I mean, at present, it's not obvious to me what within quantum mechanics definitely refers to atoms, rocks, chairs, mountains, whatever. I mean, they seem to be, at least from a human viewpoint, with our consciousness, they seem to be entities that we have good approximate descriptions for. But whether they're really in the quantum state until you bring in consciousness, I don't know. So what happened before there were ever any sentient beings? Forget human beings, any kind of sentient beings, the universe was still cooking on. Well, certainly in the viewpoint that we have, we think that in some sense, there was an emergent space-time. And that in some sense, we have a universe that's expanding from having been much hotter and smaller long in the past. But exactly how to pick out the variables to say what is the size of the universe and so on, if you just start from the bare quantum theory, which just has what we might call a Hilbert space, which is a space of states and then some quantum mechanical state, it's technically it's a ray in the Hilbert space if it's a pure state or it's a density matrix or C star algebra. I mean, there's a bunch of fancy mathematical names for these things, but they by themselves are rather abstract. I think most physicists do believe that in some sense, there must be sort of some preferred parts of the wave function, some preferred operators that have to do with space-time and with quantum fields and so on. But it's not completely clear how do you get these structures out? They do seem to be structures that have to be in addition to the quantum state. And I myself am sort of agnostic as to whether it's sufficient only to have the operators that connect it to the conscious perceptions or whether as fundamental or whether and then from those we build the ideas of space-time and of fields and so on, or whether there's also a set of fundamental fields and geometry and so on, such that the quantum state gives something like a quantum space-time and quantum fields as fundamental besides the sentient experiences. That's something I'm agnostic as to whether there's more than just the sentient experience. But how can you be agnostic because there was a time when the universe was developing and there were no sentient beings. Do you have some sort of a retroactive... Well, I'm just saying in some sense saying that there was a time is adding some structure to the quantum state. So I don't know whether there is something fundamental that you can say there is a time. I mean, we certainly talk as if that is some important, at least emergent element from the theory. But whether it's really fundamental and whether it's an additional fundamental element besides the consciousness... See, if it was only the consciousness that was fundamental and the sentient experiences, I would say, well, it would be in terms of those that we would describe things of the early universe. We would make up a story that helps us explain without going into the full quantum theory that helps us explain in somewhat more human levels what things happened in the past. But the question is, is that story really about something fundamental that did happen then? Or is it something that we use that it's a convenient way for us to get an approximate description of the quantum state that led to our sentient experience? And in that case, which sounds very strange, of course, would our sentient experience now somehow choose among various consistent histories that the past might be because of the sentient experience that we have now? Is that part of it? Well, in some sense, I suppose that the part of the quantum state that leads to our experience, in some sense... Well, in some sense, you could say it doesn't have to be the whole quantum state. So it could be the part of the quantum state in which there is some fairly particular past that the universe... That when we describe it in terms of size and so on, that the universe was much smaller and hotter and so on. Whereas if you perhaps did not restrict to the sentient experiences, I mean, maybe there's big parts in which there's no spacetime at all. I mean, people in string theory often say that maybe spacetime is not fundamental, that there's something more fundamental. Although I don't think anybody has a really clear description. It's very hard for us to describe things without using, in some sense, spacetime terms. Although there are some in terms of matrices or other mathematical entities. So how do you conclude when you look at the nature of events? You're on the side of sentient consciousness is really important. So I take sentient consciousness as being sort of fundamental. And other events, I'm more agnostic as to what extent that they are fundamental. I mean, it's certainly a very good and approximate description to talk about events. But are they really part of the fundamental building blocks? If you talk about events other than sentient experiences, I'm agnostic about it.