Transcription
Sean, it's been said that the most fundamental question we can ask is, "Why is there something rather than nothing?" But we know there is something. We see. We know what for, whatever. So therefore, the question is, why is there something rather than nothing? And physicists answer this by showing how virtual particles can come into existence from the nothingness of of of of space, or without space. But you have to have all these quantum mechanical laws to begin with. So how do you deal with that question?
Yeah, well, I think that there's a confusion between different versions of this question. Because like many questions, you can sort of casually ask on the street, a more careful, rigorous scientific examination gives you different possible meanings to the terms. So if what you meant by that question was, "How could you start in empty space or a quantum vacuum and then evolve according to the laws of physics into a universe like we see?" we have plausible answers to that question. There are physical theories that do that. We don't know whether any of them is right. We don't have the final answer to those questions, but it doesn't seem hard. There's no insuperable obstacle.
Many people have in mind the deeper question of, "But why is there quantum mechanics? Why are there laws of physics rather than no laws of physics, no thing at all?" And that, I think, is, you know, a different question. It's a respectable question to ask. And the only plausible answer is, "Why not?" Why, in the world, would you ever expect there to be nothing rather than something? It's not the kind of question to which we are ever going to get an answer that says, "Oh, it's because of this that there is something rather than nothing." So ultimately, there has to be a brute fact.
Absolutely. I think the brute facts are things we need to accept. The existence of the universe is probably one of them. So the existence of the universe, based on the laws of physics. And so the brute facts are the laws of physics, not the existence of the universe. The existence of the universe, in a sense, is a derivation of the laws of physics. That's I think that when you talk about the laws of physics existing, that's a different thing than the universe existing. So I'm not sure how to distinguish which is sort of prior or anything like that. I can't imagine the laws of physics existing without a universe existing, but the universe that we have obeys the laws of physics. So I think they come as a package, you know, the universe and the laws of physics.
That's an interesting point because that's different than saying the laws of physics are the brute fact and that, in the course of time, given enough time, it would throw up a universe. Yeah, a different. I would say your claim is that the universal laws of physics are cotemporal. I would say that there is a quantum state that exists, and it obeys the laws of physics, and the quantum state is the universe. Yes.
And so would would there have ever been, I use the word "time" right? You know that you're going down the wrong path. But could there have ever been a disaggregation between the existence of the universe, however you're defining it, and the laws of physics? Could that ever have been? In my way of thinking, no. There is a quantum state that evolves through time according to the laws of physics, and that's all there ever was. And again, I'm happy to be wrong if we come to a better understanding. That's the best picture I can come up with right now.
Well, it does seem to be more coherent because if you have the laws of physics by itself, and that throws up a universe, you have, and you assume that the laws of physics, if it was a brute force, was there forever, you know, why did it do it now? Or all those kinds of questions. Yeah, and several very specific cosmological models have exactly that problem. They have a universe that sat there doing nothing for infinity years and then started expanding. And I don't think that's a very viable way of thinking.
Now, some cosmologists say that the theory of inflation, which began our understanding of the current universe, at least, requires there to be a beginning. Yeah, they're wrong, I think. You know, for one thing, there are theorems about what spacetime can do. And you take spacetime into the past, and number one, you make some assumptions, and number two, under those assumptions, you say the classical spacetime comes to a singularity. But those assumptions might be wrong. That's always a possibility. And classical spacetime is not the fundamental answer. We know the world is not classical. We know there is quantum mechanics. No one has a quantum theory of gravity for which there's a theorem that says the universe had to begin. In fact, it is trivial to prove the opposite theorem. If you have a time-dependent quantum state, it is obviously extendable infinitely far into the past.
So your position, to be clear, is that there's a quantum mechanical state that is the universe and the laws of physics as a singular package? That's right. And so does that mean that, from our perspective at least, that the universe is infinite in both directions, past as well as future? Yes. And and that, at least has coherence, whether it's right or not. That's right. Yeah, exactly. So in my favorite cosmological model, which again is always subject to updating when new ideas or data come in, the universe doesn't have a beginning. It does not come into existence at a moment in time. It always existed. It looks different from moment to moment, and we are only observing a tiny part of it. So we don't even know what the whole thing looks like. But there's no need for an explanation to cause a beginning, something coming to existence out of nothing.
So if I'm with you on your path, I have one final question for that. And that is, your quantum mechanical state with the universe and the laws of physics coexisting as a package, is that necessary? I don't think there are any necessary things other than sort of tautological, logical, or mathematical statements. So it is, in essence, a pure brute fact. It's a contingent fact about the world, a brute fact that might not have been the case, but it is the case.
So you would say that it could have been the case that there were absolutely nothing, but that's not the case? I think, yeah, there are many possible worlds. Ours is one of them. There are others that are very different. There's nothing necessary about any one of them. What different point is there? It's necessary that there be one other than nothing? I see no reason for there to be anything necessary about the existence of a universe at all. So therefore, there could have been nothing. There could have been nothing in which there were no quantum mechanical state, no law of physics, no universe, no nothing. There could have been that. I'm perfectly willing to contemplate that nothingness, the absence of any universe or laws of physics, is absolutely a possibility that might have been in some space of possibilities. I also don't care at all. I know there are other physical universes that I think are very real. And I might be wrong about the nothingness. What I care much more about is the actual universe in which we live.