2023-03-07 Fallible Animals The Universal Constructor
Duration: 00:25:32
Transcript
Logan Chipkin
All right, I’m here with David Deutsch. David, thank you for joining me.
David Deutsch
Thank you for having me. Good afternoon.
Logan Chipkin
Good afternoon indeed. So I wanna talk about the universal constructor, which is a theoretical machine that can cause any physical transformation that can possibly be caused. Now, why is understanding the universal constructor important to understanding the nature of reality rather than it being merely an engineering curiosity?
David Deutsch
Yes, it’s more than just a curiosity, by the way. The idea of the universal constructor is basically ancient. It began with the idea in antiquity of cornucopia, which is a thing that produced an endless supply of whatever food you would like, delicious food. But then pretty soon people began to think about a machine that could produce anything you like. And this has been explored in science fiction and so on. So I don’t think it’s just a curiosity engineering-wise. It would be a dramatic and important innovation. But you ask about what is its connection with fundamental physics, it is basically a generalization of the idea of universal computation. And universal computation as conceived of by Babbage and Lovelace and then by Turing is really the only way to understand what computation actually is. A non-universal theory of computation wouldn’t be a theory of computation at all. That would be just a theory of engineering. So the theory of universal computation, which I then sort of brought into the quantum era by developing the theory of the universal quantum computer is the assertion that such a thing can exist is an assertion about the laws of physics. The laws of physics are such that there is a single machine that can mimic the computational power of any other machine to arbitrary accuracy. And all that you have to give it is fast hardware and memory. Now, the universal constructor comes in here because that universality is not the only one that could exist. And in fact, I think it is not the only one that does exist. There’s also the question of not just performing any computation, but performing any transformation of physical objects. And not if given enough memory and so on, but if given only knowledge. Because if there’s something you have to give it other than knowledge, which it itself couldn’t provide, then it’s not universal. So it has a similar but different logic from a universal computer. And its relationship with physics is a generalization of that of the universal computer.
Logan Chipkin
Now you wrote in the foundational paper on constructor theory that the possible existence of a universal constructor might be proved from independently motivated constructor theoretic principles. Now I know it’s still early, but I wonder, have you made any progress of, if not the proof itself, but what that proof might look like since the constructor theory program began?
David Deutsch
Yes, I have. In fact, I have been struggling to complete a paper on the universal constructor from within the constructor theory. And I think I have a proof, but it is rather cumbersome and clunky, and parts of it are not intuitively compelling. So as I say, I’ve been struggling with trying to complete that paper for some time now, but I have done enough to convince myself that, and to put this in a mathematical way, it is a theorem of constructor theory that the universal constructor exists. That is a machine which can be programmed to perform any transformation that any other machine can be programmed to perform.
Logan Chipkin
Let’s say hypothetically, if this proof doesn’t pan out, or if it turned out as you were working towards this proof that such a machine is possible, that it turned out that actually a universal constructor is impossible to build, what might that tell us about the laws of physics? Now, I understand it sort of depends on why the proof doesn’t work, but I wonder if you have any thoughts, for example, might it tell us that the principle of interoperability is false, or something along those lines?
David Deutsch
Yes, so as you say, what it would tell us depends on what exactly would go wrong, and what would seem to be irreparable in the proof. I think whatever it is that went wrong, it would be interesting. It would tell us that there isn’t, after all, the apparent connection between understanding the world and controlling it that there appears to be. So it could be that if there is no machine that can be given just knowledge to then perform any given transformation, then, well, I can’t quite imagine exactly what it would imply, but if there is something that you can’t program a machine to build, then that really means that there is something that can’t be built. And if there’s something that can exist, but can’t be built, then that means that there’s a, well, it might mean that there’s a resource in nature that is finite and not replenishable, not just a resource like negative entropy, but a resource like, let’s say, a monopole, a magnetic monopole, we think there aren’t any, but suppose that we’re wrong about that and suppose that there is exactly one magnetic monopole, then that would mean that any machine that included a magnetic monopole in its design, essentially, so that it couldn’t perform its function without the magnetic monopole, then that would mean that that particular machine could perform a task that no other machine can perform. And if the magnetic monopole falls out and rolls across the floor and you can’t find it, then the task can’t be performed at all. And if you can find it, it can only be performed once by that machine and there’ll be a maximum speed at which it can go and so on. So that’s the kind of thing it would say. It would be a sort of de-universalization of our fundamental understanding of the universe. We tend to think when thinking about more and more fundamental things, that the laws about fundamental things are going to not refer to specific objects. Like there isn’t just a law that applies to the Eiffel Tower. There are laws that apply to iron structures and to structures built in gravity and so on. So that any truth about the physics or engineering of the Eiffel Tower can be expressed in terms that do not refer to the Eiffel Tower. But that might be false. And if it’s false, then it would definitely mean that there’s no universal constructor.
Logan Chipkin
So if a universal constructor is possible to build, then presumably people are entities that can build them with the requisite knowledge, as you were kind of alluding to. So then why would a person not be considered a universal constructor since every transformation that a universal constructor can cause, a person plus a universal constructor could also cause?
David Deutsch
Yes, indeed. Well, the answer is imperfection. So a constructor is actually a limiting case, an unphysical limiting case of real physical objects. So there is no such thing as a literally a constructor for converting hydrogen and oxygen into water, for example. You can perform that with 99% accuracy or 99.9% accuracy, but not with 100% accuracy and 100% reliability. There’s always a probability that some of it will escape and so on. And for any given machine that can convert hydrogen and oxygen into water imperfectly, there’s another machine that one could build that would build it less imperfectly, but there is no machine that could build it with absolute perfection. Now you can regard a human being as a highly imperfect universal constructor in that given enough knowledge, a person could build a universal constructor that’s better than itself. And in fact, that’s the secret to the proof and to the theory of the universal constructor as I see it. But the thing is, suppose you need more memory than the brain has capacity for, then unlike with a computer, it’s not a trivial thing, just, oh well, we’ll give it more memory. With the universal constructor, you’ll have to say, oh well, we’ll have to tell it how to make that memory. And so we would have to be given the program for making enough memory to do the task of a universal constructor and so on. And then once we’re given all that massive amount of information to do all that, there might not be time in a human lifetime to do that. So therefore we’d have to be given a program that would extend the human lifetime and so on. So we see that the degree to which a human is a universal constructor, well, it’s rather Pickwickian in the sense because it’s so highly impractical and would require so much knowledge that we do not currently have that. And if we did have it, we could do the universal constructor thing much more easily. That it’s for most purposes not useful to consider humans as a universal constructor or a human at any rate. It could be that humans as a whole are. There’s also the fact that neither a human nor the set of all humans is obedient. A universal constructor has to be perfectly obedient and people and collections of people are disobedient. And in fact, disobedience is necessary for their more important functionality of explanatory universality.
Logan Chipkin
Have you given any thought to what the economic implications might be if and when humans commodify the universal constructor?
David Deutsch
This has been studied by many people before. I think people have had somewhat the wrong idea of what a universal constructor will look like, but it doesn’t make any difference for thinking about economic issues. I think one thing that many people may have got wrong is that the universal constructor won’t be as sudden a change, like a singularity. It won’t be a singularity because although it is true that a universal constructor can be programmed to build two more and each one of those can be programmed to build two more and so on. First of all, this will at first be done rather inefficiently, just as the very first one will have to be built by humans and inefficiently and so on. And secondly, the issue of ownership and value of raw materials does not go away once the issue of human effort goes away. The human effort will go away apart from the effort of programming universal constructors, but that’s non-trivial. So people will be writing programs in effect. I mean, that doesn’t mean that they’ll be doing the same sort of thing as programmers do today. It’s more like they’ll be doing the same sort of thing that scientists and engineers do today, mostly. They make designs in a computer. But then there will still be the issues. If you want to convert, I always give this example. If you want to convert Phobos and Deimos into busts of Napoleon, you will run into a problem that someone else wants to convert them into busts of somebody else. And this issue, we know how to resolve issues like that. It’s with ownership and private property and capitalism and also a regulatory framework that’s based on the rule of law and that kind of thing. So we know how to do that. But it does mean that you can’t just design a thing and have it built. It will still cost something. And how do you make money in a society with universal constructors? Well, you make money the same way that engineers do today by programming computers.
Logan Chipkin
Now, how might a better understanding of what is required to create a universal constructor improve our understanding of the physics of thermodynamics and information? And I ask because I know that Chiara Marletto and Vlatko Vedral and others have been doing some work with respect to how constructor theory can resolve some issues in both thermodynamics and information. And I know you’ve done work with respect to the constructor theory of information as well.
David Deutsch
Yes. Well, I think constructor theory can definitely help to provide deeper foundations to thermodynamics. Whether the universal constructor will is doubtful, but one can’t really tell until one has that theory. And I’m afraid the devil is in the detail here. Thermodynamics is important even when you build a steam engine and thermodynamics is important if you build a wide variety of machines and when they are built with universal constructors or with machines that are made by machines that are made by universal constructors. It will still be true that thermodynamics plays a role, but whether the foundations of the theory of universal constructors will have a role, I don’t know.
Logan Chipkin
You also wrote in your foundational paper of constructor theory that there must be a smallest universal constructor. Do you think it’s going to be interesting with respect to our understanding of nature and physics, the exact size of the smallest universal constructor or do you think that’s just going to be an incidental detail?
David Deutsch
My present view is, which has changed somewhat from when I wrote that paper, my present view is that it’ll be more of an incidental detail. I mean, it might be cool. It might be an interesting curiosity rather like asking what’s the simplest possible Turing machine is a curiosity, but it doesn’t help us with advancing either the theory of computation or the engineering of computers. It might do one day. I mean, it might come up and be relevant, but it doesn’t look as though it will be. And I think the same is true of universal constructor. I think the reason I had a bit of a misconception about that is that I hadn’t realized at that time how much of a bottleneck generating the knowledge to program a universal constructor will be. So say we find out one day that the smallest universal constructor is made of 37 atoms and that you provide those with the bootstrap program, which takes on board other atoms from the environment, from empty space or from the ocean or something generic. And it makes a bigger constructor, which makes a bigger and more powerful constructor and eventually gets to a usable universal constructor. Well, the thing is that your program for doing that will always begin with that same preamble. It’ll always begin with what this 37 atom thing must do to make a bigger thing, make a bigger thing and so on. And the important thing about the guts of the program will be what happens after that. So you may as well start with that universal constructor and have your other ones make that rather than make the smallest one.
Logan Chipkin
Now, David, I want to pivot to a more sociological topic. How has the research environment changed since you began your career? And what might be done to resolve any issues that have emerged since you started working?
David Deutsch
Yes, well, everybody has a unique path through life and through science and through the funding system and so on. And I’m probably one of the worst people to ask this question because I decided quite some time ago to leave the usual path. And fortunately, since I’m a theorist, I don’t have to equip my own laboratory or anything like that. So it’s relatively easy for me to work at home and to just use the facilities of university and pick and choose and not be paid and that kind of thing. So I can only tell you anecdotally what it seems to me. It seems to me that the funding system and the career structure for fundamental science has been in rather drastic decline during my lifetime. Not that it was great when I was a graduate student, but there were certain things that I have noticed. For example, when I was a graduate student, I got an interview, I was accepted, I came to a research group and on day one, I was doing research and it was research that I had discussed with my supervisor and I did that research. And from time to time, my supervisor suggested that I go to a course which he thought would be relevant to my research and I never did. And that was my experience of courses. Now that’s pretty much impossible. First of all, graduate students are compelled to go to courses and secondly, the courses aren’t chosen by their supervisor because the supervisor thinks it would be helpful. They’re chosen by the department because they think it fulfills some criterion that they have to meet to their bosses or whatever. Then a bit later when one is a postdoc, one applies for research grants. When I applied for a research grant, I had to fill in a form that was extremely short compared to today’s. I mean, it took maybe, I can’t remember, but maybe half an hour, half a day, sorry, to complete. And then I had to write an essay basically about what I was going to do and why this was interesting. That’s what the essay was about. I did not have to write additional essays about what the impact of this will be on the field and what the impact of this will be on the economy of the country and lots of impact things. And then not to mention lots of things that are not relevant at all, like for example, outreach. So the net effect of that is that the postdoc type people I know have to spend literally many weeks filling out the equivalent of that form. And then, okay, the next thing that I see, again, maybe I’ve seen only an unrepresentative subset of what is happening and it’s all much better than I think it is, but nobody has ever said to me that that is so when I complain. This application, instead of going to the person who will be your boss or the person who will be your collaborator or the department which is running a project along the lines that you want to do research in, instead of going to anyone who is actually connected with what you will be doing, it goes to a committee somewhere whose task is to examine all such applications that a given funding entity, usually a government entity is going to fund. So the people there are not connected with the particular research.
David Deutsch
They are not familiar with the particular problem. Well, of course they aren’t. In fundamental research, you’re more inventing new problems than you are in solving or almost more anyway, than you are in solving them. And the group, the research group that is working on this knows about it, but the further away you get from that research group, the less the people know about it. And it’s impossible for a committee to decide such an issue. So what they do is they construct a generic sort of questionnaire with ticks that have to be filled in boxes. And these questions in the questionnaire, because they are generic, they cannot possibly relate to any particular kind of research. So that means that the kind of research that is funded is research that can be justified by criteria that would have justified previous research, which is deemed to be successful. And that can only ever be incremental research, because nobody can determine from such a criterion that a new field or a new sub-branch of a field is worth doing research in. And still less when it comes to the boxes that are about what the impact is going to be. You can’t tell what the impact of research is going to be until you actually know what the result of your research is. We were just talking earlier about constructor theory and the theory of the universal constructor. And I was saying that I had certain questions I couldn’t really answer until I know how the proof comes out. So those are some of the things that I think have gone terribly wrong and which were nowhere near that wrong when I first entered the profession as a physicist. How to fix them, I really don’t know. I mean, I know what the state of affairs I’m looking for is, but I have deliberately steered away from administration, but also in particular from understanding how the present administrative system works. I have a horror of it in fact. So I don’t know how to fix it. I just know the attributes that a working system would have.
Logan Chipkin
Fair enough. Well, David, I appreciate all of your insights with respect to the universal constructor and also the admittedly perhaps bleak state of affairs in certain aspects of academia, but fortunately all problems are soluble. So David, thank you very much for your time. I appreciate it.
David Deutsch
I was about to say that. Yes, thank you. Thank you. Bye. Bye-bye.
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