David: Why do they want this Grand Unified Theory?

MG: I think it has a little bit to do with Occam’s razor: the idea that you want to look for the simplest explanation for everything, if possible. And if you look at nature, nature is complex: it’s very diversified. But perhaps we’re looking at nature with the wrong glasses. If you put the right glasses on, you would see that all that we see as different is really a manifestation of this single force, and so that’s Grand Unification.

David: Sounds awfully religious to me.

MG: It does, doesn’t it? Sounds like monotheism.

David: Yeah. Sounds like God in a white coat.

MG: That’s exactly what I think. I think that even though I’ve worshipped unification for many, many years in my career, I’m not like that anymore – I’ve sort of moved away.

David: Why not? What happened?

MG: Because I don’t see the point.

David: Wait a minute… What happened to you that you used to see the point, and then now you don’t? That’s a bit of a change.

MG: Yeah. So, what happened to me was that I was a full-fledged Platonist before that: I really believed in symmetry as beauty and beauty as truth.

Ard: Sure.

MG: And so what could be more beautiful and true than to have an all-encompassing theory of nature, where all different forces are really a manifestation of a single force. And you would say, everything came from the Big Bang; everything was one in the beginning, so there must have been a single force explaining all of that. It’s very compelling. I mean, we’ve had 3,000 years of monotheistic thinking, and so we are kind of biased to look for one explanation – these absolute explanations.

My whole career as a scientist has been within the expectation of unification, because I was young in the 70s, but I was doing my PhD in the 80s, and through this whole time we were, like, ‘Okay, come on, come on!’ and ‘Where is it?’

Ard: Soon it will come.

MG: Yeah, soon it will come. It’s next year. And what we’ve been seeing is it has not. So you have two choices here: one is it doesn’t matter that it’s not coming, because it’s there, and it’s just a matter of time before we find it. Faith – you know, there is faith in science, obviously. And the other one is let’s listen to nature. It’s trying to tell us something, and let’s pick it up. And what are the consequences of that?

So I came up with a solution to this dilemma which is the following – at least I’m happy with it; I don't know if everybody else is, but I’m happy with it – it’s that the most that we can expect to achieve as humans, in terms of understanding nature, is a simplified theory that could encompass everything as we know it now.

So it might be possible to have a unified theory of what we know now, but it is a fundamental mistake to call that theory a Final Theory of Everything because that goes completely against the spirit of science.

You know, science moves through a progression of ideas. We invent new tools, we find new things, and so who is to tell that we get this theory, ten years from now, the beautiful theory of everything, and then 150 years from now this new machine finds another force of nature? ‘Oops! That’s not part of our scheme. Now what do we do?’

So you have to encompass that. And there is no fundamental reason why knowledge should be final. Because the way we acquire information from nature is through experiments, through tools, and every tool has a limit. You can see that far, you can probe that small, but there is a limit to how far we can see.

Ard: So are you saying that maybe nature’s like an onion. You keep unravelling one bit and then there’s another bit beneath it and another one beneath it, and we shouldn’t ever say that we’ve gotten to the end?

MG: Right. I like to say that knowledge is like an island.

Ard: Oka, like an island? Okay.

MG: Yeah, knowledge is like an island. What we know of the world fits in an island. This island moves out, and sometimes it goes back in when we retreat. We say, ‘Oh, we understood that. No, no, we don’t understand that.’ So we go back. But as any good island, it’s surrounded by what I call the ocean of the unknown.

As this island of knowledge grows, so do the shores of our ignorance, because the perimeter of the island, which is the exposure to what we don’t know, grows as well. Because as you discover more about nature, you become equipped to ask questions you couldn’t even have anticipated before.

There is always going to be other things to find out, which I find… Some people think, ‘Oh, that’s so depressing. What’s the point?’

And to me that’s exactly the opposite. The point is there is always going to be something to find out. That’s exciting, you know. That is like we are always going to be able to be in awe and confused and trying to figure things out.

David: I like that, because one of the things that worried me listening to Frank and others is… I got this feeling that what they wanted was to get their Theory of Everything, where they’d have… We talked about a T-shirt – we’d have all the rules on it and that would be it. From that, everything in the universe would fall out. And I got the feeling that it meant that as we got closer to knowing this Theory of Everything that the universe just got quite boring.

It would just become a machine where I understood it all, and it would just be a glorified watch.

MG: Yeah, absolutely. I’m completely like that. I think it would be a sad day, the day that humanity declared it understood everything about the world. A sad day, because without the mystery we wouldn’t create any more, and that, to me, is just an awful thing.

The dream that we can figure everything out at a very fundamental level, to me, is just a fallacy. I think that just does not make sense. It doesn’t make sense from a philosophical perspective either because it’s based on an absolute, which is there is the possibility of knowing everything exists. And having an absolute is sort of like you can’t contrast that with anything else. You say, ‘the Theory of Everything is this,’ and then you say, ‘Well, how do you know it?’

‘Well, because we know all there is to know.’ And that is wrong: we do not know all there is to know, and we cannot know all there is to know. And to me that opens up this whole freedom of the surprises that come from the unknown.

David: Do you buy into the notion that some people… We’re going to talk to George Ellis about emergence, and I hinted at it there, that when the universe began, presumably there were the rules of physics, but there was no rule of natural selection. It just wasn’t here, but now it is, which seems to me that if you’ve been really quick, if you’d been a physicist around at the beginning and you worked really quickly, you could have understood all the rules of the universe, then life would have come along, and you wouldn’t know everything, because the universe had made itself up a bit. It was now more than it was and had an extra rule. Surely, if it can do it once, who are we to say it’s not going to do it again?

MG: Absolutely.

David: So this notion that we could find all the rules and that would be it seems to me you’ve found all the rules up to now.

MG: I think that’s exactly right.

David: Or is that just rubbish?

MG: No, that’s perfect. And I would say you can divide the history of the universe into four ages: the Physical Age, which is from the Big Bang to the first stars – up to that point, there was no chemistry. And then you call it the Chemical Age, which is when the first stars burn and create the periodic table of elements.

David: So that’s something new already.

MG: That’s something completely new. Then you have the Biological Age, which is when some of these chemicals self-organised to create life. And then after the Biological Age there was the Cognitive Age, which is when some of these living creatures became so sophisticated that they were able to ask questions such as the ones we’ve been talking about.

So these are the four ages, and we don’t know if that’s all there is to know. And they all have different laws. There is no way out, you know. There are fundamental limits to how we can understand what’s going on. It doesn’t matter how sophisticated you are, you still have to follow the laws of thermodynamics. There’s only so much information you can process. There’s always going to be noise in your system, and so there is always going to be some loss of information. And so ultimate knowledge, to me, is just another name for God.

Ard: Okay. And so you think these people, even though they are often arguing against God, are actually doing it in a kind of religious way? They’ve got a new kind of god, which is the god which will explain everything.

MG: Yes, they are trying to make human knowledge into the new God.

Ard: Okay.

MG: And, of course, that horrifies a lot of people, because humans are not supposed to be gods. We mess everything up. And so we should understand our limitations and go back to being humble about how we think about creation and about who we are, before we jump into this incredible notion that we can know everything.