David: You are not one of those who think that mathematics is woven into the fabric of the universe?
MG: So, the question of mathematics being the language of God, so to speak, or, sort of, the blueprint of reality, right? There is no question that there are patterns in nature. They are repetitive and they can be described through mathematics in beautiful ways.
You have not just symmetric patterns, or almost symmetric patterns – I like to make that distinction because nothing in nature is perfect. You have periodicity in the orbit of planets, and things like that. Clearly there is order, but I think to just say that this sort of symmetry in nature is the hidden code, so to speak – that all you have to look for is that symmetry – is missing half of the story.
David: What’s the other half?
MG: The other half is the role of asymmetry in nature. There is a lot of imbalance in nature, and it’s really through the complementary roles of symmetry and asymmetry that nature creates. A lot of stuff happens because of this imbalance between the two.
Ard: Give an example.
MG: I have lots of examples. One good example is in life. It turns out that proteins, which are made of chains of amino acids, like big molecules, and these amino acids they are basically molecules and they have a carbon in the centre, and then they have four sticks coming out of it. And it turns out that they come in two ways. They can be what we call left-handed and right-handed, jby the way in space they look like. And it turns out that if you go and you synthesise an amino acid in the laboratory – it was Pasteur that discovered this – you get 50/50: fifty percent with the left-handed shape and 50 percent with the right-handed shape. When you look at the amino acids in all living creatures, from bacteria to a sequoia, they all come only in the left-handed shape.
Ard: So, why…?
MG: The right-handed shape just is not there. So there is a fundamental asymmetry between the two, and without that asymmetry, the lock-and-key mechanism that proteins need to, kind of, fold and split and create, be part of reproduction, etc., wouldn’t work.
MG: And we do not know why this is true, okay? We just know it’s true. It’s there. It’s fundamental for life. So that’s an asymmetry which is very important, for example.
Ard: How about matter and antimatter?
MG: Exactly, so there you go. You know, that’s the good physics example: the fact that Dirac’s equation predicts that there should be as much matter as antimatter in the universe. And antimatter is nothing so esoteric that goes up instead of down, or anything like that. It just means a particle that has an opposite electric charge but the same mass. So, for example, the electron, which is negatively charged, has an antimatter particle called the positron, which is positively charged.
In principle, they should come in equal amounts, but when you look out, you find out that there is no antimatter out there – very, very, very little. And that’s good because if there were as much matter as antimatter in the universe, we wouldn’t be here.
David: We’d have all gone, pfft!?
MG: Exactly, because matter and antimatter, when they come together, they disintegrate into a puff of gamma rays – very high-energy radiation. So if you find your anti-person walking around, don’t shake hands. And so that’s the story, and we do not know. I spent a long time trying to understand what sort of causal processes may have happened early in the history of the universe that would have biased one form over the other, and there are all sorts of ideas – none of them is very compelling right now.
Ard: Okay. That’s a big mystery.
MG: So you need both. And I think it’s this yin and yang kind of thing, you know? You can’t just look at this reverential perfection, symmetry, as, kind of, the language of God, where nature is showing you that you really need both to make sense of things.
Ard: But there is some beauty to this combination between symmetry and broken symmetry.
MG: I think so. I have been proposing that there is what I call the aesthetic of the imperfect.
MG: Physics is a little old-fashioned, in a way, in thinking that it’s really the perfection that counts. It’s truth, right? The arts and music, they moved away from that in the early 20th century, and I think we’re still stuck in it.
Of course, symmetry’s fundamental: you cannot be a serious scientist, and physicist in particular, without having deep respect and veneration for symmetry. But symmetry is often an approximation to the real thing.
There’s this joke about the physicist that looks at a cow, and he says, ‘Consider a spherical cow as the first order approximation to what a cow is.’ And it works quite well for many things, right? If you want to collide cows at high speed, it’s a good approximation. But it’s not a good approximation if you want to milk the cows and things like that.
Ard: So do you think that when we understand biology better, that this aesthetic of symmetry won’t be the right way of thinking about it?
MG: Yes. I think life is a great example of the importance of asymmetry. You know, I have another example, which is Marilyn Monroe. So, Marilyn Monroe had a beautiful little mole. Imagine if she had two equidistant moles, how ugly she would look. So symmetry is not always beautiful. There is this breaking of symmetry, and I think we should embrace a combination of both.