Heisenberg: the Uncertainty Principle, written by Simon Stephens, is currently showing at Wyndham’s Theatre in London until 6 January 2018. It stars Anne-Marie Duff as Georgie and Kenneth Cranham as Alex and tells the tale of their chance meeting at a crowded train station and their ensuing relationship, which changes both their lives forever.

How did you first come across Werner Heisenberg’s uncertainty principle and what made you base your play on it?
The idea of the uncertainty principle is something that I came across in a conversation with a very good friend of mine, a computer scientist called Jon Sedmak, who is a significant figure in American computer engineering. He worked with Dell and Apple in the 1990s, and he’s key to the team that invented the notebook computer. In recent years he has become a big champion of British theatre and we’ve become friends. In fact, we met because there was a reference to Paul Dirac in my play Punk Rock. Jon was very excited that a playwright was referencing Dirac, so he took me out for lunch. We now meet every time he’s in London and we have lengthy conversations, during which he’ll go on an aria for 10 minutes about some scientific thought he’s had that astonishes me completely.

One of the many things that Jon said that blew my mind was his very simple definition of the uncertainty principle. This notion, as much as I understood it, means that observation and prediction render each other impossible, such that the precise observation of the whereabouts of a given particle means that the prediction of its momentum is impossible, or that a precise measurement of the momentum renders the actual observation of the particle impossible. I thought this was thrilling, not because I understand anything about physics, but because it struck me that was what life was like. If you watch people, if you know and study and think about people, the people you know best are the people who are most likely to do something or go somewhere that will completely take you by surprise. And if you have an understanding of where somebody’s going or what they’re about to do, it probably means you’re not looking at them properly. I was so excited by that, the way in which the scientific principle works as a metaphor for human behaviour, that I built the play around it.

Have you always had an interest in quantum mechanics or science in general?
I’m 46 and I come from a time when the delineation between sciences and the arts was really binary. Growing up, I defined myself as definitely into the arts, definitely into literature, definitely into music, and definitely not into maths or science. It’s a ludicrous position to take, but one I took very vehemently. It’s only through my son Oscar, who has just gone to the University of Oxford to study maths, and through my friendship with people like Jon Sedmak that I’ve come to realize that science and mathematics are as creative and vital and exciting as any kind of music I’ve grown up listening to or films I saw or plays I read or novels I read or any of that.

So did you research Heisenberg’s uncertainty principle any more than those conversations with your friend?
No, I really didn’t, which on the one hand is shaming, and on the other hand is shaming! We had a friend of the director, a scientist, come in to talk to the cast on the first day of rehearsal, and he tried to explain to us some of the implications of the thinking. I think there’s something very interesting about the emotional consequences of quantum thinking…I find, weirdly, there’s something reassuring about it. It is good to be able to accept uncertainty, unpredictability, chaos, as being a fundamental element of what it is to be alive. We don’t know what’s going to happen. We have an impulse to try to impose a narrative on the chaotic. But if we can live without doing that, if we can accept the chaotic, if we can accept the wildly unpredictable, then maybe we’ll live with a certain level of grace, and that’s a good thing, isn’t it?

Is Heisenberg the most scientifically themed script you have written?
I’d be really loathe to say that it has a scientific theme. But just as a human being, my relationship with my son Oscar has been so illuminating, especially as he became increasingly excited by pure mathematics. The notion that the scientific terrain excited and inspired somebody who was so important to me made me reconsider that world. And that reconsideration is actually found in lots of the plays that I’ve written since he’s become a cognitive adult. There’s a quiet nod to it in my stage adaptation of The Curious Incident of the Dog in the Night-Time. It’s not that I’ve written other plays inspired by scientific theories, but I’ve re-accommodated scientific thinking into my thinking.

One of the things Oscar always says to me is that the essence of science for him isn’t necessarily the rudiments of the history of scientific thought, so much as the essence of scientific approach. The idea that things can be tested and proven, and the Galilean notion that we assume things not to be the case until we test and test and test them, until we’re forced to conclude that they are the case. And that type of scientific thinking, that quite secular scientific thinking, has been something that has inspired and galvanized me as an artist.

What do you feel about the perceived boundary between arts and sciences today?
I don’t spend enough time with teenagers now to know whether it’s still as paralysing a concept as it was when I was a kid. All I can say from my own experience is that when I started to get my head around characters like Dirac or Heisenberg, when I found out about how radical their thinking was, it reminded me of the kind of radicalism of the great artists and great musicians that I grew up with. There was something as beautifully punk about Heisenberg as anything Lou Reed or Iggy Pop ever did. They might have done it differently, but the ferocity of their intellectual thinking in defiance of all received wisdom is common to them all.

The function of the artist is to be a great truth-teller, even when it defies convention, and that’s what the great scientists do as well as the great artists. They ought to be mutually dependent upon one another. How we do that is through our teachers, through the way we talk about science, through the way we talk about arts. I think it’s happening more now. I think there are more and more artists who are excited by scientists. And the scientists I’ve spent time with, they’re much more excited about the unprovable, and that seems to me to be completely the terrain of the arts, as well. I was sceptical about maths and science when I was a kid, because I thought there was a wrong answer. But the more I’ve come to learn about science, the more I’ve realized that it’s a constant, evolving, communal exploration and experiment. And to me, that is exactly like making art.