(Complicite, on tour)

"I'm here to see Complicated," said the schoolgirl in the queue at Plymouth's Theatre Royal. "You mean Complicite," the ticket seller corrected. But the schoolgirl's mistake was prescient: Theatre de Complicite's new production is complicated.

At its heart, A Disappearing Number is an account of the collaboration between the Indian genius Srinivasa Ramanujan and the English mathematician GH Hardy. Ramanujan's story is a real-life fairy tale. Born in India in 1887, he taught himself mathematics. By the age of 25, he had developed some remarkable insights. But he was working as a clerk in the accounting section of the Madras Port Trust. He wrote to Hardy, who was then at Cambridge: "I have had no university education but I have undergone the ordinary school course… I have been employing the spare time at my disposal to work at mathematics… the results I get are termed by the local mathematicians as 'startling.'" Hardy soon realised he was dealing with a genius, and arranged for Ramanujan to come to Cambridge. By the time Ramanujan died—aged only 32—he had compiled more than 3,000 theorems, some of which are now important in new kinds of mathematics, such as string theory.

Most of Ramanujan's mathematics is out of reach of the average theatregoer. So the play's problem is how to inject a sense of why his work matters and what it was about while accepting that the audience has not come for a lecture. This problem faces any theatrical treatment of science and scientists; indeed, it is the central problem of the genre.

Playwrights have found several ways of dealing with the conundrum. At one end of the spectrum are theatrical lectures. These are not plays in the traditional sense, although they can be dramatic, even thrilling. An example is Theatre of Science, which ran in London's Soho Theatre a couple of years ago. The brainchild of Richard Wiseman, a psychologist, and Simon Singh, author of Fermat's Last Theorem, this was a series of demonstrations that culminated in Singh climbing into a coffin-shaped wire mesh cage, which was then zapped with a million volts of electricity. How come he is alive today? Because the coffin served as a Faraday cage—the wire mesh conducted the electricity, and prevented it from reaching the person inside.

More usually, though, theatrical treatments of science minimise the didactic and examine what it is like to be a scientist, or explore attitudes towards knowledge and truth. Often this is done through biography. Thus Brecht's Life of Galileo (1938) is in large part a study of oppressive government, here represented by the papacy. Central to the play is the foolishness of suppressing knowledge for ideological reasons. Brecht's interest in this subject is hardly coincidental: his work was banned by the Nazis.

Michael Frayn's Copenhagen (1998), another biographical science play, deals with similarly big themes: courage, the nature of memory and the impossibility of knowing what goes on in someone else's head. The play is a clever speculation on what might have taken place at a known historical event, a meeting in Nazi-occupied Copenhagen in 1941 between Werner Heisenberg, then head of the German nuclear programme, and his former mentor and friend, the theoretical physicist Niels Bohr. The three characters—Bohr, his wife Margrethe and Heisenberg—put forward several possible accounts of that night. Was Heisenberg a hero who deliberately sabotaged the German bomb programme? Or, in concluding that such a bomb could not be built, did he just make a mathematical mistake?

Unlike Brecht, Frayn imbues the play with a sense of the science his characters were involved in. This involves some artifice: the uncertainty of what happened at the meeting is used as a metaphor for Heisenberg's principle of quantum uncertainty—an entirely different kind. (Quantum uncertainty says that the more precisely you measure one aspect of an atomic particle's behaviour, such as position, the less precisely you can measure a related aspect, such as momentum. This uncertainty is inherent: you can't know. Uncertainty about what happened on a particular day is merely caused by not having the information.) But the play succeeds in getting across the excitement of science, especially when the two men reminisce about collaborating in the 1920s.

An alternative to biographical plays are those about fictional scientists; often these feature characters who are rare in real life. The hero of David Auburn's Proof is a female mathematical genius; the hero of Cassandra Medley's new play Relativity is a black female biologist. Proof deals with questions about the nature of genius: could an amazing and newly discovered mathematical proof have been written by a young woman, rather than her late father, who was a genius before he went insane? Here, the didactic problem is sidestepped altogether, and the mathematical context is provided through light jokes, such as the fact that the number 1,729 is interesting because it is the smallest one expressible as the sum of two different pairs of cubes (if you're interested, 1,729 = 1^{3} + 12^{3} = 9^{3} + 10^{3}). Relativity examines the genetics of race: our hero's mother is a leading black supremacist, whose geneticist daughter knows her ideas to be nonsense.

Complicite's A Disappearing Number combines elements of each of these approaches, plus a dash of surrealism and the heavy use of music and video. The cast is complex: some of the characters are real, others imaginary. Among the imaginary ones, there is that rare specimen: a female maths professor. The play opens with a lecture. A woman in a white lab coat and glasses introduces us to the idea of an infinite series of numbers (such as 1, 2, 3, 4, 5… or 1, 2, 4, 9, 16, 25…). But then she starts to expound on a set of equations which quickly become so complicated as to be comical.

Layered over this lecture is a second one, given episodically, by an imaginary modern-day Indian physicist, about Ramanujan's collaboration with Hardy. As the guest lecturer talks, the events he describes unfold before us. Ramanujan sits in his dhoti, scribbling furiously on a slate; Hardy sits in his office at Trinity College, reading Ramanujan's letter; after many difficulties, Ramanujan arrives in Cambridge, where he suffers terribly from the cold; war breaks out; theorems are written; Ramanujan gets sick, invents the mock theta function, and dies.

Put like that, the narrative sounds simple. But it is not. The action is non-linear, moving back and forth in time and space in a disjointed, fast-cut fashion more common in films. Layered over the lecture on the life of Ramanujan are several extra imaginary plots and subplots. The dweebish husband of the female professor of mathematics becomes obsessed with a particular infinite series: 1, 1 1/2, 1 3/4, 1 7/8… which continues approaching, but never reaches, 2. His wife has a miscarriage; later (though we see it earlier), she dies of a brain haemorrhage in a train carriage in India; and so on.

Remarkably, the play coheres. And it leaves you with a greater sense of numbers. This is true in the trivial sense that you become more aware of the extent to which numbers are part of our lives—telephone numbers, hotel rooms, times, dates, taxi numbers (1,729 makes an appearance here too). But it is also true in a deeper sense. The magnitude, if not the significance, of Ramanujan's contribution is clear. Moreover, while much of mathematics may be out of reach to most of us, the repeated appearance of the comically complicated lecture gives a glimpse of what could be done with numbers if only we had the skill. And somehow, this play conveys a sense of the infinite—the infinity of numbers, the infinity of time.