Philip Glass and Mary Zimmerman: Stars in their eyes

Science, not politics, lies at the heart of the new opera about Galileo by Philip Glass and Mary Zimmerman. Rachel Halliburton met them in New York

"Shut yourself up with some friend in the main cabin below deck on some large ship, and have with you there some flies, butterflies, and other small flying animals. Have a large bowl of water with some fish in it; hang up a bottle that empties drop by drop into a wide vessel beneath it. With the ship standing still, observe carefully how the little animals fly with equal speed to all sides of the cabin. The fish swim indifferently in all directions; the drops fall into the vessel beneath; and, in throwing something to your friend, you need to throw it no more strongly in one direction than another, the distances being equal; jumping with your feet together, you pass equal spaces in every direction."

Those may sound like whimsical instructions to an amateur Noah with a mild interest in sport, but those interested in the history of science will know they introduce one of Galileo's most important hypotheses. In a modern world where the jargon-cluttered intricacies of advanced physics or microbiology seem increasingly to widen the distance between the artistic and the scientific mind, it is easy to be struck by the accessible poetry in the way Galileo set out his ideas on relativity. The image comes from his Dialogues Concerning the Two Chief World Systems and illustrates why, even though the Earth rotates constantly, we do not perceive its motion. The ship becomes a metaphor for the Earth, for when it sets sail, there is no effect at all on the speed at which the butterflies must fly, the fish must swim or the object must be thrown – just in the same way that we can walk, amble or remain rooted in our armchairs while our planet spins at approximately 1,040 miles an hour.

That sense of Galileo's poetry played a big part in the American director Mary Zimmerman's approach to adapting his life story as a libretto for Philip Glass's latest opera. Zimmerman is not well known in England, but her status as the directorial darling of Chicago and New York has been built up by adaptations of Leonardo da Vinci's Notebooks, The Arabian Nights, the Odyssey and, most recently, Ovid's Metamorphoses. In his New York East Village studios, Glass smilingly admits that one of the reasons he chose to work with Zimmerman is: "'Accessibility' isn't a bad word for her. Many people I've worked with – such as Robert Wilson or JoAnne Akalaitis [his first wife] – were very experimental, and there was a much tougher, hard-edged line to those productions."

Fans and detractors alike would agree that "accessibility" is a quality that has rarely graced Glass's enthralling but infuriating collaborations. Einstein on the Beach, the first, longest, most famous and possibly most difficult of his 18 operas, explored the beginnings of atomic energy and tested audiences by exploding the operatic form into a four-and-a-half-hour work, whose then-unique Eastern-influenced notions of rhythm blended with the avant-garde director Robert Wilson's arrestingly symbolic visual style. Galileo Galilei is far slighter, at one and a half hours, and has a distinct narrative, unlike Einstein's image-fuelled progress. Indeed, Zimmerman, whose trademark is to improvise a script through rehearsals, relates that Glass wouldn't write a note before she produced the whole, carefully structured libretto.

The director explains that both she and Glass decided that scientific imagery rather than the political aspects of Galileo's life was going to dominate their work. "I think that Galileo has mistakenly been made an icon of rationality because of his conflict with the church," she declares. "But I wanted to capture the great passion in his science – the fact that his groundbreaking theories were simultaneously influenced by an enchantment about the world. That was all connected to his religion."

As a director, Zimmerman can certainly do passion. New York is still buzzing with delighted reactions to her spellbinding production of the Metamorphoses, which is staged round a swimming-pool built in the middle of a theatre. Imagine a tear-stained girl on one side of that pool, begging her lover not to break their idyll of happiness by going on an ocean voyage. He tells her not to worry and strides out into the water, which suddenly takes on the bilious green of a stormy sea, chopping and churning uncontrollably until eventually he is dragged below the waves. His dying wish is for his body to be floated back to his lover, who waits for him on the shore: when she sees him, her grief is so transcendent that they are both transformed into halcyon birds – a process depicted by the two actors slowly rising up and flapping their arms with a dancer-like grace as they leave the pool.

That portrayal of the story of Alcyone and Ceyx gives an important clue to how Zimmerman approached a problem only partially answered by plays such as Michael Frayn's Copenhagen and David Auburn's Proof. That problem: what can make the dry seeds of scientific or mathematical theory bloom into life in the theatre? Her answer is to focus on scientists whose conceptual breakthroughs are imbued with an almost mythic wonder. She concedes that her subject matter – rather like the subject of Leonardo – lends itself more easily to picturesque dramatisation than to, say, the forehead-expanding equations of particle physics, and tells how her collaboration with Glass kicked off with one striking image.

"Philip was transfixed by the idea of Galileo becoming blind, and he had a picture in his head of this blind man sitting next to a telescope. This individual who transformed our way of seeing talks about his loss of sight in his letters as if it were a judgement upon him at the end of his life."

Zimmerman and Glass wanted the opera to build to an optimistic climax, so they have retold Galileo's life in reverse order, starting with Galileo questioning himself and God about the repercussions of his defence of the theory that the Earth orbits the Sun. It ends with an opera within an opera. "I found out from our conductor that Galileo's father, Vincenzo Galilei, was a famous composer, apocryphally credited with having invented the opera," Zimmerman says. "So I felt we should go back to a point where Galileo is seen as a little boy, watching an opera by his father about the Sun, Moon and stars."

Glass's score for Galileo Galilei is possibly his most melodic. "We've gone through 50 solid years of difficult music," he explains, "and I didn't want to make the music an obstacle. The issue here is not being on the cutting edge – I think that the beauty of the singing and the simple materials that we use provoke enough interest of their own."

I ask Glass if the far-reaching influence of his music makes him feel any affinity with Galileo as a man who transformed his age through his ideas, and he replies, "Some people think so, but I've never made that claim, and you rightfully would be suspicious if I did. One rather nasty critic said: you know that Philip Glass, he's not a very good composer, but he's good at working with people more talented than himself."

'Galileo Galilei', Barbican Theatre, London EC2 (020-7638 8891) 1–9 Nov