Shackleton's lifeboat James Caird, on display later this month at the National Maritime Museum's Greenwich exhibition South, inspires genuflection in New York, where Shackleton (played by Kenneth Branagh in the imminent Channel 4 film of his epic expedition) is being elevated into a paragon of enlightened leadership for American businessmen. Even Belgians joined the first Polar landrush; Ukrainians are today's unlikely tenants of the former British Faraday Station. Scott's modern successor is the British Antarctic Survey, whose far-ranging experiments, embracing study of the ice sheet, geology, zoology, terrestrial and marine biology and bacteriology, proved its major importance by first alerting us to the thinning of the ozone layer.To publicise its work and celebrate a century of British Antarctic exploration, the BAS has come up with the bright idea of commissioning with the Philharmonia Orchestra a piece of music that harmonises ­ if that is the word ­ with its longstanding record of shovelling back scientific boundaries. Unlike Vaughan Williams, who was obliged to conjure up his eerie image of Polar climes (originally destined for the John Mills film Scott of the Antarctic) from a Surrey drawing-room, Maxwell Davies has not only spent half a lifetime practising the hardy life by lugging up sacks of driftwood to off-the-beaten track Orcadian crofts, but was invited to spend four icy weeks at the BAS's Rothera Station, on the Falklands side of Antarctica.Still, for one used to charting the subtly shifting tides of the unbenign Orkneys, didn't the static white landmass seem a bit of a comedown?"Not at all. What I've sought to do is to convey the sense of awe one feels in such an extraordinary place and landscape.

You can't recreate Antarctica literally, but I've attempted to recreate something of the impression it made on me."Two things distinguish this from my preceding symphonies: the structure, which is different from anything I've done before; and also the way it breathes ­ a very particular way which I think will be very clear from the outset It has to do with slowness, vast expanses, aeratedness. You get a hint of it in the Fifth Symphony, but this is the first time I've done it on this scale."I was very taken with the BAS's scientific research ­ particularly the fact that there are single-cell creatures under the snowcap whose life and day is so long, they live thousands of years. Their sense of time, if they have such a thing, would be totally different from ours ­ a year is like a single day and a night."I remember when I was writing Ave Maris Stella being acutely aware that in the Orkney cliffs opposite I could see millions of years superposed in the rockface; and imagining then some kind of creature ­ I didn't know they actually existed ­ to which a single rising and setting of the sun would be like one second ­ a mere streak across the sky; and a whole year like a single band of light. And I recall superposing these different time patterns in Ave Maris Stella, where it almost slows down to stop.

I didn't feel I had the technique to do much with it then; but now I can make the architecture consciously refer to that kind of rhythmic structure ­ although in a 30-minute piece you can't do it literally; you have to suggest it."The timescale of the symphony articulates very slowly, and the motion of several sections is slow: I've avoided putting in so much surface material that it prevents one perceiving that. Instead, I've made it very translucent, so you get right to the core of the material. At the start everything moves very fast on the surface, but there's a very big, slow, chunky rhythm underneath it."At the end, I decided that if you were going to look ahead to a final meltdown of the ice cap, there'd just be the hard rock jutting amid water. So musically that's what I've done ­ left just the hard rock."Certain sections follow one another as if they were taking up again something that's been going on before ­ as if you're 'dipping into' something that exists continuously right through.

I think you could compose it out so that all the levels joined up; but in the symphony you get only some of them. And I wanted to make an orchestral texture that felt very cold, so I've done quite a lot of wide spacing, especially in the lower parts, which makes it feel quite chill, and creates a sound that suggests distances."Amid all this beauty I was acutely aware of 'junk' ­ both the scattered detritus of former expeditions, which is only gradually being shipped back to the Falklands for disposal, and particularly the pop music blaring out from the hangar, making the worst kind of sound pollution, together with the mechanical noise of vehicles whizzing about. So I've created a corresponding 'junkyard' section where I refer to past things I've written ­ I won't say what, but the style changes fairly abruptly, so I think it'll be fairly obvious," he says."I don't actually refer to Vaughan Williams's Sinfonia antartica, but there is some back-reference to my own music. I used the 'Dum Complerentur' plainchant in Veni Sancte Spiritus, and in several works since then.

But here it's deeply embedded: you'd have to work very hard to find it, because it's transformed through half a dozen filters of magic squares."The one piece I kept thinking of, and in a way referred to, is my own Stone Litany, an immensely stark orchestral work that immediately preceded my seven earlier symphonies. The 'Antarctic' [No 8] reminds me a bit of Tapiola, which has a possibly similar relation to Sibelius's cycle of seven symphonies. But it isn't a tone poem ­ I'm not trying to describe things as such. Apart from the brandy glasses, which I used in Stone Litany ­ a cold image that reminds me of that very individual light that comes out of an iceberg ­ there are just two specific sounds: the massive 'icebreak' near the beginning, which recurs several times, although by the end you probably wouldn't know it, because it's stripped down beyond recognition; and the 'snow avalanche', a falling of fine snow which is quieter than quieter than quiet. But there was a big sense, too, that I'm saying farewell to writing for orchestra, so it probably has something of an elegiac feeling, particularly towards the end."The 'Antarctic' Symphony receives its premiere at the Royal Festival Hall, London (020-7960 4242) this Sunday at 8pm, and will be broadcast on BBC Radio 3 on Monday 7 May at 7.30pm. Further performances at Leicester (8 May), Brighton (10 May) and Kirkwall (23 Jun). The similarities between Debussy and the leading Japanese composer of recent times, Toru Takemitsu, are almost too obvious to mention.