10 January, 1996: a disused paint factory in St John's Wood. A bomb- maker's workshop-cum-living space is chaotically crammed with incendiary devices in various states of completion and the personal detritus of its absent occupant. In the centre of a large empty room sits the sparkling sphere of a 10 kiloton nuclear bomb.
"My work is about a series of different empowerment strategies," says the artist Gregory Green, who is bringing Brixton's Cabinet Gallery and the Saatchi Gallery as close as they are likely to come to Doomsday. "I'm involved in exploring different strategies that are available to you and me and other people." Like making bombs, for instance? "I've started with what we understand to be a traditional way to achieve power, and that's through the use of violence. The bombs and the workstation mimic the tools and tactics of a low-tech or basement terrorist."
But this, of course, is art. "I'm building a nuclear bomb, but I'm also building a sculpture," says the 38-year-old American artist. Green is part of a long tradition of artists employing danger in their work - Dada events regularly ended in pitched battles, Yves Klein hurled himself off a wall and blow-torched his paintings, and in 1971 Californian performance artist Chris Burden even got a friend to shoot him in the arm in the name of art. But he also fits into an increasing tendency among many of today's artists to present art as real life. Whether it is Rirkrit Tiravanija cooking Thai food in an art gallery or Gillian Wearing videoing the reactions of south Londoners as she walks down the Walworth Road with her face bandaged, the work of these artists is intended to question the world we live in and how we function within it.
What's scary about Green's work is how easy it is to make. "I'm not a tech-head," he insists "I just know how to use a library. The technology in a 16-ft missile, for instance, is a lot simpler than you would ever guess. The amazing thing about nuclear bombs is that they are incredibly easy to build - which is quite frightening when you think about the breakdown of the controls over nuclear material nowadays."
While mechanically complete down to their timers and igniters (the pipe bombs use children's alarm clocks or cooking timers), Green's bombs contain no explosives. But that doesn't mean they can't be activated - each piece comes with a set of instructions for their completion: just add petrol to the puffy nuggets of polyurethane inside the firebombs and you have napalm, replace the baseball at the core of the nuclear bomb with a sphere of plutonium 239 exactly the same size, and you have a potential explosion half of the one used on Hiroshima. "The responsibility for actually completing a live weapon is left in the hands of the owner - until the devices are armed they have the legal status of models."
The slight, mild-mannered Green doesn't come across as a subversive art terrorist. And he doesn't see himself as one. The bombs are just a small part of his investigation into how individuals can take power. "People ask me if I want to blow things up - but I'm really not interested in doing an Arnold Schwarzenegger movie or anything like that," he says. "I don't see myself as the person with the answers, but a guide through the options. I'm going through this series of projects to illustrate different strategies that anyone can use."
Green grew up on US airforce bases in America and Europe as the son of a military air-traffic controller, but his art cannot be explained simply by his close proximity to military hardware as a child. "A lot of people have assumed that because I was a military child I became interested in weapons, but that's misleading," he insists. Instead he claims that the two crucial factors in influencing his subsequent activities were "growing up as an atom bomb baby - literally living in the battlefield of the cold war", along with the highly structured but also transient nature of military life. "I was always aware of someone else either watching me or controlling me, and I hated the fact that every few years my life was totally disrupted out of the blue," he says. "Expectation of total Armageddon and the total lack of a sense of control are the two key elements that have formed my work."
Green now describes his work as having shifted away from "what they do to us, to what we can do". However, alongside the Terror Group of bombs, he makes art that represents a range of non-violent possibilities for people to take power: from four computer viruses ("more complicated to make than a nuclear bomb") to a home-made and fully operative pirate radio station, as well as the establishment of an entirely new country - "The New Free State of Caroline", based on a small coral island 500 miles north of Tahiti, which he is in the process of legitimately establishing as an independent nation state.
Green may describe his work as "less and less violence oriented" but that doesn't make it any the less troublesome. Last summer, following the exhibition in Chicago of two works from his Sabotage series, the gallery was raided, the owner arrested and a warrant put out for Green's arrest. The local bomb squad arrived to investigate a piece called Suspicious Looking Packages, and on finding that they contained no explosives, they called in the narcotics division to examine another work entitled 10,000 doses. This consisted of glass flasks containing the undistilled ingredients for making lysergic acid - the organic form of LSD. For a while all hell broke loose as the police department's chemists claimed that the vials contained "230,000 hits, worth $1.2m", before they admitted that the lab had "misinterpreted" the results of its analysis and dropped all charges.
100,000 doses is currently on show at the Cabinet Gallery, its four 10- litre laboratory flasks containing a murky yellow brew of car starter fluid and rubbing alcohol sitting on top of seven kilos of ground-up "Heavenly Blue" morning-glory seeds purchased from a Colchester seed merchants. This, like all Green's work, is harmless and legal in its exhibited state. "Putting all this stuff in a bottle is like taking all the parts of a car and putting them in a big bag; it's a car but not a car - it's about possibilities and options, not the realisation of those possibilities."
Green's most recent scheme is to send a satellite into space. "I've discovered that it's possible to build a rocket that would be strong enough to put a small satellite into orbit. I want to re-do Sputnik. 'Gregnik' will orbit Earth for two months, and when it's passing over it will be possible to pick up its signal on the FM frequency. But instead of Sputnik's 'beep-beep' there will be a laughing track."
n Gregory Green is at the Cabinet Gallery, London SW9 (0171-274 4252) to 3 Feb. He is part of 'Young Americans' at the Saatchi Gallery, London NW8 (0171-624 8299), 25 Jan-3 March