Should, by some terrible misfortune, Ray Kurzweil shuffle off his mortal coil tomorrow, the obituaries would record an inventor of rare and visionary talent. In 1976, he created the first machine capable of reading books to the blind, and less than a decade later he built the K250: the first music synthesizer to nigh-on perfectly duplicate the sound of a grand piano. His Kurzweil 3000 educational software, which helps students with learning difficulties such as dyslexia and attention deficit disorder, is likewise typical of an innovator who has made his name by combining restless imagination with technological ingenuity and a commendable sense of social responsibility.

However, these past accomplishments, as impressive as they are, would tell only half the Kurzweil story. The rest of his biography – the essence of his very existence, he would contend – belongs to the future.

Following the publication of his 2005 book, The Singularity is Near: When Humans Transcend Biology, Kurzweil has become known, above all, as a technology speculator whose predictions have polarised opinion – from stone-cold scepticism and splenetic disagreement to dedicated hero worship and admiration. It's not just that he boldly envisions a tomorrow's world where, for example, tiny robots will reverse the effects of pollution, artificial intelligence will far outstrip (and supplement) biological human intelligence, and humankind "will be able to live indefinitely without ageing". No, the real reason Kurzweil has become such a magnet for blogospheric debate, and a tech-celebrity, is that he's convinced those future predictions – and many more just as stunning – are imminent occurrences. They will all, he steadfastly maintains, happen before the middle of the 21st century.

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Which means, regarding the earlier allusion to his mortal coil, that he doesn't plan to do any shuffling any time soon. Ray Kurzweil, 61, sincerely believes that his own immortality is a realistic proposition... and just as strongly contends that, using a combination of grave-site DNA and future technologies, he will be able to reclaim his father, Fredric Kurzweil (the victim of a fatal heart attack in 1970), from death.

Just when will this ultimate life-affirming feat be possible? In Kurzweil's estimation, we will be able to upload the human brain to a computer, capturing "a person's entire personality, memory, skills and history", by the end of the 2030s; humans and non-biological machines will then merge so effectively that the differences between them will no longer matter; and, after that, human intelligence, transformed for the better, will start to expand outward into the universe, around about 2045. With this last prediction, Kurzweil is referring not to any recognisable type of space travel, but to a kind of space infusion. "Intelligence," he writes, "will begin to saturate the matter and energy in its midst [and] spread out from its origin on Earth."

It's as well to mention at this point that, in 2005, Mikhail Gorbachev personally congratulated Kurzweil for foreseeing the pivotal role of communications technology in the collapse of the Soviet Union, and that Microsoft chairman Bill Gates calls him "the best person I know at predicting the future of artificial intelligence". A man of lesser accomplishments, touting the same head-spinning claims, would impress few beyond an inner circle of sci-fi obsessives, but Kurzweil – honoured as an inventor by US presidents Lyndon B Johnson and Bill Clinton – has rightfully earned himself a stockpile of credibility.

In person, chewing pensively on a banana, the softly spoken, slightly built Kurzweil looks chipper for his 61 years, and wears an elegantly tailored suit. A father of two, he resides in the Boston suburbs with his psychologist wife, Sonya, but has flown into Los Angeles for a private screening of Transcendent Man, the upcoming documentary that examines his life and theories over a suitably cosmic score by Philip Glass. "People don't really get their intellectual arms around the changes that are happening," he says, perched lightly on the edge of a large armchair, his overall sheen of wellbeing perhaps a shade more encouraging than you'd expect from a man of his age. "The issue is not just [that] something amazing is going to happen in 2045," he says. "There's something remarkable going on right now."

To understand exactly what he means, and why he thinks that his predictions bear up to hard scrutiny, it's necessary to return to the title of the above-mentioned book, and the grand idea on which it's based: "the singularity".

Borrowed from black-hole physics, in which the singularity is taken to signify what is unknowable, the term has been applied to technology to suggest that we haven't really got a clue what's going to happen once machines are vastly more "intelligent" than humans. The singularity, writes Kurzweil, is "a future period during which the pace of technological change will be so rapid, its impact so deep, that human life will be irreversibly transformed". He is not unique in his adoption of the idea – the information theorist John von Neumann hinted at it in the 1950s; retired maths professor and sci-fi author Vernor Vinge has been exploring it at length since the early 1980s – but Kurzweil's version is currently the most popular "singularitarian" text.

"I didn't come to these ideas because I had certain conclusions and worked backwards," he explains. "In fact, I didn't start looking for them at all. I was looking for a way to time my inventions and technology projects as I realised timing was the critical factor to success. And I made this discovery that if you measure certain underlying properties of information technology, it follows exquisitely predictable trajectories."

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For Kurzweil, the crux of the singularity is that the pace of technology is increasing at a super-fast, exponential rate. What's more, there's also "exponential growth in the rate ' of exponential growth". It is this understanding that gives him the confidence to believe that technology – through an explosion of progress in genetics, nanotechnology and robotics – will soon surpass the limits of his imagination.

It is also why, in addition to bananas and the odd beneficial glass of red wine, he follows a regime of around 200 vitamin pills daily: not so much a diet as an attempt to "aggressively re-programme" his biochemistry. He claims that tests have shown he aged only two biological years over the course of 16 actual vitamin-popping years. He also says that, thanks to the regime, he has effectively cured himself of Type 2 diabetes. Not even open-heart surgery, which he underwent last year, and from which he made a rapid recovery ("a few hours later I was in the next room, and sent an email") could dent his convictions. On the contrary, he thinks that the brevity of his convalescence is proof positive that the pills are working. If he slows down the ageing process, he reckons, he'll be around long enough to witness the arrival of technology that will prolong his life... forever.

Kurzweil was raised in Queens, New York, where two youthful obsessions – electronics and music – would lead to a guest appearance on the 1960s TV quiz show I've Got a Secret, on which (aged 17) he showcased his first major invention: a home-made computer that could compose tunes. Five years later came the death (in 1970, when Ray was 22) of his father, Fredric, a struggling composer and conductor who, Kurzweil believes, never really got his due. "I'm painfully aware of the limitations he had, which were not his fault," he says. "In that generation, information about health was not very available, and we didn't have [today's] resources for creating music. Now, a kid in a dorm room can create a whole orchestral composition on a synthesizer."

The tragedy of that loss – and the fact that the means to repair a congenital heart defect were available to him, but not his father – is clearly an intense motivation for Kurzweil. Sometime soon, he believes, he will once again be able to converse with his father, such is the potential of the scientific advances he believes will ultimately pave the way to the singularity. Not everyone, though, concurs with his appraisal of technological progress, and his belief in the imminence of immortality.

Memorably, in the Transcendent Man documentary, Kevin Kelly, founding editor of future-thinking magazine Wired, labels Kurzweil a "deluded dreamer" who is "performing the services of a prophet". In reacting to that assessment, Kurzweil's habitually mellow tone of voice takes on a hint – albeit mild – of umbrage. "It's interesting that [Kelly] says my views are 'hard-wired', when I actually think his views are hard-wired," he says. "He's a linear thinker, and linear thinking is hard-wired in our brains: it worked very well 1,000 years ago. Some people really are resistant to accepting this exponential perspective, and they're very smart people. You show them the data, and yes, they follow it, but they just cannot get past it. Other people accept it readily."

Whereas Kelly differs from Kurzweil on the grounds of interpretation and tone, other voices of dispute are rooted in a deep-seated fear of technological calamity. "The form of opposition from fundamentalist humanists, and fundamentalist naturalists – that we should make no change to nature [or] to human beings – is directly contrary to the nature of human beings, because we are the species that goes beyond our limitations," counters Kurzweil. "And I think that's quite a destructive school of thought – you can show that hundreds of thousands of kids went blind in Africa due to the opposition to [genetically engineered] golden rice. The opposition to genetically modified organisms is just a blanket, reflexive opposition to the idea of changing nature. Nature, and the natural human condition, generates tremendous suffering. We have the means to overcome that, and we should deploy it."

To those opponents who detect a thick strain of techno-evangelism in Kurzweil's basically optimistic interpretation of the singularity, he reacts with self-parody: there's a tongue-in-cheek photo in The Singularity is Near of the author wearing a sandwich board bearing the book's title, and he insists he was never "searching for an alternative to customary faith". At the same time, he says humankind's inevitable move towards non-biological intelligence is "an essentially spiritual undertaking".

Whether or not he attracts a significant following of dedicated believers in search of deliverance, ecstasy or any variation thereof (some commentators have called the singularity "the rapture for geeks"), Kurzweil has undoubtedly positioned himself at the heart of a growing singularity industry. He is a director of the non-profit Singularity Institute for Artificial Intelligence, "the only organisation that exists for the expressed purpose of achieving the potential of smarter-than-human intelligence safer and sooner"; there's a second film awaiting release (part fiction, part documentary, co-produced by Kurzweil), also based on The Singularity is Near; and in addition to his theoretical books, he has co-authored a series of health titles, including Transcend: Nine Steps to Living Well Forever and Fantastic Voyage: Live Long Enough to Live Forever. The secret of immortality, he wants you to know, is available in book form.

Those who have lent Kurzweil their support include space-travel pioneer Peter Diamandis, chairman of the X-Prize Foundation; videogame designer (and creator of Spore and SimCity) Will Wright; and Nobel Prize-winning astrophysicist George Smoot. All three can be found on the faculty and adviser list of the recently founded Singularity University (Silicon Valley), of which Kurzweil is chancellor and trustee.

If the pace of technology continues to accelerate, as Kurzweil predicts, it seems likely that discussion of the singularity will see an exponential growth of its own. Few would dispute that it's one of the 21st century's most compelling ideas, because it connects issues that intensely polarise people (God, the energy crisis, genetic engineering) with sci-fi concepts that stir the imagination (artificial intelligence, immersive virtual reality, molecular engineering). Thanks largely to Kurzweil and the singularity, scenarios once viewed as diverting entertainment are being reappraised with a new seriousness. The line between fanciful thinker and credible, scientific analyst is becoming blurred: what once would have been relegated to the realms of sci-fi is now gaining factual currency.

"People can wax philosophically," says Kurzweil. "It's very abstract – whether it's a good thing to overcome death or not – but when it comes to some new methodology that's a better treatment for cancer, there's no controversy. Nobody's picketing doctors who put computers inside people's brains for Parkinson's: it's not considered controversial."

Might that change as more people become aware of the singularity and the pace of technological change? "People can argue about it," says Kurzweil, relaxed as ever within his aura of certainty. "But when it comes down to accepting each step along the way, it's done really without much debate."

'Transcendent Man' ( transcendentman.com) screens at Sheffield Doc/Fest (0114 276 5141, sheffdocfest.com), running in association with 'The Independent', from 4-8 November

The greatest thing since sliced bread?

Ray Kurzweil's guide to incredible future technologies — and when he thinks they're likely to arrive ...

1 Reconnaissance dust

"These so-called 'smart dust' – tiny devices that are almost invisible but contain sensors, computers and communication capabilities – are already being experimented with. Practical use of these devices is likely within 10 to 15 years"

2 Nano assemblers

"Basically, these are three-dimensional printers that can create a physical object from an information file and inexpensive input materials. So we could email a blouse or a toaster or even the toast. There is already an industry of three-dimensional printers, and the resolution of the devices that can be created is getting finer and finer. The nano assembler would assemble devices from molecules and molecular fragments, and is about 20 years away"

3 Respirocytes

"A respirocyte is a nanobot (a blood cell-sized device) that is designed to replace our biological red blood cells but is 1,000 times more capable. If you replaced a portion of your biological red blood cells with these robotic versions you could do an Olympic sprint for 15 minutes without taking a breath, or sit at the bottom of a swimming pool for four hours. These are about 20 years away" '

4 Foglets

"Foglets are a form of nanobots that can reassemble themselves into a wide variety of objects in the real world, essentially bringing the rapid morphing qualities of virtual reality to real reality. Nanobots that can perform useful therapeutic functions in our bodies, essentially keeping us healthy from inside, are only about 20 years away. Foglets are more advanced and are probably 30 to 40 years away"

5 Blue goo

"The concern with full-scale nanotechnology and nanobots is that if they had the capability to replicate in a natural environment (as bacteria and other pathogens do), they could destroy humanity or even all of the biomass. This is called the grey goo concern. When that becomes feasible we will need a nanotechnology immune system. The nanobots that would be protecting us from harmful self-replicating nanobots are called blue goo (blue as in police). This scenario is 20 to 30 years away"