Oops, that's gotta hurt! It's almost too absurd to consider, but in the near future it may be a very real possibility: all life on earth is eaten up by man made machines, in what physicists euphemistically call `the gray goo problem'.It was no one less than the Nobel prize winning physicist Richard Feynman who gave rise to the `problem'. In a famous 1959 lecture, Feynman predicted that man will some day be able to make nano machines, devices so tiny that you can't even see them. A nanometer is a billionth of a meter, and a nano machine would be a thousand times smaller than the thickness of a human hair.And he was right. In 1986, the physicist K. Eric Drexler took up Feynman's ideas, and coined the term nanotechnology: `the technology of creating and working with devices only a few nanometers big', as it is defined. In 1990, the world realised that this was no longer science fiction, as a team of IBM researchers managed to arrange 35 single xenon atoms so that they spelled out the logo of IBM. Rumour has it that another research team responded to this crafty display of atom knitting by doing some intellectual nano graffiti: `Bill Gates sucks', also jotted down in single xenon atoms. Ever since then, nanotechnology has underwent a modest revolution. With the coming of the Atomic Force Microscope, which uses a tiny `needle' to explore the surface of materials, scientists have been able to `pick up' single atoms and move them elsewhere. Numerous universities and privately funded institutes engage in nanotech. Nano engineers have at their disposal a toolkit full of crafty gadgets, ranging from nano trains that transport atoms across a nano track, to a nano pen that squirts out atoms instead of ink. Also, there's a growing collection of nano switches, nano wires, nano tubes and - more recently - the first nano `engines': rotor shaped molecules that rotate under the influence of the right changes in temperature and light.
Well, but we're still alive and kicking. So where's the gray goo? O, wait and see. The end of the world may be nearer than you think.
Nano philosophers foresee that one day (some estimate around 2010) it will be possible to create a nano assembler: a man made molecule, that is `programmed' to create certain things out of raw materials. A nano assembler would for instance pick up plain carbon atoms and rearrange them into the molecular structure of a diamond. Or it would make water out of the atomic parts of plain air. Or a cheese sandwich out of dust. Or water into wine, you name it.
This notion is not as weird as it sounds. Our DNA- and RNA-molecules do it all the time! They pick up the raw materials from our food, and turn them into complex molecules. DNA and RNA are nano assemblers that manufacture whole organisms, with arms and legs, and fingers that can type the word `nanotechnology'.So, if a nano factory can be programmed to create a cheese sandwich out of atoms, why wouldn't it be able to create new nano factories? This in fact is exactly the way it will be, at least according to nanopioneers like K. Eric Drexler. Let's face it: it's a hell of a job to build a nano machine by hand. It would be much easier to make nano machines that are capable of copying themselves, much in the way DNA-molecules replicate themselves. Nano scientists claim it is even essential for a nano machine to be self-replicating. Since they are so tiny, we would need millions of them to be of any use. It would take a lifetime to make them all by hand. Nano factories are thus by definition Von Neumann machines: devices capable of creating new copies of themselves.
But there's a nasty downside. What will such a self-replicating nano machine do if you carelessly tossed it away? You guessed it: it would go on grabbing all atoms within reach, rearranging them into copies of itself. And the copies would make more copies of themselves. And those copies would make even more copies of the copies of the copies. And so on.
No, you just DON'T want to know what this means. Within only 72 hours after the release of the first molecular nano machine, every single atom on earth would be `used' to create new nano machines. In other words, all plants, animals, humans, cars, buildings and even rocks would have been `eaten up' by a vast, exponentially growing army of invisibly small nano devices.