One of the dreams of both science fiction writers and practical robot builders has been realized, at least on a simple level: Cornell University researchers have created a machine that can build copies of itself.

Admittedly the machine is just a proof of concept — it performs no useful function except to self-replicate — but the basic principle could be extended to create robots that could replicate or at least repair themselves while working in space or in hazardous environments, according to Hod Lipson, Cornell assistant professor of mechanical and aerospace engineering, and computing and information science, in whose lab the robots were built and tested…

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Read more here http://www.news.cornell.edu/stories/2005/05/researchers-build-robot-can-reproduce