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The Sciences

DNA Takes Square Roots

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Around these parts we've been known to discuss whether it makes any sense to say that the universe is a computer. There's little doubt, of course, that parts of the universe are computer-like. And in case you are wondering, you can now officially remove DNA from your personal list of "things I suspect are not computers." Caltech researchers Lulu Qian and Erik Winfree have managed to coax 130 strands of DNA into performing what is unquestionably a calculation: taking the square root of a number. (Ars Technica post; Science paper behind paywall; open-access background paper.) Not a big number: we're talking about four-digit binary numbers, so 15 at the biggest. And not very efficiently: with prodding, the calculation took eight hours. Moore's Law isn't really in danger here. Still, pretty cool stuff. Mostly it's interesting because it seems scalable: the authors claim that this kind of circuit architecture could be made much larger. It's not the first biochemical circuit; RNA and bacterial colonies have been made into logic gates. But it's the first to do something as elaborate as taking a square root. Best of all, the authors decided to illustrate their method for a wide audience by means of a ... whimsical YouTube video! Let's hope this idea catches on. [embed]http://www.youtube.com/watch?v=G2Ljgkh_v40[/embed]

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