A Singularity occurring with extreme speed and rapidity, over the course of hours or weeks rather than months or decades. Most hard takeoff scenarios involve Artificial Intelligence because of the probable ability of an AI to rapidly absorb enormous amounts of computing power, run on basic computing elements with limiting serial speeds of 2ghz (as opposed to 200Hz neurons), and recursively self-improve by rewriting one's own source code; however, it is also conceivable that a hard takeoff scenario could develop out of brain-computer interfaces. [Definition by Eliezer Yudkowsky]

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