A hypothetical mathematical figure which, when seen by a baseline or near-baseline human, sets up a feedback loop in the brain that destroys their memory and the ability to process sensory information, sending them into a permanent catatonic state. The name derives from an Iron Age myth about a being whose face turned any mortal who looked upon it into stone. It is also sometimes referred to as a "flatline fractal" or (after the Julia set it is said to resemble) "the brain-eating basilisk".
The idea was originally conceived during the early Information Age, when computers first became powerful enough to compute highly repetitive mathematical constructs such as fractals. It was not originally a widespread concept, confined mostly to various works of fiction. In more recent times, probably as a response to concern about powerful posthuman and AI superintelligences, it has undergone a significant popular revival---but this time, feared as a genuine threat.
The actual possibility of a Medusa fractal has been largely discredited. Along with the fact that human visual perception is of only limited resolution, most neurophysical research has shown that any image the brain cannot successfully process will simply be rejected as noise. However, the concept still survives as a popular urban legend in many baseline-inhabited systems. It is especially prevalent among primitivist or neo-Luddite groups, and with those who question the accuracy of - or motive behind - the dissenting research.
Text by Xaonon Initially published on 28 August 2003.