Over at Aeon, Caleb Scharf, director of Columbia's Astrobiology Center, has written an essay contemplating the substrate of minds. Technological progress has spurred many futurists to predict a singularity, a moment when machine intelligence, or AI, overtakes humanity (see also the recent development of our Go overlord). This line of thought has found its way into astrobiology (Dr. When we look for extraterrestrial life, several people have proposed that it might be worthwhile to look for machines rather than the typical little green men. The squishy nature of most biological life does not necessarily lend itself well to interstellar travel.