The "Great Filter" is a hypothetical barrier to explain why civilisations are so unlikely to progress to the point of inter-stellar colonisation that we have not encountered any in 40 years of looking. Maybe humanity has already negotiated the filter - as some massive evolutionary improbability - or perhaps it lies in our future as an almost-certain threat to our existence? We should hold our breath as we look for evidence of life on Mars.
posted by rongorongo on May 12, 2008 - 85 comments

Are You Living In A Computer Simulation? The Simulation Argument is a regularly-updated site, organized by Nick Bostrom, examining the hypothesis that we are currently living in an "ancestor simulation" run by a future "post-human" society.
posted by amyms on May 21, 2007 - 165 comments