1. The singularity. (Though that begs the question: Why wouldn't robots be observable? Perhaps they exist at a largely "virtual" level, as code, even as they replace life.)
2. Dysgenics, aka, Idiocracy. At some point, it may be evolutionarily advantageous to not become more advanced. This is certainly true at present, on average, though the distribution of intelligence is becoming bimodal. The actual filter might ultimately involve a great genocide by Morlock-esque creatures.
3. Gamma ray bursts. Could wipe out millions of civilizations all at once.
4. Ice nine. This is the author's suggestion, basically. Some sudden discovery that wipes out humanity too quickly for us to recover.
....certainly, the author is correct in observing that there are no intelligent aliens, nor could they hide themselves unless they purposefully disabled every radio transmitter for the duration of their hiding.
1. The singularity. (Though that begs the question: Why wouldn't robots be observable? Perhaps they exist at a largely "virtual" level, as code, even as they replace life.)
2. Dysgenics, aka, Idiocracy. At some point, it may be evolutionarily advantageous to not become more advanced. This is certainly true at present, on average, though the distribution of intelligence is becoming bimodal. The actual filter might ultimately involve a great genocide by Morlock-esque creatures.
3. Gamma ray bursts. Could wipe out millions of civilizations all at once.
4. Ice nine. This is the author's suggestion, basically. Some sudden discovery that wipes out humanity too quickly for us to recover.
....certainly, the author is correct in observing that there are no intelligent aliens, nor could they hide themselves unless they purposefully disabled every radio transmitter for the duration of their hiding.
ED: The wiki article is actually pretty good: http://en.wikipedia.org/wiki/Fermi_paradox