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No Intelligent Aliens Detected in Gliese 581

5 points by phreeza 14y ago

tzs 14y ago
I now think there might be a decent chance we really are alone, after reading this interesting timeline of the far future: http://en.wikipedia.org/wiki/Timeline_of_the_far_future http://en.wikipedia.org/wiki/Timeline_of_the_far_future We've only got one sample to generalize from, so let's take a look at this history of life on Earth. Complex single cell life is about 2 billion years old. Multicellular life is about a billion years old. Complex animals are about half a billion years old. In about 600 million years (assuming no intelligence intervenes) decreasing CO2 levels will make C3 photosynthesis impossible. Almost all plants will then die. That will be bad news for most animal life, too. By 800 million years from now, C4 photosynthesis will no longer be possible, and all plants go, followed by free oxygen, and we lose all multicellular life. If that's typical for planets that can bear life, there isn't a big window for intelligence to develop. From complex animals to the end of multicellular life is only about 1.3 billion years. In that time, you'll have a few super volcanoes and asteroid impacts and irradiations from nearby supernovas and several trips of your solar system around its galactic orbit (each of which can have a period of exposure to the galactic bow shock, which some scientists think causes dangerous levels of cosmic rays)--plenty of opportunities for a major extinction event to shake things up. Note that humans barely made it--the Toba super volcano around 70k years ago is though to have reduced humanity to between 1k and 10k breeding pairs. It seems quite possible that we got lucky, and developed intelligence much faster than would by typical, and that a species on a more normal pace to intelligence simply doesn't have time to evolve it before their planet becomes incapable of supporting multicellular life. Of course, it is also possible that we were slow, and that elsewhere the first complex animals to evolve go on to develop intelligence, in which case the galaxy could easily be full of intelligent life.

5 points by phreeza 14y ago

tzs 14y ago

I now think there might be a decent chance we really are alone, after reading this interesting timeline of the far future: http://en.wikipedia.org/wiki/Timeline_of_the_far_future http://en.wikipedia.org/wiki/Timeline_of_the_far_future We've only got one sample to generalize from, so let's take a look at this history of life on Earth. Complex single cell life is about 2 billion years old. Multicellular life is about a billion years old. Complex animals are about half a billion years old. In about 600 million years (assuming no intelligence intervenes) decreasing CO2 levels will make C3 photosynthesis impossible. Almost all plants will then die. That will be bad news for most animal life, too. By 800 million years from now, C4 photosynthesis will no longer be possible, and all plants go, followed by free oxygen, and we lose all multicellular life. If that's typical for planets that can bear life, there isn't a big window for intelligence to develop. From complex animals to the end of multicellular life is only about 1.3 billion years. In that time, you'll have a few super volcanoes and asteroid impacts and irradiations from nearby supernovas and several trips of your solar system around its galactic orbit (each of which can have a period of exposure to the galactic bow shock, which some scientists think causes dangerous levels of cosmic rays)--plenty of opportunities for a major extinction event to shake things up. Note that humans barely made it--the Toba super volcano around 70k years ago is though to have reduced humanity to between 1k and 10k breeding pairs. It seems quite possible that we got lucky, and developed intelligence much faster than would by typical, and that a species on a more normal pace to intelligence simply doesn't have time to evolve it before their planet becomes incapable of supporting multicellular life. Of course, it is also possible that we were slow, and that elsewhere the first complex animals to evolve go on to develop intelligence, in which case the galaxy could easily be full of intelligent life.