
No Intelligent Aliens Detected in Gliese 581 - phreeza
http://news.discovery.com/space/no-intelligent-aliens-in-gleise-581-are-home-120602.html
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tzs
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>

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.

