[ExI] Silence in the sky-but why?

[Anders Sandberg]

On 2013-08-27 19:27, BillK wrote:
> On Tue, Aug 27, 2013 at 5:41 PM, Adrian Tymes wrote:
> <snip>
>> If the odds of intelligent, tool-using life with the potential for space
>> travel arising around a star, in a given five billion years of the star's
>> lifespan, is somewhere around one trillionth (readily justifiable when you
>> multiply together all the factors it would need to overcome, even before the
>> species gains the capacity to wipe itself out), then we would indeed expect
>> there to be exactly one intelligent species by now - and here we are.  Not
>> counting anything we create, we could expect on the order of another ten
>> billion years before another species like us came along.
> Gadzooks! You mean we are the only intelligent life in the galaxy!
>
> Now that's really frightening.

OK, please hide under the cover: Stuart's and my paper multiplies the 
number of relevant stars by a factor of 10^6-10^9. So instead of one 
chance in a trillion of intelligent life, the above argument requires it 
to be one in a quintillion or one in a sextillion.

Now, I am all happy with saying intelligent life might be rare. But 
given the growth of cephalization on Earth and the fact that there are 
several species that show a not insignificant problem-solving capability 
that could perhaps evolve into true intelligence in a few ten million 
years, it seems hard to argue that the step from life to intelligence is 
*that* low probability. So if you believe in an early great filter, it 
better be that life is amazingly unlikely. That might work.

-- 
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University