[ExI] Panbiogenesis

Anders Sandberg anders at aleph.se
Fri Jan 27 10:02:38 UTC 2012

On 27/01/2012 05:04, The Avantguardian wrote:
> An unlikely scenario perhaps but it is certainly possible.

That is the important point. Panspermia depends on very unlikely events, 
but there is so long time and so many planets that it has a chance.

Consider a biosphere lasting 5 billion years, that manages to seed just 
one other planet out of (say) 10 billion available in the galaxy.  That 
means a probability of 1 in 50 billion billion per year. A slightly 
higher probability in this model, and more planets will be seeded and 
the galaxy will "quickly" be colonized.

One can try to bound probabilities in various ways, but things are very 
uncertain. However, it is not too hard to build a joint model of 
spontaneous biogenesis and panspermia, and then plug in our sole data 
point of when life appeared on Earth. That produces a fairly thin 
maximum likeliehood ridge in parameter space, showing a relationship 
between the panspermia and biogensis probabilities.

Anders Sandberg,
Future of Humanity Institute
Philosophy Faculty of Oxford University

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