[ExI] Drake Equation Musings

Anders Sandberg anders at aleph.se
Tue May 17 08:52:56 UTC 2016

On 2016-05-16 04:16, Rafal Smigrodzki wrote:
> Is the technogenesis likelihood of 10e-15 per solar mass a reasonable 
> estimate?

Our view is that is a reasonable estimate. Although it is a fair bit 
higher than what our priors suggest - one civilization per multiple 
observable universe-volume is closer to our mean. The variance of the 
prior is *big* (I actually had to do numerical voodoo for some of the 
calculations on my computer, since precision breaks down for absurdly 
small numbers).

The thing is, people tend to assume that if you see one instance of 
something out of N objects, the probability of it happening should be 
about 1/N. But this misses the observer selection effect: if you have an 
absurdly low probability but it has to happen somewhere (because it 
results in you), then the relevant class may be far larger than N. So if 
the technogenesis probability is 10^-1000 there will still be lots of 
observers in an infinite or very large universe, but they will all be 
very distant.

Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University

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