[tsoukase]

I think we should focus at the solution of Fermi paradox, especially the short time window factor. Life on earth evolved for billions of years, while one of it's creatures is capable to receive/send messages to space for only 50. That leads to a factor of billions/50 reduction at the calculated probability of alien life discovery. Multiply that with another billions/xxx at the receiver side, if they are similarly able to communicate for only a few centuries at best. I assume you agree that our and their evolution are independent.

So the new probability becomes quite low, which fits with our (non-)observation of alien life. We might not be alone, but we are far away and very short lived.

[jjk166]

Considering we started our search for extra terrestrial intelligence 67 years ago, and we likely didn't go extinct in 2009, 50 years seems a rather pessimistic estimate.