Suppose that they exist and their level of technology is very high ( of course it must be) , even so it is unlikely that they reached us because of the size of the galaxi , the distances and the speed limit
The only assumptions I made is that the physical laws are valid also for them
So the their existence and level of technology is not an assumption?
Are you not unaware of Fermi's simulation ?
I am aware of a back of the envelope "sound bite" about Fermi's Paradox. I'm unaware that he quantified his thoughts as an equation (like Drake) or that people work at proving the assumptions (again, like Drake).
He took into consideration the foundations of colonies and he came to the conclusion that our galaxies should be crowded with alien colonies and the ether full of radio frequencies
Right. An Opinion based on an Assumption with no quantifiable evidence and no resultant equation to examine.... not a simulation, not much more than one scientist's opinion at that.
The result of the Drake's equation depend on the value assigned to the parameters which are mere speculations
I have never taken this equation that seriously
Correct. But unlike other models or Fermi's opinion, this one has an equation with variables that can be tested. On the objective side, as we learn more about the number of "earth class" planets, Drake's will be modified.
So there are a number of facts (number of objects in the heavens), a number of educated guesses in there (number of habitable planets), and a number of pure guesses (number of civilizations per galaxy).... but each one is put in a way that they can be tested somehow, sometime. That is why Drake's equation is not science, but it can be and is setup so it can become science.
if the enviromental conditions are suitable life must evolve
And if we apply the Vogt-Russel theorem of Steller evolution, the same conditions must lead to the same life. Again, purely subjective arguements, but that is the way science looks into the unknown: by looking to the past for answers to the future; taking what we do know and applying it to the unknown; letting the data guide us and not our preconceptions.
