The problem is, as you said, that it seems Drake and others like the sound of billions of stars in billion of galaxies, but when it comes to an unknown number for existence of life in a planet they pick a very optimistic number, to justify their thesis of abundance of life in universe.

Maybe they take the earth as an example, the life existing under very harsh conditions and deduce that it should be a good probability given enough time. But I am skeptical of this.

If you plug values in drakes equations ou can make anything comes out. But historically with any like real numbers you get many civilizations right up until you state how long each civilization lasts. This is why Great Filters are such an important topic of discussion.

Try a calculator [1] and puch in your pessimistic and see what chances you actually get. It is really hard to get 10^20 without just getting 0, and we know the chances are higher than 0.

1 - http://www.bbc.com/future/story/20120821-how-many-alien-worl...

The calculator link you gave is doing exactly the same thing, smallest percentage is 1%. It doesn't make sense.

Well sorry, for that. Get a piece of paper and try it. The drake equation isn't too hard. It is just a bunch of probabilities multiplied by an amount of stars. You can even add your own terms if you don't like the one you have, but generally doing this takes yo further from the science...

Anyway, Here is a simple description I snagged from google search [1]:

> The Drake Equation is: > N = R * fp * ne * fl * fi * fc * L > > where: > N = The number of broadcasting civilizations. > R = Average rate of formation of suitable stars (stars/year) in the Milky Way galaxy > fp = Fraction of stars that form planets > ne = Average number of habitable planets per star > fl = Fraction of habitable planets (ne) where life emerges > fi = Fraction of habitable planets with life where intelligent evolves > fc = Fraction of planets with intelligent life capable of interstellar communication > L = Years a civilization remains detectable

Now grab a pen and cocktail and make the math do whatever you want. I think that is you stick to realistic numbers you will get reasonably high values. But we might just disagree there.

[1] http://www.astrodigital.org/astronomy/drake_equation.html

well, lets say fi < 1e-9 fl < 1e-12 and its a mostly a desert outside.

My post had the formatting screwed up, but you didn't even try to show your work. You are just presuming what you think or want to be true without putting even the theoretical work into it.

Something interesting I found in the wikipedia page:

> One reply to such criticisms is that even though the Drake equation currently involves speculation about unmeasured parameters, it was intended as a way to stimulate dialogue on these topics. Then the focus becomes how to proceed experimentally. Indeed, Drake originally formulated the equation merely as an agenda for discussion at the Green Bank conference.

The existence here on earth of fungi growing within the melted down Chernobyl reactor and possibly using Gamma radiation for it metabolism, makes me a bit more optimistic.

https://en.wikipedia.org/wiki/Radiotrophic_fungus

The difference is that existing life adapted to those conditions. It doesn't mean that it could start in them.