deletions | additions       diff --git a/Now_we_have_some_constraints__.tex b/Now_we_have_some_constraints__.tex  index 9d3a01f..a3daf15 100644  --- a/Now_we_have_some_constraints__.tex  +++ b/Now_we_have_some_constraints__.tex 
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Ok I know I know, there is \href{http://en.wikipedia.org/wiki/Roswell_UFO_incident}{Roswell}... the \href{http://en.wikipedia.org/wiki/Wow!_signal}{WOW signal}... \href{http://en.wikipedia.org/wiki/List_of_reported_UFO_sightings}{UFO} sightings... Well, I am not going into that. I will just state that the most economical explanations for all the aforementioned cases have nothing to do with E.T. and that at this time there is no clear evidence that prove we had contact with alien life.   The Fermi Paradox implies that $N$ is probably a small number\footnote{There are alternative solutions to the Fermi Paradox, some can be found in a \href{http://waitbutwhy.com/2014/05/fermi-paradox.html}{great post} from Tim Urban's} Urban's}. Our revised version of the Drake Equation then leaves two interesting alternatives: \begin{enumerate}  \item $f_i$ is a small number. That is life is common in the Universe, but intelligent life is not.  \item $L$ is a small number. Intelligent life do not spend much time in the communicative phase.  \end{enumerate}  Of course there is a third option where both $f_i$ and $L$ are small, but that doesn't change the main argument below.