deletions | additions       diff --git a/Intro1.tex b/Intro1.tex  index f44df26..bb9987c 100644  --- a/Intro1.tex  +++ b/Intro1.tex 
...
\textbf{A series of amazing discoveries in the field of astrophysics occured in the last few years. We now know that planetary systems around stars other than the Sun are the norm, not the exception. The implications for one of the most fascinating questions we can ask, "Are we alone in the Universe", are enormous. We review the Drake equation in light of these recent discoveries. The absence of a clear detection of communicative extraterrestrial civilizations tells us that at least one of these fact has to be true:}  \begin{enumerate}  \item The emergence of intelligent life is a very rare event. Life is common, but intelligent life is rare  \item Civilizations spend less than 1000\...2000 years communicating using radio frequencies frequencies. Possible reasons for this include self destruction or technological breakthroughs.  \end{enumerate}  %likely an important transition in the characteristic of the human civilization will occur in a timescale %shorter than about 1000\...2000 years.}