Originally Posted by out_here_grindin
yes exactly. Although the main problems with those are that the assume everything in terms on Earth rules. For instance the Drake equation has the probability that life can exist on a planet, but it talks about life in terms of what we think is needed for life, while an alien race from another galaxy may look at life in a strikingly different way, something we can't even begin to comprehend.
To be fair, the latest developments in the exoplanet research has been more optimistic than we would ever have imagined. There have been numerous planets discovered with telescopes and rudimentary techniques that makes it obvious how common planets actually are. We have even discovered planets bearing water, and planets in the habitable zones and even planets with both these characteristics and Earth-like sizes.
In February 2013, researchers calculated that up to 6% of small red dwarf stars may have planets with Earth-like properties. This suggests that there could be up to 4.5 billion such planets within our galaxy, and, statistically speaking, the closest "alien Earth" to the Solar System could be 13 light-years away.
Between 2000 and 2009, Drake formula has dropped to the pessimistic percentages, but now it is again going to the optimistic values. Between 2011 and 2013, there have been enough discoveries of planets to create a new field in astronomy.