We finished discussing exoplanets, and moved onto studying in more detail what are the prerequisites for finding evolved life on other planets. A planet like the Earth needs to be in the 'habitable' zone, it needs a stable, older parent star, it has to have an atmosphere to protect it from coronal mass ejections and solar flares, the crust has to be thick enough to support oceans and landmasses, and so on. We concluded with discussing Drake's equation. Frank Drake, the de facto father of the SETI program, came up with an equation in the 1960's to estimate the number of technologically advanced civilizations in the Galaxy. Of course, many parameters require speculation, but it's a good mental exercise to picture the vastness of our Galaxy.