#4 The Habitable Planet

Every once in a while, scientists – cosmologists in particular – claim that they have found a potentially habitable planet in some distant part of our galaxy. What do they mean? Do they mean there is a good chance that life exists on that planet? What drives them to declare such a strong hypothesis? And what kind of life are they talking about? Is it the kind of life we see on Earth – plants, animals, humans? Or are they talking about the presence of any kind of life – even if it is just microbial life?