 Why would I think that life is common in the universe? Well, number one, astronomers have been able to prove in recent times that there are many, many planets around other stars. That there are about as many planets as there are stars. And a lot of those planets are earth-sized. And a lot of those planets are at about the right distance from their star that they would be able to have life, liquid water on the surface. So we don't know how common liquid water is, but we know that there are a lot of places where life could potentially exist. So we know that from measurement. How long does it take to form life? We have one bit of evidence, only one, and that is that there are fossils of early life here on earth shortly after the end of the bombardment by the comets and asteroids. So that says life doesn't take very long to get started. On the other hand, it also, our history shows, it took another 3.8 billion years before we turned up. So that means that life like us is rare, even here on the planet earth. It took us this time to get here. So I think life is common, and life like us is rare.