Human beings are the only intelligent life in the universe?

  It is said that the earth is the only planet which many living things exist on.How ever,I don't think that the earth is the only planet which has many living things and human being is the only intelligent life in the universe.Recent study shown that there are many planet which has liquid water on their surface.To the life exist,there are some required condition,for example liquid water,appropriate gravity,oxygen and so on.The number of these planets is 5000×1000000000×1000000000.The digit is so huge that I couldn't write full of the number.Therefore I think the earth is not the miracle planet which only has intelligent life in the universe.