Saying that there is life on other planets is a bold claim, as there is no hard evidence that it is true. Although we can’t prove it, there are statistics and facts in favor of the claim that there is extraterrestrial life.
The Milky Way is shaped like a disk that is approximately 100,000 light years in diameter. Within the disk, there is an area known as “The Galactic Habitable Zone”. This is a ring around the center of the Milky Way that is about 23,000-29,000 light years from the direct center. As you can tell from the name, the Galactic Habitable Zone (GHZ) is the area most likely to contain planets and solar systems similar to ours (Gribbin, 75). Scientists estimate that the GHZ contains roughly 10% of all the stars in the Milky Way (Gribbin, 77). If there are about 100 billion stars in the galaxy (http://www.space.com/25959-how-many-stars-are-in-the-milky-way.html), we can use these estimates to guess that there are 10 billion stars in the GHZ. Since a fraction of these stars contain Earth-like planets (Gribbin, 11), we can conclude that there are many, habitable planets within our galaxy.