No, I don't believe there are aliens living on other planets. Unless you are talking about bacteria and other single-cell types of primitive life.
Because if, by aliens, you mean complex animal life - the chances are infinitesimally small that such life has evolved anywhere else in the universe.
The fact that other star systems have planets in their life zones, temperate climates, and liquid water does NOT guarantee that complex life will evolve. The earth had such conditions for nearly 3.5 billion years and never developed anything beyond microbes. It wasn't until about 500 million years ago, after a snowball earth event, that complex life with skeletons began to evolve on this planet.
Simple life may abound in the universe, but advanced life forms backed by intelligence -- extremely unlikely.
Rare Earth - Peter Ward, Donald Brownlee
· 1 decade ago