REUTERS/Mike BlakeThe existence of extraterrestrial life is one of the most compelling debates in science. When we ask "Are we alone?", we are wondering about how life itself begins, and what our place and function is in this universe. A new paper, published in Astrobiology, uses the most recent discoveries of exoplanets to estimate the likelihood that other technologically advanced civilizations have ever existed. The authors’ pessimistic limit is that humanity is unique if the odds of an advanced civilization existing on a planet is less than one chance in about 10 billion trillion. “One in 10 billion trillion is incredibly small.