"Human Universe - 3. Are We Alone? Brian Cox explores the ingredients needed for an intelligent civilisation to evolve in the universe - the need for a benign star, for a habitable planet, for life to spontaneously arise on such a planet and the time required for intelligent life to evolve and build a civilisation. Brian weighs the evidence and arrives at his own provocative answer to the puzzle of our apparent solitude."
The discovery of alien life; especially intelligent alien life, would have profound implications for our future. It would unite the world in a way nothing else could. It would mean that we are not alone in the universe, and it would signify that life has started independently on multiple worlds across the universe.
It is one of the biggest question waiting for an answer. "Are we alone?"
Source (BBC iPlayer)