The earliest that sentient life could develop is probably ~5 billion years after the big bang. So you should only count the last 9 billion years. :D (I'm basi

The earliest that sentient life could develop is probably ~5 billion years after the big bang. So you should only count the last 9 billion years. :D (I'm basing it off of: 1 billion years for a star to form & explode to provide the heavier elements needed for a rocky planet. Another 1 billion years for a new solar system to form, another billion years for the rocky inner planet to cool off, another 1 billion for simple life to develop, and then another billion for intelligent life to develop.)