
© NASAHelix Nebula, also known as The Helix or NGC 7293, a large planetary nebula located in the constellation of Aquarius.
Are we the lone sentient life in the universe? So far, we have no evidence to the contrary, and yet the odds that not one single other planet has evolved intelligent life would appear, from a statistical standpoint, to be quite small. There are an estimated 250 billion (2.5 x 10¹¹ ) stars in the Milky Way alone, and over 70 sextillion (7 x 10²² ) in the visible universe, and many of them are surrounded by multiple planets.
Meanwhile, our 4.5 billion-year old Solar System exists in a universe that is estimated to be between 13.5 and 14 billion years old. Experts believe that there could be advanced civilizations out there that have existed for 1.8 gigayears (one gigayear = one billion years).