Life in Our Universe

Abstract

Our galaxy appears devoid of life elsewhere, even though it may contain a billion stars with their own planetary systems possibly similar to our own solar system. As Carl Sagan wrote, “Absence of evidence is not evidence of absence.” In fact, I would be shocked to learn that our solar system was the only place in the galaxy where intelligent life had developed. The Earth is already rather crowded, and it is in our nature to want to explore—indeed, there is no reason why our descendants should not spread throughout the galaxy to form a hyper-civilisation. In the next chapter I will explain how the Sun evolves in time, and although it has maintained conditions on Earth for over four billion years that are ideal for life to flourish, in a shorter timescale this will no longer be the case.