Quote from : Doctor Who: The Silent Stars Go By Book

That's what I love about people. They have dreams and grand ambitions, and they start building towards them, even though they know they won't live to see them finished. That's how the pyramids were built. And the great cathedrals of the Middle Ages. People were prepared to invest in the future. They were prepared to donate the labor of their entire lives to a greater whole that other lives, future lives, would benefit from.