"The combined circumstance that we live on Earth and are able to see the stars--that the conditions necessary for life do not exclude those necessary for vision, or vice versa--is a remarkably improbable one.
   This is because the medium in which we live is, on the one hand, just thick enough to enable us to breath and to prevent us from being burned up by cosmic rays, while, on the other hand, it is not so opaque as to absorb entirely the light of the stars and block any view of the universe. What a fragile balance between the indispensable and the sublime."

- Hans Blumenberg, from the Introduction to "The Genesis of the Copernican World"