[W]ithout proper experiments I conclude nothing... - Johannes Kepler

We do not ask for what useful purpose the birds do sing, for song is their pleasure since they were created for singing. Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens... The diversity of the phenomena of Nature is so great and the treasures hidden in the heavens so rich, precisely in order that the human mind shall never be lacking for fresh nourishment.

I used to measure the heavens, now I measure the shadows of Earth. Although my mind was heaven-bound, the shadow of my body lies here.

[N]either this nor that supposition is worthy of the name of an astronomical hypothesis, but rather that which is implied in both alike.