Everything likes to live where it will age the most slowly, and gravity pulls it there.  The greater the slowing of time, the stronger gravity's pull....  At the surface of a black hole, time is slowed to a halt.

Kip Thorne, The Science of Interstellar

The eternal mystery of the world is its comprehensibility…. The fact that it is comprehensible is a miracle.

Albert Einstein, as quoted in the New York Review.