The Grand Canyon of the Colorado River, especially when seen in early morning or late afternoon, is a constantly-changing wonderland of light, shadow, and stone. But what boggles the mind is that these things occupy so much space. No matter how many times you visit, and no matter how long you look, you can never quite get a handle on it. One can no more "understand" the Grand Canyon than one can grasp emptiness ... or sum up a void.