Book excerpt: A tree stands on a hill by a river. As the sky changes, so does the tree, its branches filling with clouds, stars, snow, birds, mists, and the golden spring sun. One tree can mean many things. Thomas Locker's lyrical text records the changes in the tree's world just as simply as a child might observe them, and his magnificent paintings crystallize the natural phenomena that embellish the tree on each page. Questions at the bottom of each page lead to a unique discussion in the back of the book, where art and science are intertwined, and further depth is added to the wonder of Sky Tree.