President Brigham Young said: “How many earths are there? I observed this morning that you may take the particles of matter composing this earth, and if they could be enumerated they would only be a beginning to the number of the creations of God; and they are continually coming into existence, and undergoing changes and passing through the same experience that we are passing through” (in Journal of Discourses, 14:71).
http://www.lds.org/manual/the-pearl-of-great-price-student-manual/the-book-of-moses?lang=eng
