The year ends, a new millennium begins, and we are mindful of the psalmist’s question. Within this century we have expanded the universe we know to profound limits. We have learned that our Sun is a star within a galaxy of 100 billion other stars. We have counted 100 billion other galaxies racing away from each other. There is a limit to all of this. It is our role as humans to measure our universe, and someday, perhaps, to understand it.