Time Line Warriors

The possibility of the existence of multiple universes has been discussed in theoretical physics circles and has appeared in popular science magazines like Discover.  It has also been discussed on television in places like the History Chanel.   The possibility of reaching such universes is remote but makes an interesting topic for science fiction.  Writers like H. G. Wells used such concepts.  I first encountered the concept in the summer of 1950 in a story by H. Beam Piper called the Last Enemy.  The idea has fascinated me ever since.