Elsewhen Ó Robert A. Heinlein 1941
Collected in Assignment in Eternity
"Most people think of time as a track that they run on from birth to death as inexorably as a train follows its rails—they feel instinctively that time follows a straight line, the past lying behind, the future lying in front. Now I have reason to believe—to know— that time is analogous to a surface rather than a line, and a rolling hilly surface at that. Think of this track we follow over the surface of time as a winding road cut through hills. Every little way the road branches and the branches follow side canyons. At these branches the crucial decisions of your life take place. You can turn right or left into entirely different futures. Occasionally there is a switchback where one can scramble up or down a bank and skip over a few thousand or million years—if you don’t have your eyes so fixed on the road that you miss the short cut. Or, if you have the necessary intellectual strength and courage, you may leave the roads, or paths of high probability, and strike out over the hills of possible time, cutting through the roads as you come to them, following them for a little way, even following them backwards, with the past ahead of you, and the future behind you. Or you might roam around the hilltops doing nothing but the extremely improbable. I can not imagine what that would be like-perhaps a bit like Alice-through-the-Looking-Glass."
With this speech, Professor Frost introduces his class in speculative metaphysics to the concept that the world is much broader than they know. He teaches them how to use hypnosis to leave their own time and dimension and travel through this broader world as he himself had done. There they find adventures, exciting discoveries and new lives.
With story settings similar to Murray Leinster’s classic "Sidewise in Time", and L. Sprague de Camp’s stories of Professor Chalmers and Harold Shea, Heinlein takes us along on trips of discovery not only of new worlds, but of the people who discover these new worlds.
This story, one of Heinlein’s earliest, is a pre-cursor in several ways to his World-As-Myth, which he introduces explicitly in "The Number of the Beast" some 38 years later. The two most strikingly common elements are the multi-dimensional aspect of time and the part that the travelers’ personalities play in determining the worlds that are open to them.
The story rationale appears to be based on P.D. Ouspenskij’s and J.W. Dunne’s theories of time as he explicitly mentions both of these writers here in this story.
A detailed study of this work by Bill Patterson with a more complete summary can be found in "The Heinlein Journal", Issue No. 4, p. 24, January, 1999.