Dimensions

Copied from the Logic of Time Travel blog:

I am going back to basics with dimensions. Many page viewers will not need to read this post.

On the flat surface of a blank sheet of paper, there are two dimensions: horizontal and vertical. Each dimension has two directions. Horizontal: left and right. Vertical: up and down. Each dimension is at right angles to the other. Thus, it is possible to move up or down without moving left or right and vice versa.

We can let the horizontal dimension represent the temporal dimension. In that case, the vertical can represent either one of the three spatial dimensions or a second temporal dimension. In this post, it will represent the latter. A temporal dimension has a direction or "arrow" defined by causality, memory and entropy whereas a spatial dimension does not.

If the horizontal represents our familiar temporal dimension, then a horizontal straight line represents a history or "timeline" from beginning to end. Each point on the line represents a moment of time. To an observer located in one of these points, every point to the left is earlier or past and every point to the right is later or future whereas, to an external observer looking down on the sheet, the points coexist with each other simultaneously.

A second straight line drawn above and parallel to the first line can represent a second timeline existing later then the first timeline in the second temporal dimension which extends up the page. If a time traveler, reversing his arrow of time, "travels" leftwards, then he moves pastward in the first temporal dimension (T1). If he travels upwards, then he moves futureward in the second temporal dimension (T2).

The hero of Ward Moore's Bring The Jubilee leaves a timeline in which the South won the American Civil War and enters a timeline in which the North won. He moves left/pastward in T1 to a decisive battle but also up/futureward in T2 to the second timeline. Thus, he can say, from the point that he has reached in T2, that the first timeline no longer exists. However, it is still visible to an external observer of the sheet of paper. Further, it is of no concern to the inhabitants of the first timeline that they will no longer exist according to an observer in the second timeline.

Contradictions occur only when we try to cram all of these diverse events into a single temporal dimension.

Classics

The Classics are the works that are always in print. We can always buy a new copy of The Time Machine, and can even choose between editions. I do not have to name the author to identify the work.

Of the many works that do go out of print, some are remembered, referred to as "sf classics" and occasionally revived. I regard Bring The Jubilee by Ward Moore as a classic of time travel but it went out of print after two years, I bought an edition published nearly ten years later and the New English Library SF Masters Series republished it another decade after that.

When James Blish's After Such Knowledge Trilogy was published in a single volume, I did not buy it because I already owned the individual volumes and it simply did not occur to me that the single volume edition would go out of print or indeed that all the works of a writer like Blish would go out of print in my lifetime.

I am rereading Poul Anderson's Brain Wave, a good first novel, in a now out of print SF Masters Series edition with an appreciative Introduction by Brian Aldiss and am buying the Baen Books The Technic Civilization Saga, the first uniform edition of Anderson's major future history. It is to be hoped that Baen will publish Anderson's Complete Works?

The Time Travel Archives

a publishing idea

Defining statement: the Time Travel Archives would be uniform editions of good time travel stories and novels covering the basic concept, the causality paradoxes and divergent timelines but excluding stories or novels whose internal logic of time travel was regarded by the Editor as unacceptably inconsistent.

However, works by Wells, Anderson and Finney that compensate for questionable logic in other ways would be included. A rigorous application of the defining statement would rule out The Time Machine, The Time Patrol and Time and Again.

The Basic Concept, Causality Violation and Divergent Timelines

"Missing One's Coach" Anonymous
A Connecticut Yankee In King Arthur's Court by Mark Twain
The Time Machine by HG Wells
Lest Darkness Fall by L Sprague de Camp
Bring The Jubilee by Ward Moore
Past Times (a revised edition) by Poul Anderson
The Time Patrol by Poul Anderson
The Shield of Time by Poul Anderson
Jack Finney's time travel short stories collected
Time And Again by Jack Finney
From Time To Time by Jack Finney

Circular Causality

"The Chronic Argonauts" by HG Wells
"A Stitch in Time" and "Chronoclasm" by John Wyndham
"By His Bootstraps" and "-All You Zombies" by Robert Heinlein
The Door Into Summer by Robert Heinlein
The Technicolor Time Machine by Harry Harrison
Beyond The Barrier by Damon Knight
The Corridors Of Time by Poul Anderson
The Dancer From Atlantis by Poul Anderson
There Will Be Time by Poul Anderson
Bid Time Return by Richard Matheson
The Time Traveller's Wife by Audrey Niffenegger

The Curious Sub-Sub-Genre of Juvenile Historical Fantasy Time Travel Novels by English Women Writers

 A Traveller In Time by Alison Uttley
The Moon Dial by Helen Cresswell
Tom's Midnight Garden by Philippa Pearce
The Story Of The Amulet by E Nesbit
etc

Not to be included 

The End Of Eternity by Isaac Asimov
The Legion Of Time by Jack Williamson
The Big Time by Fritz Leiber
Up The Line by Robert Silverberg
The Man Who Folded Himself by David Gerrold
11/22/63 by Stephen King

For discussion of some of these works, see here and here. An extra volume of the Archives would be an Editorial explanation of inclusions and exclusions. Apart from the circular causality paradox and the curious sub-sub-genre, I found it impossible to list the categories separately. Causality violation is possibly attempted in A Connecticut Yankee and subtly implied in The Time Machine before it occurs in Lest Darkness Fall, thus initiating a divergent timeline.

"Missing One's Coach" and the first five items in the "Circular Causality" list could form a collection.

Addendum, 5/6/12: This note belongs on my "Logic of Time Travel" blog where it can also be found. It was copied here by mistake but I decided to leave it here since works by Poul Anderson are such a major part of the proposed Time Travel Archives.