Check Out Poul Anderson

I have recently discussed time travel a lot on the Poul Anderson Appreciation blog. See here.

And here.

Revisiting Successive Timelines

Rereading Poul Anderson's Time Patrol series reopens the issues of the two "Logic of Time Travel" articles at the beginning of this blog.

In the standard science fiction causality violation scenario, a time traveler originates in timeline 1 and travels to the past of that timeline but then "changes the past," thus generating timeline 2. One way to picture this is to represent timeline 1 by a horizontal line and timeline 2 by a second line emerging at an angle from the point representing the moment of the causality violation but this entails that, at that moment, the time traveler disappears from timeline 1 and creates around himself an entire new universe for timeline 2! I do not think that either the functioning of a time machine or the actions of a time traveler would be able to create all that organized matter and energy.

I think that it makes more sense to model temporal change on experienced change. Thus, in experienced change, a single temporal dimension connects states changed from to states changed to. Each of these states is a configuration of the entire three dimensional universe. Similarly, in temporal change, a second temporal dimension connects changing states. Each of these states is an entire four dimensional continuum with its own internal temporal dimension. It is these temporal dimensions that we call timelines 1, 2 etc. 

A time traveler originates in timeline 1 but either transforms timeline 1 into timeline 2 or causes timeline 2 to succeed timeline 1 along the second temporal dimension - these are alternative descriptions of a single process. In The Shield Of Time, Poul Anderson presents another scenario: a quantum change in space-time-energy transforms timeline 1 into timeline 2.

If a story were set in the timeline 2 of the quantum change scenario but without time travelers, then readers would recognize an alternative history or parallel universe story. However, "parallel" implies simultaneity or co-existence whereas I argue that timeline 1 does not coexist with timeline 2 but preexists and causes it along the second temporal dimension. In that dimension, timeline 1 is not contemporary with but earlier than timeline 2 and therefore is inaccessible to a time traveler who can either remain in timeline 2 or advance to timeline 3 but not return to timeline 1. That is how Anderson describes the relationship between the current and deleted timelines in the Time Patrol series.

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.