The SF Dialogue

Sf is, sometimes explicit, dialogue with earlier sf.

Poul Anderson's "The Man Who Came Early" replies to works by Mark Twain and L. Sprague de Camp by arguing that a modern man would not necessarily prosper, indeed would not necessarily survive, in an earlier age.

I have found three explicit back-references in:

Peter Haining, Ed., Timescapes: Stories Of Time Travel (London, 1997).

"The Gernsback Continuum" by William Gibson refers to Hugo Gernsback in its title and to several sf works, including Amazing Stories, in its text.

"The Deadly Mission of Phineas Snodgrass" by Frederick Pohl begins by telling us that its title character "...built a time machine..." (p. 152) and proceeds to inform us that, when Snodgrass transformed he Roman Empire:

"(He stole the idea from a science-fiction novel by L. Sprague de Camp, called Lest Darkness Fall.)" (ibid.)

The title character of JB Priestley's "Mr Strenberry's Tale" argues:

"'Fellows like H.G. Wells have always been writing about us taking a jump into the future, to have a look at our distant descendants, but of course we don't. We can't; we don't know enough. But what about them, taking a jump into the past, to have a look at us? That's far more likely, when you come to think of it." (p. 41)

Wells' The Time Machine: the Time Machine is invented in the author's present;

Anderson's "Flight to Forever": the time projector is invented over two decades in the future;

Anderson's Time Patrol series: time machines are invented in AD 19352.

The Time Machine and the time projector visit future periods and return to their presents. Although the Time Patrol series focuses not on the future but on history, its opening story summarizes two future periods: 2987 and 19352.

To create alternative futures - and there are now many - is to continue the dialogue with earlier speculative authors, including Wells.