Van Vogt combined this with two other stories and a little fix-up material for his 1970 publication of Quest for the Future.
In his blog, Fred Pohl wrote about how Heinlein’s agent gave permission for Pohl publish the novel in If and to cut “five or ten thousand words in the beginning that were argumentative, extraneous and kind of boring” (and Pohl agreed to pay full rate for the cut words). But apparently, Heinlein “went ballistic” when he saw the first installment, so much so that when the book appeared as a separate publication, Heinlein made sure people knew who was responsible for the previous cuts by adding a note* that “A short version of this novel, as cut and revised by Frederik Pohl, appeared in Worlds of If Magazine.”
* The version of
Heinlein’s note that Pohl recalled was much funnier than Heinlein’s actual note in
our timeline, but sadly, we have lost track of where we saw Pohl’s version.
The story includes flashbacks and previously unknown explanations of the team’s previous trip to the ’40s in Avengers #56, and at the end of the story, Goliath uses Dr. Doom’s Time Platform to banish the Scarlet Centurion back to his time—and we think this is the only time travel that actually appears in the story (apart from the flashbacks). We don’t know what happens to the alternative 1968 (now known as Earth-689, but the traveling Avengers return to the universe that we all knew and loved in the 1960s (a.k.a. Earth-616), with their memory of the whole affair wiped by the Watcher.
In Heinlein’s first version of this novel, written in 1977, the middle third of the story takes place on Barsoom, but in the 1980 published version, Barsoom was replaced by a futuristic British Mars
I watched the movie through to the end(!), but spotted only one explicit small item to indicate that the Key might transport through time as well as space: When Skeletor’s minionette locates the copy of the Key, she says that they can find it within a “parsec-eon,” which kind of sounds like a space-time measurement. In addition, those who know the He-Man franchise tell me that he is a far-future descendant of Earth humans on the planet of Eternia, which means that the trip back to current-day Earth was through time. So it is a time-travel movie(!) but that fact has no bearing on the movie’s plot.
I recognized the theory—it’s the one on which time travel is based, even though we’ve never discovered time travel, at least not in any useful way, and researchers all over the universe discourage experimentation in it. They prefer the other theory of time travel, the one that says time is not linear, that we only perceive it as linear, and to actually time travel would be to alter the human brain.
But what Squishy is telling me is that it’s possible to time travel, it’s possible to open small windows in other dimensions, and bend them to our will.
Apparently, people in early 20th-century Cambridge espouse many wise thoughts about time, parallel universes that encompass every possible combination of events again and again, and something about every decision every made creating a branch point. In the end, it's difficult to make a cohesive model of time from the plotline of Dimensions, but we tried our best to do so in our plot notes.
Joe: Wait—the what, now?
Barry: If you travel back in time to change something, then you end up being the causal factor of that event.
Cisco: Like . . . Terminator.
Joe: Ah!
Wells: Or is time plastic? Is it mutable, whereby any changes in the continuum could create an alternate timeline?
Cisco: Back to the Future.
Joe: Ah, saw that one, too.