Robert Ashton is offered a huge amount of money to carry out a foolproof plan of robbing the British Museum of its most valuable holdings.

Major Bill Allison flies the experimental X-80 into the year 2024 where a plague has turned most humans into subhuman mutants and the rest are mostly deaf, dumb, and sterile. Once there, the leaders of an underground citadel (not to be confused with the ITTDB Citadel) have plans for him to marry the beautiful telepathic (and possibly non-sterile) Princess Trirene, and thereby re-populate the world. But together with Trirene and a small group of scientists, he devises a plan to return to his own time and prevent the plague from ever occurring.

The flight to the future is explained by scientific gibberish that contains a high concentration of mumbo jumbo, but the gist of it is that the speed of Allison’s plane (around 10,000 mph) added to the rotational speed of the Earth plus the speed of the Earth’s orbit around the sun plus the speed of the Solar System around the center of the galaxy plus maybe another speed or two, managed to bring his total speed close to that of light, which brought him to the future. Apparently, reversing his plane’s path is all that’s needed to return him to the past (ideally with Trirene beside him).

A self-defeating act paradox is set up nicely (if Alison stops the plague, then the citadel in the, future won’t be there to send him back to stop the plague), but the issue is never explicitly discussed and the ending of the film is inconclusive on the matter. Nevertheless, I commend the film for being the first to raise the issue of time travel paradoxes, albeit in the background.

After an alien spore infects the entire Enterprise crew with madness, it seems that the only available action to save the ship from a rapdidly decaying orbit is a cold restart of the engines.

Darn those high-gravity black stars! Always accidentally throwing starships hither and yon through time. Although in this case, the crew of the Enterprise manages to correct all the problems they caused by beaming 1960s Air Force pilot Captain John Christopher on board.

The Enterprise and her crew make their first intentional trip back in time to study historical aspects of 1968 and the Cold War, but unexpectedly, they intercept a transporter beam that brings the mysterious Gary Seven and his feline from a faraway advanced planet.

As the brave crew of the Enterprise are returning to Earth on a Klingon Bird of Prey to stand trial for the events of the previous movie, Spock determines that Earth’s demise is imminent unless they can return to 1986 and retrieve a humpback whale (which they proceed to do).

I saw this in the theater with Deb Baker and Jon Shultis during a winter trip to Pittsburgh for a small computer science education conference.

Time travel via a spaceship that got too close to an uncharted black hole. Our hero, Caleb Hornblower, survives to have a romance with Liberty Stone, a woman from a couple hundred years before he was born. The romantic element is definitely stronger than the science, but there are some interesting discussions about past versus future technology and different social norms. There’s also a fun ride on an aircycle! And a bit of comedy when Liberty’s parents arrive unexpectedly. But only the one time travel event is documented, so this remains heavier on the Romance than the Time Travel.

The story continues in a 1990 sequel, Times Change.

Jacob (J.T.) Hornblower, astrophysicist, deliberately travels back a couple of centuries to shake some sense into his brother Caleb, who had foolishly (in J.T.’s opinion) decided to stay in the past. A little more science than the first book in this duology, but still heavier on the romance angle, as J.T. finds himself strongly attracted to Sunbeam (Sunny) Stone. Both J.T. and Sunny are opinionated and bullheaded, as well as having blackbelts, so there is also more conflict in this book. The documented return trip to the future includes a brief description of physical side-effects.

Time travel is implied right from the first episode of the CW’s rendition of The Flash where a newspaper from the future is seen in the closing scene. The rest of the first season builds a fine time-travel arc that includes a nefarious time traveler from the far future, a classic grandfather paradox with a twist (sadly not examined), a do-over day for the Flash (which Harrison Wells calls “temporal reversion”), and a final episode that sees the Flash travel back to his childhood (as well as a hint that Rip Hunter himself will soon appear on the CW scene).

Alas, Sean Carroll doesn’t pull any punches in his realistic assessment of the kinds of time travel that are or may be possible under the laws of physics as we know them in our universe. Or, as Professor Carroll himself puts it: “. . . podcasting isn’t for the squeamish.” In my layman’s understand of his most excellent explication, time travel aficionados have two physical phenomena on which to hang their Hat Things:

1. Time Dilation: Under the laws of Einstein’s special relativity, a fast traveler who leaves the Earth, zooming around for a while at near light speed before returning, will experience less passage of time than those who stay in the more-or-less fixed reference frame of Earth. How cool is that? Yes, you can travel as far into the future as you like, so long as you have a means of zooming up to a high enough speed and returning. (And according to general relativity, time dilation also occurs inside a high gravitational field, although I didn’t notice a discussion of this sort of time dilation in the podcast.)
2. Closed Timelike Curves: The second hope for time travelers are certain distributions of matter that (according to Einstein’s equations of general relativity) result in directed paths through spacetime in which a traveler along the path is always moving forward through time—and yet completing a full circuit of the path returns the traveler to the starting point in both space and time. That’s the good news. The bad news is that such paths, called closed timelike curves, might only be possible in the presense of infinitely long rotating cylinders or other physical conditions that may be impossible to engineer.

Up in the ITTDB Citadel, many of us found ourselves in a disquieted state at this point in Professor Carroll’s podcast (roughly the two-hour mark). Some went to bed early in a kind of daze; others decided it was time for a long walk through the lonely ice paths that surround the Citdel. But for those with the fortitude to keep their ears glued to the pod, there was a great reward. Carroll had already waded through the swift, waist-high currents of causality, predeterminism, free will, the A Theory of Time, the B Theory of time, and more. But now he was ready to dive into deep, uncharted waters. Yes, now he was ready to leave known physics behind, to talk about branching time that went beyond the Everettian Many Worlds of Schrödinger’s equation, and to consider what kind of a world would be needed to allow stories such as Back to the Future and Looper to consistently hold together. With this in mind, he devices a four-pronged theory that concludes with what he calls Narrative Time. For me, narrative time shares some features with the time model of Asimov’s The End of Eternity (a model that we call Hypertime in our story-tagging system), but it goes far beyond that.

Suffice it to say that when all the Librarians up in the Citadel woke from their sleeps and returned from their treks, we had a celebration that was strident enough to raise Lazurus Long himself from the dead (if he is dead, that is).

After a catastrophic start to Season 2, Q steps in to pluck Picard’s crew and the Borg Queen from certain death only to insert them into a dystopian timeline that Q himself had created via a small change in 2024.