According to astrophysicist Igor Novikov, in his 1992 whitepaper titled “The Jinn of the time machine: nontrivial self-consistent solutions”, we live in a universe where time traveling objects and events are possible. Because they are possible, potentially destructive closed time-like curvature in spacetime must also be possible. But because we still exist intact, as far as we know, there must also be genies which protect us.
The Science of Time Travel
Current science, at least the observable and less theoretical kind, says time travel to the future is possible, with massive downsides. You can rocket into deep space and eventually turn around. When you get back many more years would have passed on Earth as would have passed for you, which we accept as a natural law thanks to Einstein’s concepts of relativity. Specifically, Einstein’s own 1905 whitepaper “On the Electrodynamics of Moving Bodies” introduced the theory of “special relativity”, the difference in timeframes to bodies moving at different speeds. A concept of time travel naturally results from Special Relativity.
But still, it’ll take decades of travel out into deep space, and then back again, for this time jump to occur. You could also go out into space, disassemble, move and rebuild a neutron star around you, creating a time dilation field from the massive differences in gravitation between the inside and outside of the star. A neutron star-fueled time machine. Despite the theoretical possibilities, though, such Galactus-level energy creation and consumption seems less than economically- and technically-feasible for simple Terrans. Also, we’re talking time travel over generations, through propagation, because our limited lifespans preclude the waiting game required.
Most theories for achieving time travel describe technological solutions that allow you to experience the passing of time differently from the rest of us and, thus, arrive at a future faster than the rest of us. Standard theories less often describe a way to travel to the past. Authors like J. Richard Gott, in his “Time Travel in Einstein’s Universe: The Physical Possibilities of Travel Through Time” for instance, explore both directions, considering black holes and wormholes as possible solutions.
At this point we’ve, culturally-speaking, developed enough of an imagination, coupled with theory, to picture a future where scientific breakthroughs make bending spacetime in either direction and at a more localized level possible. We won’t being doing so with a Delorean, a blue police box, a time ship (Legends of Tomorrow) or a Speed Force (The Flash), of course. But some form of a wormhole might actually do it. This tunnel connecting two separate points in spacetime is another actual mathematical solution that results from aspects of Einstein’s theories.
In the event that time travel becomes a thing, whatever that ultimately means, then it logically follows that we will also have to deal with the paradoxes associated with this manipulation of spacetime.
The Paradox in Science Fiction
Paradoxes are fun! The practitioners of science fiction, from H.G. Wells to Heinlein to Asimov, have explained and manipulated the paradox concept in a great variety of ways. Take Back to the Future where Marty McFly travels to a time before he was born, visiting his parents before they get together. His interference in their lives causes his mother’s romantic feelings towards his father to ebb, implying that they never marry and that Marty is never born. As a result Marty begins disappearing, physically dematerializing. If he’s never born, he doesn’t exist in the future which he left to travel to the past.
A timeline for Marty’s life, his “worldline” in time travel speak, would include a looping curve tracking his time travel from the ’80s back to the ’50s, and then an end point. And then non-existence. The line would disappear. But… if Marty erases his existence then he can’t go back in time. He can’t change his parents not getting together. The next instance of the McFly family history goes about its normal course. Marty is then born and experiences the same inspirations and events as before. What-a-paradox!
Typically called the Grandfather or Grandmother Paradox, changing your past or your ancestor’s past erases your existence. The literal, if psychopathic, example involves traveling to the past to kill your own grandfather, effectively a form of suicide. Another version involves changing world history, such as going back and killing Baby Hitler. If Hitler never creates the Third Reich then the reason to time travel in the first place vanishes. So will you or did you time travel, or didn’t you?
Then there’s the chicken and the egg conundrum. What came first? Aristotle freaked out about this 2,400 years ago. “For there could not have been a first egg to give a beginning to birds, or there should have been a first bird which gave a beginning to eggs; for a bird comes from an egg.” We now know that evolution played a part in the process, but the elements of the basic question describe well a casuality dilemma.
This is a much more impressive type of paradox, this causal loop, a situation with no time-based beginning or end. It’s also called an ontological paradox or a bootstrap paradox, and in Star Trek a predestination paradox.
In the television show The Flash, which involves various time travel scenarios on a regular basis, the resident hipster scientist Cisco Ramon, looking at a photo in a newspaper from the future, responds favorably to a variation on the Flash’s suit design (S01E20 “The Trap”). “Wait a second. Suppose we now change the color on your suit. Will it be because we got the idea from this picture? That would mean we’re living in a causal nexus. This – wow – this is so trippy, like, Marty and the Polaroid trippy.”
Causal loop, causal “nexus”, tomato, tomahto. In a later episode Cisco goes ahead and changes the color on the suit. He’s already been inspired by the future, it’s already in his brain, so why not? But where does Cisco’s design inspiration originally come from? This thought process loops like a hula hoop through time with no apparent beginning or end.
The Destructive CTC
A “closed timelike curve“, a CTC, is the established term in mathematical physics for a material version of this phenomenon, where the timeline of the life of an object or event, again its “worldline”, travels in time in such a way that its origination point is obscured. To emphasize, this is a real thing defined by real, professional mathematicians with names like van Stockum and Gödel.
If CTC’s are real, then time travel to the past must also somehow be possible. And because a “Back to the Future”-type scenario could happen, then the resulting possibility and destructive effects of a Grandmother Paradox haunts the whole enterprise.
And then along comes steely-eyed astrophysicist Igor Novikov. In “The Jinn of the time machine: nontrivial self-consistent solutions”, Novikov essentially describes a mathematical proof for a natural law that consistently avoids destructive CTCs. He names the solution to the problems associated with CTCs a “Jinnee”. The term “Jinnee” comes from the jinni/djinni/genie figure popularized for Western readers in the Arabian Nights, the supernatural creatures normally concealed from our senses but, when revealed, grant wishes. The Genie offers solutions. His Genie protects us.
Novikov’s Jinnee represents the existence of self-consistent solutions to apparent paradoxes resulting from time travel. The paper explores various time travel scenarios to show how, in all cases, the probability of a destructive CTC is zero. Basically, that time paradoxes are impossible. In one particular example Nokivov and his team describe how the trajectory of a billiard ball hitting itself through a wormhole can always avoid hitting itself out of the wormhole. In proving this mathematically, the paper defines two types: “The Jinnee of the first kind–matter makes a loop” and “The Jinnee of the second kind–information makes a loop”. So Cisco’s design idea in the example from The Flash above, a CTC, must have a solution involving a 2nd level Jinn; as well, the Universe would deploy a Jinnee to somehow completely avoid Marty’s more life-threatening scenes in Back to the Future, rendering it a lot less dramatic.
Novikov suggests that his Jinnee could solve any Grandfather Paradox by staying the hand of the Grandfather-killer time traveler. Basically, the Jinnee polices time travelers, like a Time Cop or a Time Master but without all the adventure. They (it’s not really a “they”) exist to solve for CTC-level paradox everywhere in the spacetime continuum, which in turn suggests a “block universe” concept where all events in the past, present and future are already fixed, which probably in turn suggests we all live in a simulated universe concocted by advanced alien races. But let’s take a step back.
Using a fictional lens, if CTCs do easily occur, if time travel is possible (and we all kind of hope it is against our better judgements) and thus the threat of paradoxes are inevitable, then in the future a ban on time travel is probably also inevitable. Which means, of course, that time traveling criminals are inevitable, and because of these criminals Time Cops are inevitable.
This future civilization capable of developing complex Kirbyesque systems that manipulate all four dimensions of spacetime and of generating the energy required to get to specific points along it (or inside it, or around it, whatever the case may be), and ride black holes, and surf wormholes, would want to police its infrastructure to the extent that the past developmental timeline, the history of scientific innovation that led to the point where time travelers time travel, not only wasn’t destroyed but was also never under threat, was in fact consistently protected. There would be Time Cops to protect Wells, Einstein, Heinlein, and Novikov.
In a universe of time traveling objects and events that might lead to potentially destructive CTCs, there’s also gotta be naturally-occurring djinn to counteract them.
Girl, Let it Go
Or you could solve the otherwise inevitable paradoxes by simply ignoring them entirely. Let’s travel back in time to 2017, to exactly 22 minutes 22 seconds in on a ComicCon panel for The Flash, where the producers, writers and actors explain that they intend to do just that.