Ours is the best of all possible worlds, according to Gottfried Leibniz at least, who reasoned that an omnipotent, omniscient God, having surveyed these possibilities, and being inherently good, can only have chosen the best one available to us. But still, it’s not perfect. Even knowing this world may be the best one possible, wouldn’t you, given the chance, go back in time and kill baby Hitler? Despite the wide variety of ethical, philosophical, and scientific questions raised by the possibility of time travel, and despite the wide range of literature, film, and scientific discussion on the topic, this simple poser has become the default encapsulation of everything about time travel: Given the technology, would you go back in time to eliminate someone we all can agree is universally evil?

The Kill Baby Hitler Conundrum was first postulated back in 1941, before the full reach of the Third Reich’s devastation was truly understood. In July of that year, Roger Sherman Hoar published the short story “I Killed Hitler” in Weird Tales under the pseudonym Ralph Milne Farley. In the story, an American painter called up for the draft goes back in time to kill a young Hitler. (In the story, the dictator is eleven—not a baby, but close enough). Time travel being what it is, things don’t work out quite as expected. By the end of the story, Hitler’s assassin has himself, through a series of twists and turns, assumed the dictator’s place. You can violate the laws of space and time, it seems, but you can’t escape the Law of Unintended Consequences.

 Hoar’s story is just one of many time travel narratives chronicled in James Gleick’s new book, Time Travel, a survey of the various ways we’ve schemed and dreamed to overtake the ticking clock, readjusting the past and altering the future to imagine better worlds and better times. “Why do we need time travel, when we already travel through space so far and fast?” he asks. “For history. For mystery. For nostalgia. For hope. To examine our potential and explore our memories. To counter regret for the life we lived, the only life, one dimension, beginning to end.”

Gleick’s first two books were relatively straightforward biographies: One on theoretical physicist Richard Feynman, the other on the concept of chaos. His third book, Faster (1999) was, well, faster—offering a series of vignettes that slammed the reader in rapid-fire succession, enumerating a thousand different ways in which modern life has sped up time in the futile promise that we might “save” it. Time-saving conveniences, he argues, are a false messiah, the byproducts of a delusion that pushes us to consume at an ever-faster rate without offering much by way of meaningful benefit. His next book, The Information (2011), was something of a return to an earlier, slower-paced mode of storytelling, with generous chapter lengths recounting the unexpected ways in which we’ve accumulated and transmitted data through the centuries. With Time Travel, Gleick has returned again to the form of Faster, and at times it almost feels like a sequel to that earlier work, or at least a continuation on a theme. If Faster probed why we’re so obsessed with speeding up time, Time Travel asks why we’re equally obsessed with transcending it altogether.

As a time machine, Gleick’s narrative rarely proceeds chronologically, opting instead to bounce from topic to topic, back and forth along multiple axes, guided in many ways by the twin lights of H. G. Wells and Albert Einstein. Faster focused on psychology and sociology, but most of all with technology, marketing, and consumerism. How innovations promised to save us time and failed, and how marketing helped create a perpetual sense in us that we’re lagging behind. Time Travel turns instead largely to fiction (where, of course, most time travel actually happens) and physics (where it has been most strenuously explored and debated as a serious concept).

TIME TRAVEL, by James GleickPantheon, pp 352, $26.95

Among the more fascinating aspects of Gleick’s history of time travel is how new this obsession is. Prior to the nineteenth century, there were no time travel stories, no discussions of how and when it might be possible, no explorations of its possible benefits and paradoxes. “No one bothered with the future in 1516,” Gleick notes. “It was indistinguishable from the present.” Prior to the Industrial Revolution, the present—particularly in the West—was simply a held breath, a fermata between Christ’s ascension and his return. Time travel was unnecessary because it was all-but-guaranteed: If Jesus didn’t return on your watch, you died knowing that, Rip Van Winkle-like, he’d wake you up on Judgment Day.

Time only became interesting with the Industrial Revolution. Riding through the landscape on a locomotive, the world rushing strangely past, people began to see that the world no longer had one fixed tempo. Add to that the range of new technological advances in a world that was changing rapidly in the span of generations—all of it gave people the idea that even more change might lay ahead. Writers began to imagine worlds in the distant future, such as the one Edgar Allan Poe invented in his 1850 short story, “Mellonta Tauta,” where, in the year 2848, an unnamed narrator passes the time recalling the past while whizzing through the air in a hot-air balloon. As with Washington Irving’s 1819 story “Rip Van Winkle,” these early time travel narratives almost always use time travel as a means of satire and social critique, either of the present, in the case of Poe, or of the past, as in the case of Mark Twain’s A Connecticut Yankee in King Arthur’s Court (1889).

H.G. Wells’ The Time Machine (1895) became the first of many literary attempts to explore time travel not in terms of satire but in terms of wonder. Wells imagines a man who is an “omniscient observer,” standing outside of time.  To this observer, “there would be no forgotten past—no piece of time as it were that had dropped out of existence—and no blank future of things yet to be revealed.” No longer an obscure prison of fate to which we are all subject, time, for the one who can travel it, is laid bare. Wells’s novel is a product of an era when science and fiction were often much closer than they are today. “There is no difference between Time and any of the three dimensions of Space except that our consciousness moves along it,” the Time Traveler says at one point, a bit of science fiction mumbo-jumbo that, in short order, would be recognized as an established scientific fact.

In the early days of the twentieth century, as so many scientific truths were overthrown in short order, literature began to move away from satire, instead playing with these new ideas and how they might affect our day to day lives in the future to come. Pulp science fiction magazines like Weird Tales and Amazing Stories, many of which were founded in the 1920s and 30s, became a means of keeping up with scientific journals, and testing out new principles. “Let it be understood that a science fiction story must be an exposition of a scientific theme and it must also be a story,” wrote Hugo Gernsback, founder of Amazing Stories and one of the early cheerleaders of the genre. “It must be a reasonable and logical and must be based upon known scientific principles.” The lowbrow sibling of the science journal, the pulp magazine gave our imaginations space to take in these new concepts.

 At some point, though, physicists themselves seemed to go too far, increasingly abstracting what we could conceptualize as our lived experience. “If you could stop every atom in its position and direction,” a character in Tom Stoppard’s Arcadia argues, “and if your mind could comprehend all the actions thus suspended, then if you were really, really good at algebra you could write the formula for the future; and although nobody can be so clever as to do it, the formula must exist just as if one could.” It is not difficult, in this formula, to recognize that we’ve long had a name for the mind that can comprehend every action and understand the formula that binds them all: God. Despite the massive rhetorical divide between science and religion in the contemporary landscape, it’s hard not to spot the yearning that physicists have for this divine language. As with the fatalism inherent in the dogma of predestination, Gleick notes that there “is something perverse about a scientist’s believing that the future is already complete—locked down tight, no different from the past.”

Ever questing for this divine formula, this absolute truth, scientists have in the process managed to call into question some of our day-to-day experience. Physicist Freeman Dyson, writing in 1979, claimed that “the division of space-time into past, present, and future is an illusion.” That may be the case, but for most of us this is cold comfort. Quantum mechanics does little to help us face regret over our past actions, nor will the knowledge of relativity relieve our anxiety about the future. In a letter to the widow of a recently deceased friend, Einstein once wrote: “Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.” Good for him; the rest of us—even those of us who believe in physics—still have to grieve. 

Time, Gleick reminds us, is ultimately not just a dimension, a concept, a mathematical abstraction. It is a function of our memory, a record of our deeds, a measure of our lives. “What is time? Things change, and time is how we keep track.”

 At their best, time travel narratives can push us to question some of the very basic premises of what makes us human. Robert A. Heinlein, whose “By His Bootstraps” (1941) and “‘All You Zombies’” (1959) rank as some of the most intricately plotted and executed science fiction stories ever written, use time travel to ask the question: What happens when you’re forced to confront an older self, a younger self, or both at the same time? During its heyday, science fiction used breaking discoveries to ask questions like these: How does one define the self? Does one’s identity exist outside of one’s memories, or outside of one’s biology?

But as physics moved on from four dimensions to five, six, even ten dimensions, relying on formulae and terms that were increasingly removed from anything resembling our lived experience, popular science fiction began to lose interest, returning to stories in which time functions like an arrow, a predictable chronology with a path that can be altered but probably shouldn’t be. Science fiction regressed to this simplified, chronological view of history, mainly because it works. “A century after Einstein discovered that perfect simultaneity is a chimera,” Gleick writes, “the technology of our interconnected world relies on simultaneity as never before. When telephone-network switches get out of sync, they drop calls. While no physicist ‘believes in’ absolute time, humanity has established a collective official timescale, preached by a choir of atomic clocks.”

In The Terminator (1984), the past can be changed, but it’s a bad idea, and the human heroes do their best to keep things steady. By Twelve Monkeys (1996), even time travelers can’t change the past; Bruce Willis’s James Cole can go back to observe, but repeatedly has to correct people that he’s not there to stop the impending apocalypse—even then, he’s driven mad by the inability to live in multiple time periods. Whether these stories dealt with killing Hitler (including 2012’s Looper) or the follies of trying to make money with a sports almanac from the future, the time travel narratives of the last few decades have become increasingly conservative, less concerned with possibility and wonder, and more concerned with caution and apprehension. “Confusion about past and future,” Gleick concludes, “cannot be tolerated.” Just ask James Cole.

From Back to the Future II to Stephen King’s saving-JFK novel 11/23/63, the lesson one learns again and again is that trying to improve the world through time travel is a fool’s game, creating far worse problems than whatever you’d hoped to fix. Most of time travel fiction these days is one way or another designed to help us swallow the bitter pill that this life is the one we’re stuck with, that trying to make things better will only backfire. The paradoxes of time travel are never there to truly be solved; they exist only to clarify the question. The question isn’t really, “Should you kill Baby Hitler?” But rather, “How do we best come to terms with a world where evil exists?”

Reading Faster now, seventeen years after it was first published, is a dystopian exercise: Gleick, lamenting how mindlessly sped up our world was then, had no inkling yet of smartphones, of Twitter and Snapchat, of the nightmarish acceleration that has only continued without signs of abating. Consumerism demands a perpetual restlessness, an unslakable thirst, a steady anxiety that drives us at greater and greater speeds. Time Travel, by contrast, comes across as something of an antidote: a reminder of the way that one of literature’s great powers is to remind us that this might be the best of all possible worlds, and that we are here because we could be nowhere else.