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James Gleick on How Our Cultural Fascination with Time Travel Illuminates Memory, the Nature of Time, and the Central Mystery of Human Consciousness

“Every moment alters what came before. We reach across layers of time for the memories of our memories.”

James Gleick on How Our Cultural Fascination with Time Travel Illuminates Memory, the Nature of Time, and the Central Mystery of Human Consciousness

“Both in thought and in feeling, even though time be real, to realise the unimportance of time is the gate of wisdom,” Bertrand Russell asserted in 1918 as he made his beautiful case for “a largeness of contemplation” in contemplating the nature of time. “Shard by shard we are released from the tyranny of so-called time,” Patti Smith wrote nearly a century later in her magnificent meditation on time and transformation.

As a child in Bulgaria, never having heard of either Russell or Smith, one aspect of time perplexed me to the point of obsession: In my history textbooks, dates relating to significant events or historical figures of Slavic origin were listed in pairs — each had a “new style” date and an “old style” date, always thirteen days apart. So, for instance, Hristo Botev — the great revolutionary who led Bulgaria’s liberation from a five-century Ottoman slavery — was born on January 6 of 1848 according to the new style and on Christmas Day of 1847 according to the old style.

I would later learn that this was the product of the League of Nations, formed after WWI. Its Committee on Intellectual Cooperation, headed by Henri Bergson — the great French philosopher who famously opposed Einstein in a debate that changed our modern conception of time — was tasked with eradicating the Julian calendar that many countries, including Bulgaria and Russia, still used and replacing it with the Gregorian calendar as the new global standard.

This is my earliest memory of confronting the nature of time as both an abstraction humans could make with a committee and a concrete anchor of existence mooring our births, our deaths, and our entire sense of history. But most perplexing of all was the question of what happened to the people who lived through the transition — what happened to the thirteen very real days between the two fictions of the calendars. If reading history wasn’t time-travelish enough, reading about real people forced to time-travel in their real lives by an international decree was both utterly fascinating and utterly confusing. Did the person actually exist between their old-style date of birth and the new-style one — were they alive or not-yet-born? (Even today, the Wikipedia biographies of a Slavic persons from that era list both old-style and new-style dates of birth and death.) The person, of course, most definitely did exist between the day they were born and the day they died, whatever dates posterity — our living present, their unlived future — may impose on those days, now far in the past.

That thirteen-day lacuna between being and non-being was, apparently, the price of globalization. But it was also a suddenly shrill echo of an eternal question: If time bookends our existence, and if it is so easily perturbed by a calendarical convention, is it a mere abstraction?

Discus chronologicus — a German depiction of time from the early 1720s, included in Cartographies of Time. (Available as a print and as a wall clock.)

Time is the two-headed Baskerville hound chasing us as we run for our lives — and from our lives — driven by the twain terrors of tedium and urgency. Toward what, we dare not think. Meanwhile, our information-input timelines are called “feeds.” We feast on time as time feasts on us. Time and information, if they are to be disentwined at all, dictate our lives. Is it any wonder, then, that we would rebel by trying to subjugate them in return, whether by formalizing them with our calendars or by fleeing from them with our time travel fantasies?

How those time travel fantasies originated, what technological and cultural developments fomented this distinctly modern impulse of the collective imagination, and how it illuminates our greatest anxieties is what science historian and writer extraordinaire James Gleick explores in Time Travel: A History (public library) — a grand thought experiment, using physics and philosophy as the active agents, and literature as the catalyst. Embedded in the book is a bibliography for the Babel of time — a most exquisitely annotated compendium of the body of time literature. What emerges is an inquiry, the most elegant since Borges, into why we think about time, why its directionality troubles us so, and what asking these questions at all reveals about the deepest mysteries of human consciousness and about what Gleick so beguilingly calls “the fast-expanding tapestry of interwoven ideas and facts that we call our culture.”

Gleick, who examined the origin of our modern anxiety about time with remarkable prescience nearly two decades ago, traces the invention of the notion of time travel to H.G. Wells’s 1895 masterpiece The Time Machine. Although Wells — like Gleick, like any reputable physicist — knew that time travel was a scientific impossibility, he created an aesthetic of thought which never previously existed and which has since shaped the modern consciousness. Gleick argues that the art this aesthetic produced — an entire canon of time travel literature and film — not only permeated popular culture but even influenced some of the greatest scientific minds of the past century, including Stephen Hawking, who once cleverly hosted a party for time travelers and when no one showed up considered the impossibility of time travel proven, and John Archibald Wheeler, who popularized the term “black hole” and coined “wormhole,” both key tropes of time travel literature.

Illustration by Matthew Houston for a graphic interpretation of Wells’s The Time Machine

Gleick considers how a scientific impossibility can become such fertile ground for the artistic imagination:

Why do we need time travel, when we already travel through space so far and fast? 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.

Wells’s Time Machine revealed a turning in the road, an alteration in the human relationship with time. New technologies and ideas reinforced one another: the electric telegraph, the steam railroad, the earth science of Lyell and the life science of Darwin, the rise of archeology out of antiquarianism, and the perfection of clocks. When the nineteenth century turned to the twentieth, scientists and philosophers were primed to understand time in a new way. And so were we all. Time travel bloomed in the culture, its loops and twists and paradoxes.

Wells imagined time travel in an era where so much of what we take for granted was either a disorienting novelty or yet to be invented — bicycles, elevators, and balloons were new, and even the earliest visions of anything resembling the internet were half a century away. Gleick considers the direction of Wells’s imagination:

The object of Wells’s interest, bordering on obsession, was the future — that shadowy, inaccessible place. “So with a kind of madness growing upon me, I flung myself into futurity,” says the Time Traveller. Most people, Wells wrote — “the predominant type, the type of the majority of living people” — never think about the future. Or, if they do, they regard it “as a sort of blank non-existence upon which the advancing present will presently write events.” … The more modern sort of person — “the creative, organizing, or masterful type” — sees the future as our very reason for being: “Things have been, says the legal mind, and so we are here. The creative mind says we are here because things have yet to be.”

Wells wrote his masterpiece shortly before the rise of relativity remodeled our notions of time. There was Einstein, of course. And Kurt Gödel. And Hermann Minkowski, Einstein’s teacher, whose model used four numbers (x, y, z, and t) to denote a “world point” — what we now call spacetime. Gleick writes of his legacy:

“Mere shadows,” Minkowski said. That was not mere poetry. He meant it almost literally. Our perceived reality is a projection, like the shadows projected by the fire in Plato’s cave. If the world — the absolute world — is a four-dimensional continuum, then all that we perceive at any instant is a slice of the whole. Our sense of time: an illusion. Nothing passes; nothing changes. The universe — the real universe, hidden from our blinkered sight — comprises the totality of these timeless, eternal world lines.

But if we were able to conceive of this timeless totality — to integrate it into our conscious experience — the fantasy of time travel wouldn’t scintillate us so. A centerpiece of our temporal dissonance is one particular phenomenon of consciousness, a very palpable human experience: memory. “Perhaps memory is the time traveler’s subject,” Gleick observes. With an eye to Virginia Woolf’s memorable mediation on memory in Orlando, that supreme masterwork of time travel, he writes:

What is memory, for a time traveler? A conundrum. We say that memory “takes us back.” Virginia Woolf called memory a seamstress “and a capricious one at that.” … “I can’t remember things before they happen,” says Alice, and the Queen retorts, “It’s a poor sort of memory that only works backwards.” Memory both is and is not our past. It is not recorded, as we sometimes imagine; it is made, and continually remade. If the time traveler meets herself, who remembers what, and when?

Illustration by Lisbeth Zwerger for a special edition of Alice in Wonderland

The question of memory, of course, is inseparable from the question of identity, for if we live in “permanent present tense,” we are incapable of stringing together the narrative out of which our sense of self arises. This continuity of selfhood, after all, is what makes you and your childhood self the “same” person despite a lifetime of physical and psychological change. Time travel presents some serious paradoxes for memory and therefore for the self. “A person’s identity,” Amin Maalouf wrote of the genes of the soul, “is like a pattern drawn on a tightly stretched parchment. Touch just one part of it, just one allegiance, and the whole person will react, the whole drum will sound.” If we could travel back to our own past and alter even a tiny speck of the pattern, we’d be changing the entire drum — our identity would have a wholly different sound. Gleick writes:

What is the self? A question for the twentieth century to ponder, from Freud to Hofstadter and Dennett with detours through Lacan, and time travel provides some of the more profound variations on the theme. We have split personalities and alter egos galore. We have learned to doubt whether we are our younger selves, whether we will be the same person when we next look. The literature of time travel … begins to offer a way into questions that might otherwise belong to philosophers. It looks at them viscerally and naïvely — as it were, nakedly.

And so we arrive, at page 99 and no sooner, at the problem of free will. Gleick writes:

Free will cannot be easily dismissed, because we experience it directly. We make choices. No philosopher has yet sat down in a restaurant and told the waiter, “Just bring me whatever the universe has preordained.” Then again, Einstein said that he could “will” himself to light his pipe without feeling particularly free. He liked to quote Schopenhauer… Man can do what he will, but he cannot will what he wills.

The free will problem was a sleeping giant and, without particularly meaning to, Einstein and Minkowski had prodded it awake. How literally were their followers to take the space-time continuum — the “block universe,” fixed for eternity, with our blinkered three-dimensional consciousnesses moving through it?

A century later, the question has hardly budged. And yet we live our lives with such urgency and pointedness of intent — perhaps precisely because we are unwilling to relinquish the illusion of free will. Gleick observes:

Everywhere we look, people are pressing elevator buttons, turning doorknobs, hailing taxicabs, lifting sustenance to their lips, and begging their lovers’ favor. We act as though the future is, if not in our control, not yet settled… We would suffer illusions of free will, because, by happenstance, we tend to know less about the future than about the past.

Happenstance? Memory, self, free will — this Venn diagram of consciousness is indeed encircled by the lines we draw, often artificially, between causality and chance. (“No one’s fated or doomed to love anyone… The accidents happen,” wrote Adrienne Rich.) Gleick writes:

All the paradoxes are time loops. They all force us to think about causality. Can an effect precede its cause? Of course not. Obviously. By definition.


But we’re not very good at understanding causes. The first person on record as trying to analyze cause and effect by power of ratiocination was Aristotle, who created layers of complexity that have caused confusion ever after. He distinguished four distinct types of causes, which can be named (making allowances for the impossibility of transmillennial translation) the efficient, the formal, the material, and the final. Some of these are hard for us to recognize as causes. The efficient cause of a sculpture is the sculptor, but the material cause is the marble. Both are needed before the sculpture can exist. The final cause is the purpose for which it is made — its beauty, let’s say… We do well to remember that nothing, when we look closely, has a single unambiguous incontrovertible cause.

Gleick reality-checks the logicians’ causal models of reality:

If X, then Y means one thing in logic. In the physical world, it means something trickier and always (we should know by now) subject to doubt. In logic, it is rigid. In physics, there is slippage. Chance has a part to play. Accidents can happen. Uncertainty is a principle. The world is more complex than any model.


The physical laws are a construct, a convenience. They are not coextensive with the universe.

One of Antoine de Saint-Exupéry’s original watercolors for The Little Prince

Mistaking the model for what Virginia Woolf called “the thing itself” seems to be a perennial problem of science, and one particularly integral to the perplexity of time:

William Faulkner said, “The aim of every artist is to arrest motion, which is life, by artificial means and hold it fixed.” Scientists do that, too, and sometimes they forget they are using artificial means.


You can say the equations of physics make no distinction between past and future, between forward and backward in time. But if you do, you are averting your gaze from the phenomena dearest to our hearts. You leave for another day or another department the puzzles of evolution, memory, consciousness, life itself. Elementary processes may be reversible; complex processes are not. In the world of things, time’s arrow is always flying.

Illustration from a vintage children’s adaptation of Micromégas, Voltaire’s trailblazing scifi homage to Newton

With an eye to Borges’s ideas about time, Gleick returns to the puzzlement of memory, equally not coextensive with the physics of time:

We create memories or our memories create themselves. Consulting a memory converts it into a memory of a memory. The memories of memories, the thoughts of thoughts, blend into one another until we cannot tease them apart. Memory is recursive and self-referential. Mirrors. Mazes.

The formation of memory as a function of consciousness invites the chief religious opposition to science — a theological avoidance of the free will problem, the intellectually fragile contradictions of which Gleick captures elegantly in discussing the ideas in Isaac Asimov’s novel The End of Eternity:

Time is a feature of creation, and the creator remains apart from it, transcendent over it. Does that mean that all our mortal time and history is, for God, a mere instant — complete and entire? For God outside of time, God in eternity, time does not pass; events do not occur step by step; cause and effect are meaningless. He is not one-thing-after-another, but all-at-once. His “now” encompasses all time. Creation is a tapestry, or an Einsteinian block universe. Either way, one might believe that God sees it entire. For Him, the story does not have a beginning, middle, and end.

But if you believe in an interventionist god, what does that leave for him to do? A changeless being is hard for us mortals to imagine. Does he act? Does he even think? Without sequential time, thought — a process — is hard to imagine. Consciousness requires time, it seems. It requires being in time. When we think, we seem to think consecutively, one thought leading to another, in timely fashion, forming memories all the while. A god outside of time would not have memories. Omniscience doesn’t require them.

But whatever pitfalls, paradoxes, and perplexities might bedevil our individual memory, they are rendered into even sharper relief in our collective memory — nowhere more so than in the curious human obsession with time capsules, the grandest of which is the Golden Record that sailed into space aboard the Voyager in 1977, a civilizational labor of love dreamt up and rendered real by Carl Sagan and Annie Druyan that was also the record of their own love story.

The Golden Record
The Golden Record

Gleick considers what this strange millennia-old practice, this “prosthetic memory,” reveals about human nature:

When people make time capsules, they disregard a vital fact of human history. Over the millennia — slowly at first and then with gathering speed — we have evolved a collective methodology for saving information about our lives and times and transmitting that information into the future. We call it, for short, culture.

First came songs, clay pots, drawings on cave walls. Then tablets and scrolls, paintings and books. Knots in alpaca threads, recording Incan calendar data and tax receipts. These are external memory, extensions of our biological selves. Mental prostheses. Then came repositories for the preservation of these items: libraries, monasteries, museums; also theater troupes and orchestras. They may consider their mission to be entertainment or spiritual practice or the celebration of beauty, but meanwhile they transmit our symbolic memory across the generations. We can recognize these institutions of culture as distributed storage and retrieval systems. The machinery is unreliable — disorganized and discontinuous, prone to failures and omissions. They use code. They require deciphering. Then again, whether made of stone, paper, or silicon, the technology of culture has a durability that the biological originals can only dream of. This is how we tell our descendants who we were. By contrast, the recent smattering of time capsules is an oddball sideshow.

Building on the ideas he examined in his indispensable biography of information, Gleick adds:

As for knowledge itself, that is our stock in trade. When the Library of Alexandria burned, it was one of a kind. Now there are hundreds of thousands, and they are crammed to overflowing. We have developed a species memory. We leave our marks everywhere.


When people fill time capsules they are trying to stop the clock — take stock, freeze the now, arrest the incessant head-over-heels stampede into the future. The past appears fixed, but memory, the fact of it, or the process, is always in motion. That applies to our prosthetic global memory as well as the biological version. When the Library of Congress promises to archive every tweet, does it create a Borgesian paradox in real time or a giant burial chamber in progress?

Because time has this unsilenceable undertone reminding us of our morality, we grasp onto it — onto this intangible abstraction — the way we grasp onto material possessions, commodities, and all the other tangibilia by which we sustain our illusions of permanence in a universe dominated by impermanence and constant flux. From this angle, Gleick revisits the tenet that all paradoxes are time-loops:

Once we conceive of time as a quantity, we can store it up, apparently. We save it, spend it, accumulate it, and bank it. We do all this quite obsessively nowadays, but the notion is at least four hundred years old. Francis Bacon, 1612: “To choose Time, is to save Time.” The corollary of saving time is wasting it.


We go back and forth between being time’s master and its victim. Time is ours to use, and then we are at its mercy. I wasted time, and now doth time waste me, says Richard II; For now hath time made me his numbering clock. If you say that an activity wastes time, implying a substance in finite supply, and then you say that it fills time, implying a sort of container, have you contradicted yourself? Are you confused? Are you committing a failure of logic? None of those. On the contrary, you are a clever creature, when it comes to time, and you can keep more than one idea in your head. Language is imperfect; poetry, perfectly imperfect. We can occupy the time and pass the time in the same breath. We can devour time or languish in its slow-chapp’d power.

Still, memory remains. The key to understanding time, Gleick suggests, lies in understanding memory — understanding the dialogue, often dissonant, between the experiencing self and the remembering self. He writes:

The universe does what it does. We perceive change, perceive motion, and try to make sense of the teeming, blooming confusion. The hard problem, in other words, is consciousness. We’re back where we started, with Wells’s Time Traveller, insisting that the only difference between time and space is that “our consciousness moves along it,” just before Einstein and Minkowski said the same. Physicists have developed a love-hate relationship with the problem of the self. On the one hand it’s none of their business — leave it to the (mere) psychologists. On the other hand, trying to extricate the observer — the measurer, the accumulator of information — from the cool description of nature has turned out to be impossible. Our consciousness is not some magical onlooker; it is a part of the universe it tries to contemplate.

The mind is what we experience most immediately and what does the experiencing. It is subject to the arrow of time. It creates memories as it goes. It models the world and continually compares these models with their predecessors. Whatever consciousness will turn out to be, it’s not a moving flashlight illuminating successive slices of the four-dimensional space-time continuum. It is a dynamical system, occurring in time, evolving in time, able to absorb bits of information from the past and process them, and able as well to create anticipation for the future.


What is time? Things change, and time is how we keep track.

This act of keeping track, which is largely a matter of telling the present from the past, is what Gleick considers the key question of consciousness and the pillar of our very sense of self:

How do we construct the self? Can there be memory without consciousness? Obviously not. Or obviously. It depends what you mean by memory. A rat learns to run a maze — does it remember the maze? If memory is the perpetuation of information, then the least conscious of organisms possess it. So do computers, whose memory we measure in bytes. So does a gravestone. But if memory is the action of recollection, the act of remembrance, then it implies an ability to hold in the mind two constructs, one representing the present and another representing the past, and to compare them, one against the other. How did we learn to distinguish memory from experience? When something misfires and we experience the present as if it were a memory, we call that déjà vu. Considering déjà vu — an illusion or pathology — we might marvel at the ordinary business of remembering.

This dizzying tour of science, philosophy, and their interaction with literature is leading me to wonder: When a machine hums, does it hear or notice the hum? Could it be that time is the hum of consciousness?


Perhaps time is so troublesome because it foists upon us our perennial fear of missing out. Time travel, Gleick argues, is such an alluring fantasy precisely because it bridges the infinite possibility of life with the realm of the probable — by traveling in time, we get to live the myriad unlived lives which we are doomed to never experience under the physical laws of this one and only life we’ve been allotted. He captures this with uncompromising precision:

If we have only the one universe — if the universe is all there is — then time murders possibility. It erases the lives we might have had.

Time travel, then, is a thought experiment performed in the petri dish of existence itself, catalyzing its most elemental and disquieting questions. In a reframing of the central idea of the Butterfly Effect — a term Gleick himself wrested from the esoteric lexicon of meteorology and embedded in the popular imagination in 1987 with his groundbreaking first book, Chaos, which created an aesthetic for the history of science much like Wells created an aesthetic for time travel literature — he considers the logical loops of changing any one element of history, which ripples across all of being:

We have to ask these questions, don’t we? Is the world we have the only world possible? Could everything have turned out differently? What if you could not only kill Hitler and see what happens, but you could go back again and again, making improvements, tweaking the timeline, like the weatherman Phil (Bill Murray) in one of the greatest of all time-travel movies, reliving Groundhog Day until finally he gets it right.

Is this the best of all possible worlds? If you had a time machine, would you kill Hitler?

And so we arrive at the answer to the central question:

Why do we need time travel? All the answers come down to one. To elude death.

Time is a killer. Everyone knows that. Time will bury us. I wasted time, and now doth time waste me. Time makes dust of all things. Time’s winged chariot isn’t taking us anywhere good.

How aptly named, the time beyond death: the Hereafter.


But even death is strewn with the temporal asymmetry of our anxieties, which Montaigne articulated brilliantly half a millennium ago as he contemplated death and the art of living: “To lament that we shall not be alive a hundred years hence, is the same folly as to be sorry we were not alive a hundred years ago.” And yet we do dread death with infinitely greater intensity than we dread, if that’s even the appropriate term, not having lived before our birth. If the arrow of time is one-directional, so is the arrow of time-anxiety. But Gleick subverts Montaigne and delivers a sublime summation of the paradoxical impulse at the heart of our time travel yearnings:

You lived; you will always have lived. Death does not erase your life. It is mere punctuation. If only time could be seen whole, then you could see the past remaining intact, instead of vanishing in the rearview mirror. There is your immortality. Frozen in amber.

For me the price of denying death in this way is denying life.

Barring denial, our only recourse is to surrender our memory, our consciousness, our very selves to the flow of time. To borrow Sarah Manguso’s piercing observation, “time punishes us by taking everything, but it also saves us — by taking everything.” Gleick writes:

When the future vanishes into the past so quickly, what remains is a kind of atemporality, a present tense in which temporal order feels as arbitrary as alphabetical order. We say that the present is real—yet it flows through our fingers like quicksilver.


It might be fair to say that all we perceive is change — that any sense of stasis is a constructed illusion. Every moment alters what came before. We reach across layers of time for the memories of our memories.

Complement Time Travel — the kind of book that lodges itself in the imagination, planting seeds of ideas, insights, and revelations bound to go on blossoming for the remainder of this lifetime — with Bertrand Russell on the nature of time and Virginia Woolf on its astonishing elasticity, then revisit Gleick on the story behind Newton’s famous “standing on the shoulders of giants” metaphor, the source of Richard Feynman’s genius, and the origin of Type A.


The Science of Mental Time Travel and Why Our Ability to Imagine the Future Is Essential to Our Humanity

Shedding light on “the cognitive rudder that allows our brains to navigate the river of time.”

The Science of Mental Time Travel and Why Our Ability to Imagine the Future Is Essential to Our Humanity

Lewis Carroll’s Alice in Wonderland remains one of my all-time favorite books, largely because Carroll taps his training as a logician to imbue the whimsical story with an allegorical dimension that blends the poetic with the philosophical. To wit: The Red Queen remembers the future instead of the past — an absurd proposition so long as we think of time as linear and memory as beholden to the past, and yet a prescient one given how quantum physics (coincidentally, a perfect allegorical exploration of Wonderland) conceives of time and what modern cognitive science tells us about how elastic our experience of time is. As it turns out, the Red Queen is far more representative of how human memory actually works than we dare believe.

Illustration from Alice in Wonderland by Lisbeth Zwerger. (Click image for details)

“To be human,” writes Dan Falk in In Search of Time: The History, Physics, and Philosophy of Time (public library), “is to be aware of the passage of time; no concept lies closer to the core of our consciousness” — something evidenced by our millennia-old quest to map this invisible dimension. One of the most remarkable and evolutionarily essential elements of experiencing time through human consciousness is something psychologists and cognitive scientists call mental time travel — a potent bi-directional projection that combines episodic memory, which allows us to draw on our autobiographical experience and call up events, experiences, and emotions that occurred in the past, with the ability to imagine and anticipate future events. Falk puts it unambiguously:

Without it, there would be no planning, no building, no culture; without an imagined picture of the future, our civilization would not exist.

As it turns out, episodic memory — a term coined in the early 1970s by Canadian neuroscientist Endel Tulving, author of the seminal book Elements of Episodic Memory — is central to our capacity for mental time travel and, according to many scientists, fairly unique to humans. Unlike other facets of memory, such as the acquisition of new skills, which are rooted in the here-and-now, Falk points out that episodic memory allows us “to peer back across time, using our imagination to revisit just about any event that we choose.” This mental reliving of the past may be the root of some distinct human maladies — take the wistful reminiscence over a lost love, for instance — but it is also central to our evolutionary survival, allowing us to anticipate future outcomes based on past ones and thus to plan better and be more prepared for what tomorrow may bring. (The dark side of this evolutionarily beneficial faculty is that our over-planning often ends up shortchanging our happiness.)

And yet the benefits outweigh the costs, in evolutionary terms. Falk explains:

The capacity for mental time travel gave our ancestors an invaluable edge in the struggle for survival. They believe there is a profound link between remembering the past and imagining the future. The very act of remembering, they argue, gives one the “raw material” needed to construct plausible scenarios of future events and act accordingly. Mental time travel “provides increased behavioral flexibility to act in the present to increase future survival chances.” If this argument is correct, then mental time travel into the past — remembering — “is subsidiary to our ability to imagine future scenarios.” Tulving agrees: “What is the benefit of knowing what has happened in the past? Why do you care? The importance is that you’ve learned a lesson,” he says. “Perhaps the evolutionary advantage has to do with the future rather than the past.”

Modern neuroscience appears to confirm that line of reasoning: as far as your brain is concerned, the act of remembering is indeed very similar to the act of imagining the future.

Discus chronologicus — a German depiction of time from the early 1720s, included in Cartographies of Time. (Available as a print and as a wall clock.)

Though we might not be able to “remember” the future, as the Red Queen does, we do envision it in ways strikingly similar to how we picture events from the past — Falk notes that fMRI studies indicate we use similar regions in the brain’s frontal and temporal lobes when thinking about events in either direction of time. What’s more, psychologists have found that much like it’s harder for us to remember an event in the distant past than a recent one, it’s harder for us to imagine an event in the distant future than one expected to take place soon. This hints at the massively misguided way in which we think of and evaluate memory, which we falsely depict as a recording device, versus foresight. Falk writes:

When we imagine the future, we know what we picture is really just an educated guess; we may be right in the broad brushstrokes, but we are almost certainly wrong in the details. We hold memory to a higher standard. We feel — most of the time — that our memories are more than guesses, that they reflect what really happened. When confronted with a conflicting account of how last week’s party unfolded, we cling to our beliefs: He must be mistaken; I know what I saw.

Falk cites the Harvard psychologist Daniel Schacter:

[The brain is] a fundamentally prospective organ that is designed to use information from the past and the present to generate predictions about the future. Memory can be thought of as a tool used by the prospective brain to generate simulations of possible future events… We tend to think of memory as having primarily to do with the past… And maybe one reason we have it is so that we can have a warm feeling when we reminisce, and so on. But I think the thing that has been neglected is its role in allowing us to predict and simulate the future.

Artwork by Andy Goldsworthy from his project ‘Time.’ (Click image for details)

In order to mentally time-travel into the future, the brain has to accomplish a couple of things at once — we activate our “semantic memory,” which encompasses our basic knowledge of facts about the world and thus helps paint a backdrop for the imagined scene, and we call on our episodic memory, which pulls on our autobiographical library of remembered experiences to fill in specific details for this general scene. Curiously, episodic memory tends to be rather flawed but, according to two scientists Falk quotes, that’s okay since its core purpose is to provide “a more general toolbox that allowed us to escape from the present and develop foresight, and perhaps create a sense of personal identity.”

To be sure, just like elsewhere in cognitive science, human exceptionalism may be misplaced here — scientists have found that other species are also capable of varying degrees of mental time travel. Falk cites one of the most intriguing experiments, involving scrub jays. He writes:

Psychologist Nicola Clayton and her colleagues housed the birds on alternate days in two different compartments — one in which the jays always received “breakfast,” and one in which they did not. Then the birds were unexpectedly given extra food in the evening, at a location where they could access either compartment. The jays promptly cached their surplus — and they preferentially cached it in the “no breakfast” compartment. Because the birds were not hungry at the time of the caching, the researchers claim that the birds truly anticipated the hunger they would experience the next morning.

Still, the fact that humans are capable of remarkably elaborate and detailed mental time travel reveals something unique about our evolution and the development of such hallmarks of humanity as language and theory of mind. Falk writes:

In all likelihood, the capacity for mental time travel did not develop in isolation but rather alongside other crucial cognitive abilities. “To entertain a future event one needs some kind of imagination,” [the prominent psychologists Thomas] Suddendorf and [Michael] Corballis write, “some kind of representational space in our mind for the imaginary performance.” Language could also play an important role. Our language skills embrace mental time travel by the use of tenses and recursive thinking; when we say “A year from now, he will have retired,” we’re imagining a future time in which some event — which has not yet happened — will lie in the past… Mental time travel may have been “a pre-requisite to the evolution of language itself.” If mental time travel is indeed unique to humans, it may help us understand why complex language is also, apparently, unique.

In fact, the development of mental time travel may even be how the concept of time itself came into existence — according to Suddendorf and Corballis, our species emerged victorious in “an extraordinary evolutionary arms race” largely due to our growing capacity for foresight and sophisticated language, which not only gave us culture and “coordinated aggression” but also, for the first time in evolutionary history, enabled us to understand the concepts of “past” and “future.” The mental reconstruction of what has been and the imagining of what could be, they argue, created the concept of time and enabled us to understand the continuity between the past and the future. Falk, once again, puts it succinctly:

Mental time travel may indeed be the cognitive rudder that allows our brains to navigate the river of time.

In Search of Time is a fantastic read in its entirety, covering such facets of life’s most intricate dimension as how the calendar was born, why illusion and reality aren’t always so discernible from one another, and what the ultimate fate of the universe might be. Complement it with these seven excellent books on time and a fascinating read on how our memory works.


Einstein, Gödel, and the Science of Time Travel

Meeting your future grandchildren in a rotating universe.

The fabric of time remains among the most fascinating frontiers of science, and the concept of time travel among the most prolific plot lines of science fiction. In this short video from THNKR, who also brought us the BOOKD series on paradigm-shifting books, theoretical physicist Ronald Mallett goes against the present scientific consensus and argues, by way of Einstein and Gödel’s theories, that time travel might, indeed, be possible. Whether in a century we’ll look back and laugh at the wild misguidedness of his proposition or at its blatant obviousness, only time will tell.

Gödel actually showed that if we were living in a rotating universe, this universe could create loops in time — and by “loops in time” I mean you actually have a timeline that’s normally a straight line of past, present, and future, that’s turned into a loop — and you can actually go along that loop in time and go back into the past. And he based his work squarely on Einstein’s general theory of relativity.

It’s Okay To Be Smart


Stephen Hawking’s Charming Children’s Book about Time-Travel, Co-Written with His Daughter

A pig and a supercomputer walk into a black hole…

It’s not uncommon for famous authors of “adult” literature to have also penned lesser-known but no less lovely children’s books — take, for instance, those by Mark Twain, Maya Angelou, James Joyce, E. E. Cummings, and Sylvia Plath. Famous scientists, on the other hand, are more likely to become the subject of a children’s book rather than the author of one. But not so with Stephen Hawking, one of the great geniuses of our time, born on this day in 1942.

In 2007, Hawking wrote George’s Secret Key to the Universe (public library | IndieBound) — a charming, imaginative story about the mesmerism of space and the allure of time-travel, featuring lovely semi-Sendakian crosshatch illustrations by Garry Parsons. What makes the book especially endearing is that Hawking co-wrote it with his daughter Lucy.

One morning, George — a little boy raised by lo-fi, bookish parents who believe technology is evil — discovers that his pet pig Freddy has disappeared. Befuddled, he traces Freddy’s hoofprints to the neighboring house, where he meets a scientist named Greg and his daughter Annie.

Greg warms George up to science — “Science is a wonderful and fascinating subject that helps us understand the world around us and all its marvels,” he says as he shows the boy the enchanting science behind everyday phenomena in the kitchen — and introduces him to his own “pet” of sorts, Cosmos. Cosmos is the world’s most powerful computer and not only speaks but can also empower approved users to travel across space-time.

George is enormously excited about the prospect of time-travel, but he first needs to take the Oath of the Scientist — a promise to only use scientific knowledge for good — in order to become approved.

And so begin the adventures, on which George encounters black holes (and learns — of course! — about how Hawking radiation makes them slowly disintegrate) and floats across four billion years.

George’s Secret Key to the Universe is bound to tickle curious young readers into falling in love with science. Complement it with Hawking’s theory of everything, animated in 150 seconds, then revisit this fantastic 1991 Errol Morris documentary about Hawking.


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