In 1908 John McTaggart wrote The Unreality of Time, and using his A and B series of time he argued that our perception of time is an illusion. Of the A series, he argues this:
"If time exists it must be explained by the A series, which is how we normally think about time. This is a tensed series, as in past, present, and future. A cup of coffee was hot in the past, is lukewarm in the present, and cold in the future. The United States was created in the past, exists in the present, and will no longer exist in the future. In this series are three distinct instances."
McTaggart juxtaposes a B series against the A series. This series is relational, or durational. One way to think of it is as events before the now and after the now. A cup of coffee had hot temperature, is colder temperature in the present, and colder after the present. Put in another way to think about it, the United States was founded in the past, exists after its founding, and will no longer exist after its founding. From both perspectives the instances are not distinct, but relational, enduring from one into another. The B series can be likened to space. The wall is there, and a window elsewhere. They are spatially related. The B series as relational is not inherently separate (distinct) from other time-moments, just as space has no difference in it. As the wall is there, the window elsewhere, so events in the B series can be located as before and after.
Many rich and profound complications arise from thinking about the two series but the central point is that they are contradictory. One is tensed, the other tenseless. The A series depends on personal experience and perspective. "I am drinking hot coffee today." The B series does not. The experience and perspective are not there. "I recall drinking hot coffee today."
Because they are contradictory, McTaggart says time is not real. His legacy is that he left A theorists and B theorists debating which kind of time is true, continuing a discussion traced back to Parmenides (reality is timeless, unchanging) and Heraclitus ("You can't step into the same river twice").
So what is time? If nobody asks, I know. If they ask and I try to explain, I do not know. (St Augustine, Bishop of Hippo, 354-430.)
In his book, The End of Time: The Next Revolution in Physics, Julian "Barbour asserts that time simply doesn't exist." Barbour starts with the notion that time is just a way of describing change. He means that to measure time you have to have something that moves. How long does it take to get from point A to Point B?
~ "There's only change, not time. Things move around; time may just be a way of noting that. But Barbour goes further. He says there's no such thing as motion either. Instead, Barbour sees a universe filled with static instants -- instants that contain 'records' that fool any conscious beings who happen to find themselves encased in one into believing that things have moved and time has passed."
~"This common-sense view was one of many forever altered by Einstein's theories. We see time this way, he made clear, only because we move so slowly. If you could peddle your bicycle at something almost in the neighborhood of the speed of light, relative to an observer, your watch and your aging process would appear -- to that observer -- to slow. (From your own perspective, time, unfortunately, would still keep chugging along at its usual dispiriting pace, which makes it unlikely that anyone will figure out how to turn this phenomenon into a wrinkle cream.)"
~"Relativity found time a home as one of the four dimensions in something called spacetime. But it hardly settled the question of what time is. And the idea that time slows down in certain circumstances made it easier to imagine that time was just a construct of us observers, not itself a fact of nature."
~"What if, Barbour wonders, we just imagine a kingfisher to be flying? After all, it isn't exactly the same bird at perch A and perch B: Its molecules constantly change; its atoms constantly change. What if our brain has captured a few snapshots of kingfisher-in-flight that it plays -- movie-like -- in such a way that we think we see continuous motion?"
~"What if the instants we inhabit somehow happen to be filled with 'records' -- images of kingfishers with their wings spread, tread marks, 'memories,' fossils -- that manage to delude us into thinking that birds fly, cars lurch, species become extinct; 'records' that manage to delude us into thinking that we are scurrying along some sort of path from the past to the future? Isn't it true that all we know now about the past or the future comes from thoughts or objects we experience now -- in the present?"
~"What if, Barbour then asks, we're always trapped in one moment or another and everything else -- your sense, for example that X number of minutes ago you moved your hand and clicked on FEED -- is a kind of illusion, somehow evoked by the structure of this particular, all-encompassing moment? What if, in other words, our whole sense that things move is an illusion, as -- in another context -- our sense that the earth does not move proved to be an illusion."
~"This is, if it helps any, quite similar to the view of time presented in Kurt Vonnegut's 1969 novel Slaughterhouse Five, which Barbour has not yet read. ('I know,' he says. 'People keep telling me I should look at it.') Vonnegut describes most earthlings as trapped in moments like 'bugs in amber.' Billy Pilgrim, the book's main character, however, repeatedly comes 'unstuck in time': He jumps, in no particular order (though in accordance with the needs of Vonnegut's narrative), from one point in his life to another. Moreover, on the planet Tralfamadore, which Pilgrim visits, 'all time' is visible at once, as we 'might see a stretch of the Rocky Mountains. It does not change. It simply is.' That Rocky Mountain-like view of all time is remarkably similar to Barbour's Platonia."
The above comments are excerpts from a review of his book published in the now defunct Feed Magazine on July 14, 2000 by Mitchell Stephens. I wanted to link you to the review but the link is dead. More of the review is below. Or click her for a Nature article on why time is an illusion according to classical physics.
The Question of Time
Barbour's theory meets one test of important new ways of looking at the universe: It doesn't, on the face of it, make a lot of sense. That puts it right up there with relativity (Space is curved?), quantum mechanics (Particles are waves?) and Copernicus's ideas (The earth, despite all indications to the contrary, moves?). In fact, Barbour's assertion that the instants we experience do not follow each other in a temporal sequence seems as likely to elicit a "Go on!" as any theory physicists have dreamt up in the past half millennium. The question is whether his theory meets the other test of important new ways of looking at the universe: Is it, in other words, remotely possible that he is right?
There are two ways of determining that, given the absence, to date, of experimental evidence: first, by grappling with the theory itself or, second, by figuring out whether this guy seems worth trusting. Neither, in this case, is easy. Barbour's thinking is complex and his credentials eccentric.
Just what time is has always been difficult to figure. "Time is the biggest mystery," states the physicist Brian Greene, who leads an accessible and fascinating expedition through contemporary physics in his recent book, The Elegant Universe. Our sense -- and this might be called the Newtonian view -- is that a kind of perfect, invisible celestial clock, invariable and indefatigable, is ticking away somewhere out there. Sundials, Swatch watches, and the human aging process each, in its less-than-perfect way, reflects this absolute time. It seems as inescapable and inevitable as death -- its enforcer.
This common-sense view was one of many forever altered by Einstein's theories. We see time this way, he made clear, only because we move so slowly. If you could peddle your bicycle at something almost in the neighborhood of the speed of light, relative to an observer, your watch and your aging process would appear -- to that observer -- to slow. (From your own perspective, time, unfortunately, would still keep chugging along at its usual dispiriting pace, which makes it unlikely that anyone will figure out how to turn this phenomenon into a wrinkle cream.)
BARBOUR, who lives near Oxford in England, is one of the only living physicists you will read, or read about, nowadays who is not in the employ of a college or university. In fact, Barbour, while he does have a Ph.D. in physics (earned in Cologne), has never taught physics. He calls himself "an independent." Barbour supported his family for decades by translating Russian scientific publications. His physics was done in his free time, at his own pace. Since Barbour's ideas have not been blessed by a tenure committee, and are radical, "people might naturally question," as one physicist puts it, "whether he is a crackpot."
There is considerable evidence to the contrary. Barbour's book, to begin with, is published by Oxford University Press. (As an Oxford author myself, I see this as clear proof of the book's merit.) Barbour has published, sometimes in collaboration with a genuine academic, some influential papers. He gets invited to important conferences. The back of his book is graced by an impressive collection of blurbs, including one from John A. Wheeler, one of the most accomplished physicists of the second half of the twentieth century. And then there is the enthusiastic (if difficult to follow) review his book received in the New York Times ("a masterpiece"), not to mention the designation bestowed upon it in one of many respectful articles in the London broadsheets: "much talked about."
The book itself describes a personal, spirited, sometimes stubborn, and mostly lonely intellectual quest. This gives it a slightly moist feel, as if we'd been invited directly into one man's cerebral cortex. But Barbour fulfills his main task -- explaining -- with industry and cleverness.
Not many physicists, including Barbour's respectful blurb writers, seem convinced that he is right about time. "Julian and I are very happy to disagree," is how the matter is worded, with respect and affection, by Fay Dowker, a physicist at Queen Mary and Westfield College, University of London. Still, most who are familiar with his work believe, as that physicist who mentioned the term certainly does, that, very far from being a "crackpot," Barbour is "an interesting, delightfully unusual, guy," who gets his math right and understands the equations in question. "Although his work is not widely known by the high-energy community in general," Dowker explains, "among a small, diverse group of physicists it is seen as challenging and interesting."
And these physicists are hesitant to simply dismiss his radical ideas. After all, physics was transformed early in the twentieth century by a set of radical ideas emanating from a fellow who also was not employed, during many of his most productive years, by a university.
BARBOUR STARTS WITH THE NOTION that time is just a way of describing change. "If you try to measure time," he told me in a recent telephone interview, "you have to have something that moves. It is remarkable how many people haven't considered this, including even Einstein, who never thought seriously about what a clock is." (Artie will enjoy learning that he may have been a step ahead of Einstein on this one.)
Without clock hands moving (or digital numbers flashing), without any motion, Barbour is convinced, there would be no time. Then he tries to prove -- more tentatively -- that there is no such thing as motion.
What if, Barbour wonders, we just imagine a kingfisher to be flying? After all, it isn't exactly the same bird at perch A and perch B: Its molecules constantly change; its atoms constantly change. What if our brain has captured a few snapshots of kingfisher-in-flight that it plays -- movie-like -- in such a way that we think we see continuous motion? What if the instants we inhabit somehow happen to be filled with "records" -- images of kingfishers with their wings spread, tread marks, "memories," fossils -- that manage to delude us into thinking that birds fly, cars lurch, species become extinct; "records" that manage to delude us into thinking that we are scurrying along some sort of path from the past to the future? Isn't it true that all we know now about the past or the future comes from thoughts or objects we experience now -- in the present?
For Barbour, what exists is not a universe moving through time; what exists is an endless, timeless series of possible configurations of everything in the universe -- each just an instant wide. There are configurations in which we each are born, presumably configurations in which we each die, and configurations in which we read articles about weird new theories. All these many, many possible instants are sitting in a "configuration space," which Barbour dubs (with a nod to another fellow who thought we were often deluded by appearances) "Platonia." These instants -- these "nows" -- are all there, like words in a book, at once. We experience many, many such instants -- and not necessarily in chronological order.
"I'm not a solipsist," Barbour insists, reassuringly. "I'm convinced that you're there. Equally I conclude that something I can call 'myself' is in other instants of time -- all the ones I remember from my past." Nevertheless, for Barbour possible instants -- a huge number of them, some containing him or us, some not -- are collected like cards in a deck. And it is not clear what instant might be dealt next (though the word "dealt" is probably too active and "next" too time-dependent for Barbour's theory).
If there is no time, though, how come we, unlike [Kurt Vonnegut's] Tralfamadorians, believe that we are moving continuously and chronologically through it? Vonnegut has an extraterrestrial character suggest that the human perspective is akin to looking at a mountain range from a railroad car through a tiny hole: We glimpse only a narrow stream of events, not the whole, timeless vista. Barbour's answer is more complex.
It is based on the (difficult-to-get-your-mind-around) notion in quantum mechanics that, until we actually observe them, particles have no definite location. All we can do is determine, through probabilities, where they are most likely to be. Hanging over Platonia, Barbour suggests, is a "blue mist" of similar probabilities. Barbour surmises that the mist must be thickest, the probabilities highest, over those configurations of the universe that are good at deluding us into thinking time flows and things move. Those are the instants in which we are most likely to find ourselves suspended. According to his theory, there presumably was a high probability that you would find yourself in this particular instant -- an instant in which you are reading this article and believing (I assume) that a series of movements led up to your reading this article.
IT'S AMAZING how badly all this stuff goes over at dinner parties.
Most of the time you don't even get a respectful "Hmm" or a "Really?" Just a curt, "Oh, come on!" before everybody gets back to grumbling about the presidential campaign. Sure, we've all experienced some situations -- while watching Eyes Wide Shut, for example -- where time seems to slow, if not stop completely. Still, Barbour's idea that time always stands still, that nothing really moves, is, shall we say, counterintuitive, the evidence for motion in this world being rather compelling. It's not just kingfishers flying. Consider SUVs muscling down a highway, or Hillary Clinton perambulating through upstate New York. In describing the world, we feel the need to have recourse to verbs. Barbour's all-noun theory is awfully hard to accept.
For Theodore Jacobson, a professor of physics at the University of Maryland, the rub is the flow of time: We feel it. Barbour's theory denies it. Bugs trapped in amber don't flow. "Still," Jacobson cautions, "you have to be careful about being too dogmatic in dismissing Barbour's idea. It's a creative idea. I'd hate to be objecting to it because I wasn't imaginative enough to see how it could be right. Besides, from one point of view, this is what quantum gravity suggests."
That's right: quantum gravity. Barbour's "timeless" theory, like most truly ambitious physics theories these days, has a go at reconciling those two great, well-tested, but on some level incompatible twentieth-century formulations: relativity and quantum mechanics. The key seems to be coming up with a quantum description of the main player in Einstein's general relativity: gravity. (The current favorite for accomplishing this is "string theory," but Barbour hasn't yet focused much on that.)
Physicists have gotten themselves into tangles, Barbour suggests, by trying to thread time through their equations on quantum gravity. His solution? Cut the thread! "Maybe," Barbour says, "the fundamental equations of the universe don't contain time at all." (The actual equations -- the sort we general readers are known to find off-putting -- are not included in his book, but Barbour does make an earnest and enterprising effort to explain their significance.) He maintains that, when time is subtracted from some of those crucial equations, quantum gravity begins to make a kind of timeless sense.
"People working in this field have known for decades that there is a major problem with time," Barbour states. "Why am I the first to write about the possibility that time does not exist? The answer may be that I'm an independent."
There's more. Barbour argues that the best attempt to produce a quantum equation that might apply to the whole universe, an effort generally credited to John A. Wheeler and Bryce DeWitt, works best when the universe is seen as being in a stationary, i.e., timeless, state. "The Wheeler-DeWitt equation tells us," Barbour writes, "that the universe in its entirety is like some huge molecule in a stationary state and that the different possible configurations of this 'monster molecule' are the instants of time."
I haven't seen any evidence that physicists are dismissing Barbour's interpretation of these equations as obviously wrong. Although he has not read Barbour's book, Edward Witten, of the Institute for Advanced Studies, another of our most accomplished physicists, acknowledges in an e-mail exchange that in at least one set of fundamental equations "Time does not appear explicitly in the equations in the same sense that space does." And Witten, whose work has been crucial to string theory, also notes, intriguingly, that string-theory "processes with strong time dependence" have proved "perplexingly difficult to understand." Witten's conclusion? "I suspect that there is a secret hidden here, but, of course, I don't know what it is." But Barbour thinks he knows. Cut the thread!
NEVERTHELESS, even Barbour admits that his "timeless" interpretation of crucial physics equations may prove wrong. This is one point upon which there is agreement. "It might be that when we get to a new level of fundamental ideas we will see space but absolutely no glimmer of time," suggests Brian Greene, a professor of physics and mathematics at Columbia. "That's possible, but that isn't my gut feeling on how it will turn out." (Greene imagines a different, though also radical, solution: "My own feeling is that 'space' and 'time' are the wrong language to be using to begin with and that we will find some new ideas. And we will see that space and time are just approximations of these new fundamental ideas.")
Even if Barbour's approach and his eviction of time from those fundamental equations were confirmed, he would have a long way to go before he could produce a science powerful enough to explain the huge role this supposedly nonexistent time appears to play in the universe. Motion in time, for example, seems to provide a reasonably efficient explanation for how kingfishers (or their molecules or atoms) get from here to there and the universe expands. Barbour's probability "mists" in Platonia would represent just a first step toward an alternative explanation.
In the meantime, the mystery remains. What is this "dimension" of "spacetime" that, unlike the other dimensions, has the obnoxious quality of only permitting travel in one direction? Why does it appear to have such a firm grip on the world, on the universe, and on us mortals? If Barbour accomplishes nothing else, he has at least challenged other physicists to work harder to explain what it means to say that time or motion do, in fact, exist.
For us non-physicists, Barbour's radically counterintuitive speculations may be just plausible enough to warrant trying to get our minds around. After all, the wonderful thing about physics -- not counting all the practical stuff, like figuring out how to make hydrogen bombs -- is the opportunity it affords us to stretch our minds. Julian Barbour might not be Copernicus, or Einstein. He may very well turn out to be as wrong as he seems to be. But he does get you thinking.
Here is a link to Mitchell Stephens works.