does time ever stop

8/14/2019 Does Time Ever Stop

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Does Time Ever Stop?Can the PastBe Altered?It is impossible to meditate on time and the mystery of the creativepassage of nature without an overwhelming emotion at the limitations of hu-man intelligence.

-ALFRED NORTHWHITEHEADThe oncept of Nature

T ere has been a great deal of interest among physicists of latein whether or not there are events on the elementary-particlel e v e l hat cannot be time-reversed, that is, events for whichimagining a reversal in the direction of motion of all the par-ticles involved is imagining an event that cannot happen innature. Richard Feynman has suggested an approach toquantum mechanics in which antipart icles are viewed as par-ticles momentarily traveling backward in time. Cosmologistshave speculated about two universes for which all the eventsin one are reversed relative to the direction of time in theother: in each universe intelligent organisms would live nor-mally from past to future, but if the organisms in one universecould in some way observe events in the other which many


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physicists consider an impossibility), they would find thoseevent ; going in the opposite direction. It has even been con-jectured that if our universe stops expanding and starts tocontract, there will be a time reversal, but it is far from clearwhat that would mean. Most of the speculations of this kindare quite recent, and interested readers will find many of themexamined in four chapters of my N ew Ambidextrous Universe.

Iri this chapter I shall consider two bizarre questions abouttime 1.-hat are not discussed in the book. Indeed, these ques-tions are of so little concern to scientists that only philoso-phers and writers of fantasy and science fiction have had muchto say about them: I s it meaningful to speak of time stopping?Is it meaningful to speak of altering the past?

Neither question should be confused with the familiarsubject of time's relativity. Newton believed the universe waspervaded by a single absolute time that could be symbolizedby an imaginary clock off somewhere in space (perhaps out-side the cosmos). By means of this clock the rates of all theevents in the universe could be measured. The notion workswell within a single inertial frame of reference such as thesurface of the earth, but it does not work for inertial systemsmoving in relation to each other a t high speeds. According tothe theory of relativity, if a spaceship were to travel from oursolar system to another solar system with a velocity close tothat of light, events would proceed much slower on the space-ship than they would on the earth. In a sense, then, such aspaceship is traveling through time into the future. Passen-gers on the spaceship might experience a round-trip voyageas taking only a few years, but they would return to find thatcentu.ries of earth-years had elapsed.The notion that different parts of the universe can changeat different rates of time is much older than the theory of rel-ativity. In the Scholastic theology of the Middle Ages angelswere considered to be nonmaterial intelligences living by atime different from that of earthly creatures; God himself wasthought to be entirely outside of time. In the first act of LordByron's play, Cain, Mystery, the fallen angel Lucifer says:

W ith us acts are exempt from time.and weC a n crowd eternity into a n hourOr stretch a n h our into eternityWe breathe not by a m ortalmeasurement-But that s a mystery.


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Doer Time Euer Stop? Can the Part Be ~ b m d ? 43

In the 20th century hundreds of science-fiction stories haveplayed with the relativity of time in different inertial systems,but the view that time can speed up or slow down in differentparts of our universe is central to many older tales. A popularmedieval legend tells of a monk who is entranced for a minuteor two by the song of a magical bird. When the bird stopssinging, the monk discovers that several hundred years havepassed. In a Moslem legend Mohammed is carried by a mareinto the seventh heaven. After a long visit the prophet returnsto the earth just in time to catch a jar of water the horse hadkicked over before starting its ascent.

Washington Irving's Rip Van Winkle is this country'sbest-known story about someone who sleeps for what seemsto him to be a normal time while two decades of earth-yearsrush by. King Arthur's daughter Gyneth slept for 500 yearsunder a spell cast by Merlin. Every culture has similar sleeperlegends. H. G. Wells used the device in When the Sleeper Wakesand it is a common practice in science fiction to put astro-nauts into a cryogenic sleep so they can survive interstellarvoyages that are longer than their normal life span. In Wells'sshort story The New Accelerator a scientist discovers a wayto speed up a person's biological time so that the world seemsto come almost to a halt. This device too is frequently en-countered in later science fiction.

The issue under consideration here, however, is not howtime can vary but whether time can be said to stop entirely.It is clearly meaningful to speak of all motion ceasing in onepart of the universe, whether or not such a part exists. In thetheory of relativity the speed of light is an unattainable limitfor any object with mass. If a spaceship could attain the speedof light (which the theory of relativity rules out because themass of the ship would increase to infinity), then time on thespaceship would stop in the sense that all change on it wouldcease. In earth time it might take 100 years for the spaceshipto reach a destination, but to astronauts on the spaceship thedestination would be reached instantaneously. One can alsoimagine a piece of matter or even a human being reduced tosuch a low temperature (by some as yet unknown means) thateven all subatomic motions would be halted. For that pieceof matter, then, one could say that time had stopped. Actuallyit is hard to understand why the piece of matter would notvanish.The idea of time stopping creates no problems for writersof fantasy, who are not constrained by the real world. For


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examlple, in L. Frank Baum's The Capture of Father Time,one of the stories in his American Fairy Tales (now back inprint in a Dover facsimile edition), a small boy lassoes Time,and for a while everything except the movements of the boyand Father Time stops completely. In Chapter of JamesBranch Cabell's Jurgen: A Comedy of Justice outside timesleeps while Jurgen enjoys a pleasurable stay in Cocaigne withQueein Anai'tis. Later in the novel Jurgen stares into the eyesof the God of his grandmother and is absolutely motionlessfor 35' days. In Jorge Luis Borges' story The Secret Miraclea writer is executed by a firing squad. Between the commandto fire and the writer's death God stops all time outside thewriter's brain, giving him a year to complete his masterpiece.

Many similar examples from legend and literature showthat the notion of time stopping in some part of the universeis not logically inconsistent. But what about the idea of timestopping throughout the universe? Does the notion that every-thing stops moving for a while and then start s again have anymeaning?

If it is assumed that there is an outside observer-per-haps a god-watching the universe from a region of hyper-time, then of course the notion of time stopping does havemeaning, just as imagining a god in hyperspace gives meaningto the notion of everything in the universe turning upside down.The history of our universe may be like a three-dimensionalmotioln picture a god is enjoying. When the god turns off theproje~ctor o do something else, a few millenniums may go bybefore he comes back and turns it on again. (After all, whatare a few millenniums to a god?) For all we can know a billioncenturies of hypertime may have elapsed between my typingthe first and the second word of this sentence.

Suppose, however, all outside observers are ruled out anduniverse is taken to mean everything there is. Is there stilla way to give a meaning to the idea of all change stopping fora while? Although most philosophers and scientists would saythere is not, a few have argued for the other side. For ex-ample, in Time without Change Sydney S. Shoemaker, nowa philosopher at Cornell University, makes an unusual argu-ment in support of the possibility of change stopping.

Slhoemaker is concerned not with the real world but withpossible worlds designed to prove that the notion of timestoppling everywhere can be given a reasonable meaning. Heproposes several worlds of this kind, all of them based on the


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same idea. I shall describe only one such world here, in aslightly dramatized form.Imagine a universe divided into regions A, B and C. Innormal times inhabitants of each region can observe the in-habitants of the other two and communicate with them. Everynow and then, however, a mysterious purple glow permeatesone of the regions. The glow always lasts for a week and isinvariably followed by a year in which all change in the regionceases. In other words, for one year absolutely nothing hap-pens there. Shoemaker calls the phenomenon a local freeze.Since no events take place, light cannot leave the region, andso the region seems to vanish for a year. When it returns toview, its inhabitants are unaware of any passage of time, butthey learn from their neighbors that a year, as measured byclocks in the other two regions, has elapsed. To the inhabi-tants of the region that experienced the local freeze it seemsthat instantaneous changes have taken place in the other tworegions. As Shoemaker puts it: People and objects will ap-pear to have moved in a discontinuous manner or to have van-ished into thin air or to have materialized out of thin air; sa-plings will appear to have grown instantaneously into maturetrees, and so on.

In the history of each of the three regions local freezes,invariably preceded by a week of purple light, have happenedthousands of times. Now suppose that suddenly, for the firsttime in history, purple light appears simultaneously in re-gions A B and C and lasts for a week. Would it not be rea-sonable, Shoemaker asks, for scientists in the three regionsto conclude that change had ceased for a year throughout theentire universe even though no minds were aware of it?Shoemaker considers several objections to his thesis andcounters all of them ingeniously. Interested readers can con-sult his paper and then read a technical analysis of it in thefifth chapter of G Schlesinger's Confirmation and Confirma-bility. Schlesinger agrees with Shoemaker that an empirical,logically consistent meaning can be found for the sentence Aperiod of time has passed during which absolutely nothinghappened. Note that similar arguments about possible worldscan provide meanings for such notions as everything in a uni-verse turning upside down, mirror-reversing, doubling in sizeand so on.The question of whether the past can be changed is evenstranger than that of whether time can stop. Writers have often

Does Time Ever Stop Can the Past Be Altered? 95


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speculated about what might have happened if the past hadtaken a different turn. J. B. Priestley's play Dangerous Cornerdealt with this question, and there have been innumerablewhat if stories in both science fiction and other kinds ofliterature. In all time-travel stories where someone enters thepast, the past is necessarily altered. The only way the logicalcontradictions created by such a premise can be resolved isby posi1:ing a universe that splits into separate branches theinstant the past is entered. In other words, while time in theold branch gurgles on (a phrase from Emily Dickinson) timein the new branch gurgles on in a different way toward a dif-ferent future. When speak of altering the past, however,mean altering it throughout a single universe with no forkingtime paths. (Pseudoalterations of the past, such as the rewrit-ing of history satirized by George Orwell in 1984, obviouslydo not qualify.) Given this context, can an event, once it hashappened, ever be made not to have happened?

The question is older than Aristotle, who in his Ethics(Book 6) writes: It is to be noted that nothing that is past isan object of choice, for example, no one chooses to have sackedTroy; for no one deliberates about the past, but about what isfuture and capable of being otherwise, while what is past isnot capable of not having taken place; hence Agathon is rightin saying: 'For this alone is lacking even to God, to make un-done things that have once been done.'

Thomas Aquinas believed God to be outside of time andthus capable of seeing all his creation's past and future in oneblinding instant. (Even though human beings have genuinepower of choice, God knows how each one will choose; it isin this way that Aquinas sought to harmonize predestinationand free will.) For Aquinas it was not possible for God to doabsolutely impossible things, namely those that involve logi-cal contradiction. For example, God could not make a crea-ture that was both a human being and a horse (that is, a com-plete huinan being and a complete horse, rather than a mythicalcombination of parts such as a centaur), because that wouldinvolve Ithe contradiction of assuming a creature to be simul-taneously rational and nonrational.Similarly, God cannot alter the past. That would be thesame as asserting that the sack of Troy both took place anddid not take place. Aquinas agreed with Aristotle that the pastmust forever be what it was, and it was this view that becamethe official position of medieval Scholasticism. It is not so much


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that God's omnipotence is limited by the law of contradictionbut rather that the law is part of God's nature. It is best tosay, Aquinas wrote, that what involves contradiction cannotbe done rather than that God cannot do it. Modern philoso-phers would say it this way. God can't make a four-sided tri-angle, not because he can't make objects with four sides butbecause a triangle is defined as a three-sided polygon. Thephrase four-sided triangle is therefore a nonsense phrase,one without meaning.

Edwyn Bevan, in a discussion of time in his book Sym-bolism and Belief finds it odd that Aquinas would deny Godthe ability to alter the past and a t the same time allow God toalter the future. In the 10th question of Summa Theologica(Ia. 10, article 5 . 3 , Aquinas wrote: God can cause an angelnot to exist in the future, even if he cannot cause it not toexist while it exists, or not to have existed when it alreadyhas. For Aquinas to have suggested that for God the past isunalterable and the future is not unalterable, Bevan reasons,is surely to place God in some kind of time, thus contradict-ing the assertion that God is outside of time.

I know of no scientist or secular philosopher who has se-riously believed the past could be altered, but a small minor-ity of theologians have maintained that it could be. The great-est of them was Peter Damian, the zealous Italian reformer ofthe Roman Catholic church in the 1l th century. In On DivineOmnipotence his most controversial treatise, Damian arguedthat God is in no way bound by the law of contradiction, thathis omnipotence gives him the power to do all contradictorythings including changing the past. Although Damian, whostarted out as a hermit monk, argued his extreme views skill-fully, he regarded all reasoning as superfluous, useful only forsupporting revealed theology. It appears that he, like LewisCarroll's White Queen, would have defended everyone's rightto believe six impossible things before breakfast. (Damian wasalso a great promoter of self-flagellation as a form of penance,a practice that became such a fad during his lifetime that somemonks flogged themselves to death.)

One of my favorite Lord Dunsany stories is the best ex-ample know of from the literature of fantasy that illustratesDamian's belief in the possibility of altering the past. It istitled The King That Was Not, and you will find it in Dun-sany's early book of wonder tales Time and the Gods. It beginsas follows: The land of Runazar hath no King nor ever had

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one; a.nd this is the law of the land of Runazar that, seeingthat it. hath never had a King, it shall not have one for ever.Therefore in Runazar the priests hold sway, who tell the peo-ple that never in Runazar hath there been a King."

The start of the second paragraph is surprising: "Altha-zar, King of Runazar. . The story goes on to recount howA1tha;sar ordered his sculptors to carve marble statues of thegods. His command was obeyed, but when the great statueswere undraped, their faces were very much like the face ofthe king. Althazar was pleased and rewarded his sculptorshandsomely with gold, but up in Peggna (Dunsany's MountOlympus) the gods were outraged. One of them, Mung, leanedforward to make his sign against Althazar, but the other godsstopped him: "Slay him not, for it is not enough that Althazarshall die, who hath made the faces of the gods to be like thefaces of men, but he must not even have ever been."

Spa ke we of Althazar, a King?asked one o f the gods.Na y, we spake not.Dreamed we o f one Althazar?N a y, we dreamed not.

Below Pegana, in the royal palace, Althazar suddenlypassed out of the memory of the gods and so "became no longera thing that was or had ever been." When the priests and thepeople entered the throne room, they found only a robe and acrown. "The gods have cast away the fragment of a garment,"said the priests, "and lo from the fingers of the gods hathslipped one little ring."

When wrote about time stopping was using a colloquialexpression to mean that change ceases. Because there are nomoving "clocks" of any sort for measuring time, one can sayin a loose sense that time stops. Of course time does not moveor stop any more than length can extend or not extend. It isthe universe that moves. You can refute the notion that time"flows" like a river simply by asking: "At what rate does itflow?" Shoemaker wanted to show in his paper not that time


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Does ime Euer Stop an the ast Be Altered 99

stops, then starts again, but that all change can stop and somesort of transcendental hypertime still persists. Change re-quires time, but perhaps, Shoemaker argued, time does notrequire change in our universe.

Harold A. Segal, in a letter in the New York Times (Jan-uary 1 1, 1987) quoted a marvelous passage from Shake-speare's As You Like t (Act 111, Scene 2 in which Rosalindexplains how time can amble, trot, gallop, or stand still fordifferent persons in different circumstances. It trots for the"young maid" between her engagement and marriage. It am-bles for a priest who knows no Latin because he is free fromthe burden of "wasteful learning." It ambles for the rich manin good health who "lives merrily because he feels no pain."It gallops for the thief who awaits his hanging. For whom doesit stand still? "With lawyers in the vacation; for they sleepbetween term and term, and then they perceive not how Timemoves."

Isaac Asimov, in an editorial in Asimov's Science-FictionMagazine (June, 1986) explained why it would not be possiblefor a person to walk about and observe a world in which allchange had stopped. To move, she would have to push asidemolecules, and this would inject time into the outside world.She would be as frozen as the universe, even though dancingatoms in her brain might continue to let her think. Asimovcould have added that she would not even be able to see theworld because sight depends on photons speeding from theworld into one's eyes.Two readers, Edward Adams and Henry Lambert, inde-pendently wrote to say that the god Koschei, in Jurgen, couldalter the past. At the end of the novel he eliminates all ofJurgen's adventures as never having happened. However,Jurgen recalls that Horvendile (the name Cabell often usedfor himself) once told him that he (Horvendile) and Koscheiwere one and the same

Edward Fredkin is a computer scientist who likes to thinkof the universe as a vast cellular automaton run by an incon-ceivably complex algorithm that tells the universe how to jumpconstantly from one state to the next. Whoever or whatever isrunning the program could, of course, shut it down at any time,then later start it running again. We who are part of the pro-gram would have no awareness of such gaps in time.

On the unalterability of the past, readers reminded me ofthe stanza in Omar's Rubaiyat about the moving finger that


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having writ moves on, and all our piety and wit cannot call itback to cancel half a line. Or as Ogden Nash once put it:O n e t hi ng about the past.It s l i ke ly to las t .

I touched only briefly on the many science-fiction storiesand novels that deal with time slowing down or halting. Forreferences on some of the major tales see the section Whentime stands still on page 153 of The Visual Encyclopedia ofScience Fiction. The most startling possibility, now seriouslyadvanced by some physicists, is that the universe comes to acomplete stop billions of times every microsecond, then s tart sup again. Like a cellular automaton it jumps from state tostate. Between the jumps, nothing changes. The universesimply does not exist. Time is quantized. An electron doesn'tmove smoothly from here to there. It moves in tiny jumps,occupying no space in between.

The fundamental unit of quantized time has been calledthe chronon. Between chronons one can imagine one or moreparallel universes operating within our space, but totally un-known to us. Think of a film with two unrelated motion pic-tures running on alternate frames. Between the frames of ouruniverse, who knows what other exotic worlds are unrollingin the intervals between our chronons? Both motion picturesand cellular automata are deterministic, but in this vision ofparallel universes running in the same space, there is no needto assume determinism. Chance and free will could still playcreative roles in making the future of each universe unpre-dictable in principle.

Seven Sleepers and Sleepers . E. Cobham Brewer, in TheReader s Handbook, revised edition. Lippincott, 1898.Time. C. D. Broad, in Encyclopedia of Religion and Ethics,James Hastings (ed.). Scribner's, 1922.Travelers in Time: Strange Tales of Man s Journeying into the,Past and the Future. Philip Van Doren Stern (ed.). Dou-

bleday, 1947.Symbolism and Belief. Edwyn Bevan. Kennikar Press, 1968.


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Doer ime Ever Stop a n the art B e A h r e d 2 1

Time W i thou t Change . S idney S Shoe ma ker , in The Journalof Philosophy 66 , 196 9 , pages 363-381 .

Confirmation and Confirmability. G. Sch les inge r . Oxford Uni -ve rs i ty Press , 1974 .T i me a n d N t h D ime n s io n s . K e n n e t h B u l me r , i n The VisualEncyclopedia of Science Fiction. Harmony Books , 1977 ,pages 145-154.Time Travel . Anonymous, in The Science Fiction Encyclope-dia. P e t e r N icho ll s (ed .) . Doub leday , 1979 .T ime Trave l an d O the r Un ive rses. Anonymous, in The Sci-ence in Science Fiction C h a p t e r 5 . P e t e r N i c h ol ls ( e d . )Knopf, 1983.T ime Trave l . M ar t in Ga rdn er , in Time Travel and OtherMathematical Bewilderments. W. H Fre e ma n , 1 9 8 8 .The New Ambidextrous Universe. Mart in Gardner . W. HF r e e m a n , 1 9 9 0 .

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