dimensions of particle physics

volume 01

issue 02

dec 04/jan 05

symmetry | volume 01 | issue 02 | dec 04/jan 05

p.3 Commentary: Michael Turner

“Scientists and the public alike are beginning to celebrate the100th anniversary of Einstein’s annus mirabilis.”

p.4 Voices: Strong Interaction

A particle physics theorist and a nuclear physics experimentalistshare their view on the 2004 Nobel Prize in physics.

p.6 Signal to Background

Smart scarecrow. Virtual cake. Seiche fascination. A fine-tuningriddle. Trends in extra dimensions. Boxes of data. Review.

p.10 Sold on Cold

Why have particle physicists lowered the temperature on a newaccelerator? How cold will the International Linear Collider be?

p.12 The Growth of Inflation

For 25 years cosmologists have struggled to adapt one of thegreatest inventions: inflation. Is a final solution near?

p.18 SESAME: An Oasis of Peace in the Middle East?

With help from Europe and the US, scientists in Jordan arebuilding a lab for collaboration among neighboring countries.

p.24 Gallery: Dawn Meson

Her paintings reflect her personal understanding of the conceptsand theories of modern physics.

p.28 Deconstruction: Visa Quest

For Nikolay Solyak, an approval letter was no guarantee forquickly obtaining an H1-B visa at the US embassy in Berlin.

p.30 Essay: Rob Semper

The story of the tremendous changes in our view of the universeis not getting much traction. What can be done?

ibc Logbook: Inflation

A page of Alan Guth’s 1978 notebook documents what mighthave been one of the greatest Eureka moments in cosmology.

bc 60 Seconds: Gravitational Lenses

A wineglass makes a good model to explain a unique aspect ofEinstein’s General Theory of Relativity.

On the cover

The artist Dawn Neal Meson describes her diptych Entanglementreproduced on the cover and inside cover: “Two isolated particlesthat have interacted with each other can become correlated. This piece explores the strange resulting phenomenon: at themoment the spin of one of these two particles is measured, the other particle, no matter where it is located, simultaneouslymanifests the opposite spin.”

Office of ScienceU.S. Department of Energy

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from the editor

Science plays many different roles in society. And as much assome scientists might want to remain “pure” and

insulated from non-scientific concerns, there is no escaping the vital andimportant links that exist.

Sometimes scientists explicitly use science to achieve more than the latest research results. For example, the sesame synchrotron project in the Middle East adopts the unesco slogan “science for peace” as a fundamental part of its mission. In this issue of symmetry, Mike Perriconespeaks with scientists and policy leaders about the role of sesame, how it works as a way for physics to drive a larger agenda, and how it provides much needed scientificinfrastructure for a scientifically underrepresented part of the world. But as is clear, this progress can only happen with the support of the American, European and Asian scientific communities. It iscertain that this support will be repaid in many ways in the future as a more global, better devel-oped scientific community grows.

In a completely different sort of interaction, science influences art. In recent years, there seemsto have been an explosion of science-inspired art with a huge variety of projects exploring linksbetween the fields. While some of the relationships between science and art in these projects aresuperficial at best, others seem to tap into something deeper. In this issue, we are pleased toshowcase a gallery of particle- and quantum-physics-inspired paintings that we feel surpasses thenorm of science-inspired art. Not just an educational tool, nor a simplistic representation, the workby Dawn Neal Meson captures something of the process of understanding physics. Many scien-tists are sure to recognize in the paintings their own efforts at visual comprehension and modelingof complex ideas. But how much can physics and art really benefit each other? Can art givesomething back to science? It’s a complex issue that we shall explore in a future issue. For nowwe present this view of imagery that we hope will please the eye and challenge the mind.

A reflection on the interactions between physics and other human endeavors is apt as we moveinto 2005, the World Year of Physics, as recognized by the United Nations. Next year is an oppor-tunity for physicists to show what they do and why the rest of the world should care. It is also agreat chance for the physics community to learn more about how its work is perceived outside thehalls of academia and industry. In symmetry, we’ll be kicking off 2005 with an issue in late Januarythat includes special commentaries and features to celebrate the 100th anniversary of Einstein’smiraculous year.

David HarrisEditor-in-Chief

SymmetryPO Box 500MS 206Batavia Illinois 60510USA

630 840 3351 telephone630 840 8780 faxwww.symmetrymagazine.orgmail@symmetrymagazine.org

(c) 2004 symmetry All rightsreserved

symmetry is published 10 times per year by FermiNational AcceleratorLaboratory and StanfordLinear Accelerator Center,funded by the USDepartment of Energy Office of Science.

Editor-in-ChiefDavid Harris650 926 8580

Executive EditorMike Perricone

Managing EditorKurt Riesselmann

Web EditorElizabeth Clements

Staff WritersHeather Rock Woods

InternsDavide CastelvecchiRaven Hanna

PublishersNeil Calder, SLACJudy Jackson, FNAL

Contributing EditorsRoberta Antolini, LNGSDominique Armand, IN2P3Peter Barratt, PPARCBobbi Bowen, ANLReid Edwards, LBNLPetra Folkerts, DESYBarbara Gallavotti, INFNJames Gillies, CERNSilvia Giromini, LNFJacky Hutchinson, RALYouhei Morita, KEKMarcello Pavan, TRIUMFMona Rowe, BNLYuri Ryabov, IHEP ProtvinoYves Sacquin, CEA-SaclayBoris Starchenko, JINRMaury Tigner, LEPPJacques Visser, NIKHEFLinda Ware, JLabTongzhou Xu, IHEP Beijing

Print Design and ProductionSandbox StudioChicago, Illinois

Art DirectorMichael Branigan

DesignersAaron GrantSharon OigaMatt Stone

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Web Design and ProductionXeno MediaHinsdale, Illinois

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Web DesignKaren Acklin

Web ProgrammerMike Acklin

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commentary: michael turner

“A new generation of physicists has at last taken on the challenge of creating

a complete theory—one capable of explaining, in Einstein’s words, ‘every element

of the physical reality.’ And judging from the progress they have made, the next

[21st] century could usher in an intellectual revolution even more exciting than the

one Einstein helped launch in the early 1900s.”

J. Madeleine Nash, Time magazine, January 3, 2000

Outgrowing Einstein2005 has been designated the World Year ofPhysics. Around the world scientists and thepublic alike are beginning to celebrate the 100thanniversary of Einstein’s annus mirabilis, theyear in which he wrote five papers that foreverchanged physics. Five years ago, Time maga-zine jumped the gun by naming Albert EinsteinPerson of the Century. And all of this for goodreason: these papers laid the foundations fortwo towering intellectual achievements of 20thcentury physics—quantum theory and relativitytheory. These two theories not only revolution-ized physics, but led to sea changes in many

other aspectsof life. NobelLaureateLeonLedermanhas boldlystated thatquantummechanicsaccounts forone-third ofour GDP, andit’s hard to

argue with him. Just imagine turning off quan-tum mechanics for a few minutes. Quantummechanics and relativity have also changed the way we think about reality: God does playdice; time is relative; and space is flexible.

It has taken nearly a century to get ourheads fully around all the implications of quan-tum mechanics and relativity. Quantum theoryhas progressed from the photoelectric effectand wave mechanics to quantum field theoryand the Standard Model of particle physics. The Standard Model explains essentially all ofthe phenomena of the world around us, andhas opened the door to discussing the earliestmoments of creation and how the universebegan. And of course, myriad inventions basedupon quantum mechanics have changed theway we live.

Today, all but one of the basic predictions ofEinstein’s theory of general relativity have been

tested. That lone holdout—the direct detection ofgravitational waves—is not likely to last muchlonger, as LIGO, Geo, Virgo and other gravity-wave detectors hit their stride. Theorists havetaken almost a whole century to fully plumb themathematical depths of general relativity. Today,Einstein’s theory provides the basis for under-standing the origin and evolution of the universeand the black holes that power quasars—and is critical, as well, to the accurate functioning ofthe Global Positioning System.

Now, one hundred years after the annusmirabilis, physicists have outgrown Einstein andare ready to move beyond. This is normal; inscience, no theory lives forever. Though in thatregard, Einstein’s general relativity ranks sec-ond only to Newton’s theory of gravity inlongevity. The success of a theory lies not onlyin how much it explains, but in how it preparesus to further deepen our understanding ofnature. On both accounts we have much reasonto celebrate the annus mirabilis. Quantum the-ory and relativity have allowed us to understandthe universe from quarks to the cosmos. Theyhave also allowed us to ask—and have readiedus to answer—some of the biggest questionsever tackled: What are space and time? Did theuniverse have a beginning? What is our cosmicdestiny?

Today, I believe that we are truly on the edgeof discovery and on the verge of the next revo-lution in our understanding of the universe. Wecan only imagine the surprises that lie aheadand their broader impact for all of society. Twothings are certain, however: particle physicists,using both accelerators and telescopes, will be at the forefront in this grand adventure, andthe news from the front lines will be reportedright here in symmetry.

Michael S. Turner heads the National Science Foundation’sDirectorate for Mathematical and Physical Sciences, which pro-vides $1 billion a year to support fundamental research. He isalso the Rauner Distinguished Service Professor at TheUniversity of Chicago. Turner’s research on early universe cos-mology helped to bring the fields of cosmology and particlephysics together, and he chaired the National Research CouncilCommittee that produced the influential report, ConnectingQuarks with the Cosmos.

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voices: strong interaction

More than thirty years after publishing two scientific papers on the theory of the

strong interaction, David Gross, David Politzer, and Frank Wilczek received

the 2004 Nobel Prize in Physics. symmetry asked two physicists—a particle physics

theorist and a nuclear physics experimentalist—to explain how the papers

paved the way for one of the most successful theories in physics and how new

experiments are testing its predictions.

The Advent of QCDI was delighted to wake up onthe morning of October 5 andfind that David Gross, DavidPolitzer and Frank Wilczek hadbeen awarded the 2004 NobelPrize for the discovery ofasymptotic freedom in the the-ory of the strong interaction.Their discovery in 1973 resur-rected the role of field theoryin strong interactions and initiated the development ofQuantum Chromodynamics(QCD). In one fell swoop, allthe methods of QuantumElectrodynamics (QED) couldbe applied in the new theory,albeit with a number of subtledifferences.

However, the discovery ofasymptotic freedom did notmean that Quantum Chromo-dynamics was immediatelyaccepted as the theory of thestrong interaction. RichardFeynman, in particular, wasunconvinced until about 1980,believing that a correct theoryshould quickly explain and predict many phenomena, as it had with QED. The effectspredicted by QCD vary only as the logarithm of the energyscale. At low energy the

logarithms are confused withother preasymptotic effects; at high energy, a large leverarm in energy is required toobserve these logarithmiceffects. So it took some timeuntil these logarithmic effectswere confirmed.

The work of many peoplewas required to turn the fledging theory into a reliablecalculable structure. DavidPolitzer was particularly activein this stage, teaching us that perturbation theory con-tained both long distanceparts and short distance parts,which need to be separated.Since, at useful energy scales,the coupling was about 10times larger than the QEDcoupling, it was quickly appre-ciated that radiative correctionswould be of great importancein the verification of this theory.In this regard, I would like toacknowledge the contributionof William Caswell, who showedthat the behavior found byGross, Wilczek and Politzerpersists when the calculationis improved by including radia-tive effects. Further details of the joy and frustrations ofQCD radiative corrections can be found in the poignantobituary of Caswell, written by Frank Wilczek and CurtCallan, and published in PhysicsToday in December 2001.

One of the problems ofasymptotic freedom is the dif-ficulty of providing a cogentand simple explanation of the phenomenon. To say that it is all to do with a minus sign, which is true, somehow

belittles the achievement andmakes it seem like a banality.It is often said that the forcebetween quarks is weak atshort distances and strong at long distances; and on Nobel morning, more than one commentator described theanalogy of a stretched rubberband whose restoring forcediminishes as the two endsare brought closer together.But in fact, asymptotic freedomonly provides a logarithmicvariation on top of the QCDequivalent of the Coulombforce. The force betweenquarks does not become weakat short distances; it is onlyslightly weaker than it mighthave been with a fixed cou-pling. So it is more correct tosay that the coupling getssmaller at high energy. It is the smallness of this couplingwhich allows us to predictphenomena at the Tevatronand the Large Hadron Collider.These predictions are the true legacy of the discovery byGross, Politzer and Wilczek.

R. Keith Ellis is a theoretical physicist atFermilab. He is the co-author, with BryanWebber of Cavendish Laboratory,University of Cambridge, and JamesStirling, University of Durham, of QCDand Collider Physics.

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Testing QCD withNuclear CollisionsThe discovery that earned DavidGross, David Politzer, and FrankWilczek the 2004 Nobel Prizein Physics—that the strong, or “color,” force binding quarkstogether grows weaker as twoquarks become closer, and isstronger as quarks are pulledapart—spawned a new physicstheory with a profound impacton experimental nuclear andparticle physics. Many aspectsof the new theory have beenconfirmed, and new insightsrevealed, in high-energy colli-sions of elementary particles(electrons, protons, and anti-protons) carried out usinglarge accelerators at labora-tories around the world.

Motivated by this new theory, known as QuantumChromodynamics (QCD), acompletely new class of high-energy collision experimentshas become a major part ofthe international effort, withbeams of heavy nuclei pro-duced at the highest energiesavailable at today’s accelera-tors. The collisions create newforms of matter at tempera-tures and densities character-istic of the very early universe,a few millionths of a secondafter the big bang. Over thepast two decades physicistshave adapted existing majoraccelerators to handle beamsof large nuclei. High-energynuclear beams became avail-able at Brookhaven Lab’sAlternating GradientSynchrotron and CERN’s

Super Proton Synchrotronduring the 1980’s.

In the wake of these prom-ising first experiments, the USDepartment of Energy con-structed the Relativistic HeavyIon Collider (RHIC) atBrookhaven. RHIC wasdesigned specifically to exploitthis new window into thestrong interaction by collidingtwo beams of heavy nuclei(gold ions) at energies previ-ously accessible only for thehighest energy elementaryparticle collisions. At thesehigh energies, the predictionsof QCD come directly into play.

These extraordinary colli-sions yield a new testingground for QCD, providing anenvironment in which quarksand gluons might be freedfrom their normal confinementinside protons, neutrons orother strongly interacting parti-cles. Scientists expect the collisions to create a state ofmatter consisting of a simple,large system of quarks andgluons—a “quark-gluonplasma.” The existence of thequark-gluon plasma is a keyprediction of the QCD theory.The production of this stateunder controlled conditionscould open a powerful newavenue for research into thebasic structure of the stronglyinteracting particles that com-prise atomic nuclei, accountingfor essentially all of the observ-able mass in our universe.

After three years of opera-tion, the early RHIC resultshave begun to verify the QCDprediction of this new state of matter. The data show thatthe concentration of energy, or “energy density,” producedin the collisions is up to 50times greater than the densityof a normal nucleus. The tem-perature at the center of thesecollisions is about one trilliondegrees Celsius, ten thousandtimes hotter than the center of the sun. These extreme

conditions are well within thepredicted range for producingthe quark-gluon plasma.Detailed studies of these phe-nomena include the observa-tion of high-energy “jets” ofparticles emerging from deepwithin the hot dense matterproduced in the collisions.These jets are the manifesta-tion of very energetic head-oncollisions between pairs ofquarks, or quarks and gluons.Their properties can be accu-rately calculated using QCDtheory, and the alterations theyexperience while traversingthe dense plasma provide a sensitive probe of this newstate of matter.

Such measurements, alongwith improved understandingof the theory as more precisedata become available, areproviding the keys to identify-ing and understanding thenew form of matter unveiledby the theory of QCD. Theyreveal the fundamental proper-ties of the strong interaction.

Thomas Ludlam is a nuclear physicist atBrookhaven National Laboratory, workingon the STAR experiment. From 1999 to 2001 he served as deputy associatedirector for High Energy and NuclearPhysics at BNL.

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signal to background

Smart scarecrow“See, that’s Albert Einstein!”

“Huh?” was the most commonresponse from caramel-apple-wielding pre-school kids to their parents.

“Albert Einstein! He was a reallyfamous scientist.”

It was a classic pre-Halloweenweekend in St. Charles, an old Illinois town now engulfedby Chicago’s metropolis. At the local scarecrow competi-tion, Fermilab’s entry inducedmore reverence than most.

“Einstein” was sitting on achair, complete with his fleece,slippers, uncombed hair, and deep science questions

hovering over his head. A team from Fermilab’s

Lederman Science EducationCenter made the scarecrow,filling old clothes with dryprairie grass from Fermilab’sprairie reconstruction project.During a Friday afternoon rain, a tarp helped ProfessorEinstein stay dry. On Saturdayand Sunday, he enjoyed some

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Fermilab’s Einstein scarecrow; a special cake for CERN’s anniversary; two million

CDs in your bedroom; observing seiches across the world; a mathematical riddle

to illustrate fine-tuning; revival of theoretical ideas proposed in the 1920s; a book

with tabloid-worthy details on a famous scientist.

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sunshine as thousands of festival-goers streamed pasthis chair, with kids taking areally close look at his face.

For the scarecrow, theFermilab team had a budget of $200 at their disposal. Thefinal cost: $11.50.Davide Castelvecchi

Virtual cakeCelebrating anniversaries ofglobal organizations presentsunique challenges and asksfor creative solutions. To congratulate the Europeanlaboratory CERN on its 50thanniversary, US scientists created a special birthdaycake. But CERN employeesnever got to eat a slice ofcake. Instead they receivedthe cake virtually, as an image—appropriate for the laboratory that invented theWorld Wide Web.

The highly decorated cakerepresented the many connec-tions that the US particlephysics community has with its European partners. Custom-made candles displayed logos of several US nationallaboratories as well as the

National Science Foundationand the Department of Energy.

“Candles of Honor” carried theimages of Raymond Orbach,Director of the DOE’s Officeof Science; Michael Turner,Assistant Director forMathematical and PhysicalSciences, NSF; and RobinStaffin, Associate Director ofthe Office of High EnergyPhysics at DOE—and they allwere afire.

The United States is con-tributing a total of $531 milliontowards the Large HadronCollider and its detectors,which are currently under construction. From buildingsuperconducting magnets to producing components forthe ATLAS and CMS experi-ments, many US national laboratories and universitiesare playing key roles in theLHC project.

Fifty years from now scien-tists may know a way of transmitting a real cake in a matter of seconds. ThenCERN employees can havetheir cake—and eat it too.Kurt Riesselmann

Data by the boxloadHow many CDs are in thebox? “100,” a child guessed.

“1000,” said another. Theanswer was 2000, the equiva-lent of just 0.1 percent of thedatabase capabilities at SLAC.

“Imagine 2 million CDs in yourbedroom.”

Several US Department ofEnergy laboratories, includingSLAC and Fermilab, gave 600Chicago-area 11-13 year-olds a glimpse of the science ofthe future on October 14, 2004.The What’s Next: FutureScience for Future Scientistsfair at Navy Pier featuredexhibits intended to interestand amaze. Sponsored by theDepartment of Energy, andfeaturing DOE laboratoriesand industry partners, the pro-gram strives to retain students’interest in the sciences beyondthe junior high school years.

SLAC contributed “HighSpeed Data Transfer WillRevolutionize Your Lives,” anexhibit about the large andfast database it has developed.Along with impressing the students with a large box ofCDs and an illustration show-ing a CD stack spanning thelength of the Golden GateBridge, the exhibit included alarge plasma screen withsuperimposed popular moviesin high quality. In comparisonto how long it takes for onestreaming video to downloadover a DSL line, SLAC’s speedof data transfer would allow100 DVDs to be transferred inhigh quality simultaneously.

Other exhibits had the stu-dents isolating their own DNAand preserving it in a necklace(from Lawrence LivermoreLaboratory) and burning, literally, CDs in a microwaveoven (from the UnderwritersLaboratory).Raven Hanna

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signal to background

SeichingMaori lore says that the risingand falling of the water level in Lake Wakatipu every 51 min-utes is due to the breathing of the giant sleeping beneath.

I learned this many yearsago from a caption on a pho-tograph in an Auckland artgallery, while between ses-sions of a conference. Thecaption explained that the sci-entific phenomenon is that ofseiching (pronounced “saysh-ing”), a type of standing wave.It is most often seen in a cupof coffee when you walk withit, or at times in a bathtubwhen you rise quickly, and isrecognizable by the nearly flatsurface of the liquid as itsloshes back and forth. Whilein the art gallery, I remem-bered the first time I had seen the word was in an oldInternational Physics Olympiadproblem asking us to modelthe seiche in Lake Geneva.

I recalled that gallery visitwhile contemplating the roundfountain at Fermilab’sFeynman Computing Center.As the fountain’s single verti-cal jet oscillates between a torrent and a dribble, thewater in the center of thepond rises and falls in synch—a peculiar motion that is

hypnotic to watch in its raresimplicity. But then I remem-bered one other circularseiche I had witnessed. It wasdriven by us, a group of youngkids, jumping up and down inthe center of a shallow circu-lar swimming pool until thewater would splash over theentire circumference at once.

My recall sloshed back andforth in time, renewing my life-long fascination with seiches.David Harris

Fine-tune thisQuick, what’s 987654321divided by 123456789?

The answer is close to 8,but not exactly 8. Why doesthe result differ by about a tenth of a million, yielding8.0000000729...?

During a recent talk atFermilab, Greg Landsberg ofBrown University promised a bottle of wine to anyonewho could explain this riddleby the end of the talk. The riddle, mind you, was not tofind the result (Landsberggave that away), but to explainwhy it is so weird—or not.

Landsberg tried to make apoint about physics. There are

numbers in nature that justhappen to be “fine-tuned.” Forinstance, when viewed fromearth, the sun and the moonappear to be roughly thesame size. This effect, whichcan easily be explained, is a “freak accident.” But otherbalancing acts that lookmiraculous—like Landsberg’sriddle—can instead beexplained by deeper-runningprinciples.

In physics, Landsberg said,there are cases of fine-tuningthat are still mysterious. Forexample, three of the fourbasic forces of nature havecomparable strength, whencontrasted to the muchweaker force of gravity.Nobody knows if there’s anyspecial reason behind that, or if it’s pure chance.

Landsberg’s numericexample, it turns out, is part of a general fact about theway we represent numbers in a particular base, n.Dividing the two numbers with digits running from n-1 to 1 and that reversed, the answer approaches n-2 as n increases. For the decimal representation

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PLOT of citations by year

1975

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0 25 50 75 100

Reviewed by Heather Rock Woods

Einstein A to ZKaren C. Fox and Aries KeckWiley, Hoboken, New Jersey, 2004

Everybody knows E=mc2 andthe hair, but did you knowEinstein had an extramaritalaffair with his cousin thenmarried her at the urging ofhis mother?

Einstein A to Z is a hand-book on the celebrity scientist,offering short alphabeticalentries on everything from hisconvoluted relationships to his superb science.

Despite some of the tabloid-worthy details, the book is not sensational. The entries are bright, down to earth, informative and easy to dip into randomly or otherwise. Thepassages on general and special relativity give clear background and context on how Einstein came up with thetheories, what they mean, and how they were received and proven—all as valuable for non-physicist aficionados asknowing his Nobel Prize was for the photoelectric effect, and that he did not want a gravesite for fear it would becomea tourist attraction.

The authors draw heavily on the numerous Einstein biog-raphies, leaving you to wonder why the world needs yetanother such tome. But the public and even scientists can’tseem to get enough of the man who died half a century ago and is still the poster boy for brilliance—and on the adver-tising poster for the 2005 World Year of Physics.

used in Landsberg’s example, n equals 10.

Fermilab director MikeWitherell solved Landsberg’smathematical quiz in time to claim the prize: a bottle ofSakonnet red from the state of Rhode Island, home of Brown University.Davide Castelvecchi

Trends in extradimensionsSometimes old papers can behighly influential, decadesafter their publication. TheodorKaluza and Oskar Klein, work-ing independently, sought tounify Einstein’s gravity withMaxwell’s electromagnetismthrough the introduction of afifth dimension. These ideaswere published in two papersin the 1920s.

Though an idea thatimpressed Einstein, the initialinterest in this topic faded

with the rise of quantummechanics. Using the spiresdatabases, we counted thenumber of citations of Klein’swork in each of the yearssince 1975, to see how this 80-year-old idea has beeninfluencing modern high-energy physics (Kaluza’s paperis in a more obscure journaland is, unfortunately, less well-cited in spires).

By the late 1970s interest inextra dimensions was growing,with a number of influentialpapers referring to the work ofKaluza and Klein (KK). Afterthe mid-’80s heyday, interestin KK theory appeared to havegone into remission only toexperience a resurgence inthe late ’90s. This was spurredby suggestions in 1998 thatthe KK extra dimensionsmight be large enough to be detectable at present orplanned colliders and

experimentalists at CERN andFermilab are actively lookingfor them. This connection evenresulted in a few citationsfrom experimental collabora-tions, for a paper that was pre-viously the domain of theorists.

The history of this one ideareveals much about the trendsand ideas of the last 25 yearsof high-energy physics.Heath O’Connell, Fermilab

Below: Citations of O. Klein, “Quantumtheory and five-dimensional theory of relativity”, Z. Phys. 37:895-906 (1926).Source: spires

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One hot day in August, particle physicists turnedcold. That’s the day the International TechnologyRecommendation Panel (ITRP) announced the decision to pursue “cold” superconductingtechnology for what physicists hope will be the world’s next big particle accelerator, theInternational Linear Collider. Going cold, insteadof recommending a “warm” option that had also been under development, has far-reachingconsequences for laboratories, scientists, industries and governments across the globe.What does “cold” mean, and why did particlephysics choose superconducting technology?

The technology for the ILC is called coldbecause it is cold—really, really cold, as in veryclose to absolute zero, as cold as you can get.That’s the temperature at which low-tempera-ture superconductors work their special magic,conducting electric current with no loss ofenergy. That means that in a superconducting

accelerator, almost all the electrical energygoes into accelerating the beam, rather thaninto heating up the accelerating structuresthemselves. Since electricity is a major chunk of the cost of running a particle accelerator, theenergy savings from superconductors endearthem to accelerator builders. Of course, chillingdown to near zero has a price, but the bottomline on operating costs still comes out ahead.

Filling cavitiesThe accelerator builder uses a voltage genera-tor to fill a hollow structure called a cavity with an electric field. The voltage of the fieldchanges with a certain frequency—a radio frequency, or rf. Charged particles feel the force of the electric field and accelerate. Buildthe cavity of superconductor and chill it to nearzero and voilà: a “superconducting rf cavity.”String enough of these cavities together, and

S O L D on C O L D

Particle physics has chosen low-temperature supercon-

ducting technology for the International Linear Collider.

What is “cold,” and why have particle physicists lowered

the temperature on a new accelerator?

by Judy Jackson

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technology. Why cold? There are less chilly ways of

accelerating particles. The ITRP offered severalreasons for its choice. First, there are thoseenergy savings. Over the long lifetime of a particle accelerator, they definitely add up. Butthere are other advantages too:

Superconducting cavities have a relativelylarge opening for the beam to pass through.Sending particles through a large openingrather than a small one makes the beam lesssensitive to ground motion and may permit a more powerful beam.

Cold technology has applications beyond theILC. Other accelerators are using it, or areabout to use it, too. The CEBAF accelerator at Jefferson Laboratory in Virginia and theSpallation Neutron Source at Oak Ridge inTennessee both use superconducting rf. TheDepartment of Energy’s proposed RadioactiveIsotope Accelerator will go cold. And atGermany’s DESY laboratory, where scientistspioneered the development of cold technology,physicists building a new superconducting light source will develop ILC-type cavities andtest them in operation.

The risk factor—can cavities be built at a reason-able cost in a reasonable time and will theywork?—is lower for cold rf systems than for warm.

Industrialization of most of the major pieces ofa cold accelerator has already begun.

We’re all cold togetherAlthough scientists from laboratories in theUnited States and Asia made contributions, theTESLA collaboration at Germany’s DESY led the way in developing high-gradient (lots

of acceleration per meter) superconducting rfcavities. Japan’s KEK laboratory and theStanford Linear Accelerator Center concentratedon the warm alternative. Now that the technol-ogy choice is made, physicists from across the globe will join together to design—and, theyhope, to build—the new cold accelerator.

“I am proud of the work that TESLA has doneto bring superconducting rf technology to this point,” said DESY Director Albrecht Wagner.

“Now it is time for a new collaboration of themost talented and experienced scientists andengineers from the world’s laboratories and universities to take cold technology to the nextstage and to design the ILC. Success willrequire a level of international collaborationbeyond anything that even particle physics hasseen before.”

Indeed, US laboratories including SLAC,Fermilab, Brookhaven, Cornell, Jefferson,Berkeley and Lawrence Livermore, in closepartnership with Asian and European collabo-rators, have already begun to organize for continued R&D and to start the design of thenew accelerator.

“This [cold] recommendation is made with the understanding that we are recommending a technology, not a design,” the ITRP’s reportemphasized. “We expect the final design to bedeveloped by a team drawn from the combinedwarm and cold linear collider communities, taking full advantage of the experience andexpertise of both.”

The particle physics community is now form-ing a global design team, to be located in a single location with an international director, tolead and orchestrate the many national andregional contributions that will add up to adesign for a truly global new accelerator. Whenit comes to linear colliders, cold is the new hot.

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Superconducting rf cavityEach ILC cavity will have nine cells. The shape,size and geometry of cells and cavities optimizethe electric field. Cavities are made of super-conducting niobium which conducts electricitywithout loss of energy.

The electrons always feel a force in the forward direction.

An electron source injects particles into the cavity in phase with the variable voltage.

A voltage generator induces an electric fieldinside the rf cavity. Its voltage oscillates with a radio frequency of 1.3 Gigahertz or 1.3billion times per second.

The electrons never feel a force in the backward direction.

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The Growthof Inflation

Twenty-five years after Alan Guthturned cosmology on its head, what’s the latest story of the universe’sfirst moments?by Davide Castelvecchi

Photography by Fred Ullrich

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“I never thought that anybody would everactually measure these things. I thought wewere just calculating for the fun of it.”Alan Guth

It was a true Eureka moment if there ever wasone. On the night of December 6, 1979, anobscure Stanford Linear Accelerator Centerpostdoc was up late, sweating over an evenmore obscure problem about particles calledmagnetic monopoles. Looking at his calcula-tions the next day, the usually low-key AlanGuth annotated the words “SPECTACULARREALIZATION” at the top of the page. Guthhad discovered cosmic inflation, an idea whichsome have later called the most important incosmology since the big bang.

As recounted in his 1997 book TheInflationary Universe, Guth had been a youngparticle theorist, struggling for many years tofind a stable job. And he did not know muchabout cosmology. Before giving his first infla-tion talk to other SLAC particle theorists, Guthhad to cram in some basics from a popularaccount, Steven Weinberg’s The First ThreeMinutes. Weeks later, his first meeting withStanford University cosmologists broke downinto a babel of incompatible jargons.

Today, Guth is a celebrated icon of cosmology.Inflation, while still an incomplete theory, is thestandard “working model,” the “dominant para-digm” for the birth of the universe. But does thatmean the paradigm is true?

“Certainly the details we don’t know yet, but I think it’s very convincing that the basic mechanism of inflation is correct,” says Guth,now at the Massachusetts Institute ofTechnology. The evidence in favor is mounting.That can’t be a coincidence, many cosmologistsbelieve, and new experiments could close thecase for good within the next decade.

Theorists have proposed countless flavors ofinflation—among them, “old” and “new,” “chaotic,”

“hybrid,” “extended,” “eternal” and “self-reproduc-ing,” even “supernatural”—but all boil down toGuth’s original concept: a mind-bogglingly briefevent, at the very beginning of the big bang,

during which the entire universe went frommicroscopic to cosmic size. In principle, Guththought, a kind of anti-gravity—people now sayan inflaton (pronounced IN-flah-ton) field—could fill empty space with energy. That “vac-uum energy,” he realized, would push the fabricof space to expand, but without diluting itself in the process. Hence, if you have a drop-sizeduniverse filled with vacuum energy, after aninstant you’ll have a drop twice as large, andfilled with twice the energy; one more instantand it will be four times as large, then sixteen.In other words, an exponential growth. What distinguishes the many flavors of inflation is thenature of the inflaton.

Unknown to Western cosmologists, AndreiLinde and Gennady Chibisov, in the SovietUnion, had been thinking about vacuum energy,and Alexei Starobinsky had come up with amechanism for inflation earlier in 1979. However,says Linde, who is now at Stanford University,

“Starobinsky didn’t know why this would beinteresting.”

Inflation was interesting, Guth realized, notonly because it helped with his magneticmonopoles. Inflation could solve two cosmologi-cal mysteries. The first was the apparent flat-ness of space. According to Albert Einstein’stheory of general relativity, matter curves space,meaning that the rules of Euclidean geometrydon’t exactly apply. But on a very large scale,the universe appears to be flat, with stars andgalaxies creating only small bumps. The othermystery was the boring smoothness of theearly universe, and with it, the mostly uniformdistribution of galaxies that telescopes see inthe sky today.

A universe that had expanded dramaticallyduring inflation, Guth realized, would necessarilybe very close to flat, just as the surface of aballoon becomes less and less curved as theballoon inflates. At the same time, the universe

would be the blow-up of a region so small thatfluctuations in temperature and density wouldbe very small, explaining its smoothness.

Cosmologists soon reckoned that inflation,while creating a very uniform universe, wouldalso explain why and how the early cosmoswould be lumpy enough that the stars andgalaxies could form in the first place. In 1982,Jim Bardeen, of the University of Washington,and others calculated that inflation predictedthe so-called density perturbations in the cosmic broth that emerged from the big bang.Density perturbations, cosmologists thoughteven before Guth, had to have a fairly precisecharacter called scale invariance, and Bardeenshowed that inflation was consistent with that.

All those predictions have since been con-firmed with increasing accuracy, through exten-sive surveys of galaxies, quasars, and, reachingback in time, the cosmic microwave back-ground. The CMB is to a cosmologist what theearliest fossils are to a natural historian. It is,quite literally, the afterglow of the big bang,traveling for the past 14 billion years in all direc-tions of space. Its electromagnetic waves havestretched during the universe’s expansion, andwhat’s left is now microwave radiation.

It was the discovery of the CMB in the1960s that convinced people of the whole bigbang idea. At first, though, the CMB seemedcompletely uniform—bearing no sign of density perturbations—until in 1992 NASA’s COBEexperiment finally found small fluctuations, onthe order of one part in 100,000. Subsequentexperiments, culminating in last year’s WilkinsonMicrowave Anisotropy Probe (WMAP) results,found striking confirmation of scale invariance.The WMAP data also gave the most convincinghints yet of the flatness of the universe, yieldinganother triumph for inflation.

Back in the early 1980s, many cosmologistsdidn’t think that CMB fluctuations would be discovered in their lifetimes. “I really neverthought that anybody would ever actually meas-ure these things,” says Guth. “I thought we were just calculating for the fun of it. And nowthey’re measuring them with such high preci-sion—it really is just fantastic.”

But while the experiments have made thecase for inflation “very compelling,” as Guth cau-tiously puts it, there hasn’t been much progresson how inflation worked in the first place.

The model in Guth’s original paper, publishedin Physical Review D in 1980, admittedly did not work. Michael Turner of the University ofChicago, who took part in Bardeen’s calculationof the density perturbations, says Guth hadbeen brave. “One of the striking things about[Guth’s] paper,” Turner says, “was that he said:‘Look, guys, the model I am putting forwarddoes not work. I can prove it doesn’t work. But I think the basic idea is really important.’ ”

In fact, Guth’s “old” inflation ended too soon,and too messily. A “graceful exit” was neededto make the universe look remotely similar toours. In 1982 Paul Steinhardt, another co-authorof Bardeen’s calculation, solved the gracefulexit problem together with Andreas Albrecht;Linde also found a solution independently. Their

“new” inflation worked by adjusting the shape of the potential function, a sort of mathematicalroller-coaster that defines the properties of the inflaton.

Most of the mechanisms proposed ever sincerely on carefully adjusting the shape of thehypothetical potential function. None, it seems,has been too convincing. “All these modelsseem so awkward, and so finely tuned,” saysMark Wise, a cosmologist at the CaliforniaInstitute of Technology.

Physicists would like a theory that avoidssuch gimmicks, one that shows how thingsought to be from first principles—or at least withthe smallest possible number of assumptions.

“Fine tuning” is the opposite. It was two fine-tuning problems, two such

implausible balancing acts, that inflation wassupposed to have solved. “You’re trying toexplain away certain features of the universethat seem fine-tuned—like its homogeneity, orits flatness,” says Steinhardt, now at PrincetonUniversity, “but you do it by a mechanism thatitself requires fine tuning. And that concern,which was there from the beginning, remainsnow.” As Albrecht, now at the University ofCalifornia at Davis, puts it, inflation is not yet a

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The surface of a very inflatedsphere looks virtually flat.Similarly, the apparent flat-ness of our universe could bethe result of cosmic inflation.

theory: “It is more of a nice idea at this point.”Linde and others have even observed that,

through inflation, countless, perhaps infinitelymany universes could sprout from the vacuumenergy like bubbles, each with its own funda-mental constants of nature. That would be theultimate Copernican revolution, with our entirecosmos an insignificant bubble in the froth of an incomprehensible “multiverse.” If so, finetuning could be just a matter of chance.

Most physicists believe that solving the riddledepends more than ever on progress in particlephysics. In the late 1970s, for young particlephysicists like Guth, Albrecht and Steinhardt,the early universe was suddenly a hot subject.That seems to be the case again. “I really feelthat cosmology is coming around to the flavor it had 25 years ago,” says Albrecht. Luckily, saysGuth, the interchange of ideas has improvedsince his communications break-down with theStanford cosmologists. “Now, I think everybodyrecognizes that there is a strong interfacebetween these two fields.”

And the 1998 discovery of the acceleratingexpansion of the universe has only made theconnections more mysterious. While not asexplosive as inflation, the current accelerationcould also be driven by a form of anti-gravity,what Turner dubbed dark energy. The quantumtheory that underpins particle physics allowsthe existence of vacuum energy. The trouble is,quantum theory predicts vacuum energy that’senormously stronger than anything realistic.That, Guth points out, is nothing new. “The vac-uum energy,” he says, “has been a hauntingquestion for particle theorists since the adventof quantum field theory in the 1930s.”

An increasing number of theoretical physi-cists are starting to think that these and otherproblems will eventually find their solution in the purported ultimate theory of everything.

“Cosmology is moving toward describing things

in terms of string theory,” says Guth. String the-ory is an ambitious—but still hypothetical—attempt to combine all laws of physics into onemathematical framework. All particles andforces of nature would be explained as notesplayed by tiny vibrating strings living in a ten- oreleven-dimensional world.

Cosmology, says Fermilab string theorist JoeLykken, may have been portraying the early universe too simplistically. “Unlike playingaround with toy models, once you get to stringtheory you either solve everything at once, oryou solve nothing,” Lykken says. But untilrecently, no one knew how to explain inflationusing string theory. It’s not that string theorycouldn’t produce an inflaton, says Lykken; theproblem is that it produced too many.

The wake-up call, Linde says, came at aMumbai conference in 2001, when Princeton’sEd Witten, a recognized string theory guru,admitted that he didn’t know how to explaininflation using string theory. “At first,” jokesLinde, “string theorists said ‘Too bad for inflation,’while cosmologists said ‘Too bad for string the-ory.’ ” Soon, however, Linde started collaboratingwith several string theorists—including SLAC’sEva Silverstein and Shamit Kachru—and beganto fix the situation.

In string theory, says Kachru, the inflatoncandidates are what determine the shape ofspace in the extra dimensions, those invisible to us. In previous calculations, as inflationunfolded, the geometry of the extra dimensionswould go berserk, either curling up or explodingout of control. A paper published last year byKachru and Linde together with Stanford’sRenata Kallosh and Sandip Trivedi of the TataInstitute of Fundamental Research, India, madea breakthrough. “We have new theoretical toolsto fix those shapes,” Kachru says.

That was a huge step forward, says Lykken,who is not connected to the study. It was a

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“Unlike playing around with toy models, onceyou get to string theory you either solveeverything at once, or you solve nothing.”Joe Lykken

tour de force that took many specialists by sur-prise. “I would have said that we were 10 yearsaway from being able to do that,” he says.

The authors admit that this is only anencouraging first step. For one thing, “stringy”inflation seems to require a very complicatedfine tuning, as Linde found in a paper withseven other authors. Linde says that was arecord number for him. “The reason is, it tookeight authors to fine-tune the parameters to get a nice inflation,” he says.

Still, the new developments have generatedconsiderable hype, which some critics havedubbed the “Stanford propaganda.” Some find it troubling that the results of Linde and thestring theorists seem to point to a “landscape”of possible universes—again, a multiverse ofunpredictable bubbles. Far from being progress,Steinhardt says, this shows that the theory is in “retrogress.” “People are beginning to throwup their hands and talk about landscapes,” hesays. “Consider where we started from. We weregoing to explain everything, now we explainalmost nothing.”

With Neil Turok of Cambridge University andother collaborators, Steinhardt has for the pastthree years been pursuing an idea that wouldget rid of inflation altogether. In their cyclic universe model, our universe would be part of a larger universe, one of two parallel, three-dimensional membranes separated by a tinygap in the fourth dimension. A collision of thetwo membranes would release enough energyto cause the big bang—in fact, many big bangs,coming at regular intervals of perhaps severaltrillion years. Steinhardt says theirs is a “holistic”approach, because it explains the big bang and dark energy at once. “Provided that the bigbang is something tractable, something thatthings can pass through, from before to after,[our model] can produce the homogeneity, flat-ness, and density perturbations that you getfrom inflation.” A periodic big bang, he says,would also solve the “singularity problem,” thequestion of what came before the big bang.That’s something inflation can’t do, because itstarts with a singularity, a point in time wherethe laws of physics break down.

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What the night sky overChicago might look like if our eyes could see in themicrowave spectrum.(Emissions from televisionantennas would look verybright, but are not shown.)

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Lykken says the cyclic universe could be avery good idea, but it’s still in its infancy. “It’sright at the moment you’re most interested in,when the membranes are sort-of bouncing, thatyou get into physics that’s not well understood,”he says. “So you’ve traded one thing you don’tunderstand [the singularity] for another thing youdon’t understand.”

And, in its current form, the cyclic model alsoneeds a good amount of—you guessed it—finetuning. But Steinhardt thinks it looks at least aspromising as inflation.

New experiments could settle many of thesequestions in the next ten years or so. New data coming from WMAP, and especially fromPlanck, a probe the European Space Agencyplans to launch in 2007, will greatly improve thepicture of the CMB sky. “Right now, we’vemeasured the universe to be flat to a precisionof 2 percent,” says Turner. “That’s very good. But by the time Planck is done, we’ll be downto one-tenth of a percent. And I think that willbe a much more spectacular test.”

But while inflation predicts flatness, flatnessdoes not imply inflation—there could be otherreasons for it. The same applies to the scaleinvariance of the density perturbations calcu-lated by Bardeen, Steinhardt and Turner. But,Turner says, current error margins cannot dis-criminate between inflation and “vanilla” scaleinvariance. “One of the things I’ve tried toemphasize for twenty-some years is that infla-tion doesn’t predict scale invariance. It predictsalmost scale invariance,” he says. If bettermeasurements could tell the difference, thatcould be a big success for inflation.

Virtually all experts agree that, eventually,the definitive proof could come from an entirelynew kind of observation. Einstein’s general rela-tivity predicts that inflation would have releasedgravitational waves, deformations in the geome-try of space that would have traveled around

the universe ever since. By now, those waveswould probably be too weak to measure—noone ever has. But some marks of their passagecould have affected the early universe, leavingripples frozen in time in the picture of the CMBsky. At first, cosmologists thought those markswould be so weak that they would be drownedby the density perturbations. But in 1997, twodifferent teams figured out independently thatthe gravitational waves would leave a charac-teristic signature. “That gave us a hope ofmeasuring the gravitational waves even thoughthey have a much smaller effect than the density fluctuations,” says Fermilab’s AlbertStebbins, a member of one of the teams.

A new generation of radio telescopes isbeing developed to hunt for the gravitationalwaves. The measurements could be very diffi-cult, or even impossible. But then, experimental-ists have defeated skeptics time and again, withresults that once sounded like science fiction.

“That seems to happen almost every year now,”says Guth.

For now, Guth has cemented his ideas ofinflation in the cosmological canon. In the AdlerPlanetarium and Astronomy Museum inChicago, an exhibit honors the greatastronomers and cosmologists from the past,from Galileo and Copernicus to Herschel andHubble. And at the end of the exhibit—with anote pointing out that this is still work inprogress—is Alan Guth’s notebook, with hisoriginal calculations and the “SPECTACULARREALIZATION.” Like the earth-centric cosmol-ogy of Ptolemy, also featured in the exhibit,inflation could be one of the ideas that were soinfluential in their time that they are still seenas a milestone, even though they turned out tobe wrong. Only time will tell if Guth’s idea ishere to stay, or if another Copernican revolutionwill eventually replace it.

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“Consider where we started from: We weregoing to explain everything, now we explainalmost nothing.”Paul Steinhardt

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SESAMECAN A RECYCLED SYNCHROTRON BECOME ANOASIS OF PEACE IN THE MIDDLE EAST?

BY MIKE PERRICONE

BESSY I, a 15-year-old, 0.8 GeV synchrotron accelerator, was destined tobe designated as “junk.” The field was demanding higher energies in1997, and the Berlin Electron Storage Ring Company for SynchrotronRadiation was planning a new machine, seeking the lowest price to havethe old and soon-to-be decommissioned ring hauled away for scrap.

Herman Winick learned of the plan in a September 1997 meeting ofthe BESSY II Machine Advisory Committee in Berlin, preparing for thesuccessor machine. Winick and a friend and colleague of nearly 40 years,Gustav-Adolf “Gus” Voss of Deutsches Elektronen-Synchrotron (DESY) in Hamburg, believed the old machine had plenty of good science left init: it had, after all, been a world-class facility in its time.

“Our top laboratories operate under budget strictures, yet we usuallyhave the resources to obtain the newest and best equipment forupgrades to our facilities,” says Winick, who is based at the StanfordSynchrotron Radiation Laboratory, California, but follows his research farand wide as scientists do. “Isn’t it better to use that old equipment,”Winick reasoned, “to recycle the surplus items, to put them in the handsof projects struggling for funds? Instead of just putting [the equipment] in a corner and forgetting it for 10 years?”

There had to be uses, somewhere, for the kinds of research applica-tions that BESSY I had successfully performed since 1982. Synchrotronaccelerators use magnets to create a circular path for electrons travelingat nearly the speed of light, producing a beam of bright ultraviolet and X-ray light, about the diameter of a human hair, that is directed down beam-lines to experiment end stations. Synchrotron radiation is widely used inmaterials science and biomedical applications, including lithography forcomputer chips; absorption and scattering measurements; high-pressureapplications to create artificial diamonds and other substances; and pro-tein crystallography (the double-helical structure of DNA was establishedthrough X-ray diffraction patterns).

Other synchrotrons were offering higher energies for more demandingwork. But Winick and Voss believed that, beyond first-in-the-field sciencecapabilities, BESSY I could also serve a higher calling in a region wantingfor scientific development, perhaps the Middle East. A destination pre-sented itself just a few months later, when Voss met several MiddleEastern scientists at a conference organized by Sergio Fubino and othersin Torino, Italy. Fubino, a prominent theoretical physicist from CERN, hadbeen a founder of the Middle East Science Committee (MESC). The con-ference theme focused on seeking ways to support science in the MiddleEast, and the idea of donating the BESSY I synchrotron took a strongand immediate hold.

“When Gus mentioned the possibility, he got a very positive response,”Winick recalls. “He wrote to me, we fleshed out some details, and hecontacted some people in the German government. Gus had good con-nections in Germany.”

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The BESSY I synchrotron-lightsource (above and top of pageopposite) was originally operatedat the Berlin Electron Storage Ring Company for SynchrotronRadiation (bottom of page oppo-site). Now the old apparatus isawaiting its new site in Jordan,providing useful science—and,hopefully, an oasis of peace for the Middle East. (Images courtesy of BESSY.)

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Winick, Voss and many others began theprocess that nurtured the recycling of BESSY Iinto the International Centre for Synchrotron-light for Experimental Science and Applicationsfor the Middle East (sesame), now under construction at Al-Balqa’ Applied University inJordan. Can the re-engineered synchrotron also serve as an agent for change in the MiddleEast? With the partnership of the UnitedNations Educational, Scientific and CulturalOrganization (unesco), sesame’s goals inter-twine the furthering of science and the nurtur-ing of connections among scientists fromthroughout the Middle East and beyond. “I con-sider the unesco slogan ‘science for peace’ tobe as important an objective for sesame as thescience and training aspects,” says HerwigSchopper, President of the sesame Council andformer Director-General of CERN, theEuropean Particle Physics Laboratory inGeneva, Switzerland. “Indeed, this was one ofthe main motivations for establishing sesame, tocontribute to a better understanding amongpeople of different traditions, religions and political systems.”

A tent near the Red SeaThe idea of using science for peace in theMiddle East had been forming in many minds,and the connections were waiting to be made.At CERN, Fubino and Israeli physicist EliezerRabinovici were active advocates for MESC,which had been seeking opportunities for Israeliand Arab scientists to work together. Rabinovici,a string theorist and now a member of thesesame Council for Israel, recalled an especiallypoignant meeting in 1995, hosted by theEgyptian government near the Red Sea resortof Dahab. In attendance were scientists fromthroughout the Middle East—Israel, Egypt,Jordan, Morocco, and the Palestinian Authority—

and from Europe and the United States, includ-ing physicists Ed Witten and Nathan Seiberg of the Institute for Advanced Study at PrincetonUniversity, and Robert Laughlin of Stanford(who would win the 1998 Nobel Prize in physics).

“There had been an earthquake in the area,measuring 7 on the Richter scale, and we weremeeting in a Bedouin tent,” recalls Rabinovici, ofRacah Institute of Physics at Hebrew Universityin Jerusalem. “There was another significantevent—[Israeli Prime Minister] Yitzhak Rabinhad been murdered several weeks before themeeting. The Minister of Science of Egypt,Venice Gouda, asked everyone to stand andhonor Rabin. We all stood; people from Al AzharUniversity in Cairo, people from Israel, peoplefrom Jordan—it was very touching... It gave ushope for ‘little’ science, that scientists fromArab countries felt comfortable cooperating inthis situation. By ‘little’ science, I mean scien-tists meeting and working at a one-to-one level.It was an outstanding meeting, and we contin-ued our efforts.”

Those continued efforts encompassed theTorino meeting, after which Rabinovici andFubino elicited the interest of Schopper, theCERN Director-General from 1980 to 1988. At a 1998 MESC meeting in Uppsala, Sweden,Winick and Voss presented their proposal forrecycling BESSY I as the basis for a synchro-tron-light source laboratory in the Middle East.Voss and Schopper worked to confirm anagreement with the German government for

The International Centre for Synchrotron-light for Experimental Science andApplications for the Middle East (sesame) is now under construction at Al-Balqa’ Applied University in Al-Salt City, Jordan. Al-Balqa’ Applied University,founded in 1997, offers Bachelor and Associate degrees for more than 21,000students. Fields of study are Applied Sciences; Engineering; TechnologicalAgriculture; Planning Management; Graduate Studies and Scientific Research;and a Traditional Islamic Arts Institute. The university also has oversight for 19community colleges in the region. (Image courtesy of sesame.)

Groundbreaking took place on January6, 2003 for construction of the sesamesite at Al-Balqa’ Applied University. Thecollaboration hopes to have the newsynchrotron facility in operation in 2009.(Image courtesy of sesame.)

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05donating the machine. Schopper contacted

Federico Mayor, then-Director of unesco, whofollowed up by calling a consultative meeting inParis in June 1999 with 12 prospective MiddleEast members attending. Voss and Winickagain made their presentation, and unescoformed an Interim Council to launch the pro-posed synchrotron-light source center.

Efforts were also evolving among Palestinianscientists. Said Assaf, Director-General of thePalestinian Authority’s Arafat National ScientificCenter for Applied Research in Ramallah, WestBank, was invited to a 1998 seminar at Israel’sWeizmann Institute of Science where he learnedof the synchrotron center proposal. Assaf initi-ated a meeting for himself, Schopper andMaurizio Iaccarino, unesco Director-General ofScience, with Palestinian Authority ChairmanYasser Arafat. Assaf reported that Arafat (whohas a degree in engineering from Egypt’s KingFahd University) was enthusiastic about theproject and offered “strong recommendations to host sesame in the Palestinian Authorityarea.” Assaf, who received his PhD in biophysicsand biochemistry from Iowa State University,recalled that it was he and Winick who formu-lated the sesame acronym. Assaf also pressedfor—and won—the endorsement for a sesamesatellite center, the Middle East Life SciencesInstitute for Research (melsir), located inPalestinian territory.

Schopper was named chair of the InterimCouncil. He retained the chair when thePermanent Council was formed in 2003. In April2004, sesame was formally established as an autonomous intergovernmental organizationfollowing the model of CERN. At least sixmembers had to accept the statutes by a letterfrom the head of state or foreign minister. If a state wants to join sesame, a letter must besent to the Director-General of unesco. Thecurrent members are Bahrain, Egypt, Iran, Israel,Jordan, Pakistan, the Palestinian Authority, andTurkey; some others (for example, the UnitedArab Emirates and Oman) are still involved inlegal procedures requiring signatures at thehead-of-state level; Greece, Germany, Italy,Japan, the United States, the United Kingdom,Kuwait and Libya are observers, with the partic-ipation of others under discussion.

The unesco umbrella had been used inmuch the same way in the years following WorldWar II to bring together two initiatives: one originating from physicists, the other pushed bypoliticians to use science as a pathway forregional cooperation and cohesion in Europe.That early “science for peace” effort built theEuropean Particle Physics Laboratory inGeneva, Switzerland—CERN. Schopper statesthat the Council originally created by unescofor the project retains a symbolic presence in

the “C” in CERN, which is still governed by aCouncil with ultimate authority in all scientific,technical and administrative matters.

Exchange of ideasThere are some 45 synchrotron facilities aroundthe world. sesame, which hopes to begin opera-tions in 2009, is not specifically aimed at com-peting with any or all of them, though it mightenjoy a local advantage. In the region that gavebirth to civilization, archeology offers an intrigu-ing new application for sesame: synchrotron lightcan be used to study concentrations of metalsand other elements as evidence of ancient envi-ronments and environmental change. Yet sesamehopes for a broader reach.

“Establishing a cutting-edge synchrotron inthe Middle East, where none exists, advancesscientific research in this region in the manyfields where synchrotron radiation is used,” saysMoshe Deutsch of Israel’s Bar-Ilan University, a synchrotron user for nearly 25 years, chair ofthe National Synchrotron Committee of Israel’sNational Academy of Sciences and Humanities,and member of the sesame Council. “The easyaccess provided by a nearby facility will addgreatly to the ability to do cutting-edge researchin all the countries in the region. Moreover, as a central meeting point for researchers for anumber of countries, it will provide opportunitiesfor an exchange of ideas.”

sesame researchers come from 24 countries and the Palestinian Authority. At the third annual users meeting, held in Antalya, Turkey, in October 2004, Herman Winick noted the addition of more than 100 new researchers. (Chart courtesy of sesame.)

Number of users by citizenship

0 20 40 60 80 100 120

Turkey 116Armenia 74Israel 39Iran 29Algeria 14Palestine 14Jordan 10USA 10Lebanon 6Greece 7Saudi Arabia 4Egypt 3UK 2Sir Lanka 2Pakistan 2Azerbaijan 4Syria 1Poland 1Morocco 1Italy 2Iceland 1Germany 1Cyprus 1China 1Canada 1

Working in Middle East/Mediterranean Basin

Working outside Middle East/Mediterranean Basin

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When operations begin, the annual budget is anticipated at about US$4 million; the current$660,000 annual budget is achieved throughassessments on members. unesco has contributed about $700,000, in addition to itsorganizational oversight; the US Department ofEnergy has contributed some $500,000. TheUnited States is an “observer” in sesame, butnot a member, and the US representative tounesco has attended several sesame Councilmeetings. Germany’s contribution of BESSY I,largely the injector components of the machine,is hard to assess in dollars but would certainlytotal several millions. Stanford LinearAccelerator Center (SLAC), in California, andLaboratoire pour l’Utilisation du RayonnementElectromagnétique (LURE), in France, have alsodonated several million dollars worth of equip-ment. Pakistan will take the lead in constructingone beamline; six beamlines are planned, ranging from hard (high-energy) X-rays to theinfrared range. Schopper said sesame is hopingfor some €10 million from the EuropeanCommunity for the upgrading of the machine,with the possibility of additional funding fromthe United States. The project also hopes for funding from the International AtomicEnergy Agency (IAEA) in Vienna for trainingand beamlines.

“The injectors from BESSY I are sitting inJordan now, in a warehouse northeast ofAmman,” Winick says. “We have 100 pallets ofmagnets and power supplies. As soon as thebuilding is ready, we can start moving in theinjectors and work on buying ring components.”

The new ring will have a circumference of116 meters; the original BESSY I ring was 62meters. Upgrades will be directed by DieterEinfeld and sesame Technical Director GaetanoVignola. Jordan’s contribution of land and infra-structure is hard to estimate, but the construc-tion of the building alone is worth some $8-10million. The site was selected by a vote of theCouncil among the seven bidders submittingproposals: Armenia, Egypt, Iran, Jordan, Oman,the Palestinian Authority and Turkey. Jordan’sAl-Balqa’ Applied University, founded in 1997,has more than 21,000 students and is the hubfor 19 community colleges in the area. Groundwas broken in June 2003 with constructionbeginning that fall and completion slated forsummer 2005.

“Parallel universe”Open access was a critical requirement forhosting sesame. Schopper noted that a hoststate agreement was signed giving sesame thesame level of diplomatic privileges as thoseenjoyed at CERN. With the enthusiastic back-ing of King Abdullah II and his EducationMinister, Professor Khaled Toukan, for the proj-ect, Jordan gave its guarantee of open access,and Schopper stated that there have been novisa problems over the last three years, “exceptwhen people sometimes applied too late. Evensecurity problems could be solved in all cases.”

Among Council members and collaborators,the descriptions of the working relationshipsportray an environment that is generally positivedespite the net of tensions constraining theregion. To be sure, there are undercurrents,though not always the expected ones.

“The Palestinian role is certainly importantfrom the political point of view,” says Councilmember Salman M. Salman of A-Najah NationalUniversity in Nablus, West Bank, who served onthe site selection committee and is a long-standing member of the technical committee.

“But we also like to see equal appreciation of thePalestinian participation on the scientific level.Sometimes we feel we are not given that recog-nition. Sometimes we feel our role is directed as a front for the sealing of the political part, that the Palestinian political cause is used topursue projects and activities that do not give[Palestinians] proportional weight in the benefitsor responsibilities. We have a lot of experienceusing our cause for the benefit of other causes.We do not mind using that for others, but weexpect to get our own benefits, too.”

Herwig Schopper (left), Chairman of the sesame Council,meets with Yasser Arafat, President of the Palestinian NationalAuthority. Also at the 1998 meeting was Maurizio Iaccarino,then Director-General of Science for unesco. (Image courtesyof Said Assaf.)

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Salman, a high-energy physicist who hascollaborated at Fermilab, Brookhaven andCESR at Cornell, says the Palestinians do havesome concerns about free access, but he alsonotes: “However, we do not see pre-set mindsconcerning the Palestinian role with sesame.”

Schopper emphasizes the importance ofinternational collaboration extending to “admin-istrators and politicians up to the highest levels,”which came into play with some intensity duringmeetings at the diplomatic levels to discusshow the Palestinian Authority should be referredto officially in the statutes of the project. At thecollaboration level, Rabinovici notes that manymembers have begun to assume leadershiproles; the October 2004 users meeting inAntalya, Turkey, was organized and chaired bySehra Zayers of Turkey, and Samar Hasnain ofPakistan and the United Kingdom. Scientiststhemselves report their interactions to be coop-erative and convivial, sometimes surprisingly so.

“My experience of sesame is one of living in aparallel universe,” says Rabinovici. “It’s been soamazing from the beginning. We live in a politi-cal world, with many oscillations, good days andbad days. It is the same with the Arabs. Theyhave good days and tough days. Yet I’ve neverfelt that inside the meeting room. There, wewere scientists working for a common goal,building this accelerator for the benefit ofeveryone in the area… It’s a model of how ouruniverse could have been. It gives me someoptimism, sometimes in a period when it is notso easy to hold onto optimism.”

Deutsch has observed the rituals of daily lifesoftening the pressures of politics: dinnerdefusing differences.

“The relations with our Palestinian counter-parts are friendly and good,” Deutsch says. “Somuch so that on occasions, we even dareapproach political issues, very carefully, very

cautiously, never going past the point where thediscussion may turn too heated. Knowing theland, the towns, the people, the politics, thefood of each other from first-hand experiencehelps in some cases to understand better each other. If nothing more, we can make com-mon jokes on some of the political figures inthe region, which would not be understood bysomeone from further away.”

Still, the scientists understand that theirsesame experience cannot be insulated fromtheir larger world. In fact, the stakes will beraised by increasing numbers of scientists and students with more frequent comings andgoings when sesame becomes an activeresearch facility. The parallel universe wouldmerge with reality.

“In the present situation,” says Deutsch, refer-ring to the state of violence, “no Israeli—orAmerican or British—[researcher] would dare tocross the West Bank to Jordan, travel throughJordan, and stay there two weeks to doresearch. Restoration of at least a measure of normality to everyday life is an absolutenecessity for the well-being and progress ofsesame. We all hope and pray that this willcome soon.”

Those same hopes and prayers live in bothIsraelis and Palestinians. “If peace cannot beestablished with justice to all,” says Salman, “thecontribution of the project will suffer.”

Science for peace will also need peace forscience.

Jordan’s donation of land and infrastruc-ture for sesame is valued at $8-10 mil-lion. The Council hopes to being operat-ing the synchrotron-light source in 2009.(Image courtesy of sesame.)

saudi arabia

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Salt City

gallery: dawn meson

From cave paintings of bison to Monet landscapes, artists have studied

and interpreted the natural world. Dawn Neal Meson, a San Francisco

artist, has taken this theme one level further, or, rather, many orders of

magnitude smaller.

The subjects of Sum Over Histories, Meson’s latest series of acrylic

paintings, feature aspects of nature at the particle physics level:

colliding electrons, multidimensional surfaces, entangled particles, and

string theory. Her goal is to illuminate invisible worlds, unseen and

unseeable. Through these works she answers her own question, what

can art contribute beyond photography?

by Raven Hanna

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“Scientists and artists are

the official noticers of society.”

Frank Oppenheimer

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Meson’s paintings document her personalprocess of understanding the concepts andtheories of modern physics. Her paintings arenot intended as scientific illustrations thatinstruct, but she hopes they might inspire.

Trained as a fine artist, Meson remembershaving interest in her college physics class;but it took her 10 years to reunite with thesubject. She began by reading popular modernphysics books, from the likes of RichardFeynman, David Lindley, and Brian Greene,digesting the concepts through equations andsketches in her notebook. She then soughthelp. “Nothing like having a brilliant theoreticalphysicist to answer questions,” she says.

Stephon Alexander, a physicist at StanfordLinear Accelerator Center, met with Meson tohelp her work through the mathematics behindthe more perplexing physics. “She has good

“Dawn Meson has good

intuition—she asks

good questions.... There

is both an artistic and

scientific process in

both art and science.”

Stephon Alexander

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EntanglementMeson was attracted to the subject of particle entanglementand action at a distance because it poses a mystery. “Wackythings do happen and have mathematical bases,” she says.Each of the two canvases shows a particle; similar in theircoloration to show that they are the same type of particle, forexample both electrons. Painting unseen particles at suchdetail presented challenges. Meson had to devise visualanalogies to such abstract concepts such as spin. “Spin hasnothing to do with visual reality.” She painted the particles tospiral in opposite directions as a symbol for having oppositespin. Like entangled particles, the paintings began physicallyjoined, but the two canvases can be placed far from eachother in a room and still maintain a connection.

intuition—she asks good questions,” he says.Alexander is enthusiastic about the mix of science and art in Meson’s work. “There is bothan artistic and scientific process in both artand science.”

To express complex theoretical concepts,Meson invented systems of symbols andshorthand. When painting actions, such as par-ticles colliding, she chose to use a billiard ballrepresentation and show stages of the inter-action superimposed. When the subjects werethe particles themselves, she chose to repre-sent their wave nature, reminiscent of flowers,with the petals symbolizing probability waves,color-coded so that the more saturated huescorrespond to the highest probabilities.

What does it mean to see a subatomicentity? Color and shape have no meaning forthe very small. Yet, many physicists think in images. Alexander says he “approachesresearch from an intuitive, visual space.”

A difference between most art inspired bynature, and Meson’s paintings: most viewerswill have less familiarity with her subject mat-ter. In gallery shows, Meson’s paintings areaccompanied by paragraphs explaining theirscientific basis. She notes that her work canbe appreciated on multiple levels, for theesthetics and the science. For non-scientists,Meson would like her work to interest them in science. For scientists, she hopes her workwill be inspirational.

The rest of this gallery and Dawn Neal Meson’s other work canbe viewed at www.dawnmeson.com

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“Spin has nothing

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Dawn Meson

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Collision IIBased on the Standard Model of the interactions of funda-mental particles, Collision II shows a time-lapse view of twoparticles colliding. The collision was painted in chronologicalorder, with the positions of two elementary particles comingfrom the right of the canvas, towards their collision in thecenter. The spirals show the paths of the resulting particles,which have a wave component. This inclusion of the dimen-sion of time, chronologically painted although simultaneouslydisplayed, is important to Meson, who made videos docu-menting the evolution of the paintings.

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deconstruction: visa quest

Russian physicist Nikolay Solyak is an expert on particle accelerators andhelps to develop superconducting technology for a future

International Linear Collider. He has been a Fermilab employee since 1999. When he left theUnited States in September 2003, a short trip abroad turned into a four-month odyssey, separatinghim from his work and family in the United States. His documents tell the story.

August 27, 2002: The US Immigration and NaturalizationServices notifies Fermilab of the approval of an H1-B status forNikolay Solyak. The approval notice allows Solyak to continueworking at Fermilab. The new status is valid for three years, the maximum duration. Should he or his family choose to traveloutside the United States, they must obtain visas at a USembassy or consulate to return. In June 2003, Solyak’s wifeand 16-year-old son travel to Russia to visit relatives. Six weekslater they return with their new H4 visas. Solyak himself, whohad to work over the summer, plans to get his new visa on aninternational business trip in the fall of 2003.

September 7, 2003: Solyak travels via Amsterdam to Hamburgto attend a scientific meeting and to collaborate withresearchers at the German particle physics laboratory DESY.He expects his one-month stay in Germany to be sufficient to obtain an H1-B visa. Solyak’s family stays in the United States,with his son attending classes at a high school.

September 12, 2003: Solyak takes his passport and visa appli-cation, the H1-B status approval notice, and other documentsto the Consular section of the US embassy in Berlin. The Visa Unit accepts Solyak’s application but rejects hard copiesof his curriculum vitae and his list of scientific publications.Fortunately, Solyak has computer access upon his return toHamburg, and he produces and submits electronically therequired plain text files the next day. He expects to obtain thevisa in a couple of weeks.

September 25, 2003: Two weeks after presenting all his docu-ments at the embassy, Solyak receives an email asking him for additional information, such as “Flight plans to and from theUS” and “Are you a resident of Germany?” He immediately submits the information, all of which he was prepared to provideat his visit of the embassy in Berlin.

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October 1, 2003: Solyak calls the US embassy in Berlin at itstoll-charged “900” number, paying close to $2 per minute, toask for weekly updates on his visa application. He’s told thathis documents had been sent to Washington for clearance.With his German visa about to expire, Solyak makes arrange-ments with Fermilab and DESY to continue his research visit at the German lab. He applies for, and is granted, an extensionof his German visa.

December 23, 2004: Still without news from the US Embassy,Solyak realizes he won’t be able to spend Christmas with hisfamily in the United States. Rather than celebrating Christmasby himself, he visits friends in Sweden over the holidays.

January 21, 2004: After more than four months, Solyak obtainshis H1-B visa in Berlin. Six days later he travels back to theUnited States, eagerly awaited by his wife and son. Solyak’snew visa is valid until August 31, 2005, in line with the originalthree-year request.

October 9, 2003: The US Embassy in Berlin replies to an emailinquiry by Solyak: “Before issuing your visa, the NonimmigrantVisa Unit had to send a telegram to Washington, D.C. andawait its reply.” Fermilab’s Director, Michael Witherell, sends aletter to the US Embassy in Berlin: “Fermilab is home to scien-tists and other experts from more than 20 countries, and doesnot perform any classified work.... [The presence of Dr. Solyakis needed] to help fulfill the mission of this national laboratory.”During the next three months, Solyak and Fermilab administra-tors inform the US Department of State, the US Department ofEnergy, US Representative Dennis Hastert, the NationalAcademies, and other institutions in Washington, D.C.

November 30, 2003: Solyak’s visa extension for Germany isabout to expire and he has to leave the country. Unable toreturn to the United States without an H1-B visa, he contactsscientists at the European laboratory CERN and makesarrangements to visit them in Geneva, Switzerland, for twoweeks. On December 5, he obtains a new visa at the GermanConsulate in Geneva and returns to Hamburg.

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Subject: RE: visa processing status?

From: CONS, Berlin <ConsBerlin>

Date: Thu, 09 Oct 2003 14:08:53 +0200

To: solyak

Dear Mr. Solyak:

Before issuing your visa, the Nonimmigrant Visa Unit had to send a telegram to

Washington, D.C. and await its reply. The processing time for issuing your visa

may vary from several weeks to several months. Your visa cannot be issued until

this process is complete.

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Authentic ScienceThe search for the workings of the “quantumuniverse” is one of the most exciting adventuresin science today. Recent discoveries concerning

the existence of darkmatter and darkenergy have upendedour fundamentalunderstanding of thevery nature of matter.While this ongoingrevolution is generat-ing extreme excite-ment in the physicsresearch community, it is a story that hasnot, for the most part,

entered the awareness of the broader public tothe extent one would have expected.

Of course the usual media representationsare present, such as books by scientists andjournalists, articles in newspapers and maga-zines, and richly produced science documen-taries. And there have been a few popularbreakout presentations on some of the edgierparts of the theory. But in the competitive worldof public attention, the story of the tremendouschanges in our view of the universe is not get-ting much traction.

I think that the issue is not just a matter ofgetting more airtime for this particular story, butrather represents a more fundamental problemin our approach to addressing the public under-standing of science. In our presentations to the public we have tended to talk mostly aboutthe results of our thinking and the conclusionsof our research. To reach the public in a morecompelling way, I think it is imperative that wego beyond just trying to tell the intellectualstory. We must talk about the process of doingthe science, and tell the human side of thestory of research and discovery.

It is not surprising that the work that we doas scientists is so unfamiliar to the public. Formost people, the last direct experience theyhad with the “doing of science” was their partic-ipation in a high school chemistry or biologylaboratory. Most scientists would agree that thislab experience is as similar to doing real sci-ence as eating airplane food is to real dining. Tohelp people experience the world of science we need to go beyond producing books aboutthe grand unified theory or the documentarieson the origins of matter, wonderful as theseprojects are. We need to create opportunitiesfor the public to experience the process of realscientists doing real science in real places.

Real scientists: The scientific enterprise is

driven by curiosity, a very human trait. But oftenwhen we talk about the work that we do, welose this personal side of the story. The majorquestions of the field, as exemplified in thewonderful Connecting Quarks with the Cosmosand even more accessibly in Quantum Universe,are clearly fascinating to the public and mark a great beginning for an adventure story of sci-entific discovery. To follow through we need to create a vehicle for continuing the narrativeof discovery as our work evolves over the nextten years.

Real science: The story of science is asmuch about “How Do We Know What WeKnow?” as it is “What Do We Know?” It is astory of creating detectors and developing soft-ware and inventing analytic tools. And yet therehas been very little done for the public on thenature of scientific evidence since The Ring ofTruth, Phil and Phylis Morrison’s wonderful bookand television series of a number of years ago.We need to develop more discussions aboutthe nature of the process of science and howwe go about finding things out.

Real places: In visiting a number of acceler-ator laboratories recently I was struck again byhow interesting these facilities really are. Theuniqueness of design, the mixture of electronicsand mechanical systems, the variety of supportsystems needed to keep these instrumentsalive is really amazing. These labs represent anextraordinary enterprise built and maintained by a talented and committed set of individuals.We need to do more to develop authenticonsite and online opportunities for people toview these facilities.

The good news is that the field does notneed to do this work alone but rather can prof-itably partner with intermediaries who can bothsupport the design of new approaches and canbring audiences to the table. Science museumsare ideal candidates for this intermediary role.They are filled with the people who make a living in interpreting science for a general audi-ence. They have scientists, educators, design-ers, objects, facilities and means of distribution.They develop exhibits, media programs, schoolactivities, outreach opportunities and publicevents. And they already have a cultivated audi-ence. It is through a working partnership withthese agencies of public communication andeducation that much of this public understand-ing of research agenda for the field can becompleted.

Rob Semper, a physicist and science educator, is ExecutiveAssociate Director of the Exploratorium, and is responsible forleading the institution’s work in developing programs of teachingand learning using exhibits, media and Internet resources.

essay: rob semper

logbook: inflation

In 1978 Alan Guth heard about the “flatnessproblem” of the universe while attending

a talk on cosmology—a field he was only marginally curi-ous about—by Princeton University’s Robert Dicke. A year later, working late at night as a postdoc at SLAC,Guth found a solution. At the beginning of the big bang,for an incredibly small fraction of a second, the universecould have expanded exponentially fast, rapidly transform-ing curved space into flat one. Quickly running out ofenergy, the expansion would slow down, eventually reach-

ing today’s sluggish pace. Such an initial explosive rush,which Guth later called inflation, could solve a number ofcosmic paradoxes (see story on page 12).

Although scientists still debate the driving forcebehind inflation—Guth soon realized his original idea of

“supercooling” wouldn’t work—the concept of inflation has become the leading theme and the crux of moderncosmology.

Guth’s notebook is now part of a permanent exhibit atthe Adler Planetarium and Astronomy Museum in Chicago.

“So, after a few of the mostproductive hours I hadever spent at my desk, I had learned somethingremarkable. Would thesupercooled phase transi-tion affect the expansionrate of the universe? By1:00 a.m. I knew theanswer: Yes, more than Icould have ever imagined.”

From Alan Guth, The Inflationary Universe,Cambridge, Mass., 1998.

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SymmetryA joint Fermilab/SLAC publicationPO Box 500 MS 206Batavia Illinois 60510USA

explain it in 60 seconds

Office of ScienceU.S. Department of Energy

Gravitational Lensesare a use-ful tool

in the belt of the modern cosmologist: massive bodiesdeflect light, focusing it toward the observer and causingdistant objects to appear magnified and distorted, oreven as multiple images. Einstein’s General Theory ofRelativity tells us exactly how light rays are affected by the warped space around a galaxy or cluster actingas a lens. Interestingly, the lensing effect is strongerthan expected for the amount of mass we can see. This adds weight to the idea that the main constituentof galaxies and clusters is an unseen “dark matter.”

The density of a galaxy increases towards its center,much like the thickness of the base of a wineglass. In fact, a wineglass makes a good model gravitational lens: look into the glass from the top and through itsstem toward a light to discern the effect. By seeing howit distorts the light, it is possible to work out the glass’shape and thickness. In the same way, observing distantgalaxies through gravitational lenses allows the densitydistribution of the clumpy, transparent dark matter to be mapped out. Gravitational lensing may not yet beable to tell us what the dark matter is, but it is telling uswhere to look. Phil Marshall, Kavli Institute for ParticleAstrophysics and Cosmology