Collider Part 7

We refer here to civilian scientific research-designed to press forward human knowledge. In an age of consent forms and the omnipresent potential for lawsuits if events go awry, experimental scientists today are generally extremely careful not to expose the public to hazards. People do sometimes make mistakes, but, if anything, scientists are particularly thorough. "Nutty Professor" stereotypes aside, if you read in the paper about a chemical explosion-which would be the more likely cause, an industrial accident or a botched scientific experiment? I would venture to say that it would be the former in almost every case.

It's true that in times of war, scientists have been recruited to conduct far, far riskier experiments. The expectation that war incurs horrific dangers makes that a completely different story. Those involved in the Manhattan Project, for example, knew that they were constructing and testing weapons of unmatched destructive power. In the Trinity test, in which the plutonium bomb was detonated for the first time in the aptly named region of New Mexico called Jornada del Muerto (Journey of the Dead Man), n.o.body knew for sure what would be the effect of a nuclear explosion. Would the blast be confined to that desert basin or would it race out of control and cause untold damage-perhaps even destroy the world?

In a macabre kind of gambling, right before detonation Fermi offered to take bets on whether a chain reaction would occur that would vaporize the atmosphere. Wagerers could decide if just New Mexico would be wiped out or if it would be the whole Earth. In retrospect, the idea that an experiment could be conducted with an unknown impact on the fate of the entire planet is shocking-and physicists joking about apocalyptic outcomes is highly disconcerting.

As we know now, although the bomb test lit up the sky like a "thousand suns"-as J. Robert Oppenheimer described, borrowing language from the Bhagavad Gita, the Hindu holy book-it did not annihilate the world, of course. The blast produced a crater something like 10 feet deep and 2,400 feet in diameter. Its energy was estimated to be approximately 20 kilotons, equivalent to 20,000 tons of TNT.

Explosions are virtually never measured in terms of TeV, because that unit represents a far smaller quant.i.ty of energy. Nothing stops us from making the conversion, however, and we determine that the nuclear explosion at Trinity was equivalent to 5.0 1020 TeV. That's 5 followed by 20 zeroes-an enormous figure-something like the average number of stars in a billion galaxies. Thus, even the most rudimentary atomic bomb releases astronomically more energy than any of the particle collisions we've discussed. TeV. That's 5 followed by 20 zeroes-an enormous figure-something like the average number of stars in a billion galaxies. Thus, even the most rudimentary atomic bomb releases astronomically more energy than any of the particle collisions we've discussed.

Only a few weeks after the Trinity test, bombs were dropped over Hiros.h.i.+ma and Nagasaki, leading to the devastation of those j.a.panese cities and the end of World War II. The dawn of the atomic age brought increased apprehension about the possibility that scientific miscalculation, combined perhaps with political blunders, would lead to Earth's apocalyptic demise. It didn't help matters that brilliant scientists such as Edward Teller and Herman Kahn would dispa.s.sionately discuss the effectiveness of new types of nuclear weaponry in scenarios involving ma.s.s casualties.

In an era of trepidation, horror films provided a welcome release valve for anxiety. Fictional threats from aliens that could be warded off through concerted effort were easier to handle emotionally than factual dangers from ourselves that seemed to defy ready solution. The 1958 movie The Blob The Blob, about a rapidly growing creature from outer s.p.a.ce, offers a case in point. Its plot is simple: an alien meteorite delivers a gelatinous cargo that turns out to be a ravenous eater. Each time the blob ingests something, it becomes larger. Soon it is humongous and pining for human "snacks" found in a movie theater and a diner. People flee in terror from the gluttonous menace until the film's hero, played by Steve McQueen, manages to freeze it using fire extinguishers.

In a poll about which astronomical objects the public deemed most bloblike, black holes, the compact relics of ma.s.sive stars, would surely come in first place. The image of such an astronomical object stealthily entering a theater, absorbing all of the patrons, enlarging itself, and moving on to another venue might not be all that far from the popular stereotype. Several black hole properties bring blobs to mind. If a black hole is near an active star, for instance as a binary system, it can gradually acquire matter from the star, due to its mutual gravitational attraction, and become more ma.s.sive over time. Nothing is mysterious or unusual about this process except that black holes form particularly steep gravitational wells. Astronomers observe this acc.u.mulation of material through images of the radiation emitted as it falls inward toward the black hole.

The physics of black holes derives from Einstein's general theory of relativity. In 1915, with the ink on Einstein's gravitational theory barely dry, German physicist Karl Schwarzschild, while serving on the Russian front in the First World War, discovered an exact solution. He solved Einstein's equations for a static, uniform, nonrotating ball of matter, and mapped out the geometry of the s.p.a.ce surrounding it. The Schwarzschild solution, as it is called, represents the gravitational influence of simple, spherical astronomical bodies. It describes precisely how a sphere of matter, such as a star or a planet, dents the geometry of s.p.a.ce-time and forces nearby objects to move along curved paths. Whether these objects flee, orbit, or crash depends on whether their speeds exceed the escape velocity required to take off. Those nearby objects without enough escape speed, such as an insufficiently fueled rocket, are doomed for impact.

One curious aspect of the Schwarzschild solution that at first seemed simply a mathematical anomaly, but later became the basis of serious astronomical consideration, is that for dense enough objects there exists a spherical sh.e.l.l, called the event horizon, within which nothing that enters can escape, not even light. That's because the escape velocity within the event horizon is faster than the speed of light. Therefore no object can reach such a speed and flee. In the 1960s, John Wheeler coined the term black hole black hole to describe such a perpetually dark, ultracompact object. Black holes represent the ultimate dents in the fabric of s.p.a.ce-time-the "bottomless pits" of astronomy. to describe such a perpetually dark, ultracompact object. Black holes represent the ultimate dents in the fabric of s.p.a.ce-time-the "bottomless pits" of astronomy.

The idea of inaccessible regions of s.p.a.ce raises profound questions about the laws of physics in such enclaves. Are physical principles the same inside and outside a black hole's event horizon? How would we know, if no one could venture inside and come back to tell the tale? Wheeler was puzzled in particular by the question of what would happen to disordered matter entering the point of no return. According to the long-established law of entropy, for any closed system, any natural process must either preserve or increase the total amount of entropy. Entropy is a measure of the amount of disordered energy, or waste, in a physical system. Thus, although natural processes can convert ordered energy into waste (such as a forest fire turning a stately grove into ashes), they can never do the trick of transforming waste energy completely into fuel. Although it is an open question whether the law of entropy applies to the cosmos as a whole, Wheeler was troubled by the idea that we could fling our waste into black holes, it would vanish without a trace, and the total fraction of orderly energy in the universe would increase. Could black holes serve as the cosmetic of cosmology, gobble up signs of aging, and make the universe seem more youthful?

In 1972, Jacob Bekenstein, a student of Wheeler's, proposed a remarkable solution to the question of black hole entropy. According to Bekenstein's notion-which was further developed by Stephen Hawking-any entropy introduced by absorbed matter falling into a black hole would lead to an increase in the area of its event horizon. Therefore, with a modest increase in entropy, the event horizon of a black hole would become slightly bigger. The signs of aging in the universe would thereby manifest themselves through the bloating of black holes.

As Hawking demonstrated, Bekenstein's theory offers startling implications about the ultimate fate of black holes. Although nothing can escape a black hole's event horizon intact intact, Hawking astonished the astrophysics community by theorizing that black holes gradually radiate away their ma.s.s. Hawking radiation, as it is called, is a natural consequence of another conjecture by Bekenstein. In addition to defining the entropy of black holes, Bekenstein showed that they also have temperature. Because anything in nature with finite temperature, from lava to stars, tends to glow (either visibly or invisibly), Hawking speculated that black holes radiate, too. To evade the event horizon's barrier, this would be a quantum tunneling process, akin to how alpha particles escape the strong attraction of nuclei. A painstakingly slow trickle of particles, much too protracted to observe, would emerge over the eons. The more ma.s.sive the black hole, the lower its temperature, and the longer it would take for it to completely evaporate. For a black hole produced by a collapsed star ten times the ma.s.s of the Sun, it would take an estimated 10 1070 ( (1 followed by followed by 70 70 zeroes) years for the whole thing to radiate away-far, far longer than the age of the universe. Because of such a prolonged time span, Hawking radiation has yet to be observed. zeroes) years for the whole thing to radiate away-far, far longer than the age of the universe. Because of such a prolonged time span, Hawking radiation has yet to be observed.

Less ma.s.sive black holes would evaporate more quickly. These would need to be produced, however, through a completely different mechanism than stellar collapse. Stars of solar ma.s.s, for example, end up as the faint objects called white dwarfs, not black holes. Rather than collapsing further, their internal pressure supports their weight and they simply fade away over time.

Nevertheless, the Schwarzschild solution makes no mention of a minimal black hole ma.s.s. Rather, it defines a Schwarzschild radius-the distance from the center to the event horizon-for any given ma.s.s, no matter how small. The lighter an object, the tinier its Schwarzschild radius.

A black hole ten times solar ma.s.s, for instance, would have a Schwarzschild radius of almost nineteen miles, allowing it to fit comfortably within the state of Rhode Island. If an incredibly powerful force could somehow squeeze Earth so that it was smaller than its Schwarzschild radius, it would be only the size of a marble. A human being shrunk down to less than his or her Schwarzschild radius would be billions of times smaller than an atomic nucleus-clearly below the threshold of direct measurement.

In 2001, Savas Dimopoulos, along with Brown University physicist Greg Landsberg, published an influential paper speculating that microscopic black holes could be found at the LHC. These would have Schwarzschild radii comparable to the Planck length, less than 10-33 inches-or one quadrillionth of the size of a nucleus. Basing their work on theories of large extra dimensions, the researchers estimated that the LHC would churn out ten million microscopic black holes each year, similar to the annual rate of Z particles that were produced at the LEP. inches-or one quadrillionth of the size of a nucleus. Basing their work on theories of large extra dimensions, the researchers estimated that the LHC would churn out ten million microscopic black holes each year, similar to the annual rate of Z particles that were produced at the LEP.

Dimopoulos and Landsberg pointed out that any microscopic black holes produced at the LHC could be used as delicate tests of the number of extra dimensions in the universe-potentially verifying the braneworld hypothesis that gravitons leak into a parallel realm. That's because the ma.s.s of these minute compact objects depends on how many dimensions s.p.a.ce contains. Because Hawking radiation vanquishes lighter bodies at a faster rate, they would evaporate almost instantly, decaying into potentially detectable particle by-products. Their discovery would thereby present an ideal way to study the process of Hawking radiation, as well as examining dimensionality.

A simulation of the production and decay of a microscopic black hole in the ATLAS detector.

The existence of microscopic black holes is at this point purely hypothetical. Stellar-size black holes are still not fully understood, let alone theorized miniature variations. Dimopoulos and Landsberg emphasized that their calculations involved "semicla.s.sical arguments" set in the nebulous zone between general relativity and certain theories of quantum gravity-particularly string theory and M-theory. "Because of the unknown stringy corrections," they wrote, "our results are approximate estimates."1 When a subject is as little known as the application of quantum theory to gravity at the smallest scales in nature, it is hard to say for sure which theoretical predictions will yield tangible results. The brilliance of detectors such as ATLAS and CMS is that they are general purpose. Data they collect will be a.n.a.lyzed by various groups all over the world and matched up against all different kinds of hypotheses. Until then, microscopic black holes remain fascinating to consider but highly speculative.

If microscopic black holes do pop up, they would have virtually no time to interact with their environment, which would just be the evacuated, low-temperature, hermetically sealed collision site. Produced by interacting quarks from two colliding protons, they would immediately decay into other elementary particles. During their brief existence, they would weigh little more than heavy atomic nuclei and would be far enough away from everything else that their gravitational interactions would be negligible. No fireworks, or even a blip on a screen, would announce their appearance. The only way anyone at the LHC would recognize that they came and went would be through meticulous data a.n.a.lysis that could well take many months.

Psychological perceptions of risk don't always match up to actuality. Exotic threats, when matched against familiar hazards, often seem much scarier. People don't spend their time worrying about the national injury rate due to slipping on bathroom floors or falling down bas.e.m.e.nt stairs unless it unfortunately happens to their loved ones or to them. Yet there's something about the bloblike image of black holes that stirs apprehension, even if the chances that such objects, particularly on a microscopic scale, will affect people's lives are about as close to zero as you can imagine.

In 2008, Walter L. Wagner and Luis Sancho filed a lawsuit in Hawaii's U.S. District Court seeking a restraining order that would halt operations of the LHC until safety issues involving potential threats to Earth were fully investigated. The named defendants included the U.S. Department of Energy, Fermilab, CERN, and the National Science Foundation. In a twenty-six-page decision, the judge hearing the case dismissed the suit, stating that the court did not have jurisdiction over the matter.

Trained in nuclear physics, Wagner heads a group called Citizens Against the Large Hadron Collider that he has established to warn against potential doomsday scenarios. One such scenario is the production of microscopic black holes that somehow manage to persist. This could happen, he conjectures, if Hawking radiation proves ineffective or nonexistent. After all, he points out, it has never actually been observed. The enduring mini-black hole would either pa.s.s right through Earth, like a neutrino, or be captured by Earth's gravity. Suppose the latter is true. Once embedded in the core of our planet, he speculates, it could engorge itself with more and more material, grow bigger and bigger, and threaten our very existence. As Sancho and Wagner describe in their complaint: Eventually, all of earth would fall into such growing micro-black-hole, converting earth into a medium-sized black hole, around which would continue to orbit the moon, satellites, the ISS [International s.p.a.ce Station], etc.2 This doomsday scenario is reminiscent of the catastrophe described in David Brin's 1990 novel, Earth Earth. In that science fiction epic set in the year 2038, scientists create a miniature black hole that accidentally escapes from its magnetic cage. After plunging into Earth's interior, it is primed to gobble up the whole planet. A chase ensues to find the voracious beast before it is too late.

The anti-LHC group urges us not to wait that long. If there is even the slightest chance of a black hole destroying the world, the group argues, why take the risk? Why not rule out all conceivable hazards before before the particle roulette begins? It would be a compelling case only if mini-black holes could really grow like blobs from microscopic to Earth-threatening sizes-but no credible scientific theory indicates that they could. the particle roulette begins? It would be a compelling case only if mini-black holes could really grow like blobs from microscopic to Earth-threatening sizes-but no credible scientific theory indicates that they could.

Another concern of Wagner's group is the possibility of the LHC engendering "strangelets" or particle cl.u.s.ters with equal numbers of up, down, and strange quarks. According to the strange matter hypothesis, such combinations would be more stable under certain circ.u.mstances than ordinary nuclear matter. Like heat changing a runny egg into a solid glob, the energy of the LHC could catalyze such an amalgamation. Then, according to Sancho and Wagner's complaint: Its enhanced stability compared to normal matter would allow it to fuse with normal matter, converting the normal matter into an even larger strangelet. Repeated fusions would result in a runaway fusion reaction, eventually converting all of Earth into a single large "strangelet" of huge size.3 Yet another purported global threat is magnetic monopoles. These would be magnets with only north or south poles, not both. Chop a bar magnet in half and you get two smaller magnets, each with north and south poles. No matter what, there would always be two poles per magnet. Monopoles, in contrast, would have just one. Dirac predicted their existence in the 1930s, and they are an important component of certain Grand Unified Theories (GUTs).

Although monopoles have never been seen in nature, some theorists antic.i.p.ate that they would be extremely ma.s.sive and possibly turn up in LHC debris.

Sancho and Wagner ponder a scenario in which two ma.s.sive monopoles, one north and the other south, would be produced at the LHC. Interacting with ordinary matter, theoretically they might hasten certain GUT processes and induce protons to decay. Suppose this caused a chain reaction, causing proton after proton-and atom after atom-to disintegrate into other particles. Eventually, the whole world would be a lifeless...o...b..of inhospitable decay products.

Given the story of the Trinity test, such dire scenarios might lead us to believe that CERN researchers are now taking bets on the fate of Earth. Could LHC workers be wagering each lunchtime on whether black holes, strangelets, monopoles, or another bizarre creation will gobble up the French soil as if it were toast, bore holes through the Swiss mountains as if they were cheese, make haste toward Bologna, recklessly slice it up, and still not be satisfied? Could there be a hidden plot to conceal the true dangers of the world's largest collider?

On the contrary, CERN prides itself on its openness. Secrecy is anathema to its mission. Isidor Rabi, who partic.i.p.ated in the Manhattan Project and witnessed the Trinity test, founded CERN as a way for Europeans after the war to rebuild peaceful, civilian science on a cooperative basis. He emphasized that CERN would not have nuclear reactors and that none of its findings would be cla.s.sified-to preclude the possibility that its research could be used for destructive purposes.

Scientists at CERN sometimes joke about the hullabaloo over mini-black holes. With gallows humor, some jest with a wink and a smile about being at the epicenter of imminent catastrophe-then go right back to coding their software. "[Friends] know that I'm not an evil scientist trying to kill the world," said graduate student researcher Julia Gray.4 Theorists realize that quantum uncertainty offers a minuscule chance for an astonis.h.i.+ngly diverse range of eventualities. Why spend time worrying about these? Through an extraordinarily unlikely roll of quantum dice, Nima Arkani-Hamed remarked that "the Large Hadron Collider might make dragons that might eat us up."5 Despite the lighthearted att.i.tude of many of its researchers, though, the CERN organization itself, for the sake of maintaining a candid and amicable relations.h.i.+p with the international community, takes any public fears very seriously. It doesn't want people to suspect that something sinister is going on in its tunnels and caverns.

Although CERN conducted a comprehensive safety study in 2003 that found no danger from mini-black holes, strangelets, and magnetic monopoles, it agreed to complete a follow-up report that was released in June 2008. The new report concurred with the original findings, offering a number of powerful arguments why microscopic black holes, strangelets, and monopoles, if they truly exist, would pose no threat to Earth.

In the case of miniature black holes, the report showed how conservation principles would preclude them from being stable. Following the maxim that anything not forbidden is allowed, if they are produced by elementary particles, they could also decompose into elementary particles. Thus, aside from the question of whether Hawking's description of black hole radiation is correct, mini-black holes must decay.

Moreover, produced in proton-proton collisions, chances are that microscopic black holes would carry positive charge and thereby be repelled by other positive charges on Earth. Hence, they'd have a hard time approaching atomic nuclei. Even if they could somehow survive and overcome the forces of electrical repulsion, their rate of accreting matter through gravitational attraction would be inordinately slow. In short, any Lilliputian blobs produced at the LHC would not have long for this world. They'd be the goners, not us.

Strangelets, the report's authors point out, would be most likely to be produced during heavy ion collisions rather than proton collisions. In fact, some theorists antic.i.p.ated their production at the Relativistic Heavy Ion Collider (RHIC), a facility at Brookhaven that opened in 2000. Interestingly, Wagner filed lawsuits against that collider too, unsuccessfully trying to prevent it from going on line. Yet during the RHIC's run, absolutely no strangelets have turned up. The nearby Hamptons beach resort continues to attract the rich and famous to its glistening sand and surf, untainted by strange matter. If strangelets never appeared where they were most expected, why worry about them showing up at a less likely place?

There's good reason to expect that any strangelets produced in collisions would be extremely unstable. They'd break up at temperatures much lower than those generated in ion crashes. The report compares the chances of stable strangelet production under such searing conditions to the "likelihood of producing an icecube in a furnace."

Monopoles were explored at length in the 2003 study, as the authors of the 2008 report point out. If they managed to disintegrate protons-an extremely hypothetical scenario supported only in certain GUTs-they could gobble up barely a fraction of a cubic inch of material before being blasted harmlessly into s.p.a.ce by the energy produced in the decays. A tiny hole in an LHC detector would be, at most, the only souvenir of their fleeting existence.

Finally, in arguing against the dangers of black holes, strangelets, monopoles, and other hypothetical high-energy hazards, perhaps the CERN safety team's most compelling argument is that if any apocalyptic scenarios could occur, they would have happened already in cosmic ray events. Cosmic rays are enormously more energetic than what the LHC or any other collider provides. As the report points out: Over 3 1022 cosmic rays with energies of 10 cosmic rays with energies of 1017 eV or more, equal to or greater than the LHC energy, have struck the Earth's surface since its formation. This means that Nature has already conducted the equivalent of about a hundred thousand LHC experimental programmes on Earth already-and the planet still exists. eV or more, equal to or greater than the LHC energy, have struck the Earth's surface since its formation. This means that Nature has already conducted the equivalent of about a hundred thousand LHC experimental programmes on Earth already-and the planet still exists.6 If CERN's rea.s.surances aren't enough, perhaps we can be comforted by the lack of warning signals from the future. According to Russian mathematicians Irina Aref 'eva and Igor Volovich, the LHC might have the energy to create traversable wormholes in s.p.a.ce-time linking the present with the future. If the LHC represented a danger, perhaps, as in the case of Gregory Benford's novel Timescape Timescape (1980), scientists from the future would relay messages back in time to warn us. Or maybe, as in John Cramer's novel (1980), scientists from the future would relay messages back in time to warn us. Or maybe, as in John Cramer's novel Einstein's Bridge Einstein's Bridge (1997), they would try to change history and prevent the LHC from being completed. (1997), they would try to change history and prevent the LHC from being completed.

A traversable wormhole is a solution of Einstein's equations of general relativity that connects two different parts of s.p.a.ce-time. Like black holes, wormholes are formed when matter distorts the fabric of the universe enough to create a deep gravitational well. However, because of a hypothetical extra ingredient called phantom matter (or exotic matter) with negative ma.s.s and negative energy, wormholes respond differently to intruders. While matter dropping into a black hole would be crushed, the phantom matter in a traversable wormhole would prop it open and allow pa.s.sage through a kind of a s.p.a.ce-time "throat" to another cosmic region. The difference would be a bit like attempting pa.s.sage through a garbage disposal versus through an open pipe.

Researchers have speculated since the late 1980s that certain kinds of traversable wormhole configurations could offer the closed timelike curves (CTCs) that permit backward time travel. CTCs are hypothetical loops in s.p.a.ce-time in which the forward direction in time of a certain event connects with its own past, like a dog chasing its own tail. For large enough wormholes, by following such a loop completely around, an intrepid voyager (in a s.p.a.ces.h.i.+p, for example) could theoretically travel back to any time after the CTC's creation. Smaller wormholes would just allow the pa.s.sage of particles and information. Still, they might allow people to contact younger versions of themselves.

Aref 'eva and Volovich conjecture that the LHC's energetic cauldron could brew up wormholes that allow backward communication. LHC researchers might learn of this first if they receive bizarre messages on their computer screens dated years ahead. Perhaps their e-mail in-boxes would suddenly become clogged with spam from companies yet to exist.

As numerous science fiction tales relate, backward time travel could create paradoxes involving the violation of causality: the law that a cause must precede its own effect. For example, suppose an LHC technician discovers a message from future researchers who have discovered how to send interpretable signals backward in time through wormholes created in the machine. The message warns of the creation of a new type of particle that will start to decimate Earth. After receiving the warning, CERN administrators decide to shut down the LHC. In that eventuality, the original future wouldn't exist. How then could the future researchers have sent the signals? It would be an effect (turning off the machine) with either a cause from the future or no cause at all.

In such paradoxical situations, that's where parallel universes would come in handy. If, in a manner similar to the Many Worlds scenario, each time information, things, or people travel backward in time, the universe bifurcates into several versions, the cause in one strand could precipitate an effect in another without contradiction.

Currently, most high-energy physicists have more pressing concerns about the future than hypothetical global disasters or whether backward-traveling signals are possible. When you are running a machine as complex as the LHC, and planning future upgrades and projects, pragmatic considerations generally overshadow abstract speculations. The LHC detectors have so many delicate components, subject to extreme conditions such as temperatures near absolute zero, it takes an incredible amount of effort to make sure they are working properly.

In between tinkering with current technologies, if a high-energy physicist has time to contemplate the future, he or she might well be thinking about the future of the field itself. How will the LHC results-however they turn out-affect the direction of particle physics? At what level of funding and commitment will the public continue to support one of the most expensive scientific disciplines? Is it reasonable to encourage young students to pursue high-energy careers given such uncertainty? What will particle research look like decades from now?

Conclusion

The Future of High-Energy Physics The International Linear Collider and Beyond

The future of particle physics is unthinkable without intense international collaboration.-LEV OKUN (PANEL DISCUSSION ON THE FUTURE OF PARTICLE PHYSICS, 2003)

Where to go from here? After more than seventy-five years of breathtaking progress, the future of high-energy physics is by no means certain. Much depends on what is found at the Large Hadron Collider (LHC).

In the most disappointing case, if no new physics were found at the LHC, the physics community would have to rethink its priorities. Would pressing collider energies even higher to probe greater particle ma.s.ses be worth the cost? In an era of tight budgets, could governments around the world even be convinced to fork over the colossal sums needed to construct new ultra-powerful machines for a possibly illusive search? If the LHC came up empty, mustering political support for an even larger device would be an unlikely prospect. "It will probably be the end of particle physics,"1 said Martinus Veltman, referring to the possibility of the Higgs existing but not turning up at the LHC. said Martinus Veltman, referring to the possibility of the Higgs existing but not turning up at the LHC.

There's no reason to expect such a bleak outcome, however. a.s.suming that the LHC does discover new particles, such as the Higgs or supersymmetric companions, heralds potential sources of dark matter, opens the door to an exploration of new dimensions, and/or finds something altogether unexpected, the theorists would work through the data and determine which models the results support. Then they would a.s.sess what new information would be needed to fill in any gaps.

Ideally, novel findings at the LHC would help decide to what extent the Standard Model is an accurate depiction of nature at a wide range of energy levels. It could also rule out the purest version of the Standard Model in favor of supersymmetric theories or other alternatives. Whittling down theories to the likeliest possibilities would be a happy outcome indeed. If past experience is any judge, however, given the creativity of theorists, there could well be more alternatives than ever before. What to do then?

Because of the Superconducting Super Collider (SSC) debacle, the prospect of American laboratories picking up where CERN leaves off are extremely poor. Aside from contributions to European and international projects, which have proven extremely vital, American high-energy physics looks cloudy in general. No new accelerator labs are in the planning, and the existing ones are grappling with severe reductions in funding.

Fermilab has been living on borrowed time for more than two decades. When the decision was made to locate the SSC in Texas, researchers in Batavia braced themselves for the final spins of their beloved particle carousel-even before the ride truly started. Fate would extend the merry-go-round's run, however. The SSC's cancellation in 1993 and the discovery of the top quark at the Tevatron in 1995 showed why the latter was so critical to particle physics. Instead of the machine shutting down permanently, it was temporarily closed for a thorough upgrade.

From 1996 until 2000, a $260 million makeover aspired to transform the Tevatron into an even more stunning collider. After the surgical st.i.tches were taken out, a second series of experiments began, called Run II, and researchers examined the results of the face-lift. Run II produced many notable achievements, including enhanced measurements of the top quark ma.s.s, lower bounds on the Higgs ma.s.s, and examinations of hadrons containing bottom quarks. Yet, during the early part of the 2000s, its collision rate was not as high as hoped. Fermilab's directors.h.i.+p realized that to maximize the chances for important discoveries before the LHC went online, they would have to get the machine running even more efficiently.

Fortunately, further efforts during scheduled shutdowns in winter 2004-2005 and in spring 2006 boosted the Tevatron's luminosity to record levels. To accomplish this extraordinary feat, machine experts integrated the Recycler antiproton storage ring (a method for acc.u.mulating antiprotons) more effectively into the Tevatron workings and used the method of electron cooling to tighten up the antiproton beam. This granted the Tevatron yet a few more years of life.

Once the LHC is fully operational, though, the impetus to preserve the Tevatron will largely disappear. With a maximum energy of 2 TeV, it is unlikely that discoveries would be made with the Tevatron that aren't found first with the LHC. The only way to significantly increase the Tevatron's energy would be to build a new ring, which is not in the cards. Furthermore, the Tevatron's use of antiprotons impedes its luminosity compared to proton-proton colliders such as the LHC. Antiprotons are much harder to engender than protons, given that the latter are easily ma.s.s-produced from ordinary hydrogen gas. In short, after midwifing particle events far longer than expected, the Tevatron could well be on the brink of retirement. As postdoctoral researcher Adam Yurkewicz jokingly remarked, the Tevatron has been "running so long, puffs of steam are coming out."2 Given the uncertain future of U.S. laboratories, young American researchers planning to enter the field of high-energy physics had best expect to spend much time in Europe-or alternatively to conduct all of their research remotely. Either possibility has potential drawbacks. Traveling back and forth to Europe can be hard on families and also-if unfunded by stipends-on the wallet. To be safe, researchers antic.i.p.ating spending time in Geneva might wish to choose partners and friends who are international diplomats, bankers, or fondue chefs-wealthy ones, preferably.

The alternative, conducting all of one's research remotely, also has its perils. If researchers-in-training are based at CERN during a time in which hardware is being installed or repaired, they might gain valuable knowledge about instrumentation. But if they are spending their prime educational years at a remote inst.i.tution that happens to be connected to CERN's computational Grid, they might never have a chance. Suppose a graduate student never has hardware experience and specializes exclusively in computer a.n.a.lysis. He or she becomes a postdoctoral researcher and continues to concentrate in perfecting software packages. Then comes time for a professors.h.i.+p. Would a university be willing to gamble on hiring an experimentalist who doesn't know a thing about calibrating calorimeters or wiring up electronics?

The concentration of the field of high-energy physics in just a handful of labs-and soon perhaps in a single site-coupled with the rise of larger, more complex detectors has effectively reduced the possibilities for direct experience with the tangible aspects of the field. The days of sitting in trailers parked near tunnels waiting for telltale signals-an emblem of experimental work during the latter decades of the twentieth century-have come to a close. Instead, except for those lucky enough to be present during the building or upgrading of detectors, high-energy physics is largely becoming a hands-off occupation. Given that physical measurements are now conducted in supercooled chambers hundreds of feet beneath the ground, where radiation exposure can be perilous, such a progression is logical. Yet, will sitting in front of computer monitors, either in Geneva or elsewhere, and running statistical software be an exciting enough enterprise to attract the next generation of high-energy physicists?

In the mid-2010s, hands-on expertise will once again be key, when the LHC completes a planned upgrade to what is sometimes called the Super Large Hadron Collider. The main purpose of the enhancement is to boost the machine's luminosity and increase the rate of productive collisions even further. When the collider is shut down for the upgrade, the detectors will also be taken apart. Burned-out electronics, baked by years of radiation damage, will be replaced and other instrumentation upgraded to improve the detectors' performance.

Aside from the Super LHC, the next great hope for particle physics is an exciting new project called the International Linear Collider (ILC). As its name suggests, it is the first collider to be planned and funded by the international community, rather than mainly by the United States or Europe. The Superconducting Super Collider (SSC) was supposed supposed to be international, but that never quite worked out. CERN accepts funding from beyond the European community specifically to support detector projects (ATLAS, CMS, and so forth) but not for the machines themselves. Thus if the ILC transpires, it would represent a milestone for global scientific endeavors. to be international, but that never quite worked out. CERN accepts funding from beyond the European community specifically to support detector projects (ATLAS, CMS, and so forth) but not for the machines themselves. Thus if the ILC transpires, it would represent a milestone for global scientific endeavors.

The ILC is planned to be twin linear accelerators facing each other-one energizing electrons and the other positrons-housed in a tunnel more than twenty miles long. The reason for its linearity is to avoid energy losses due to synchrotron radiation-a major problem for high-speed orbiting electrons and positrons but not for those traveling in a straight path. To accelerate bunches of these particles close to light-speed, more than eight thousand superconducting niobium radio frequency cavities (perfecting conducting metal sheets used to transfer radio frequency energy to particles), each more than three feet long, will deliver a series of thirty million volt kicks. All told, these will boost the electrons and positrons up to 250 GeV each. Hence when they collide they will yield 500 GeV of energy, some of which will transform into ma.s.sive particles. A vertex detector at the collision site will track the decay products of anything interesting that is produced.

Electron-positron collisions are relatively clean and thus ideal for precise measurements of ma.s.s. Consequently, though the ILC will be much less energetic than the LHC, its utility will be in pinning down the ma.s.ses of any particles discovered at the more energetic device. For example, if the LHC produces a potential component of dark matter, the ILC will weigh it and thus inform astronomers what chunk of the cosmos might consist of that ingredient. Knowing the density of the universe would then offer clues as to its ultimate fate. Thus, the ILC would offer a valuable high-precision measuring device-a kind of electronic scale for the world of ultraheavy particles.

So far, the ILC is still in its early planning stages. A site has yet to be chosen-with countries such as Russia making offers. Coordinating the efforts to attract funding and design the project is Barry Barish, the ILC's director, who formerly led the GEM (Gammas, Electrons, and Muons) project (for the aborted SSC) and the Laser Interferometer Gravitational Wave Observatory. After an initially enthusiastic response to the ILC from many different countries, he has been dismayed that some have started to back away from their prior commitments.

In 2007, after initially supporting research and development of the ILC at the level of $60 million, Congress abruptly reduced funding to $15 million. By October of that year, the ILC had spent much of the allocation, even though the funding was supposed to last until 2008. In a December news release, Barish noted, "The consequences for ILC are dire."3 Many Europeans are frustrated that American support for scientific projects is unreliable. "In the U.S. everything has to be approved on a year-to-year basis," said physicist Venetios Polychronakos. "n.o.body is going to trust the U.S. to be a partner."4 After years of reliability, U.K. funding for science has also gone wobbly. In December 2007, Britain's Science and Technology Facilities Council (STFC) issued a report with dreary news for the ILC. "We will cease investment in the International Linear Collider," it stated. "We do not see a practicable path towards the realisation of this facility as currently conceived on a reasonable timescale."5 Recalling, perhaps, a happier age when British nuclear scientists were the "champions of the world," Queen guitarist-turned-astronomer Brian May decried the funding cuts. Addressing a ceremonial gathering honoring his appointment as chancellor of Liverpool John Moores University, he said, "I think it is a big mistake and we are putting our future internationally at risk in science. . . . We need support for the great scientific nation we have been."6 Because of the U.S. and U.K. decisions, the ILC is by no means a sure thing. Much depends on a restoration of the commitment by wealthier countries to pure science. Given the global economic crisis, funding for basic research has been a tough sell. Perhaps discoveries made by the LHC will attract enough interest to bolster support for a new collider. If the ILC is to avoid the same fate as ISABELLE and the SSC, its proponents will need to make the strongest possible case that precise measurements of ma.s.sive particles will be critical to the future of physics.

Though there is much speculation, there are no concrete plans in the works for colliders more energetic than the LHC. Conceivably, the CERN machine will prove the end of the line. In the absence of new accelerator data, physicists would lose an important means of testing hypotheses about the realm of fundamental forces and substances. Astronomical measurements of the very early universe, through detailed probes of the microwave background-higher-precision successors to the Wilkinson Microwave Anisotropy Probe survey perhaps-would become the main way of confirming field theories. Perhaps the ultimate secret of unifying all the forces of nature would be found that way.

Until the day when colliders are a thing of the past, let's celebrate the glorious achievements of particle physics and wish the LHC a long and prosperous life. We herald the extraordinary contributions of Rutherford, Lawrence, Wilson, Rubbia, and so many others in revealing the order and beauty of the hidden subatomic kingdom. May the LHC open up new treasure vaults and uncover even more splendor. Like Schliemann's excavations of Troy, the deeper layers it unearths should prove a sparkling find.

Notes.

Introduction. The Machinery of Perfection

1 Steven Weinberg, in Graham Farmelo, "Beautiful Equations to Die For," Steven Weinberg, in Graham Farmelo, "Beautiful Equations to Die For," Daily Telegraph Daily Telegraph, February 20, 2002, p. 20.

2 Bryce DeWitt, telephone conversation with author, December 4, 2002. Bryce DeWitt, telephone conversation with author, December 4, 2002.

3 President William J. Clinton, Letter to the House Committee on Appropriations, June 16, 1993. President William J. Clinton, Letter to the House Committee on Appropriations, June 16, 1993.

4 Lyn Evans, "First Beam in the LHC-Accelerating Science," CERN press release, September 10, 2008, Lyn Evans, "First Beam in the LHC-Accelerating Science," CERN press release, September 10, 2008, press.web.cern.ch/press/PressReleases/Releases2008/PR08.08E.html (accessed March 2, 2009). (accessed March 2, 2009).

5 Peter Higgs, in "In Search of the G.o.d Particle," Peter Higgs, in "In Search of the G.o.d Particle," Independent Independent, April 8, 2008, www.independent.co.uk/news/science/in-search-of-the-G.o.d-particle-805757.html (accessed April 18, 2008). (accessed April 18, 2008).

6 Lyn Evans in "Meet Evans the Atom, Who Will End the World on Wednesday," Lyn Evans in "Meet Evans the Atom, Who Will End the World on Wednesday," Daily Mail Daily Mail, September 7, 2008, www.mailonsunday.co.uk/sciencetech/article-1053091/Meet-Evans-Atom-end-world-Wednesday.html (accessed March 4, 2009). (accessed March 4, 2009).

7 J. P. Blaizot et al., "Study of Potentially Dangerous Events during Heavy-Ion Collisions at the LHC: Report of the LHC Safety Study Group," J. P. Blaizot et al., "Study of Potentially Dangerous Events during Heavy-Ion Collisions at the LHC: Report of the LHC Safety Study Group," CERN Report 2003-001 CERN Report 2003-001, February 28, 2003, p. 10.

1. The Secrets of Creation 1 Isaac Newton, Isaac Newton, Opticks Opticks, 4th ed. (London: William Innys, 1730), p. 400.

2. The Quest for a Theory of Everything 1 L. M. Brown et al., "Spontaneous Breaking of Symmetry," in Lillian Hoddeson et al., eds., L. M. Brown et al., "Spontaneous Breaking of Symmetry," in Lillian Hoddeson et al., eds., The Rise of the Standard Model: Particle Physics in the 1960s and 1970s The Rise of the Standard Model: Particle Physics in the 1960s and 1970s (Cambridge: Cambridge University Press, 1997), p. 508. (Cambridge: Cambridge University Press, 1997), p. 508.

3. Striking Gold: Rutherford's Scattering Experiments 1 Mark Oliphant, "The Two Ernests, Part I," Mark Oliphant, "The Two Ernests, Part I," Physics Today Physics Today (September 1966): 36. (September 1966): 36.

2 David Wilson, David Wilson, Rutherford, Simple Genius Rutherford, Simple Genius (Cambridge, MA: MIT Press, 1983), p. 62. (Cambridge, MA: MIT Press, 1983), p. 62.

3 J. J. Thomson, J. J. Thomson, Recollections and Reflections Recollections and Reflections (New York: Macmillan, 1937), pp. 138-139. (New York: Macmillan, 1937), pp. 138-139.

4 Ernest Rutherford to Mary Newton, August 1896, in Wilson, Ernest Rutherford to Mary Newton, August 1896, in Wilson, Rutherford, Simple Genius Rutherford, Simple Genius, pp. 122-123.

5 Ernest Rutherford to Mary Newton, February 21, 1896, in ibid., p. 68. Ernest Rutherford to Mary Newton, February 21, 1896, in ibid., p. 68.

6 Thomson, Thomson, Recollections and Reflections Recollections and Reflections, p. 341.

7 Arthur S. Eve, in Lawrence Badash, "The Importance of Being Ernest Rutherford," Arthur S. Eve, in Lawrence Badash, "The Importance of Being Ernest Rutherford," Science Science 173 (September 3, 1971): 871. 173 (September 3, 1971): 871.

8 Chaim Weizmann, Chaim Weizmann, Trial and Error Trial and Error (New York: Harper & Bros., 1949), p. 118. (New York: Harper & Bros., 1949), p. 118.

9 Ibid. Ibid.

10 Ernest Rutherford, "The Development of the Theory of Atomic Structure," in Joseph Needham and Walter Pagel, eds., Ernest Rutherford, "The Development of the Theory of Atomic Structure," in Joseph Needham and Walter Pagel, eds., Background to Modern Science Background to Modern Science (Cambridge: Cambridge University Press, 1938), p. 68. (Cambridge: Cambridge University Press, 1938), p. 68.

11 Ibid. Ibid.

12 Ernest Rutherford to B. Boltwood, December 14, 1910, in L. Badash, Ernest Rutherford to B. Boltwood, December 14, 1910, in L. Badash, Rutherford and Boltwood Rutherford and Boltwood (New Haven, CT: Yale University Press, 1969), p. 235. (New Haven, CT: Yale University Press, 1969), p. 235.

13 Ernest Rutherford to Niels Bohr, March 20, 1913, in Niels Bohr, Ernest Rutherford to Niels Bohr, March 20, 1913, in Niels Bohr, Collected Works Collected Works, vol. 2 (Amsterdam: North Holland, 1972), p. 583.

14 Werner Heisenberg, Werner Heisenberg, Physics and Beyond: Encounters and Conservations Physics and Beyond: Encounters and Conservations (New York: Harper & Row, 1971), p. 61. (New York: Harper & Row, 1971), p. 61.