At the beginning of the last century—so it goes in the popular science books—there were two great revolutions in physics. You can skip down a few paragraphs if you’ve heard this one before. Because in such volumes, the story’s well-rehearsed: Planck explains the blackbody curve, Einstein explains light’s constant speed, and from these two discoveries arrive two of the great cornerstones of 20th century physics: quantum mechanics and relativity. Further explications follow. A decade after his original unveiling, Einstein forges ahead and applies relativistic thinking to gravity, thus inventing general relativity. In the next twenty years, quantum physics, too, skips from success to success, from Bohr’s atom to de Broglie’s matter-waves to Schrödinger’s wave equation.
Tragic versions of this story weave these strands together with the research of Szilárd, who understands that the quantum decay of the nucleus coupled to the relativistic equivalence of matter and energy could create a chain reaction—an insight that, with the additional research of Fermi, will lead to the atomic bomb.
But triumphant versions can’t stop there. After all, the greatest marriage of relativity and quantum mechanics won’t occur until later, with the rise of quantum field theory, the fully relativistic treatment of those old quantum waves. In post-war years, particle smashers grow ever larger, ever more unwieldy, and along with these impressive machines come large, unwieldy methods. Physicists divide infinity by infinity to find their answers—which match the experiments, nevertheless, up to the 11th digit. So they press onward, trying new theories against new experiments, one after the other, until successful quantum field theories have been constructed for electromagnetism and the weak forces that make particles decay (electroweak theory, spontaneously broken via the Higgs mechanism), and for the strong forces that make them stick together (quantum chromodynamics).
Flash forward, then, to 4 July 2012, to a conference at the Large Hadron Collider. The LHC is the world’s biggest machine, a proton-smashing ring whose 27-km circumference stretches from France to Switzerland and back, and on this day its two major experiments, CMS (the Compact Muon Solenoid, hailing from France) and ATLAS (A Toroidal LHC Apparatus, from Switzerland) have gathered to announce their latest results. They’re still testing those quantum field theories—theories, over the years, that have blandly become “the standard model”—of whose parts only one remains unverified: the Higgs field, with its evidence, a boson.
Interest is high. For the week prior, #HiggsRumors has trended on Twitter. And why shouldn’t it? On how many $10 billion projects, non-military, can we expect world governments to collaborate? Hasn’t it been a while since the last “fundamental particles” were discovered—2000 for the tau neutrino, 1995 for the top quark? And with the standard model itself around since 1974, isn’t it about time we know, one way or the other? It’s tense around 10AM (4AM EST), when news comes. But yes! Cue cheering, followed by dashed-off reports. “This is the day,” liveblogs Jester, a Parisian physycist. “The most important day for particle physics in this century, and probably ever.” Definitive evidence of the Higgs boson—or (better to err with caution) of a “Higgs-like particle”—has finally arrived.
Except…now what?
CERN, the LHC’s funder and HQ, has had its share of high-profile cameos (remember that anti-matter briefcase in Angels and Demons?), but readers wanting an inside scoop might eventually track down some from the slew of books detailing the machine’s promised glories. Or better, just two: Lisa Randall’s Knocking on Heaven’s Door, published a few months before the Higgs discovery, and Sean Carroll’s The Particle at the End of the Universe, published a few after. Before digging in, I may as well admit that although Randall’s book is long and somewhat boring, it’s accessible to the layperson and contains a lot of good info, and that although Carroll’s book is short and more consistently interesting, it contains much of the same good info and may be a tough slog for those readers whose trips to the science section of the bookstore are less frequent. But instead of jumping directly to a thumbs up-or-down just from considerations of brevity or ease, it’s worth considering how these superficial similarities give way to rhetorical differences—differences that reveal tough problems of the genre, and maybe even of the subject itself.
Randall and Carroll are both active scientists, both theorists, with Randall focused on high-energy physics a la the LHC, and Carroll focused on theoretical cosmology. Both, too, are sophomore popular science writers, each with a previous book nearer their areas of research than these outings. Warped Passages: Unraveling the Mysteries of the Universe’s Hidden Dimensions positioned Randall’s extra-dimensional theories within the framework of modern physics; From Eternity to Here: The Quest for the Ultimate Theory of Time allowed Carroll to discuss time and thermodynamics from a cosmological perspective. Of course, their positions as working scientists-cum-science popularizers are nothing new. The case could be made that the tradition stretches back to Galileo, when he framed his Dialogue Concerning the Two Chief World Systems between two natural philosophers arguing their cases to an intelligent layman.
Galileo, however, had certain advantages. He was able, more or less, to bring his readers to the current state of knowledge within a few pages, whereas modern popular science writers have to judiciously select highlights from the past 500+ years of scientific backstory, lest bored readers quit before they reach the new stuff. It’s a tricky balance. Randall includes more background than Carroll—enough that readers with any scientific training will have a hard time not branding her a pedantic bore. Carroll, on the other hand, moves briskly from one narrative checkpoint to the next, but this very briskness may outpace readers better suited to Randall’s slow burn.
Randall, after all, has crafted her book with novices explicitly in mind. From the intro: “Modern physics might appear to some to be too far removed from our daily lives to be relevant or even readily comprehensible, but an appreciation of the philosophical and methodological underpinnings that guide our thinking should clarify both the science and the relevance of scientific thinking—as we’ll see in many examples. Conversely, one will only fully grasp the basic elements of scientific thinking with some actual science to ground the ideas. Readers with a greater taste for one or the other might choose to skim or skip one of the courses, but the two together make for a well-balanced meal.”
Reader preferences are, of course, personal, but that bit about our needing a “well-balanced meal” made at least one reader feel that this might not be a trip he wanted to take. But, longtime student of physics that I am, my tolerance for condescension is high, and through the wordy marshes I continued my tramp. In the first seventy pages, Randall makes great pains not to go too fast (we slow learners could not be expected to keep up) and spends entire pages dismantling the doctrines of The Secret, gently explaining why the precepts of scientific materialism can’t sync with the Oprah-endorsed gospel of wealth through positive thinking. We’re forced to wade through discussions of science and religion, risk and expertise, and other topics that practically beg for bullet-point summary.
Even when we get to chapters on the LHC (“One Ring to Rule Them All” is followed by—wait for it—”The Return of the Ring”), the delivery is hampered by pomp. “I am not one prone to overstatement, since I usually find that great events or achievements speak for themselves,” Randall declares. “The reluctance to embellish can get me into trouble in America, where people overuse superlatives so much that mere praise without an ‘est’ at the end is sometimes misinterpreted as slander by faint praise. I’m frequently encouraged to add a few buzzwords or adverbs to my statements of support to avoid any misunderstanding. But in the case of the LHC I’ll go out on a limb and say there is no question that it’s a stupendous achievement.”
Stupendous! Though it may be a courtesy that she goes “out on a limb” in this way, on the next page, prior the LHC vitals, she includes a clotted recitation of authorities, just so we’re sure what to think. “The actor and science enthusiast Alan Alda, when moderating a panel about the LHC, likened it to one of the wonders of the ancient world. The physicist David Gross compared it to the pyramids. The engineer and entrepreneur Elon Musk—who cofounded PayPal, runs Tesla (the company that makes electric cars), and developed and operates SpaceX (which constructs rockets that will deliver machinery and products to the International Space Station)—said about the LHC, ‘Definitely one of humanity’s greatest achievements.'”
One has to wonder why these advertisements remain a part of the text. After enough celebrity cameos (a few paragraphs on Nate Silver in the risk chapter, a meeting with Bill Clinton in which he agrees, of the 1993 Superconducting Super Collider cancellation, that “humanity had forfeited a valuable opportunity”), I began to wonder if Randall’s odd stodginess might have something to do with her veneration of authority—a suspicion that was strengthened in reading “The Role of Experts,” a subsection where Randall forwards a number of dubious claims.
It starts reasonably enough. She explains why, despite global alarm, there never was a credible threat of a black hole apocalypse (N.B. the cosmic rays of higher energy than any possible LHC production), and uses this springboard to lecture on why, while “experts” may have let us down in the last financial brouhaha, such disappointments aren’t likely to emerge from the hallowed halls of science. “Science is not democratic in the sense that we all get together and vote on the right answer. But if anyone has a valid scientific point, it will ultimately be heard.” She cites the example of a young theorist, Lubos Motl, who solved a problem in the Czech Republic and was immediately recognized by a more prominent scientist, Tom Banks, from Rugters. “Not everyone is so receptive,” she admits, “But so long as a few people pay attention, an idea, if good and correct, will ultimately enter scientific discourse.”
This is an amazing level of optimism. It implies that members of established scientific institutions are aware not only of many good and interesting ideas, but indeed of all the thoughts worth thinking, all the good ideas bouncing through this world of seven billion souls—a magical feeling! Perhaps, as Randall suggests, the Internet may change everything, but one can’t help but recall science history’s retrospectively important obscurities (the Teslas, the Mendels) whose contributions are recognized only in far hindsight.
Carroll has learned from the missteps of Knocking on Heaven’s Door (the book appears in his “Further Reading”), and in The Particle at the End of the Universe, from the title’s Douglas Adams nod on, he speaks directly to the nerds, to those readers ready to paw directly into the thickets of detail. On the first page of Chapter 1, he notes how particle physics is a “curious activity” of “essentially no impact on the daily lives of anyone who is not a particle physicist.” This refusal to justify the LHC in terms of anything but itself, however, seems a natural way to cue self-selecting readers to whether or not they’d be interested in this voyage. One shouldn’t pick such a volume because it’s important. “Particle physics arises directly from our restless desire to understand our world; it’s not the particles that motivate us, it’s our human desire to figure out what we don’t understand.”
And we’re off! Within the first 20 pages, we’ve already visited the LHC and know how the Higgs boson fits into the Standard Model of particle physics; in another ten, we’re deep inside a discussion of how the Higgs boson is significant only as evidence of the Higgs field, and how calling it the “God Particle” will invoke most physicists’ wrath.
If this sounds daunting, maybe it is. Carroll’s assumption of audience foreknowledge should delight techies, but it’s at the risk of alienating everyone else. The clear benefit, though, is in the enormous amount of material that’s covered in a very brief span, and with a light enough touch so as not to exclude occasional wit. (Sample geek joke: “SLAC originally stood for ‘Stanford Linear Accelerator Center,’ but in 2008, the Department of Energy officially changed it to ‘SLAC Linear Accelerator Center,’ perhaps because someone in a position of power is fond of infinite recursion.”) Where Randall’s book is discursive, Carroll’s is direct, following a half-logical, half-historical route toward enlightenment. But rather than expecting that he’ll need to coax us into being interested, he cuts straight to the chase.
E.g., after some of the best chapters on quantum fields I’ve seen in a book at this level, here’s the lede for Carroll’s Higgs Discovery How-To:
Let’s take a step back and think about what it takes to discover the Higgs boson, or even find tantalizing evidence for its existence. To dramatically oversimplify things, we can boil it down to a three-step process:
1. Make Higgs bosons.
2. Detect the particles they decay into.
3. Convince yourself that the particles really came from the Higgs, and not something else.
We can examine each step in turn.
Remarkably enough, he then proceeds with a section on each step of the process—exactly as promised. These pages alone are worth the price of admission.
However, the précis above may suggest a bigger separation between the books than actually exists. With such close overlap of purpose, there’s bound to be a lot of shared material, even down to the anecdotes. Both relate how the CMS experiment was delayed six months when the site was found to contain Gallo-Roman ruins. Both give ample space to why the particle detectors are layered like cylindrical onions, with the inner tracker surrounded by the electromagnetic calorimeter surrounded by the hadron calorimeter surrounded by the muon detector, and why it matters they’re in that order. And both remind us of how, despite the LHC’s boasts of high-tech swag, it nonetheless won’t match the onetime projections for the Superconducting Super Collider, that American project whose 1993 cancellation followed our sinking $2 billion into an empty tunnel outside Waxahachie, Texas.
The main thing that separates these projects is their distinct attitudes toward their own scientific authority. Whenever I’m reading a popular physics book, I instinctively place it somewhere on a self-invented scale: the Hawking-Penrose Continuum, after Stephen Hawking and Roger Penrose, those two old lions of the genre. Hawking’s approach to writing for the public—an approach, given A Brief History of Time‘s 10 million copies sold, that’s sort of hard to dismiss—is to skip explanations in favor of answers…which is to say, in favor of whatever conclusions smart guys like himself have managed to conclude. Penrose, in contrast, is an explainer. His books—The Emperor’s New Mind, The Road to Reality—are tough enough to attract few imitators, but their taut expositions turn readers into informed critics of their arguments. Paired together, Hawking and Penrose illuminate pop science’s basic double-bind: Hawking seems egalitarian (anyone can read him), but his refusal to explain his answers raises scientists to the level of prophets; whereas Penrose omits no explanation, but the density of his arguments excludes all readers but the most committed.
On this scale, Randall edges toward Hawking, Carroll toward Penrose. When Randall tells us about a project she undertook to address the LHC’s black hole production, she remarks without elaboration, “With a more careful calculation, we found that the number was much less than physicists had originally optimistically predicted.” How this calculation might have been accomplished, we’re not expected to ask. While Carroll avoids any equations, it’s hard to imagine his including that remark without at least a vague sketch of the process. He manages to avoid such obfuscation through the whole main text, only breaking down in Appendix One (pg. 289), when he finally begs pardon. “Trust me here. It’s hard to think of a sensible explanation that doesn’t amount to going through all the math.”
But in the end, publication dates may turn out to be just as fundamental a difference between these two books as their rhetorical orientations. Randall, recall, has a horse in the race—her extra-dimensional models are being tested at the LHC even now—and, again recall, her book was released pre-Higgs Announcement. She has reason for hope. This hopefulness can’t mask, though, that the preemptive suggestions of what the LHC might find are all pretty darn tentative. “The first, and perhaps most worrisome [reason to doubt supersymmetry], is that we have not yet seen any experimental evidence.” “Not yet having seen any evidence poses a significant constraint on technicolor models.” “Clearly, since we don’t see them, these new dimensions of space must be hidden.” Regardless of such small quibbles as exactly zero evidence, she gives this confident summary: “The wait is a little anxiety provoking, but the results will be mind-blowing.”
The reasons for hope and fear aren’t so far separated. And in Carroll’s case—post-Announcement—I wonder if the timeline of unrealized promise has been replaced by one of forced cheer. Sure, Chapter 12 covers the same proposals as Randall, but his titular “end of the universe” could just as easily refer to the uncertainty that accompanies the Higgs discovery. The finale of Particle echoes its earlier coverage of the SSC, where physicists opposing that project objected to its huge $-inputs, arguing that smaller projects would yield better science-outputs. Even with its peppy reminders that past government investments have returned a handsome 28%, the last chapter’s insistence that the fate of a next-gen collider “is for the human race as a whole to decide” seems dicey, especially with estimates for the International Linear Collider that “range anywhere from $7 billion to $25 billion.”
This just masks the obvious question: What if the LHC uncovers nothing? What if, after all the heroic efforts and high hopes, it turns out that the standard model is perfectly adequate all the way through the highest available energies?
By now, evocations of physics entering the death-spiral of its own success have entered the standard set of pop-sci tropes. Neither of the titles here lets such worries rise naked to the surface, but it’s hard to deny some existential nervousness. Back in 1996, John Horgan published The End of Science, a volume whose framing device was to ask science luminaries if, after so many centuries of false starts, maybe the fundamentals are finally in place. An automatic rebuttal—which, to be fair, Horgan addressed—is that we’ve been embarrassingly wrong about such things before (cf. the comments of Albert A. Mickelson, 1884: “It seems probable that most of the grand underlying principles have now been firmly established”). But with the discovery of the Higgs boson, support for the last remaining piece of the standard model, such questions may easily resurrect. Could this time be different?
Could be. Could be, though, that it’s not science as a whole, but only the accelerator tradition, in its current maximalism, that’s reaching the end of its possible permutations. These books arrive at what may be the terminal edge of that font of known unknowns, and it happens just as the standard model passes from the arena that works of popular science are best suited to explore—from the world of the barely discovered, of the still possibly incorrect—well into textbook territory. This isn’t a bad thing; look back far enough, and the same happened to Newtonian gravity, or Maxwellian electromagnetism, or all the rest. Discoveries won’t stop (both books, for instance, bring word of competing experiments that are busy in their attempts to detect ambient dark matter), but it may be that we’re approaching the end of an era when we knew from which direction new discoveries would arrive.
What we now need, and what physics writers now struggle to produce, is a post-revolutionary lit: works that can stop being so impressed by the breakthroughs of the 20th century that they forget we’re in the 21st. The revolution is here, and we’re ready for something new.
The Homing Pigeon Experience 