A short history of nearly everything

What it really takes to find particles these days is money and lots of it. There is a curious inverse relationship in modern physics between the tininess of the thing being sought and the scale of facilities required to do the searching. CERN, the European Organization for Nuclear Research, is like a little city. Straddling the border of France and Switzerland, it employs three thousand people and occupies a site that is measured in square miles. CERN boasts a string of magnets that weigh more than the Eiffel Tower and an underground tunnel over sixteen miles around.

Breaking up atoms, as James Trefil has noted, is easy; you do it each time you switch on a fluorescent light. Breaking up atomic nuclei, however, requires quite a lot of money and a generous supply of electricity. Getting down to the level of quarks-the particles that make up particles-requires still more: trillions of volts of electricity and the budget of a small Central American nation. CERN’s new Large Hadron Collider, scheduled to begin operations in 2005, will achieve fourteen trillion volts of energy and cost something over $1.5 billion to construct.[25]

But these numbers are as nothing compared with what could have been achieved by, and spent upon, the vast and now unfortunately never-to-be Superconducting Supercollider, which began being constructed near Waxahachie, Texas, in the 1980s, before experiencing a supercollision of its own with the United States Congress. The intention of the collider was to let scientists probe “the ultimate nature of matter,” as it is always put, by re- creating as nearly as possible the conditions in the universe during its first ten thousand billionths of a second. The plan was to fling particles through a tunnel fifty-two miles long, achieving a truly staggering ninety-nine trillion volts of energy. It was a grand scheme, but would also have cost $8 billion to build (a figure that eventually rose to $10 billion) and hundreds of millions of dollars a year to run.

In perhaps the finest example in history of pouring money into a hole in the ground, Congress spent $2 billion on the project, then canceled it in 1993 after fourteen miles of tunnel had been dug. So Texas now boasts the most expensive hole in the universe. The site is, I am told by my friend Jeff Guinn of the Fort Worth Star-Telegram, “essentially a vast, cleared field dotted along the circumference by a series of disappointed small towns.”

Since the supercollider debacle particle physicists have set their sights a little lower, but even comparatively modest projects can be quite breathtakingly costly when compared with, well, almost anything. A proposed neutrino observatory at the old Homestake Mine in Lead, South Dakota, would cost $500 million to build- this in a mine that is already dug-before you even look at the annual running costs. There would also be $281 million of “general conversion costs.” A particle accelerator at Fermilab in Illinois, meanwhile, cost $260 million merely to refit.

Particle physics, in short, is a hugely expensive enterprise-but it is a productive one. Today the particle count is well over 150, with a further 100 or so suspected, but unfortunately, in the words of Richard Feynman, “it is very difficult to understand the relationships of all these particles, and what nature wants them for, or what the connections are from one to another.” Inevitably each time we manage to unlock a box, we find that there is another locked box inside. Some people think there are particles called tachyons, which can travel faster than the speed of light. Others long to find gravitons-the seat of gravity. At what point we reach the irreducible bottom is not easy to say. Carl Sagan in Cosmos raised the possibility that if you traveled downward into an electron, you might find that it contained a universe of its own, recalling all those science fiction stories of the fifties. “Within it, organized into the local equivalent of galaxies and smaller structures, are an immense number of other, much tinier elementary particles, which are themselves universes at the next level and so on forever-an infinite downward regression, universes within universes, endlessly. And upward as well.”

For most of us it is a world that surpasses understanding. To read even an elementary guide to particle physics nowadays you must now find your way through lexical thickets such as this: “The charged pion and antipion decay respectively into a muon plus antineutrino and an antimuon plus neutrino with an average lifetime of 2.603 x 10^-8 seconds, the neutral pion decays into two photons with an average lifetime of about 0.8 x 10^-16 seconds, and the muon and antimuon decay respectively into . . .” And so it runs on-and this from a book for the general reader by one of the (normally) most lucid of interpreters, Steven Weinberg.

In the 1960s, in an attempt to bring just a little simplicity to matters, the Caltech physicist Murray Gell- Mann invented a new class of particles, essentially, in the words of Steven Weinberg, “to restore some economy to the multitude of hadrons”-a collective term used by physicists for protons, neutrons, and other particles governed by the strong nuclear force. Gell-Mann’s theory was that all hadrons were made up of still smaller, even more fundamental particles. His colleague Richard Feynman wanted to call these new basic particles partons, as in Dolly, but was overruled. Instead they became known as quarks.

Gell-Mann took the name from a line in Finnegans Wake: “Three quarks for Muster Mark!” (Discriminating physicists rhyme the word with storks, not larks, even though the latter is almost certainly the pronunciation Joyce had in mind.) The fundamental simplicity of quarks was not long lived. As they became better understood it was necessary to introduce subdivisions. Although quarks are much too small to have color or taste or any other physical characteristics we would recognize, they became clumped into six categories-up, down, strange, charm, top, and bottom-which physicists oddly refer to as their “flavors,” and these are further divided into the colors red, green, and blue. (One suspects that it was not altogether coincidental that these terms were first applied in California during the age of psychedelia.)

Eventually out of all this emerged what is called the Standard Model, which is essentially a sort of parts kit for the subatomic world. The Standard Model consists of six quarks, six leptons, five known bosons and a postulated sixth, the Higgs boson (named for a Scottish scientist, Peter Higgs), plus three of the four physical forces: the strong and weak nuclear forces and electromagnetism.

The arrangement essentially is that among the basic building blocks of matter are quarks; these are held together by particles called gluons; and together quarks and gluons form protons and neutrons, the stuff of the atom’s nucleus. Leptons are the source of electrons and neutrinos. Quarks and leptons together are called fermions. Bosons (named for the Indian physicist S. N. Bose) are particles that produce and carry forces, and include photons and gluons. The Higgs boson may or may not actually exist; it was invented simply as a way of endowing particles with mass.

It is all, as you can see, just a little unwieldy, but it is the simplest model that can explain all that happens in the world of particles. Most particle physicists feel, as Leon Lederman remarked in a 1985 PBS documentary, that the Standard Model lacks elegance and simplicity. “It is too complicated. It has too many arbitrary parameters,” Lederman said. “We don’t really see the creator twiddling twenty knobs to set twenty parameters to create the universe as we know it.” Physics is really nothing more than a search for ultimate simplicity, but so far all we have is a kind of elegant messiness-or as Lederman put it: “There is a deep feeling that the picture is not beautiful.”

The Standard Model is not only ungainly but incomplete. For one thing, it has nothing at all to say about gravity. Search through the Standard Model as you will, and you won’t find anything to explain why when you place a hat on a table it doesn’t float up to the ceiling. Nor, as we’ve just noted, can it explain mass. In order to give particles any mass at all we have to introduce the notional Higgs boson; whether it actually exists is a matter for twenty-first-century physics. As Feynman cheerfully observed: “So we are stuck with a theory, and we do not know whether it is right or wrong, but we do know that it is a little wrong, or at least incomplete.”

In an attempt to draw everything together, physicists have come up with something called superstring theory. This postulates that all those little things like quarks and leptons that we had previously thought of as particles are actually “strings”-vibrating strands of energy that oscillate in eleven dimensions, consisting of the three we know already plus time and seven other dimensions that are, well, unknowable to us. The strings are very tiny-tiny enough to pass for point particles.

By introducing extra dimensions, superstring theory enables physicists to pull together quantum laws and gravitational ones into one comparatively tidy package, but it also means that anything scientists say about the theory begins to sound worryingly like the sort of thoughts that would make you edge away if conveyed to you by a stranger on a park bench. Here, for example, is the physicist Michio Kaku explaining the structure of the universe from a superstring perspective: “The heterotic string consists of a closed string that has two types of vibrations,