A short history of nearly everything - Bill Bryson [82]
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, clockwise and counterclockwise, which are treated differently. The clockwise vibrations live in a ten-dimensional space. The counterclockwise live in a twenty-six-dimensional space, of which sixteen dimensions have been compactified. (We recall that in Kaluza's original five-dimensional, the fifth dimension was compactified by being wrapped up into a circle.)” And so it goes, for some 350 pages.
String theory has further spawned something called “M theory,” which incorporates surfaces known as membranes—or simply “branes” to the hipper souls of the world of physics. I'm afraid this is the stop on the knowledge highway where most of us must get off. Here is a sentence from the New York Times, explaining this as simply as possible to a general audience: “The ekpyrotic process