I want to know What this show Is all about Before it's out. --Danish poet Piet Hein.

IT ALL BEGAN in the 1930's, when Cockroft, Walton, Van de Graaf and Lawrence invented the first particle beam machines, atom smashers that carried particles like the electron to unheard of speeds and forced particle collisions at undreamed of energies.

Out of the first accelerators came scientific history. They produced particles able to break open the nucleus of the atom, giving birth to the field of nuclear physics and giving science its first look at particles 10,000 times smaller than the atom. Now physicists are on the threshold of machines so powerful that they hope to use them to peer in on particles so small and basic they have not been seen since the onset of creation 10 billion years ago.

"We are building accelerators that are going to tell us what's going on at distance scales of less than one hundred trillionth of an inch," says Dr. Sidney Drell, associate director of the Stanford Linear Accelerator Center where the newest of these new machines is located. "That's one million times smaller than the atom."

This is the realm Nobel Prize winner Steven Weinberg calls "microscopic physics," where tiny exotic particles called leptons, mesons, baryons, bosons and hadrons dwell. Some weigh 70 times what others weigh even though they're the same size. Others spin differently or have different electrical charges. A few have lives so brief that even though they travel 140,000 miles a second they go such a short distance that they don't leave a trace of their tracks. Not a trace.

Why bother spending so much time and money looking for things that are so small? Who cares if we find them? What difference does it make if each new particle is smaller than the one before it?

"Smaller and smaller, that's what all of us consist of, it's what nature is," Harvard University's Dr. Norman Ramsey says. "We're trying to understand nature."

"If time were infinitely long, there are lots of questions in more mundane physics I'd like to investigate," says Dr. John A. Wheeler, onetime Princeton University physicist now at the University of Texas. "But there isn't much time and so one wants to go to the central thing." Which is? Understanding the universe, which Harvard's Dr. Steven Weinberg says "is one of the few things that lifts human life above the level of farce."

Understanding it all is not without its more substantive rewards. The 1979 Nobel Prize winners in physics and medicine were particle physicists. The winner in medicine was the man who developed the CAT scanner, which revolutionized the diagnosis of human disease by giving doctors their first three-dimensional look at the body's vital organs.

Nuclear energy came from particle physics. Laser light came from particle physics. The attempt to create limitless fusion power from the control of thermonuclear energy comes from particle physics.

The study of how things behave at supercold temperatures is a result of particle physics. The newest computers owe their blinding speed and shrinking size to particle physics. The use of radioactive tracers in the human body to diagnose disease comes from particle physics.

Cancer is being treated with particle beams. Most metals now undergo analysis by particle beams. Archeologists use particle beams to date the artifacts they dig. Fossils are dated the same way, with particle beams. Beams of neutrons are being used by crime detectors to identify strands of human hair.

Almost all the exotic energy research in the United States now involves the use and understanding of particle physics. "I don't know how to get it out yet, but I do know that a glass of water has enough energy in it to run the country," says Dr. Leon Lederman, director of the Fermilab outside Chicago where a new particle beam machine is being built. "I also know that without understanding it, I'll never get it out."

The goal in all high-energy physics research is the quark. The quark and the gluon. The quark is presumed to be the simplest, smallest and most elementary of all particles. The gluon is what holds the quark together. Neither has ever been seen, only predicted by theory and hinted at by experiment.

Scientists speculate that at the moment of creation, the universe was nothing more than a giant sphere of liquid quarks cooking at a temperature of 2 million degrees. Then, when the quarks expanded and began to cool off, they turned into larger protons and neutrons. Never again were quarks on their own. They've been locked inside the larger particles ever since.

The quark got its name in a stroke of whimsy from Novel physicist Murray Gell-Mann, who took it from James Joyce's "Finnegan's Wake," where it appears in the puzzling phrase: "Three quarks for Muster Mark." Gell-Mann liked the sound of the word and predicted it would take three quarks to make a proton.

The three quarks have since grown to six. All six have whimsical names, just like their parent. There is an "up" quark, a "down" quark, a "strange" quark, a "charmed" quark, a "top" quark and a "bottom" quark. They get their names from their fractional electrical charge, a peculiarity no other particle possesses.

The hunt for the elusive quark takes on a new urgency next month, when the colliding beam machine at Stanford begin operations. The Stanford machine will collide a beam of electrons moving at 140,000 miles a second with a beam of positrons circling at the same speed in a tunnel buried six feet under the Santa Cruz foothills.

The positron-electron machine at Stanford is the first of three being built in the United States that will force particle collisions at energies up to 800 billion electron volts. The other two are at Fermilab outside Chicago and at Long Island's Brookhaven National Laboratory, both scheduled for operation in the next five years.

"Who knows what we'll find?" asks Stanford's Sidney Drell. "Nature has always surprised us. Nature's imagination has been richer than ours every step of the way."

If the past is prologue, the quark will elude the colliding beams at Stanford, Fermilab and Brookhaven or, worse still, the quark will be found but will turn out to be made of smaller, more elementary particles than itself. Says Fermilab Director Lederman: "Earth-air-fire-and-water didn't work. Who knows? Maybe nothing will work."