LEDERMAN: So you Greeks accepted the concept of space. The void.
DEMOCRITUS: Sure. My partner Leucippus and I invented the atom. Then we needed someplace to put it. Leucippus got himself all tied up in knots (and a little drunk) trying to define the empty space in which we could put our atoms. If it is empty, it is nothing, and how can you define nothing? Parmenides had ironclad proof that empty space cannot exist. We finally decided his proof didn't exist. [Chuckle.] Heck of a problem. Took a lot of retsina. During the time of air-earth-fire-water, the void was considered the fifth essence—quintessential is your word. It gave us quite a problem. You moderns accept nothingness unflinchingly?
LEDERMAN: One has to. Nothing works without, well, nothing. But even today it's a difficult and complex concept. However, as you reminded us, our "nothing," the vacuum, is constantly filling up with theoretical concepts: aether, radiation, a negative energy sea, Higgs. Like attic storage space. I don't know what we'd do without it.
DEMOCRITUS: You can imagine how difficult it was in 420 B.C. to explain the void. Parmenides had denied the reality of empty space. Leucippus was the first to say there could be no motion without a void, therefore a void had to exist. But Empedocles had a clever retort that fooled people for a time. He said that motion could take place without empty space. Look at a fish swimming through the ocean, he said. The water parts for the fish's head, then instantaneously moves into the space left by the moving fish at the tail. The two, fish and water, are always in contact. Forget about empty space.
LEDERMAN: And people bought this argument?
DEMOCRITUS: Empedocles was a bright man, and he had effectively demolished void arguments before. The Pythagoreans, for example—contemporaries of Empedocles—accepted the void for the obvious reason that units had to be kept apart.
LEDERMAN: Weren't they the philosophers who refused to eat beans?
DEMOCRITUS: Yes, and that's not such a bad idea in any era. They had some other trivial beliefs, like you shouldn't sit on a bushel or stand on your own toenail clippings. But they also did some interesting things with math and geometry, as you well know. On this void business, though, Empedocles had them because they said the void is filled with air. Empedocles destroyed this argument simply by showing that air was corporeal.
LEDERMAN: So how did you come to accept the void? You had respect for the thinking of Empedocles, no?
DEMOCRITUS: Indeed, and this point defeated me for a long time. I have trouble with emptiness. How do I describe it? If it is truly nothing, then how can it exist? My hands touch your desk here. On the way to the desk top, my palm feels the gentle rush of air that fills the void between me and the desk's surface. Yet air cannot be the void itself, as Empedocles so ably pointed out. How can I imagine my atoms if I cannot feel the void in which they must move? And yet, if I want to somehow account for the world by atoms, I must first define something that seems to be undefinable because it is devoid of properties.
LEDERMAN: So what did you do?
DEMOCRITUS [laughing]: I decided not to worry. I a-voided the issue.
LEDERMAN: Oi Vay!
DEMOCRITUS: Σoρρψ. [Sorry.] Seriously, I solved the problem with my knife.
LEDERMAN: Your imaginary knife that cuts cheese into atoms?
DEMOCRITUS: No, a real knife, cutting, say, a real apple. The blade must find empty places where it can penetrate.
LEDERMAN: What if the apple is composed of solid atoms, packed together with no space?
DEMOCRITUS: Then it would be impenetrable, because atoms are impenetrable. No, all matter that we can see and feel is cuttable if you have a sharp enough blade. Therefore the void exists. But mostly I said to myself back then, and I believe it still, that one must not forever be stalled by logical impasses. We go on, we continue as if nothingness can be accepted. This will be an important exercise if we are to continue to search for a key to how everything works. We must be prepared to risk falls as we pick our way along the knife edge of logic. I suppose you modern experimentalists would be shocked by this attitude. You need to prove each and every point in order to progress.
LEDERMAN: No, your approach is very modern. We do the same thing. We make assumptions, or we'd never get anywhere. Sometimes we even pay attention to what theorists say. And we have been known to bypass puzzles, leaving them for future physicists to solve.
DEMOCRITUS: You're starting to make some sense.
LEDERMAN: So, to sum up, your universe is quite simple.
DEMOCRITUS: Nothing exists except atoms and empty space; everything else is opinion.
LEDERMAN: If you've figured it all out, why are you here, at the tail end of the twentieth century?
DEMOCRITUS: As I said, I've been time-hopping to see when and if the opinions of man finally coincide with reality. I know that my countrymen rejected the a-tom, the ultimate particle. I understand that people in 1993 not only accept it but believe they have found it.
LEDERMAN: Yes and no. We believe there is an ultimate particle, but not quite the way you said.
DEMOCRITUS: How so?
LEDERMAN: First of all, while you believe in the a-tom as the essential building block, you actually believe there are many kinds of a-toms: liquids have round a-toms; a-toms for metals have locks; smooth a-toms form sugar and other sweet things; sharp a-toms make up lemons, sour stuff. Et cetera.
DEMOCRITUS: And your point is?
LEDERMAN: Too complicated. Our a-tom is much simpler. In your model there would be too large a variety of a-toms. You might as well have one for each type of substance. We hope to find but one single "a-tom."
DEMOCRITUS: I admire such a quest for simplicity, but how could such a model work? How do you get variety from one a-tom, and just what is this a-tom?
LEDERMAN: At this stage we have a small number of a-toms. We call one type of a-tom "quark" and another type "lepton," and we recognize six forms of each type.
DEMOCRITUS: How are they like my a-tom?
LEDERMAN: They are indivisible, solid, structureless. They are invisible. They are ... small.
DEMOCRITUS: How small?
LEDERMAN: We think the quark is pointlike. It has no dimension, and, unlike your a-tom, it therefore has no shape.
DEMOCRITUS: No dimension? Yet it exists, it is solid?
LEDERMAN: We believe it to be a mathematical point, and then the issue of its solidity is moot. The apparent solidity of matter depends on the details of how quarks combine with one another and with leptons.
DEMOCRITUS: This is hard to think about. But give me time. I do understand your theoretical problem here. I believe I can accept this quark, this substance with no dimension. However, how can you explain the variety of the world around us—trees and geese and Macintoshes—with so few particles?
LEDERMAN: The quarks and leptons combine to make everything else in the universe. And we have six of each. We can make billions of different things with just two quarks and one lepton. For a while we thought that was all one needed. But nature wants more.
DEMOCRITUS: I agree that twelve particles is a lot simpler than my numerous a-toms, but twelve is still a large number.
LEDERMAN: The six kinds of quarks are perhaps different manifestations of the same thing. We say there are six "flavors" of quarks. What this allows us to do is to combine the various quarks to make up all sorts of matter. But one doesn't have to have a separate flavor of quark for each type of object in the universe—one for fire, one for oxygen, one for lead—as is necessary in your model.
DEMOCRITUS: How do these quarks combine?
LEDERMAN: There is a strong force between quarks, a very curious kind of force that behaves very differently from the electrical forces, which are also involved.
DEMOCRITUS: Yes, I know about this electricity business. I had a brief talk with that Faraday fellow back in the nineteenth century.
LEDERMAN: A brilliant scientist.
DEMOCRITUS: Perhaps so, but his math was terrible. He would never have made it in Egypt, wh
ere I studied. But I digress. You say a strong force. Are you referring to this gravitational force I've heard about?
LEDERMAN: Gravity? Much too weak. The quarks are actually held together by particles we call gluons.
DEMOCRITUS: Ah, your gluons. Now we're talking about a whole new kind of particle. I thought the quarks were it, that they made matter.
LEDERMAN: They do. But don't forget about forces. There are also particles we call gauge bosons. These bosons have a mission. Their job is to carry information about the force from particle A to particle B and back again to A. Otherwise, how would B know that A is exerting a force on it?
DEMOCRITUS: Wow! Eureka! What a Grecian idea! Thales would love it.
LEDERMAN: The gauge bosons or force carriers or, as we call them, mediators of the force have properties—mass, spin, charge—which in fact determine the behavior of the force. So, for example, the photons, which carry the electromagnetic force, have zero mass, enabling them to travel very fast. This indicates that the force has a very long reach. The strong force, carried by zero-mass gluons, also reaches out to infinity, but the force is so strong that quarks can never get very far from one another. The heavy W and Z particles, which carry what we call the weak force, have a short reach. They work only over very tiny distances. We have a particle for gravity, which we have named the "graviton," even though we have yet to see one or even write down a good theory for one.
DEMOCRITUS: And this is what you call "simpler" than my model?
LEDERMAN: How did you atomists account for the various forces?
DEMOCRITUS: We didn't. Leucippus and I knew that the atoms had to be in constant motion, and we simply accepted this idea. We gave no reason why the world should originally have this restless atomic motion, except perhaps in the Milesian sense that the cause of motion is part of the attribute of the atom. The world is what it is, and one has to accept certain basic characteristics. With all your theories about the four different forces, can you disagree with this idea?
LEDERMAN: Not really. But does this mean that the atomists believed strongly in fate, or chance?
DEMOCRITUS: Everything existing in the universe is the fruit of chance and necessity.
LEDERMAN: Chance and necessity—two opposing concepts.
DEMOCRITUS: Nevertheless, nature obeys them both. It is true that a poppy seed always gives rise to a poppy, never a thistle. That's necessity at work. But the number of poppy seeds formed by the collisions of atoms may well have strong elements of chance.
LEDERMAN: What you're saying is that nature deals us a particular poker hand, which is a matter of chance. But that hand has necessary consequences.
DEMOCRITUS: A vulgar simile, but yes, that's the way it works. This is so alien to you?
LEDERMAN: No, what you've just described is something like one of the fundamental beliefs of modern physics. We call it quantum theory.
DEMOCRITUS: Oh yes, those young Turks in the nineteen-twenties and thirties. I didn't tarry in that era for long. All those fights with that Einstein fellow—never did make much sense to me.
LEDERMAN: You didn't enjoy those wonderful debates between the quantum cabal—Niels Bohr, Werner Heisenberg, Max Born, and their crowd—and such physicists as Erwin Schrödinger and Albert Einstein, who argued against the idea of chance determining nature's way?
DEMOCRITUS: Don't get me wrong. Brilliant men, all of them. But their arguments always concluded with one party or the other bringing up the name of God and Her supposed motivations.
LEDERMAN: Einstein said he couldn't accept that God plays dice with the universe.
DEMOCRITUS: Yes, they always pull the God trump card when the debate goes poorly. Believe me, I had enough of that in ancient Greece. Even my defender Aristotle raked me over the coals for my beliefs in chance and for accepting motion as a given.
LEDERMAN: How did you like quantum theory?
DEMOCRITUS: Definitely I liked it, I think. Later I met Richard Feynman, and he confided that he had never understood quantum theory either. I always had trouble with ... Wait a minute! You've changed the subject. Let's get back to those "simple" particles you were prattling about. You were explaining how the quarks stick together to make up ... to make what?
LEDERMAN: Quarks are building blocks of a large class of objects that we call hadrons. This is a Greek word meaning "heavy."
DEMOCRITUS: Really!
LEDERMAN: It's the least we can do. The most famous object made of quarks is the proton. It takes three quarks to make a proton. In fact, it takes three quarks to make the many cousins of the proton, but with six different quarks, there are plenty of combinations of three quarks—I think it's two hundred sixteen. Most of these hadrons have been discovered and given Greek-letter names like lambda (A), sigma (Σ), et cetera.
DEMOCRITUS: The proton is one of these hadrons?
LEDERMAN: And the most popular in our present universe. You can stick three quarks together to get a proton or a neutron, for instance. Then you can make an atom by adding an electron, which belongs to the class of particles called leptons, to one proton. That particular atom is called hydrogen. With eight protons and an equal number of neutrons and eight electrons you can build an oxygen atom. The neutrons and protons huddle together in a tiny clump that we call the nucleus. Stick two hydrogen atoms and one oxygen atom together and you get water. A little water, a little carbon, some oxygen, a few nitrogens, and sooner or later you have gnats, horses, and Greeks.
DEMOCRITUS: And it all starts with quarks.
LEDERMAN: Yup.
DEMOCRITUS: And that's all you need.
LEDERMAN: Not exactly. You need something that allows atoms to stay together and then to stick to other atoms.
DEMOCRITUS: The gluons again.
LEDERMAN: No, they only stick quarks together.
DEMOCRITUS: ΓOOδ γριℇφ!([Good grief!]
LEDERMAN: That's where Faraday and the other electricians, such as Chuck Coulomb, come in. They studied the electrical forces that hold electrons to the nucleus. Atoms attract each other by a complicated dance of nuclei and electrons.
DEMOCRITUS: These electrons, they are also behind electricity?
LEDERMAN: It's one of their main bags.
DEMOCRITUS: So these are gauge bosons, too, like photons and W's and Z's?
LEDERMAN: No, electrons are particles of matter. They belong to the lepton family. Quarks and leptons make up matter. Photons, gluons, W's, Z's, and gravitons make up forces. One of the most intriguing developments today is that the very distinction between force and matter is blurring. It's all particles. A new simplicity.
DEMOCRITUS: I like my system better. My complexity seems simpler than your simplicity. So what are the other five leptons?
LEDERMAN: There are three varieties of neutrinos, plus two leptons called the muon and the tau. But let's not get into that now. The electron is by far the most important lepton in today's global economy.
DEMOCRITUS: So I should worry only about the electron and the six quarks. These explain the birds, the sea, the clouds...
LEDERMAN: In truth, almost everything in the universe today is composed of only two of the quarks—the up and the down—and the electron. The neutrino zings around the universe freely and pops out of our radioactive nuclei, but most of the other quarks and leptons must be manufactured in our laboratories.
DEMOCRITUS: Then why do we need them?
LEDERMAN: That's a good question. We believe this: there are twelve basic particles of matter. Six quarks, six leptons. Only a few exist in abundance today. But they were all here on an equal footing during the Big Bang, the birth of the universe.
DEMOCRITUS: And who believes all this, the six quarks and six leptons? A handful of you? A few renegades? All of you?
LEDERMAN : All of us. At least, all the intelligent particle physicists. But this concept is pretty much accepted by all scientists. They trust us on this one.
DEMOCRITUS: So where do we disagree? I said there was an uncuttab
le atom. But there were many, many of them. And they combined because they had complementary shape characteristics. You say there are only six or twelve such "a-toms." And they do not have shapes, but they combine because they have complementary electrical charges. Your quarks and leptons are also uncuttable. Now, are you sure there are only twelve?
LEDERMAN: Well ... depends on how you count. There are also six antiquarks and six antileptons and—
DEMOCRITUS: Γρℇατ Zℇυσ∋σ υνδℇρπαντσ [Great Zeus's underpants!]
LEDERMAN: It's not as bad as it sounds. We agree much more than we disagree. But in spite of what you told me, I am still amazed that such a primitive, ignorant heathen could come up with the atom, which we call the quark. What kind of experiments did you do to verify the idea? Here we spend billions of drachmas to test each concept. How did you work so cheaply?
DEMOCRITUS: We did it the old-fashioned way. Not having a Department of Energy or a National Science Foundation, we had to use Pure Reason.
LEDERMAN: So you spun your theories out of whole cloth.
DEMOCRITUS: No, even we ancient Greeks had clues from which we molded our ideas. As I said, we saw that poppy seeds always grow into poppies. The spring always comes after the winter. The sun rises and sets. Empedocles studied water clocks and whirling buckets. One can form conclusions by keeping one's eyes open.
LEDERMAN: "You can observe a lot just by looking," as one of my contemporaries once said.
DEMOCRITUS: Exactly! Who is this sage, so Grecian in his perspective?
LEDERMAN: Yogi Berra.
DEMOCRITUS: One of your greatest philosophers, no doubt.
LEDERMAN: You could say that. But why do you distrust experiment?
DEMOCRITUS: The mind is better than the senses. It contains trueborn knowledge. The second kind of knowledge is bastard knowledge, which comes from the senses—sight, hearing, smell, taste, touch. Think about it. The drink that tastes sweet to you may taste sour to me. A woman who appears beautiful to you is nothing to me. An ugly child appears beautiful to its mother. How can we trust such information?
The God Particle: If the Universe Is the Answer, What Is the Question? Page 7