And another old paper I discovered:
QUARKIAN PHILOSOPHY: IT’S A SMALL WORLD, AFTER ALL
John S. Cline
Few people can escape marveling at the grand scale of our universe. When they see photos of galaxies and nebulae, awe and a certain uneasy humbling are the usual result. Imagining the swirling maelstrom of a black hole, or the explosive ignition of a new star, or even realizing that the 3K background heralds the birth of our universe, usually results in a desire to burst into poetry. When we begin looking back, shrinking our perspective to the very small, however, awe and amazement soon turn to queasiness and befuddlement. Nothing works the way we have come to believe it should when we enter the realm of the subatomic. This can be very unsettling, and has caused no end of speculation and metaphysical legerdemain. Most unsettling, perhaps, is the realization that the operating principle behind the smallest bits of “matter” is actually the principle behind all that we see, if only we alter our perspective [2, 5, 6, 8, 10, 14, 17].
The subatomic world is a place of bustling activity and incredible energy. It is populated by a veritable zoo of creatures we call particles, ranging from the familiar electron and proton to elusive and often mysteriously-named beasts such as the graviton and Z-boson. Even more fundamental to the structure of this microscopic universe is the most basic building block of what we call “matter”, the quark. This particle, along with the neutrinos, photon and the electron, make up all of the physical, material substance of the universe [4, 16, 21].
Although often discussed as being a single particle, the quark is actually a whole family of particles, with such fanciful characteristics as color, spin, charge, and mass. Overall, however, there are six main subgroups of quark (and their twins, the anitquarks), which have equally imaginative names: Top, Bottom, Up, Down, Strange, and Charm . One mnemonic invented to remember them goes something like this:
“Whether you look at a quark from the Top or the Bottom, turn it Up or Down, Strange as it may seem, it’s still Charming.”
Like many subatomic particles, physicists constantly argue over the question of whether the quark is really “there” [6, 12, 18]. Does it exist as a particle, a wave, or a probability? Does it exist at all as an independent entity? This indeterminate nature has given rise to much speculation on the construction of our universe on the grand scale as well as the microscopic, and begs us to consider the question of “what is reality?”
Quarks were first hypothesized in 1963 by Murray Gell-Mann and George Zweig, and all the different flavors have been mathematically predicted through symmetry and relativistic quantum field theory (QFT). Experimental evidence had to wait until 1977 when the bottom quark was first detected, but other quarks have since been found in more and more powerful particle accelerators. The top quark, one of the most elusive, was finally detected in 1995 .
According to QFT, all quarks are divided up into three families of fermions (matter particles) and bosons (messenger particles). The first group consists of the up and down quarks, electrons and electron neutrinos, and their antiparticles. The quarks combine into triads to form neutrons and protons. When a neutron decays into a proton, it releases an electron neutrino and one of the quarks “flips” into a different state, changing the neutron’s fundamental properties. The second and third groups have not been found in ordinary matter, but can be produced in accelerators; they consist of the charm and strange quarks, the muon and muon neutrino, and their antiparticles in one group, and the top and bottom quarks, the tau and tau neutrino, and their antiparticles for the third group .
We know from examining the neutron and proton that they indeed have structure, so the question of the “reality” of the quark must certainly be moot. Unfortunately, we are left with a few fundamental questions which remain to bother us, not the least of which is “is there anything smaller than a quark?” In every theory presented so far in quantum mechanics, we have not been able to predict the presence of any other smaller particles because as far as we know, the quark has no structure, no physical shape, and no size [4, 6, 12, 13, 15].
Is it any wonder, therefore, that physicists debate the essential substance of quarks, and similar particles? At the same time as we can measure the quark’s mass, spin, charge, and color, we are still unable to measure its dimensions. How can a thing that is essentially “not there”, “be there”? It is an area which lends itself well to both physics and metaphysics, a philosophy of the quark, one might say [5, 6, 8, 9, 14].
Quantum philosophy is hardly new, having sprung into existence almost coincidentally with Heisenberg’s Uncertainty Principle [8, 14, 17]. Various branches of metaphysics devote themselves to accepting a universal worldview based on quantum theory. By these accounts, the entire universe is a quantum particle, with its own quantum state, and our observations of the universe simply “collapse” bits and pieces of the universe (or its wave function) into recognizable and measurable phenomena. One way to picture this is to imagine that nothing in the universe exists without someone or something to observe it… it simply floats in a quantum probability field until its wave function is collapsed. Venus was simply a glowing dot in the sky until Galileo turned his telescope on it and found it to have phases; therefore, Galileo collapsed the wave function of Venus and created the planet we see today [6, 14].
This remarkably egocentric-sounding viewpoint actually has a firm basis in modern quantum theory. In essence, quantum theory holds that unless a quantum particle (in this case, Venus) is observed or measured in some way, it is simply an undefined grouping of probabilities. The act of viewing forces the particle to assume one of its many probabilistic forms; Venus could have “chosen” to assume the form of an amorphous cloud of used car salesmen (it was a real but horribly unsettling possibility).
So what is a quark “choosing” to become when we measure it? We find six distinct varieties, only two of which appear in “ordinary” matter. We can assume, therefore, that quarks, for all of their resemblance to something that is “not there”, must somehow “know” that they must appear in certain forms within certain particles. We would not find, for instance, a strange or a charm quark residing within a proton, though we might expect to find such creatures within other kinds of fermions. We have been singularly ineffective in breaking quarks or photons into any constituent particles, though experiments involving high-energy bombardment of hadrons (protons, neutrons, etc.) produce a quark “jet”, a burst of hadronic material having the same spin characteristics as the original quark [2, 4, 12, 13, 16]. This allows us to not only “observe” the quark inside of the proton, but also know its characteristics. Some theorists suggest that either a quark is the combination of these particles, or that there is in actuality no “real” difference between photons, leptons, and quarks: they may all be the same particle, but in different “states of being” [1, 2, 5, 6, 11, 12, 13, 15, 16, 17, 18, 21]. A quark, for instance, cannot exist outside of its proton or neutron, it must be bound with other quarks. However, if a quark were to “tunnel” out of a neutron, the result could be a shower of neutrinos and photons, which are essentially “immortal” particles. Neutrons are know to decay into protons, and now we know that protons will eventually decay (in something like 1063 years) into neutrinos, photons, and other particles. If they do not change their states of being, where then did the quarks go?
One interesting theory suggests that the universe will not end with a Big Crunch (to mirror the original Big Bang), but will end up a “soup” of loose quarks and other free particles once the proton decay finally occurs. This quark soup would be too dissolute to recombine into hadrons again, except for chance encounters, so a hypothetical observer would find himself swimming in an infinite sea of elementary particles, free-roaming photons, and the occasional island of still-intact matter [5, 7, 9, 10, 16, 20].
Another subject of debate among physicists and astronomers is the possible existence of a middle-ground between the neutron star and the black hole. In this scenario, the quark itself supports the enormous crushing force of the collapsing star, preventing it from achieving a singularity. Called a quark star, this stellar remnant utilizes one of the components of quarkdom, color charge, to provide the repulsive force required. In a typical collapsing star, the core of the star collapses into a “white dwarf” stage, which resists further compression by electrostatic forces. For a more massive star, this is not enough and the star continues to compress to the neutron star stage, where the entire star essentially becomes a huge neutron (all protons have combined with electrons to form neutrons). Though incredibly stable, this process can be taken yet another step, to where the neutron pressure is no longer able to sustain the star and the whole thing collapses into an infinitely-small point with infinite gravity called a singularity.
In the quark star model, the crushing pressures and gravity of the collapsing black hole squeeze neutrons together, essentially “bursting” them and forcing quarks to come into close contact with each other without the benefit of the binding particle, the gluon. Since the quarks inside a neutron have (combined) a neutral color charge, when they are forced together they resist the effort mightily. This forms a temporary, stable framework to maintain the structure of the star. Unlike the fairly stable equilibrium of the neutron star, however, this shadowy territory between quark star and singularity is very slim. Depending on the original mass of the collapsing star, it may only take the influx of a few hundred billion tons of additional matter to finish the process (the equivalent of a couple Jupiters). In some cases, calculations show that quark stars would look very much like regular neutron stars; they would, in fact, have a neutron shell over a core of quarks. In other cases, speculations that the quark star would be so massive as to form an event horizon around it or just within its outer layers present themselves, but one has to wonder what essential difference such a quark star would have from a black hole; in each case, information about the collapsed star is limited to spin, charge, and mass. Finding a quark star is thought to be relatively easy, if one exists: Find a neutron star that is too massive or a black hole that is too light. One of the most exciting discoveries of the last couple years is the potential discovery of a quark star (distinctive by the particular emission of x-rays and gamma-rays one would produce) near our own galactic center called 1E1740.7-2942 [19, 20].
It is in cosmological laboratories such as 1E1740.7-2942 as well as earthly particle accelerators that we can study the nature of the quark. Some possibilities for the future include producing a true absolute zero temperature in the lab, in which even the slightest subatomic movement is squelched. This in essence is the same as setting all quantum probability states to zero… some theorists even feel that if we were ever able to produce such a state, the atom itself would vanish! This makes a weird kind of sense, because with the probability that the given particle exists at any given state set at zero, then the probability that the particle exists at all becomes zero [6, 9, 14, 18, 20].
In this sudsy, soupy quarkian universe we occupy, where probability and uncertainty guide the workings of everything within, it is little wonder that the quark and other similar particles are fast becoming the most fascinating constituents of the subatomic world. Applications from relativistic quantum theory to quantum models of the universe itself present themselves for our testing and imaginations. Most intriguing of all is that our universe may have once consisted of a tightly-compacted group of quarks and other leptons, all in intimate contact with one another, and that they each “remember” their fellow companions [1-21] . If this is true, then in a very real sense we and the universe are all tied together in a common “Oneness”, or as the late Carl Sagan was so fond of saying, “We are all star-stuff”.
SOURCES AND CITATIONS
1. Lederman, Leon. The God Particle. Houghton Mifflin Co. 1993.
2. Han, M.Y. The Secret Life of Quanta. Tab Books. 1990.
3. Gregory, Bruce. Inventing Reality: Physics as Language. John Wiley & Sons. 1988.
4. Fritzsch, Harald. Quarks: The Stuff of Matter. Basic Books, Inc. 1983.
5. Stenger, Victor J. The Unconscious Quantum: Metaphysics in Modern Physics and Cosmology. Prometheus Books. 1995.
6. Herbert, Nick. Quantum Reality. Anchor Press/Doubleday. 1985.
7. Osserman, Robert. Poetry of the Universe. Anchor Press/Doubleday. 1995.
8. Friedman, Norman. Bridging Science and Spirit. Living Lake Books. 1994.
9. LeShan, Lawrence L. Einstein’s Space and Van Gogh’s Sky. Macmillan Publishing Co., Inc. 1982.
10. Davies, Paul. The Mind of God. Simon & Schuster. 1992.
11. Zukav, Gary. The Dancing Wu Li Masters. William Morrow Co. 1979.
12. Close, Frank. The Particle Explosion. Oxford University Press. 1987.
13. Gell-Mann, Murray. The Quark and the Jaguar. W.H. Freeman and Company. 1994.
14. Clayton, William R. Matter and Spirit. Philosophical Library. 1981.
15. Riordan, Michael. The Hunting of the Quark. Simon & Schuster. 1987.
16. Kane, G. L. The Particle Garden. Addison-Wesley Publishing. 1995.
17. Capra, Fritjof. The Tao of Physics. Shambhala Publications. 1991.
18. Davies, Paul and Gribbon, John. The Matter Myth. Simon & Schuster. 1992.
19. Cline, John S. Quark Soup, Anyone? Opinion Column, Exponent, University of Alabama in Huntsville, September 1997.
20. Cline, John S. Quark Stars. Oral/Written Presentation for Dr. Carol Strong’s Astronomy 107 Class, University of Alabama in Huntsville, Spring Semester, 1998.
21. Microsoft Encarta 97 Encyclopedia. [Quark]/[Gluon]/[Standard Model]/[Elementary Particles]. Microsoft Corp. 1996.