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Cosmic Ray Air Showers are the phenomena which allow us to view and make observations into cosmic rays. These are simply the showers of elementary particles produced by high energy particles hitting the atmosphere at velocities that are significant fractions of the speed of light.

Energies

A Cosmic Ray particle can have a general maximum kinetic energy on the order of 500 EeV, which is a meaningless number when you consider it in electron volts because few people realize how incredibly big an Exa-something is. This energy can be converted to about 5 Joules, for a single particle on the order of a proton, alpha particle or sometimes an iron nucleus. For further clarification, you might do well to consider that a thrown baseball generally has kinetic energy of 10 J. While the vast majority of CR particles are not in this range, the likelihood of an air shower produced by such particles is much higher than for particles with lower energy. There is an exception to this rule which was about 10 times as powerful as this high end figure.

Note: It is an interesting prospect to think about such energies in the context of space travel, where the mercy of our atmosphere is not present. Cosmic rays have been known to leave spider cracks in the windows of space habitats and space suits.

Energetic Interaction

When all of this energy comes in contact with particles in the atmosphere the result is tiny, short-lived fission events that release large numbers of high energy elementary particles. The act of hitting the atmosphere with that much energy releases a cascade of X-Rays, as well as every other elementary or theoretical particle imaginable. The closest humanity has come to reproducing these sort of interactions and explosions of particles is within particle accelerators where only now are large hadrons being accelerated to energies in the TeV range. The energies involved here are still a million times greater than what we can produce. As a result the study of cosmic ray air showers is of particular importance to particle physics.

When the particle hits some nucleus in the atmosphere, it splits and in splitting releases a number of positive and neutral pions as well as secondary cosmic rays, which are the now very energetic nuclei produced in the collision. Some of the pions manage to hit other particles and cause furthers splitting. These particles continue to lose energy but are eventually visible at various prepared observation arrays set up with X-Ray cameras, Geiger-tubes and underground photomultiplier pools, looking for that Cherenkov glow.

Interesting observations

So far the record held for most energetic particle is a whopping 4.8 ZeV, or 48 J. If you can imagine almost all the energy of a man with baseball bat hitting the nucleus of an oxygen atom, you can see that this is a huge number. This event was called the Oh-my-God particle, named amusingly for the Higgs Boson, which is sometimes referred to as the 'God Particle.' This was detected in 1991 by the Fly's Eye, a multifaceted photomultiplier tube detection unit.
For more information, browse here.

FFTW is C subroutine library, available for free, that when used with a program allows it to do Discrete Fourier Transforms(DFT). The FFTW package was developed by Matteo Frigo and Steven G. Johnson at MIT, with the intent of being a preferred FFT library for scientists and interested programmers. The library has won awards for usefulness and speed.

The Name

FFTW stands for "The Fastest Fourier Transform in the West" which is a tongue in cheek reference to gunslingers in the Old West. One might point out that MIT is nowhere near the Western US and is in fact on the East Coast, in fact its not very west at all, to which Frigo will reply "not to an Italian."

The Purpose

FFTW is meant as an open-source solution to FFT needs for anyone who wants to implement it. Matlab uses FFTW for its FFT needs and it is at the same time an optimal implementation of FFT, providing O(nLog(n)) runtime for large(prime) data sets and is capable multidimensional work. Being so featured it took the J. H. Wilkinson Prize for Numerical software. Furthermore, FFTW is written in ANSI C, so that it is easily portable to any computer and no other language cannot boast the same(With the exception of Java, which is generally unsuited for numerical computation).

FFTW is a useful tool for any scientist or engineer who needs to process some sort of signal data and considers the time spent writing a program to run the library on a set of data worth the money spent buying a program that has already been written, such as Matlab. This FFT performs better in a number of ways compared to other FFTs, according to the benchmarks on their site. FFTW generally performs more accurately, but with the same level of precision, than most of the other FFTs they tested. If you are a hacker with a scientific bent or a scientist who can allocate or de-allocate memory successfully, I recommend this library for numerous research applications.

The Website

http://www.fftw.org/

We are targets. Every millisecond, hundreds of neutrinos blast through us as if we were not here. And, to a neutrino, we're not. Cosmic rays, high-energy particles created by such events as supernovae, also pass through us, though at much smaller numbers. They are, however, more hazardous, in that their considerable mass (relative to a neutrino) means they are capable of causing damage in sufficient quantity. To those of us on the Earth's surface, cosmic rays are not a serious problem. To inhabitants of the International Space Station, however, there is reason for interest, and perhaps even concern.

Before the advent of sophisticated and sensitive particle detectors, researchers employed an apparatus known as a cloud chamber to observe the properties and behaviors of particles created as a result of radioactive decay. The chamber, also known as a Wilson chamber (after Charles T. R. Wilson, who went on to earn a Nobel Prize for his invention), operated on the principle that air which is completely saturated withan evaporant is very sensitive to any disturbance, and any particles within it that can act as a condensation nucleus will be readily evident. In the case of a cloud chamber, the evaporant is alcohol. An electrically-charged cosmic ray, in passing through alcohol-saturated air, will create an ionized trail, which will cause the alcohol vapor to condense in its wake. It's not at all unlike the contrail left by a jet at altitude, which may often widen to hundreds or thousands of times the width of the original craft as high-level moisture condenses in its wake.

Contemporary researchers have abandoned the cloud chamber for more powerful and exacting instruments, but it is still amazingly satisfying to be able to construct a device which will make visible the presence of particles thousands of times smaller than a virus. It's both easy and inexpensive, and the result is that you can not only explore the behavior of subatomic particles with no special equipment more advanced than a slide projector, you can also be a witness to some of the most violent events in the galaxy, all in the comfort of your own home.

For instructions on how to build a simple cloud chamber which will allow you to observe cosmic rays at the rate of about one per second, visit Andy Foland's Cloud Chamber page at http://www.lns.cornell.edu/~adf4/cloud.html

This writeup is an exclusive to Everything2®

Introduction

What follows is a critical review of Skin and Bones: The Management of People and Natural Resources, by Jane W. Gibson. Her ethnography recounts the “history, shared memories, and traditions” of Shellcracker Haven, Florida, as they intersect with competing measures of conservation and development (Gibson xiii). First and foremost, this review is an exploration of issues of managing natural and social environments. While Gibson’s book is central to this discussion, additional ideas, material, and analysis are incorporated where relevant.

History and Context

The story of Shellcracker Haven begins with the 1842 Armed Occupation Act, which forced the Seminole Indians further south, creating opportunities for white settlers in the pine flat-woods, wetlands and lakes of the region (Gibson 16). Gibson writes, “a mainstream view of the relationship between people and the natural world held by North Americans sets nature and culture apart and prioritizes the needs of people over all other species and the needs of some people over others” (xii). This relationship of power and priority may be demonstrated throughout the history of Shellcracker Haven. Just as the needs of white settlers were prioritized over those of the Seminole in the past, the needs of sport fishermen have been prioritized over those of Shellcracker Haven’s commercial fishing industry in more recent times because “recreational fishing may provide more monetary return to the state of Florida than does commercial fishing” (Gibson 53). For the residents of Shellcracker Haven though, fishing is more than recreation or even business; it’s a way of life, many of these people rely on subsistence fishing and hunting to put food on the table. As Gibson writes, “They made their living with their own hands applied directly to the land, the forests, and the lakes of the region. To this living they felt entitled, because they worked for the fruits of nature’s bounty provided by God” (43). Furthermore, the values of family and community loyalty fostered by this subsistence strategy are reflected in the close-nit structure of the group, which serves as a “social and economic safety net” (Gibson 5). How this structure helps Shellcracker Haven change and adapt as a community to state management of Florida’s fisheries and wildlife is a central question of Skin and Bones.

The life ways of the people from Shellcracker Haven reinforce the boundaries of their community; which is to say, there are insiders and outsiders in this town. Moreover, to be a part of this community confers on the member “loyalty, mutual support, and protection from outsiders” (Gibson 6). This begs the question, how does an anthropologist gain access to, much less the acceptance of, such a community? As Gibson comments:

I had arrived in a state of naiveté about cultural difference and sameness. We looked alike, spoke the same language, and shared certain aspects of cultural heritage. But I did not share their social position in the larger society, nor important experiences, and I had no locally recognized ties to the community-kinship and permanent residence in particular (3).

In short, she appeared to come from a different world than the people of Shellcracker Haven, yet this characterization belies her eventual acceptance.

In “Beyond the Words: The Power of Resonance,” Unni Wikan writes of “the power of resonance,” on how looking for “commonality of experience” can facilitate ethnographic study (Wikan 463). She believes that the relationship between resonance and language is such that our ability to communicate with and understand others relies on some shared sense of human experience. To be able to comprehend and relate to not only the words spoken, but also the intent behind them, is vital. This “willingness to engage with another world, life or idea” is the crux of what Wikan means when she writes of “going beyond the words” (Wikan 463, 466). Furthermore, there is a hidden world of meaning “that resides neither in words, ‘facts,’ nor text but are evoked in the meeting of one experiencing subject with another or with a text” (Wikan 463).

After struggling to communicate with the people of Shellcracker Haven, Gibson took on a job with a regional newspaper writing feel-good stories on subjects like “Aunt Zea’s visit from Jacksonville, Stella’s birthday party, and the church ‘sing’” and “after a couple of months, the door opened…” (Gibson 4). Essentially, she had to become more integrated in the community to gain access to the people of Shellcracker Haven. Her actions demonstrated a “willingness to engage” with world and ways of these people. Moreover, the following interaction between Gibson and Mr. Knight of Shellcracker Haven illustrates the hidden world of meaning Wikan evokes:

I asked Mr. Knight about his experience of hunting alligators: “Tell me what it’s like. How do you go about it?” Never a man to “talk your ear off,” he paused and answered, “You just see his eye, go to him, and try to get him. That’s about all you can do.” I waited for more to follow this efficient answer, but when no other comments came, I finally asked, “Do you enjoy it?” At once, Mr. Knight became animated. He leaned forward in the cypress swing, his eyes sparkling, and his smile wide. “Yeah! I love it, you know!” Then he leaned back abruptly, punctuating the profundity of his testimonial (Gibson 84).

However, Gibson still constructs the people of Shellcracker Haven as an ethnographic other in her writing, and she acknowledges this bluntly, “…they spoke a distinctive dialect, one that set them apart from others and marked them as members, and me as an outsider. These and other differences served as a constant reminder of the histories, values, and, more importantly, the expectations we did not share. I would eventually leave for a very different life somewhere else” (3). This suggests that there is a difference between being accepted by a community and being a part of a community. What makes this case study relevant to issues of managing natural and social resources is the complex relationship Gibson explores between the people of Shellcracker Haven, who are dependent on access to local natural resources, and the state, which has “the power to withhold that access” (66). Shellcracker Haven was helpless to protect itself from the reaches of state bureaucracy, as “small-scale commercial fishermen lost control over the fisheries on which they and their families depended” to the Florida Game and Fresh Water Fish Commission (GFC) in 1946 (Gibson 44). She continues:

These measures were taken in fulfillment of an agreement with sport fishers who agreed to support the constitutional amendment that would create the agency and give it autonomy. In exchange, the agency prohibited the use of most commercial fishing technologies in public waters, prohibited the sale of game fish (black bass, crappie, redbreast, bluegill, shellcrackers, bream, pickerel and pike), and limited the legal gear by which catfish and rough fish might be taken. These actions resulted directly from political pressure exerted by organized sport fishers who believed that commercial fishing undermined sport fishing. With the stroke of a pen in the state capitol, Florida’s traditional commercial freshwater fishermen were transformed into outlaws (49).

Everything changed. And while nothing looked any different, the application of the law and subsequent its enforcement represented a fundamental change in the relationship between the community and its natural resources. For the first time, they had to answer to an intermediary body. The limiting factor on the commercial fishermen of Shellcracker Haven became one of accessibility. They had, for the most part, unregulated access to the natural resources of Shellcracker Lake, until the GFC revoked that access as a provision of being given the power to withhold that access. Needless to say, as their environment changed, the people of Shellcracker Haven changed and adapted. Moreover, in a sense, they continued to do what they had always done, which is doing whatever it takes to put food on the table.

The economy of Shellcracker Haven is built on the natural resources of the region. Goods produced here flow through local, state, national, and international markets and include: “highly prized alligator meat, the largest hides and most expensive alligator leather, hunting trophies, wild catfish, freshwater shrimp and other fishing bait, frog legs, turtle meat, artificial trees, boats, small craft items, honey, and fighting cocks” (Gibson 13). We will begin our discussion of natural resource management with alligators. In 1943, the GFC began regulating alligator hunting in response to “a dramatic drop in the reported harvest: 190,000 skins reported in 1929 and 6,800 skins reported in 1943” (Gibson 67). Conservation measures stipulated that alligators smaller than four feet in length could not be taken. As the population continued to decline, the length requirement was increased to six feet. Gibson notes that, “seasonal regulation and size limitations were determined primarily by the intuition of biologists, wildlife officers, administrators, environmental groups, and legislators” (67). Then, in 1962, the GFC banned the hunting of alligators. However, by 1978 alligator populations appeared to have rebounded (Hines argued that they were never endangered to begin with), so much so that a statewide Nuisance Alligator Control Program (NACP) was implemented (Gibson 68).

Issues of Social and Natural Resource Management

The Alligator Management Program (of which the NACP is a part of) operates on the premise of value-added conservation, “a theory that those with a vested interest in a resource will work to conserve it” (Gibson 69). Berkes describes a similar approach to settling resource conflicts through participatory, community-based resource management:

The fundamental issue is one of defining property rights to common property resources such as forests, grazing lands, wildlife, and fisheries. Over historical time, property rights in resources in many parts of the world have been transformed from communal property (in which access and management rights are controlled by an identifiable group) to open access (free-for-all). Restoring traditional resource tenure can pave the way to establishing property rights in areas in which resource harvesting had previously operated under nonsustainable, open-access conditions. Once property rights and resource use rules have been established, both the costs and benefits of any management action will be borne by the same individual or group, thus providing incentive to conserve (181).

In the case of the AMP’s alligator management program the “levels of harvest would… be based on actions construed ‘to result in the greatest long-term benefit to the resource.’” Additionally, these benefits would be determined by means of “the economic values providing direct incentives to conserve alligators” and “the development of a broad constituency who are most likely to support wetland preservation and enhancement” (Gibson 70). That broad constituency includes the residents of Shellcracker Haven.

Another topic of relevance to our discussion of natural resource management is the history of the relationship between Shellcracker Haven and the practice of seining. Gibson reports that, “commercial fishing on a large scale had been practiced in Florida’s freshwaters since before 1890” and that “the most common methods of taking commercial species were haul seines such as those used on Shellcracker Lake, wire pots and traps that Shellcracker fishermen located in the bonnets (water lilies), trotlines, pound nets, and hoop nets” (45). While the practice of seining was eventually outlawed, as discussed above, local fishermen lament its loss not only on the grounds of lost livelihood, but also, the loss of two valuable side effects of the practice:

Local fishermen also used their nets to eliminate “trash fish,” also called rough fish, from the lake. Fishermen believed, and fisheries biologists confirmed, that gar, mudfish, and shad competed with marketable species. Seining, fishermen claimed, helped clear the lake bottom of the unwanted vegetation that has since overtaken the lake more than once, and whose control now is undertaken with aquatic herbicides (Gibson 45).

Thus, natural resource management is not as simple as banning technology as a means of limiting access. Natural systems are complex; for each and every thing a resource management decision influences, a reaction must be expected. However, the outcomes of such actions are inherently difficult to predict.

Frog legs may be hard to come by in Shellcracker Haven in coming years. Open-access frog gigging on Shellcracker Lake has decimated bullfrog populations, and could become a full-scale “tragedy of the commons” if nothing is done (Gibson 91). Gibson recounts Hardin’s “tragedy” with this in mind, as such,

…each farmer enjoys the full benefit of every cow he feeds from a shared grassland while the cost to the grassland is distributed across the total number of farmers. At some point, since farmers do not experience the full cost of adding more cows, the herds exceed the carrying capacity of the pastures and the grassland collapses, presumably taking the cattle and the farmers’ livelihood with it (91-92).

This situation is analogous to that of Shellcracker Haven’s declining bullfrog populations; in both cases, resources lack “institutionalized rules concerning access”(Gibson 92). Furthermore, Gibson extends the discussion of frog gigging to a broader evaluation of participatory, community-based resource management:

Incorporation of traditional users into management programs will be necessary to fortify rural communities whose members’ affective ties may lead them to protect healthy ecosystems and biodiversity. But their contributions alone will not be sufficient. External conditions within which members of rural communities exist and relate have to be changed (92).

Thus, Gibson is arguing that even well designed conservation efforts will fall short if the role of external factors is not acknowledged and addressed.

Smith and Wishnie (2000) outline “conditions under which conservation is likely” as well as “conditions that make deliberate and effective conservation much less likely to emerge or be stable” (505-6). Their insights are applicable in understanding and evaluating the environmental context and likely success of conservation design measures discussed in Skin and Bones.

Positive factors for conservation include:

  1. Controlled or exclusive access (stable land rights);
  2. Distinct or confined resource populations (to which controlled access can apply);
  3. Resource populations that are resilient or rapidly renewing (hence likely to respond to management controls);
  4. Low discount rates, such that the value of sustained yield exceeds the value of immediate yield; and
  5. Social parameters (e.g. small group size and stable membership and institutions (monitoring and sanctioning) that counter free-riding (505-6).

Negative factors for conservation include:

  1. High demand from external markets;
  2. Rapid population growth;
  3. Acute resource scarcity;
  4. Adequate substitutes for threatened resources;
  5. Acquisition of novel technology or migration into novel habitats; and
  6. Ease in relocating production (expandable frontiers, mobile capital) (506).

The application of these conditions to conservation and natural resource management efforts in Shellcracker Haven sheds light on both positive and negative variables influencing the success of these programs. Aside from the case of frog gigging, controlled access has been established regarding fishing and alligator hunting. The fish populations in Shellcracker Lake are inherently confined, facilitating their regulation. However, the question remains as to whether alligator populations as mobile capital, may be considered distinct or confined, as their habitat extends well beyond Shellcracker Haven. Frog, fish, and alligators all represent resilient or rapidly renewing resource populations, however, while these factors may influence into how these populations respond to management controls, it does not guarantee that their environments will remain in tact:

…the cause of Florida’s environmental crisis rests largely with unrestrained population growth and unrestrained urban sprawl. The problem will not be solved by attacking those who value wildlife in diverse ways, some of whom must take it to make a living, but rather in standing against those who can see it only in economic terms (Gibson 94).

Thus, one must set aside short-term gains to enable sustainable long-term gains. Furthermore, the participatory, community based approach to natural resource management promotes social parameters limiting the exploitation of resources, though as Gibson writes,

Far from the “silver bullet” we might wish for, participation of communities associated with fragile ecosystems is nevertheless deemed necessary to turn conflict into cooperation in achieving shared management goals. It has been proposed that local people should be involved from the beginning in the design, management, monitoring, and evaluation of projects and programs instituted to reverse a history of destruction (93-94).

The involvement of “people such as those in Shellcracker Haven” in resource management programs introduces an entirely new set of “knowledge and skills, social arrangements, and production systems that have allowed them to live in and from precious environments for generations” (Gibson 95). Moreover, just as rural communities must learn to accept scientific management, traditional knowledge must be allowed to complement such methods. Weeks and Packard (1997) propose the following:

…we assert that acceptance of scientific management depends on the combination of (1) the availability of other resources that communities can mobilize (science is but one resource; others include political pressure, money, and moral arguments); (2) the social relationships between the resource users and resource managers; (3) the extent to which resource users’ cognitive models of “how the resource works” fits scientific models; and (4) the conceptual fit between managers’ and resource users’ perspectives regarding the appropriate relationship between humans and nature (237).

For the FWC to achieve its conservation goals of protecting the biodiversity of Florida’s freshwater ecosystems, special attention must be paid to Weeks and Packard’s (1997) fourth consideration. Its scope is not limited to subsistence fishermen or hunters, but rather extends to all those who use the land, including developers. If the conceptual differences between the economic forces of development in Florida and the FWC are not resolved, biodiversity will continue to decline.

According to Smith and Wishnie (2000):

…conservation is inherently much harder to verify empirically than is depletion, for one must determine not only that coexistence or sustainable use occurs, but also that it is due to human actions designed to secure this end (as is the case for any valid claim involving adaptive functions of human behavior) (502).

This presents an interesting problem. To understand whether any given outcome is the result of human action, particularly in the case of a complex system, requires that all factors influencing that system be acknowledged and understood. Furthermore, as one’s understanding of a system grows, the system itself is likely to grow (as a conceptual model, not in reality), as relationships between internal and external elements reveal themselves. Development and globalization virtually ensure the presence of external economic forces.

Conclusion

In my opinion, Gibson’s most intriguing comments in Skin and Bones regard the preservation of both biodiversity and cultural diversity,

…there are those for whom alligators, fish, lakes, and marshes mean more than money. Their views are important because freshwater ecosystems contain tremendous biological diversity: Many species make a living in wetland, river, and lake environments. They matter because some of these fragile ecosystems, long treated as wastelands, are home to people whose worlds collectively constitute equally essential cultural diversity (95).

It is to these ends, Gibson argues, that conservationists must strive; to protect both biological and social environments from the harmful side effects of uncontrolled development and growth.

Works Cited:

Berkes, Fikret. Sacred Ecology: Traditional Ecological Knowledge and Resource 
Management. Philadelphia: Taylor & Francis, 1999. 

Gibson, Jane W. Skin and Bones: The Management of People and Natural Resources in 
Shellcracker Haven, Florida. Toronto: Wadsworth, 2004.

Smith, Eric Alden and Mark Wishnie. “Conservation and Subsistence in Small-Scale 
Societies.” Annual Review of Anthropology, Vol. 29. (2000) pp. 493-524.

Weeks, Priscilla and Jane M. Packard. “Acceptance of Scientific Management by Natural 
Resource Dependent Communities.” Conservation Biology, Vol. 11, No. 1. (Feb., 
1997), pp. 236-245.

Wikan, Unni. “Beyond the Words: The Power of Resonance.” American Ethnologist, 
Vol. 19, No. 3 (Aug., 1992), 460-482.    

Particle physicists treat all matter as being composed of elementary particles; the most complicated (and most whimsically-named) of these are the six quarks. The two lightest quarks make up most of the ordinary matter in the universe, while the other four combine to make exotic, short lived particles only found using particle accelerators and in the earliest instants following the Big Bang. Despite their ubiquity, we never see quarks on their own, or 'bare', rather, they appear in composite particles called 'hadrons'. The most common hadrons are the proton and the neutron, which together compose the nuclei of atoms.

The History of the Quark

Early in the development of subatomic physics, during the 1930s, the world of elementary particles was a simple one. We had the proton, the electron, and the neutron, and these three particles made up everything we see, both in our ordinary lives and in the laboratory. The addition of antiparticles by Dirac was a relatively minor complication, and the addition of the neutrino by Pauli seemed to have no practical benefit outside of nuclear physics. Alas, this simple picture of the universe was not to last.

The 1940's saw the discovery of the first meson, predicted by Yukawa to bind the nucleus together. Or rather, the first two mesons: the pi meson or pion, which is the meson that Yukawa expected, and the mu meson or muon, which turned out to have nothing to do with the Yukawa meson and was instead a particle just like the electron, but 200 times more massive. Nobody expected to find heavy electrons; Rabi famously asked, "Who ordered that?". Soon, dozens of unstable, apparently 'elementary', particles were being discovered, mostly using with the burgeoning new technology of the particle accelerator.

This bewildering array of particles was a source of frustration to many physicists, as there initially seemed to be very little pattern to these new particles. Many, remembering the analogous case of the chemical elements and the periodic table, hoped that a system of classification would eventually present itself and lead, like the periodic table, to an explanation of the apparent complexity of the universe in terms of a much simpler set of objects.

Murray Gell-Mann finally developed a classification system in the early 1960s. By separating the known particles into groups by their intrinsic spin, and then ordering them into a two-dimensional grid by two quantum numbers, 'isospin' and 'strangeness', he found that each group (or 'multiplet') had a geometrical form predicted by the mathematics of group theory. While this is much less straightforward than the periodic table, which fell into nice columns using only the mass, it is built on powerful mathematics that were useful for making predictions. In particular, as with the periodic table a century before, there were conspicuous gaps whose notional occupants had well-defined properties. The simplest of these theorized new particles was named the 'omega-minus' by Gell-Mann, and the discovery of this particle in the laboratory was a decisive proof of the validity of Gell-Mann's "Eightfold Way", winning him the 1969 Nobel Prize in Physics.

The mathematical representation used by Gell-Mann in the Eightfold Way had a curious property; the most fundamental multiplet consisted of three particles, none of which had ever been observed. This multiplet was fundamental in the sense that all the particles in the larger multiplets could be 'assembled' from combinations of these three particles and their antimatter counterparts. Gell-Mann hypothesized that this process of assembly was the true origin of the particles described by the Eighfold Way, and named the three fundamental particles 'quarks', after a passage from James Joyce's novel Finnegans Wake:

Three quarks for Muster Mark!
Sure he hasn't got much of a bark
And sure any he has it's all a beside the mark.
But O, Wreneagle Almighty, wouldn't un be sky of a lark
To see that old buzzard whooping about for uns shirt in the dark
Or he huntin' round uns speckled trousers along by Palmerstown Park!"
The three quarks that Gell-Mann hypothesized were given the labels up, down, and strange, the latter name coming because it was the only quark with a nonzero strangeness.

For many years this 'quark model' wasn't taken very seriously in the larger world of particle physics. Experiments continued to fail at producing particles matching the descriptions of the three quarks, leading many to argue that they were merely a mathematical abstraction and an artifact of the theory of the Eightfold Way. Even the theorists that proposed a fourth quark, in all seriousness, had no objections to naming it the 'charmed' or 'charm' quark. (Some people stolidly insisted on calling the strange quark the 'sideways' quark, but no analogous term arose for the charm quark.) All of this changed with the 1974 discovery of a particle, the J/ψ meson, whose properties strongly suggested that it was composed of charm quarks. Once these properties were verified, the scientists involved concluded not only that the quark model was correct, but also that they'd discovered a new one!

Once the quark model was thus confirmed, the floodgates opened to the discovery of new particles, but with a comforting framework for understanding their properties: hadrons are made of quarks. An additional pair of quarks was postulated: the 'truth' and 'beauty' quarks, though sadly the new seriousness of the endeavour caused them to be renamed 'top' and 'bottom', respectively. The bottom quark was discovered promptly, in 1977, but the heavy top quark remained unseen until 1995. Since the discovery of the top quark, most physicists have believed that the set of quarks is now complete, and that these six quarks and their antiparticles are adequate to describe any hadron that could possibly be produced, returning the number of truly elementary particles to a manageable quantity.

Properties of Quarks

The six known quarks are, in order of mass, the down, up, strange, charm, bottom, and top quarks. The up, charm, and top quarks have a positive electric charge, 2/3 of the proton charge, while the other three quarks have a negative charge that is 1/3 of the electron charge. The quarks are paired up into three 'generations', each containing a positive and negative quark; the two quarks in each generation are relatively close in mass and they are intrinsically connected by the weak nuclear force. (There are subtleties here, see Cabibbo Kobayashi Maskawa matrix for more details)

Quarks are bound together into hadrons by the strong nuclear force, which is by far the strongest of the four fundamental forces; the next closest is the electromagnetic force at 1/137 of the strength. The strong nuclear force acts between particles that have 'colour charge', which can be one of three 'colours', usually named red, blue, and green. (We can call them whatever we want because they have nothing to do with the colours of light, despite the name.) Each quark has a single unit of colour charge, in one of the three colours. Antiquarks have negative colour charge, or 'anticolour'. All other matter particles have a colour charge of zero.

The strong nuclear force binds together quarks in combinations where the amount of each colour is the same. The two simplest way of doing this are to have one quark of each colour, or to have a quark and antiquark of the same colour. The former results in a combination of three quarks (or three antiquarks), called a 'baryon', while the latter combination is referred to as a 'meson'. Protons and neutrons are baryons: the proton is the combination of two up quarks and a down quark, and the neutron contains two down quarks and an up quark.

The binding provided by the strong nuclear force is very strong; although the force is weak between two particles when they are close together, it increases drastically with increasing distance. The energy required to remove a quark from a hadron is so large that at a certain point it will, through Einstein's equation E = mc2, produce a quark/antiquark pair from the vacuum. One of these joins the original hadron and the other joins with the quark being removed to form a new hadron. This property is called 'quark confinement'. The single exception to this situation is the top quark, which has such a short lifetime that by the time the strong force is able to 'dress' it in other quarks it has already decayed.

Quark Physics and You

For most of the activities that we, as humans, perform with matter, the existence of quarks is irrelevant. Even most of nuclear physics works just the same with the 1930s picture of the proton and neutron as elementary particles. Nevertheless, one important phenomenon that we all depend on is thought to be a consequence of quark-level physics. This phenomenon is the strange imbalance between matter and antimatter in the observable universe, namely that everything we see is made out of matter and antimatter is an exotic material produced in particle accelerators.

This is puzzling to particle physicists and cosmologists because the laws of physics are, for the most part, symmetric between matter and antimatter. Two fundamental forces are known to be completely symmetric between matter and antimatter: the strong nuclear force and the electromagnetic force. Where asymmetry between matter and antimatter appears is in the weak nuclear force; this asymmetry is referred to as CP violation.

The CP-violating part of the weak force acts directly at the quark level, and has been observed with both strange quarks and bottom quarks. This preference for quarks over antiquarks, though, is a small and subtle effect, far from the gross violations that would be necessary to produce a matter-filled universe. Violations involving other elementary particles, mainly neutrinos, have been postulated to fill this gap, but no definite evidence has yet been found.


Sources include my undergraduate and graduate particle physics courses, conversations with my thesis supervisor, and David Griffiths's text Introduction to Elementary Particles.
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This writeup is copyright 2006 D.G. Roberge and is released under the Creative Commons Attribution-NoDerivs-NonCommercial licence. Details can be found at http://creativecommons.org/licenses/by-nd-nc/2.5/ .