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This is a Fun Test- Spiderman ! Dan
- Posted by: [email hidden]
- Date: 02/15/10 6:14PM EST
Before the Standard Model (SM) was developed in the 1970s (the key
elements of the Standard Model known as quarks were proposed by
Gell-Mann and Zweig in 1964), physicists observed hundreds of different
kinds of particles in particle accelerators. These were organized into
relationships on their physical properties in a largely ad-hoc system of
hierarchies, not entirely unlike the way taxonomy grouped animals based
on their physical features. Not surprisingly, the huge number of
particles was referred to as the "particle zoo".
The Standard Model, which is now the prevailing model of particle
physics, dramatically simplified this picture by showing that most of
the observed particles were mesons, which are combinations of two
quarks, or baryons which are combinations of three quarks, plus a
handful of other particles. The particles being seen in the
ever-more-powerful accelerators were, according to the theory, typically
nothing more than combinations of these quarks.
Within the Standard Model, there are several different types of
particles. One of these, the quarks, has six different kinds, of which
there are three varieties in each (dubbed "colors", red, green, and
blue, giving rise to QCD: quantum chromodynamics). Additionally, there
are six different types of what are known as leptons. Of these six
leptons, there are three charged particles: the electron, muon, and
tauon. The neutrinos comprise the other three leptons, and for each
neutrino there is a corresponding member from the other set of three
leptons. In the Standard Model, there are also bosons, including the
photons, W+, W-, and Z particles, gluons, and a few open spaces left for
the graviton and Higgs boson, which have not yet been discovered. Almost
all of these particles come in "left-handed" and "right-handed" versions
(see chirality). The quarks, leptons and W boson all have antiparticles
with opposite electric charge.
The Standard Model also has a number of problems which have not been
entirely solved. In particular, no successful theory of gravitation
based on a particle theory has yet been proposed. Although the Model
assumes the existence of a graviton, all attempts to produce a
consistent theory based on them have failed. Additionally, mass remains
a mystery in the Standard Model. Although the mass of each successive
particle follows certain patterns, predictions of the rest mass of most
particles can not be made precisely. The Higgs boson is assumed to
"solve" this problem, but to date the Higgs mechanism remains unproven.
The Model also has problems predicting the large scale structure of the
universe. For instance, the Model generally predicts equal amounts of
matter and anti-matter in the universe, something that is observably not
the case. A number of attempts have been made to "fix" this through a
variety of mechanisms, but to date none have won widespread support.
Likewise, basic adaptations of the Model suggest the presence of proton
decay, which has not yet been observed.
Preon theory is motivated by a desire to replicate the achievements of
the periodic table, and the later Standard Model which tamed the
"particle zoo", by finding more fundamental answers to the huge number
of arbitrary constants present in the Standard Model.
Preon theory is one of several models to have been put forward in an
attempt to provide a more fundamental explanation of the results in
experimental and theoretical particle physics. The preon model has
attracted comparatively little interest to date among the particle
physics community.
