For a long time, it was thought that the proton, neutron, and electron were the elementary particles, as well as the smallest. Since the Atomic Theory was formulated, many new particles have been discovered. The new theories concerning these particles and predicted particles attempts to explain every phenomena in physics. This is also called the Universal Theory of Matter. Dark Matter and Dark Energy Dark matter is an assumed kind of matter which unlike ordinary matter does not emit or reflect enough light, X-rays or other electromagnetic radiation.
Therefore, it is not directly detectable by our instruments. However many astrophysical evidences points to the presence of such matter. In fact dark matter supposedly is much more abundant than ordinary matter. The amount of observable matter in our Milky Way galaxy is only about twenty percent of the mass that is needed to keep the system stable and holds on to the stars in the outer orbits of the galaxy. Therefore, it is conjectured that %80 percent of the matter in the Milky Way galaxy is dark matter. NASA speculates the origin and nature of dark matter as: Dark matter has been a nagging problem for astronomy for more than 30 years. Stars within galaxies and galaxies within clusters move in a way that indicates there is more matter there than we can see. This unseen matter seems to be in a spherical halo that extends probably 10 times farther than the visible stellar halo around galaxies. Early proposals that the invisible matter is comprised of burnt-out stars or heavy neutrinos have not panned out, and the current favorite candidates are exotic particles variously called neutrilinos, axions or other hypothetical super symmetric particles.
Because these exotic particles interact with ordinary matter through gravity only, not via electromagnetic waves, they emit no light. ”38 The concept of dark matter has been presented because the observable mass of galaxies has failed to equal the needed gravity to keep them stable. Gravity has to counteract the centrifugal force of stars in outer orbits in order to keep them stable in their place. So we assumed a kind of unobservable mass, which provides the needed extra space-wrapping.
It is difficult to figure out how concentrated localized globes of dark matter can be distributed across a galaxy and be able to establish the harmonic orbits of billions of stars contained in it. Such a matter has to be diffused in every point of galaxy to exhibit such an effect. It is the current belief that 90% of dark matter is in the shape of particles and shows at spherical halo around the galaxies. To find the particles creating dark matter, Physicists are looking from Machos to Neutrinos. Here is another speculation based on proposed model.
Can the gravity attributed to dark matter originate from the Planck arena activities? Zero point energy effect can create pair of short life particles. Nevertheless, they will have enough life-time to exert the necessary gravity effect. Accumulative gravitational effect of countless short lived particles may count for dark matter effect. Maybe we do not need to look for origin of neutrinos at the beginning of time. Maybe particles do not need to be made only at the Big Bang era. Maybe every single pore in space-time universe (Planck space) has the potential to produce mass at any time.
Please note the further we go from the center of galaxy the more disperse the stars are. This of course means less gravity from visible mass at the center of galaxy and more angular velocity and centrifugal force for the stars in periphery. At the same time more empty space to exhibit the above assumed counter-effect. In his recent (March 2005) article “Black holes ‘do not exist’” George Chapline from Lawrence Livermore, National Laboratory in California published in Nature38 mentioned that collapse of big stars creates a zone which differs from ordinary space-time and contains much larger vacuum energy.
He calls this zone dark energy star which is different from condensed mass zero-point singularity of a black hole. Subatomic particles Also, there have been discovered that the proton and neutron themselves are made of even smaller particles, called quarks. These particles are then held together by particles called gluons. An atom is made up of subatomic particles. Although the Proton, Neutron and Electron have been considered the fundamental particles of an atom, recent discoveries from experiments with atomic accelerators have shown that there are actually 12 subatomic particles.
These subatomic particles are divided into two classes, consisting of Leptons and Quarks. The proton and neutron are no longer considered fundamental particles in this subatomic classification but are actually made up of smaller subatomic particles. Finally, there is a theory that these sub-atomic particles are not particles at all, but really vibrating strings. Many scientists accepted this until recently when it was determined that According to Subatomic Theory, the fundamental particles now consist of 6 Lepton particles and 6 Quark particles. Other particles are made up of combination of Quarks.
An Electron is still a fundamental particle, but Protons and Neutrons have been found to be combinations of Quarks. there is no way to prove or disprove this theory. It is purely mathematical speculation. Anti-matter particles There are anti-matter particles,that are the mirror image of existing particles. For example, there is the positron,that is a (+) charged electron. There is a (?) charged proton and a neutron that spins in the opposite direction as the standard neutron. Subatomic particle In physics or chemistry, subatomic particles are the particles smaller than an atom. 1] There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles.  Particle physics and nuclear physics study these particles and how they interact.  The elementary particles of the Standard Model include: * Six “flavors” of quarks: up, down, bottom, top, strange, and charm; * Six types of leptons: electron, electron neutrino, muon, muon neutrino, tau, tau neutrino; * Twelve gauge bosons (force carriers): the photon of electromagnetism, the three W and Z bosons of the weak force, and the eight gluons of thestrong force; * The Higgs boson.
Various extensions of the Standard Model predict the existence of an elementary graviton particle and many other elementary particles. Composite subatomic particles (such as protons or atomic nuclei) are bound states of two or more elementary particles. For example, a proton is made of two up quarks and one down quark, while the atomic nucleus of helium-4 is composed of two protons and two neutrons. Composite particles include all hadrons, a group composed of baryons (e. g. , protons and neutrons) and mesons (e. g. , pions and kaons). Elementary Particle
In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure, thus it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made. In the Standard Model of particle physics, the elementary particles include the fundamental fermions (including quarks, leptons, and their antiparticles), and the fundamental bosons (including gauge bosons and the Higgs boson).
Historically, the hadrons (mesons and baryons such as the proton and neutron) and even whole atoms were once regarded as elementary particles (indeed, the word “atom” means “indivisible”). A central feature in elementary particle theory is the early 20th century idea of “quanta”, which revolutionized the understanding of electromagnetic radiation and brought about quantum mechanics. For mathematical purposes, elementary particles are normally treated as point particles, although some particle theories such as string theory posit a physical dimension.
Composite Particle Hadrons Hadrons are defined as strongly interacting composite particles. Hadrons are either: * Composite fermions, in which case they are called baryons. * Composite bosons, in which case they are called mesons. Quark models, first proposed in 1964 independently by Murray Gell-Mann and George Zweig (who called quarks “aces”), describe the known hadrons as composed of valence quarks and/or antiquarks, tightly bound by the color force, which is mediated by gluons. A “sea” of virtual quark-antiquark pairs is also present in each hadron. Baryons
A combination of three u, d or s-quarks with a total spin of 3?2 form the so-called baryon decuplet. Proton quark structure: 2 up quarks and 1 down quark. Ordinary baryons (composite fermions) contain three valence quarks or three valence antiquarks each. * Nucleons are the fermionic constituents of normal atomic nuclei: * Protons, composed of two up and one down quark (uud) * Neutrons, composed of two down and one up quark (ddu) * Hyperons, such as the ?, ?, ?, and ? particles, which contain one or more strange quarks, are short-lived and heavier than nucleons.
Although not normally present in atomic nuclei, they can appear in short-lived hypernuclei. * A number of charmed and bottom baryons have also been observed. Some hints at the existence of exotic baryons have been found recently; however, negative results have also been reported. Their existence is uncertain. * Pentaquarks consist of four valence quarks and one valence antiquark. Mesons Mesons of spin 0 form a nonet Ordinary mesons are made up of a valence quark and a valence antiquark. Because mesons have spin of 0 or 1 and are not themselves elementary particles, they are composite bosons.
Examples of mesons include the pion, kaon, the J/?. In quantum hydrodynamic models, mesons mediate theresidual strong force between nucleons. At one time or another, positive signatures have been reported for all of the following exotic mesons but their existence has yet to be confirmed. * A tetraquark consists of two valence quarks and two valence antiquarks; * A glueball is a bound state of gluons with no valence quarks; * Hybrid mesons consist of one or more valence quark-antiquark pairs and one or more real gluons. Atomic nuclei A semi-accurate depiction of the helium atom.
In the nucleus, the protons are in red and neutrons are in purple. In reality, the nucleus is also spherically symmetrical. Atomic nuclei consist of protons and neutrons. Each type of nucleus contains a specific number of protons and a specific number of neutrons, and is called a nuclide or isotope. Nuclear reactions can change one nuclide into another. See table of nuclides for a complete list of isotopes. Classes of Subatomic Particle Leptons These are particles such as muons and electrons, there are 6 leptons in total, each with their anti-lepton counterpart.
For the electron, muon and taon (which are referred to as different flavours of the lepton) there is a corresponding neutrino (a lepton) associated with it. Leptons do not participate in the strong interaction and are generally not seen within the nucleus. Quarks The term ‘quark’ was introduced by Murray Gell-Mann, the word originating from the book ‘Finnegan’s Wake’ by James Joyce in which the quotation ‘Three quarks for Muster Mark’ appears. We now know there are are six quarks (or called flavours of quarks), which are grouped into 3 pairs (or generations); up & down, charmed & strange and top and bottom.
It is these fundamental particles which form neutrons, protons etc, which are collectively known as hadrons, (it is mainly the up and down which form the world around us). The quarks are peculiar as they posses a charge which is a fraction of that for the electron. Take for example the proton, it has charge +1 and is formed from up and down quarks so the only combination available is 2 up quarks and a down. Anti-Matter Particles In particle physics, antimatter is material composed of antiparticles, which have the same mass as particles of ordinary matter but have opposite charge and quantum spin.
Antiparticles bind with each other to form antimatter in the same way that normal particles bind to form normal matter. For example, a positron (the antiparticle of the electron, with symbol e+) and an antiproton (symbol p) can form an antihydrogen atom. Furthermore, mixing matter and antimatter can lead to the annihilation of both, in the same way that mixing antiparticles and particles does, thus giving rise to high-energy photons (gamma rays) or other particle–antiparticle pairs.
The end result of antimatter meeting matter is a release of energy proportional to the mass as the mass-energy equivalence equation, E=mc2shows.  There is considerable speculation as to why the observable universe is apparently composed almost entirely of matter (as opposed to a mixture of matter and antimatter), whether there exist other places that are almost entirely composed of antimatter instead, and what sorts of technology might be possible if antimatter could be harnessed.
At this time, the apparent asymmetry of matter and antimatter in the visible universe is one of the greatest unsolved problems in physics. The process by which this asymmetry between particles and antiparticles developed is called baryogenesis. Quantum Theory of Matter Quantum theory evolved as a new branch of theoretical physics during the first few decades of the 20th century in an endeavour to understand the fundamental properties of matter. It began with the study of the interactions of matter and radiation.
Certain radiation effects could neither be explained by classical mechanics, nor by the theory of electromagnetism. In particular, physicists were puzzled by the nature of light. Peculiar lines in the spectrum of sunlight had been discovered earlier by Joseph von Fraunhofer (1787-1826). These spectral lines were then systematically catalogued for various substances, yet nobody could explain why the spectral lines are there and why they would differ for each substance. It took about one hundred years, until a plausible explanation was supplied by quantum theory.
Quantum theory is about the nature of matter. In contrast to Einstein’s Relativity, which is about the largest things in the universe, quantum theory deals with the tiniest things we know, the particles that atoms are made of, which we call “subatomic” particles. In contrast to Relativity, quantum theory was not the work of one individual, but the collaborative effort of some of the most brilliant physicists of the 20th century, among them Niels Bohr, Erwin Schrodinger, Wolfgang Pauli, and Max Born. Two names clearly stand out: Max Planck (1858-1947) and Werner Heisenberg (1901-1976).
Planck is recognised as the originator of the quantum theory, while Heisenberg formulated one of the most eminent laws of quantum theory, the Uncertainty Principle, which is occasionally also referred to as the principle of indeterminacy. String Theory String theory is an active research framework in particle physics that attempts to reconcile quantum mechanics and general relativity. It is a contender for a theory of everything (TOE), a self-contained mathematical model that describes all fundamental forces and forms of matter. String theory posits that the elementary particles (i. . , electrons and quarks) within an atom are not 0-dimensional objects, but rather 1-dimensional oscillating lines (“strings”). The earliest string model, the bosonic string, incorporated only bosons, although this view developed to the superstring theory, which posits that a connection (a “supersymmetry”) exists between bosons and fermions. String theories also require the existence of several extra dimensions to the universe that have been compactified into extremely small scales, in addition to the four known spacetime dimensions.
The theory has its origins in an effort to understand the strong force, the dual resonance model (1969). Subsequent to this, five superstring theories were developed that incorporated fermions and possessed other properties necessary for a theory of everything. Since the mid-1990s, in particular due to insights from dualities shown to relate the five theories, an eleven-dimensional theory called M-theory is believed to encompass all of the previously distinct superstring theories. citation needed] Many theoretical physicists (among them Stephen Hawking, Edward Witten, Juan Maldacena and Leonard Susskind) believe that string theory is a step towards the correct fundamental description of nature. This is because string theory allows for the consistent combination of quantum field theoryand general relativity, agrees with general insights in quantum gravity (such as the holographic principle and black hole thermodynamics), and because it has passed many non-trivial checks of its internal consistency.
According to Hawking in particular, “M-theory is the only candidate for a complete theory of the universe. “] Nevertheless, other physicists, such as Feynman and Glashow, have criticized string theory for not providing novel experimental predictions at accessible energy scales. String theory posits that the electrons and quarks within an atom are not 0-dimensional objects, but made up of 1-dimensional strings. These strings can oscillate, giving the observed particles heir flavor, charge, mass and spin. Among the modes of oscillation of the string is a massless, spin-two state—a graviton. The existence of this graviton state and the fact that the equations describing string theory include Einstein’s equations for general relativity mean that string theory is a quantum theory of gravity. Since string theory is widely believed to be mathematically consistent, many hope that it fully describes our universe, making it a theory of everything.
String theory is known to contain configurations that describe all the observed fundamental forces and matter but with a zero cosmological constant and some new fields. Other configurations have different values of the cosmological constant, and are metastable but long-lived. This leads many to believe that there is at least one metastable solution that is quantitatively identical with the standard model, with a small cosmological constant, containing dark matter and a plausible mechanism for cosmic inflation.
It is not yet known whether string theory has such a solution, nor how much freedom the theory allows to choose the details. String theories also include objects other than strings, called branes. The word brane, derived from “membrane”, refers to a variety of interrelated objects, such as D-branes, black p-branes and Neveu–Schwarz 5-branes. These are extended objects that are charged sources for differential form generalizations of the vector potential electromagnetic field. These objects are related to one another by a variety of dualities.
Black hole-like black p-branes are identified with D-branes, which are endpoints for strings, and this identification is called Gauge-gravity duality. Research on this equivalence has led to new insights on quantum chromodynamics, the fundamental theory of the strong nuclear force. The strings make closed loops unless they encounter D-branes, where they can open up into 1-dimensional lines. The endpoints of the string cannot break off the D-brane, but they can slide around on it.