Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. Electrically charged particles are discernable by the curves they trace in the detector's magnetic field.

Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. It is also called "high energy physics", because many elementary particles do not occur under normal circumstances in nature, but can be created and detected during energetic collisions of other particles, as is done in particle accelerators. Download high resolution version (1226x946, 452 KB)First Gold Beam-Beam Collision Events at RHIC at 100 - 100 GeV/c per beam recorded by the STAR detector. ... Download high resolution version (1226x946, 452 KB)First Gold Beam-Beam Collision Events at RHIC at 100 - 100 GeV/c per beam recorded by the STAR detector. ... A GEV (or Ground Effect Vehicle) is vehicle that takes advantage of the aerodynamic principle of ground effect (or Wing-in-ground). ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... The STAR detector [1] is one of the four experiments at the Relativistic Heavy Ion Collider (RHIC) in Brookhaven National Laboratry. ... The Relativistic Heavy Ion Collider at Brookhaven National Laboratory. ... The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density. ... In particle physics, an elementary particle or fundamental particle is a particle not known to have substructure; that is, it is not made up of smaller particles. ... Matter is commonly defined as the substance of which physical objects are composed. ... Radiation in physics is a process of emission of energy or particles. ... Galunggung in 1982, showing a combination of natural events. ... // Physical collision Dynamics Deflection happens when an object hits a plane surface In physics, collision means the action of bodies striking or coming together (touching). ... A 1960s single stage 2MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric and/or magnetic fields to propel electrically charged particles to high speeds. ...

Subatomic particles

Modern particle physics research is focused on subatomic particles, which have less structure than atoms. These include atomic constituents such as electrons, protons, and neutrons (protons and neutrons are actually composite particles, made up of quarks), particles produced by radiative and scattering processes, such as photons, neutrinos, and muons, as well as a wide range of exotic particles. A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ... Properties In chemistry and physics, an atom (Greek άτομον meaning indivisible) is the smallest possible particle of a chemical element that retains its chemical properties. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... Quarks are one of the two basic constituents of matter in the Standard Model of particle physics. ... In this Feynman diagram, electrons annihilate and become a quark-antiquark pair. ... In particle physics, scattering is a class of phenomena by which particles are deflected by collisions with other particles. ... In quantum physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field (light). ... The neutrino is an elementary particle. ... The moons shadow, as seen in muons 700m below ground at the Soudan 2 detector. ... An exotic particle is a kind of theoretical particle said to exist by some areas of modern physics whose alleged properties are extremely unusual. ...

Strictly speaking, the term particle is a misnomer because the dynamics of particle physics are governed by quantum mechanics. As such, they exhibit wave-particle duality, displaying particle-like behavior under certain experimental conditions and wave-like behavior in others (more technically they are described by state vectors in a Hilbert space; see quantum field theory). Following the convention of particle physicists, we will use "elementary particles" to refer to objects such as electrons and photons, with the understanding that these "particles" display wave-like properties as well. For a non-technical introduction to the topic, please see Introduction to Quantum mechanics. ... In physics, wave-particle duality holds that light and matter exhibit properties of both waves and of particles. ... A wave is a disturbance that propagates through space, often transferring energy. ... One of the remarkable characteristics of the mathematical formulation of quantum mechanics, which distinguishes it from mathematical formulations of theories developed prior to the early 1900s, is its use of abstract mathematical structures, such as Hilbert spaces and operators on these spaces. ... In mathematics, a Hilbert space is a generalization of Euclidean space which is not restricted to finite dimensions. ... Quantum field theory (QFT) is the application of quantum mechanics to fields. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... In quantum physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field (light). ...

All the particles and their interactions observed to date can be described by a quantum field theory called the Standard Model. The Standard Model has 40 species of elementary particles (24 fermions, 12 vector bosons, and 4 scalars), which can combine to form composite particles, accounting for the hundreds of other species of particles discovered since the 1960s. The Standard Model has been found to agree with almost all the experimental tests conducted to date. However, most particle physicists believe that it is an incomplete description of Nature, and that a more fundamental theory awaits discovery. In recent years, measurements of neutrino mass have provided the first experimental deviations from the Standard Model. Quantum field theory (QFT) is the application of quantum mechanics to fields. ... The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... In particle physics, fermions, (named after Enrico Fermi), are particles with semi-integer spin. ... In physics, bosons, named after Satyendra Nath Bose, are particles with integer spin. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... The neutrino is an elementary particle. ... Mass is a property of a physical object that quantifies the amount of matter and energy it is equivalent to. ...

Particle physics has had a large impact on the philosophy of science. Some particle physicists adhere to reductionism, a point of view that has been criticized by philosophers and scientists. Part of the debate is described below. Philosophy of science is the branch of philosophy that studies the philosophical assumptions, foundations, and implications of science, including the formal sciences, natural sciences, and social sciences. ... Reductionism in philosophy describes a number of related, contentious theories that hold, very roughly, that the nature of complex things can always be reduced to (be explained by) simpler or more fundamental things. ...

History

The idea that all matter is composed of elementary particles dates to at least the 6th century BC. The philosophical doctrine of atomism was studied by ancient Greek philosophers such as Leucippus, Democritus, and Epicurus. Although Isaac Newton in the 17th century thought that matter was made up of particles, it was John Dalton who formally stated in 1802 that everything is made from tiny atoms. Matter is commonly defined as the substance of which physical objects are composed. ... (2nd millennium BC - 1st millennium BC - 1st millennium) The 6th century BC started on January 1, 600 BC and ended on December 31, 501 BC. // Overview Monument 1, an Olmec colossal head at La Venta The 5th and 6th centuries BC were a time of empires, but more importantly, a... In natural philosophy, atomism is the theory that all the objects in the universe are composed of very small, indestructible elements - atoms. ... Ancient Greece is the term used to describe the Greek-speaking world in ancient times. ... A philosopher is a person who thinks deeply regarding people, society, the world, and/or the universe. ... This article is about the philosopher. ... Hendrick ter Brugghen, Democritus Laughing (1629) Democritus (Greek: Δημόκριτος) was a pre-Socratic Greek philosopher (born at Abdera in Thrace around 450 BC; died in about 370 BC). ... Roman marble bust of Epicurus Epicurus (Epikouros or Ἐπίκουρος in Greek) (341 BC, Samos – 270 BC, Athens) was an ancient Greek philosopher, the founder of Epicureanism, one of the most popular schools of Hellenistic Philosophy. ... Sir Isaac Newton, President of the Royal Society, (4 January 1643 – 31 March 1727) [OS: 25 December 1642 – 20 March 1727] was an English mathematician, physicist, astronomer, alchemist, and natural philosopher who is generally regarded as one of the greatest scientists and mathematicians in history. ... (16th century - 17th century - 18th century - more centuries) As a means of recording the passage of time, the 17th century was that century which lasted from 1601-1700. ... John Dalton John Dalton (September 6, 1766 – July 27, 1844) was a British chemist and physicist, born at Eaglesfield, near Cockermouth in Cumberland. ... --69. ... Properties In chemistry and physics, an atom (Greek άτομον meaning indivisible) is the smallest possible particle of a chemical element that retains its chemical properties. ...

Dmitri Mendeleev's first periodic table in 1869 helped cement the view, prevalent throughout the 19th century, that matter was made of atoms. Work by J.J. Thomson in the late 1890s established that atoms are composed of light electrons and massive protons. Ernest Rutherford established in 1911 that the protons are concentrated in a compact nucleus. The nucleus was initially thought to be composed of protons and confined electrons (in order to explain the difference between nuclear charge and mass number), but was later found to be composed of protons and neutrons. Portrait of Dmitri Mendeleev by Ilya Repin Dmitri Mendeleev (Russian: , Dmitriy Ivanovich Mendeleyev ) (8 February [O.S. 27 January] 1834 in Tobolsk – 2 February [O.S. 20 January] 1907 in Saint Petersburg), was a Russian chemist. ... The periodic table of the chemical elements is a tabular method of displaying the chemical elements, first devised in 1869 by the Russian chemist Dmitri Mendeleev. ... 1869 (MDCCCLXIX) is a common year starting on Friday (link will take you to calendar) of the Gregorian calendar or a common year starting on Sunday of the 12-day-slower Julian calendar. ... Alternative meaning: Nineteenth Century (periodical) (18th century — 19th century — 20th century — more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... Sir Joseph John Thomson, OM , FRS (December 18, 1756 – August 30, 1940) often known as J. J. Thomson, was an English physicist, the discoverer of the electron. ... The 1890s were sometimes referred to as the Mauve Decade, because William Henry Perkins aniline dye allowed the widespread use of that colour in fashion, and also as the Gay Nineties, under the then-current usage of the word gay which referred simply to merriment and frivolity, with no... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Ernest Rutherford Ernest Rutherford, 1st Baron Rutherford of Nelson, OM, PC, FRS (August 30, 1871 – October 19, 1937), was a nuclear physicist from New Zealand. ... 1911 (MCMXI) was a common year starting on Sunday (click on link for calendar). ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ...

The early 20th century explorations of nuclear physics and quantum physics culminated in proofs of nuclear fission in 1939 by Lise Meitner (based on experiments by Otto Hahn), and nuclear fusion by Hans Bethe in the same year. These discoveries gave rise to an active industry of generating one atom from another, even rendering possible (although not profitable) the transmutation of lead into gold. They also led to the development of nuclear weapons. (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901–2000 in the sense of the Gregorian calendar (1900–1999 in the... Nuclear physics is the branch of physics concerned with the nucleus of the atom. ... Fig. ... An induced nuclear fission event. ... 1939 (MCMXXXIX) was a common year starting on Sunday (link will take you to calendar). ... Lise Meitner ca. ... Otto Hahn (March 8, 1879 – July 28, 1968) was a German chemist. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Hans Bethe in 1945. ... For other uses, see Alchemy (disambiguation). ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ...

Throughout the 1950s and 1960s, a bewildering variety of particles was found in scattering experiments. This was referred to as the "particle zoo". This term was deprecated after the formulation of the Standard Model during the 1970s in which the large number of particles was explained as combinations of a (relatively) small number of fundamental particles. The 1950s were the decade that traditionally speaking, spanned the years 1950 through 1959. ... The 1960s decade refers to the years from 1960 to 1969, inclusive. ... The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... The 1970s decade refers to the years from 1970 to 1979, inclusive. ...

The Standard Model

Main article: Standard Model

The current state of the classification of elementary particles is the Standard Model. It describes the strong, weak, and electromagnetic fundamental forces, using mediating gauge bosons. The species of gauge bosons are the gluons, W^- and W⁺ and Z bosons, and the photons, respectively. The model also contains 24 fundamental particles, which are the constituents of matter. Finally, it predicts the existence of a type of boson known as the Higgs boson, which has yet to be discovered. The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... The strong nuclear force or strong interaction (also called color force or colour force) is a fundamental force of nature which affects only quarks and antiquarks, and is mediated by gluons in a similar fashion to how the electromagnetic force is mediated by photons. ... The weak nuclear force or weak interaction is one of the four fundamental forces of nature. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, which exerts a force on those particles that possess the property of electric charge, and is in turn affected by the presence and motion of such particles. ... A fundamental interaction is a mechanism by which particles interact with each other, and which cannot be explained by another more fundamental interaction. ... Gauge bosons are bosonic particles which act as carriers of the fundamental forces of Nature. ... In particle physics, gluons are vector gauge bosons that mediate strong color charge interactions of quarks in quantum chromodynamics (QCD). ... In physics, the W and Z bosons are the elementary particles that mediate the weak nuclear force. ... In physics, the W and Z bosons are the elementary particles that mediate the weak nuclear force. ... In physics, the photon (from Greek φως, phōs, meaning light) is the quantum of the electromagnetic field; for instance, light. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ... Matter is commonly defined as the substance of which physical objects are composed. ... In physics, bosons, named after Satyendra Nath Bose, are particles with integer spin. ... The Higgs boson is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. ...

Experiment

In particle physics, the major international collaborations are:

• Brookhaven National Laboratory, located on Long Island, USA. Its main facility is the Relativistic Heavy Ion Colliderwhich collides heavy ions such as gold ions (it is the first heavy ion collider) and protons.

• Budker Institute of Nuclear Physics [1] (Novosibirsk, Russia)]

• CERN, located on the French-Swiss border near Geneva. Its main project is now LHC, or the Large Hadron Collider, which is currently under construction. The LHC will be in operation in 2007 and will be the world's most energetic collider upon completion. Earlier facilities include LEP, the Large Electron Positron collider, which was stopped in 2001 and which is now dismantled to give way for LHC; and SPS, or the Super Proton Synchrotron.

• DESY, located in Hamburg, Germany. Its main facility is HERA, which collides electrons or positrons and protons.

• Fermilab, located near Chicago, USA. Its main facility is the Tevatron, which collides protons and antiprotons and is presently the highest energy particle collider in the world.

• KEK The High Energy Accelerator Research Organization of Japan located in Tsukuba, Japan. It is the home of a number of interesting experiments such as K2K, a neutrino oscillation experiment and Belle, an experiment measuring the CP-symmetry violation in the B-meson.

• SLAC, located near Palo Alto, USA. Its main facility is PEP-II, which collides electrons and positrons.

Many other particle accelerators exist. Aerial view of Brookhaven National Laboratory. ... Heavy-ion refers to ion of atom which is usually heavier than carbon. ... General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... The Budker Institute in Winter The Budker Institute of Nuclear Physics is one of the major centres of advanced study of nuclear physics in Russia. ... Official website: http://www. ... CERN logo The European Organization for Nuclear Research (French: Organisation Européenne pour la Recherche Nucléaire), commonly known as CERN, is the worlds largest particle physics laboratory, situated just west of Geneva on the border between France and Switzerland. ... Geneva (pronunciation //; French: Genève //, German: //, Italian: Ginevra) is the second most populous city in Switzerland, and is the most populous city of Romandy (the French-speaking part of Switzerland). ... The Large Hadron Collider (short LHC) is a particle accelerator and collider located at CERN, near Geneva, Switzerland. ... In particle physics, a hadron is a subatomic particle which experiences the strong nuclear force. ... A collider is a type of a particle accelerator with two opposite beams of the particles. ... The Large Electron-Positron Collider (usually called LEP for short. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... 2001: A Space Odyssey. ... The Socialist Party of Serbia (Serbian: Socijalistička partija Srbije) is a political party in Serbia. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... A synchrotron is a particular type of cyclic particle accelerator in which the magnetic field (to turn the particles so they circulate) and the electric field (to accelerate the particles) are carefully synchronized with the travelling particle beam. ... The DESY (Deutsches Elektronen Synchrotron, German Electron Synchrotron) is the biggest German research center for particle physics, with sites in Hamburg and Zeuthen. ... Hamburgs motto: May the posterity endeavour with dignity to conserve the freedom, which the forefathers acquired. ... HERA (Hadron-Elektron-Ringanlage, or Hadron-Electron Ring Accelerator) is a particle accelerator at DESY in Hamburg. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Fermilabs Tevatron Robert Rathbun Wilson Hall Fermi National Accelerator Laboratory (Fermilab), located in Batavia near Chicago, Illinois, (Google Sat Map) is a U.S. Department of Energy national laboratory specializing in high-energy particle physics, operated for the Department of Energy by the Universities Research Association (URA). ... Tevatron is a circular particle accelerator (or synchrotron) at the Fermi National Accelerator Laboratory in Batavia, Illinois. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... Properties In physics, the proton (Greek proton = first) is a subatomic particle with an electric charge of one positive fundamental unit (1. ... It has been suggested that this article or section be merged with List of Internet slang. ... CP-symmetry is a symmetry obtained by a combination of the C-symmetry and the P-symmetry. ... The Stanford Linear Accelerator Center (SLAC) is a U.S. national laboratory operated by Stanford University for the U.S. Department of Energy. ... Properties The electron is a lightweight fundamental subatomic particle that carries a negative electric charge. ... The first detection of the positron in 1932 by Carl D. Anderson The positron is the antiparticle or the antimatter counterpart of the electron. ... A 1960s single stage 2MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric and/or magnetic fields to propel electrically charged particles to high speeds. ...

The techniques required to do modern experimental particle physics are quite varied and complex, constituting a subspecialty nearly completely distinct from the theoretical side of the field. See Category:Experimental particle physics for a partial list of the ideas required for such experiments.

Theory

Theoretical particle physics attempts to develop the models, theoretical framework, and mathematical tools to understand current experiments and make predictions for future experiments. See also theoretical physics. There are several major efforts in theoretical particle physics today and each includes a range of different activities. The efforts in each area are interrelated. Theoretical physics employs mathematical models and abstractions, as opposed to experimental processes, in an attempt to understand Nature. ...

One of the major activities in theoretical particle physics is the attempt to better understand the standard model and its tests. By extracting the parameters of the standard model from experiments with less uncertainty, this work probes the limits of the standard model and therefore expands our understanding of nature. These efforts are made challenging by the difficult nature of calculating many quantities in quantum chromodynamics. Some theorists making these efforts refer to themselves as phenomenologists and may use the tools of quantum field theory and effective field theory. Others make use of lattice field theory and call themselves lattice theorists. The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... Quantum chromodynamics (QCD) is the theory of the strong interaction, a fundamental force describing the interactions of the quarks and gluons found in nucleons (such as the proton and neutron). ... This article does not cite its references or sources. ... Quantum field theory (QFT) is the application of quantum mechanics to fields. ... In physics, an effective field theory is an approximate theory (usually a quantum field theory) that contains the appropriate degrees of freedom to describe physical phenomena occurring at a chosen length scale, but ignores the substructure and the degrees of freedom at shorter distances (or, equivalently, higher energies). ... It has been suggested that Lattice gauge theory be merged into this article or section. ...

Another major effort is in model building where model builders develop ideas for what physics may lie beyond the standard model (at higher energies or smaller distances). This work is often motivated by the hierarchy problem and is constrained by existing experimental data. It may involve work on supersymmetry, alternatives to the Higgs mechanism, extra spatial dimensions (such as the Randall-Sundrum models), Preon theory, combinations of these, or other ideas. It has been suggested that this article or section be merged with model builder. ... In theoretical physics, a hierarchy problem is a confusing observation that two fundamental quantities with the same units have vastly different values, and therefore the naïve calculation based on dimensional analysis can lead to incorrect results. ... This article or section is in need of attention from an expert on the subject. ... The Higgs mechanism, originally discovered by the British physicist Peter Higgs (building on a previous suggestion by Philip Anderson in condensed matter physics), is the mechanism that gives masses to all elementary particles in particle physics. ... In physics, Randall-Sundrum models imagine that the real world is a higher-dimensional Universe described by warped geometry. ... In particle physics, Preons are postulated pointlike particles, that are subparticles of quarks and leptons. ...

A third major effort in theoretical particle physics is string theory. String theorists attempt to construct a unified description of quantum mechanics and general relativity by building a theory based on small strings, and branes rather than particles. If the theory is successful, it may be considered a "Theory of Everything". Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory String theory is a model of fundamental physics whose building blocks are one-dimensional extended objects (strings) rather than the zero-dimensional points (particles... For a non-technical introduction to the topic, please see Introduction to Quantum mechanics. ... General relativity (GR) is the geometrical theory of gravitation published by Albert Einstein in 1915. ... P-branes or branes are terms from quantum superstring theory used to refer to membrane-like structures of one to eleven dimensions that arise in equations of this heavily mathematical theory. ... This article or section is in need of attention from an expert on the subject. ...

There are also other areas of work in theoretical particle physics ranging from particle cosmology to loop quantum gravity. Loop quantum gravity (LQG), also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the seemingly incompatible theories of quantum mechanics and general relativity. ...

This divide of efforts in particle physics is reflected in the names of categories on the preprint archive [2]: hep-th (theory), hep-ph (phenomenology), hep-ex (experiments), hep-lat (lattice gauge theory). arXiv (pronounced archive, as if the X were the Greek letter χ) is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and biology which can be accessed via the internet. ... It has been suggested that this article or section be merged into Lattice field theory. ...

Reductionism

Throughout the development of particle physics, there have been many objections to the extreme reductionist (or greedy reductionist) approach of attempting to explain everything in terms of elementary particles and their interaction. These objections have been raised by people from a wide array of fields, including many modern particle physicists, solid state physicists, chemists, biologists, and metaphysical holists. While the Standard Model itself is not challenged, it is contended that the properties of elementary particles are no more (or less) fundamental than the emergent properties of atoms and molecules, and especially statistically large ensembles of those. Some critics of reductionism claim that even a complete knowledge of the underlying elementary particles will not lend a thorough understanding of more complicated natural processes, while others doubt that a complete knowledge of particle behavior (as part of a larger process) could even be attained, thanks to quantum indeterminacy. The term scientific reductionism has been used to describe various reductionist ideas about science. ... Greedy reductionism is a term coined by Daniel Dennett, in the book Darwins Dangerous Idea, to distinguish between acceptable and erroneous forms of reductionism. ... Solid-state physics, the largest branch of condensed matter physics, is the study of rigid matter, or solids. ... Chemistry (from the Greek word χημεία (chemeia) meaning cast together or pour together) is the science of matter at the atomic to molecular scale, dealing primarily with collections of atoms (such as molecules, crystals, and metals). ... Biology is the branch of science dealing with the study of life. ... Holism (from holos, a Greek word meaning all, entire, total) is the idea that all the properties of a given system (biological, chemical, social, economic, mental, linguistic, etc. ... In science, fundamental science is the part of science that describes the most basic objects, forces, relations between them and laws governing them, such that all other phenomena may be in principle derived from them, following the logic of scientific reductionism. ... A termite cathedral mound produced by a termite colony: a classic example of emergence in nature. ... Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics. ...

Reductionists typically claim that all progress in the sciences has involved reductionism to some extent.

Public policy

Experimental results in particle physics are often obtained using enormous particle accelerators which are very expensive (typically several billion US dollars) and require large amounts of government funding. Because of this, particle physics research involves issues of public policy. A 1960s single stage 2MeV linear Van de Graaff accelerator, here opened for maintenance A particle accelerator is a device that uses electric and/or magnetic fields to propel electrically charged particles to high speeds. ...

Many have argued that the potential advances do not justify the money spent, and that in fact particle physics takes money away from more important research and education efforts. In 1993, the US Congress stopped the Superconducting Super Collider (SSC) because of similar concerns, after US$2 billion had already been spent on its construction. Many scientists, both supporters and opponents of the SSC, believe that the decision to stop construction of the SSC was due in part to the end of the Cold War which removed scientific competition with the Soviet Union as a rationale for spending large amounts of money on the SSC. 1993 (MCMXCIII) was a common year starting on Friday of the Gregorian calendar and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003). ... The Superconducting Super Collider (often abbreviated as SSC) was a ring particle accelerator which was planned to be built in the area around Waxahachie, Texas. ... The Cold War (Russian: Холодная война Kholodnaya Voina) was the protracted geopolitical, ideological, and economic struggle that emerged after World War II between the global superpowers of the Soviet Union and the United States, supported by their military alliance partners. ...

Some within the scientific community believe that particle physics has also been adversely affected by the aging population. The belief is that the aging population is much more concerned with immediate issues of their health and their parents' health and that this has driven scientific funding away from physics toward the biological and health sciences. In addition, many opponents question the ability of any single country to support the expense of particle physics results and fault the SSC for not seeking greater international funding.

Proponents of particle accelerators hold that the investigation of the most basic theories deserves adequate funding, and that this funding benefits other fields of science in various ways. They point out that all accelerators today are international projects and question the claim that money not spent on accelerators would then necessarily be used for other scientific or educational purposes.

The future

Particle physicists internationally agree on the most important goals of particle physics research in the near and intermediate future. The overarching goal, which is pursued in several distinct ways, is to find and understand what physics may lie beyond the standard model. There are several powerful experimental reasons to expect new physics, including dark matter and neutrino mass. There are also theoretical hints that this new physics should be found at accessible energy scales. Most importantly, though, there may be unexpected and unpredicted surprises which will give us the most opportunity to learn about nature. The Standard Model of Fundamental Particles and Interactions The Standard Model of particle physics is a theory which describes the strong, weak, and electromagnetic fundamental forces, as well as the fundamental particles that make up all matter. ... In astrophysics, dark matter refers to matter that does not emit or reflect enough electromagnetic radiation (such as light, x-rays and so on) to be detected directly, but whose presence may be inferred from its gravitational effects on visible matter. ... The neutrino is an elementary particle. ...

Much of the efforts to find this new physics are focused on new collider experiments. A (relatively) near term goal is the completion of the Large Hadron Collider (LHC) in 2007 which will continue the search for the Higgs boson, supersymmetric particles, and other new physics. An intermediate goal is the construction of the International Linear Collider (ILC) which will complement the LHC by allowing more precise measurements of the properties of newly found particles. A decision for the technology of the ILC has been taken in August 2004, but the site has still to be agreed upon. For the pop group, see Les Horribles Cernettes Construction of the CMS detector for LHC at CERN The Large Hadron Collider (short LHC) is a particle accelerator and collider located at CERN. It is currently under construction and scheduled to start operation in 2007. ... 2007 (MMVII) will be a common year starting on Monday of the Gregorian calendar. ... The Higgs boson is a hypothetical massive scalar elementary particle predicted to exist by the Standard Model of particle physics. ... In particle physics, supersymmetry is a hypothetical symmetry that relates bosons and fermions. ... The International Linear Collider is a proposed linear particle accelerator. ... 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ...

Additionally, there are important non-collider experiments which also attempt to find and understand physics beyond the standard model. One important non-collider effort is the determination of the neutrino masses since these masses may arise from neutrinos mixing with very heavy particles. In addition, cosmological observations provide many useful constraints on the dark matter, although it may be impossible to determine the exact nature of the dark matter without the colliders. Finally, lower bounds on the very long life time of the proton put constraints on Grand Unification Theories at energy scales much higher than collider experiments will be able to probe any time soon. The neutrino is an elementary particle. ... Cosmology, as a branch of astrophysics, is the study of the large-scale structure of the universe and is concerned with fundamental questions about its formation and evolution. ... The decay of a proton, a baryon, into non-baryonic matter, does not occur perturbatively in the Standard Model. ... Grand unification, grand unified theory, or GUT is a theory in physics that unifies the strong interaction and electroweak interaction. ...

See also

• Atomic physics
• Introduction to quantum mechanics
• Fundamental particle
• List of particles
• List of accelerators in particle physics
• Subatomic particle
• High pressure physics

Atomic physics (or atom physics) is the field of physics that studies atoms as isolated systems comprised of electrons and an atomic nucleus. ... Quantum mechanics is a physical science dealing with the behaviour of matter and waves on the scale of atoms and subatomic particles. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ... This is a list of particles in particle physics, including currently known and hypothetical elementary particles, as well as the composite particles that can be built up from them. ... A list of particle accelerators used for particle physics experiments. ... A subatomic particle is a particle smaller than an atom: it may be elementary or composite. ... High pressure physics is a specialized field in physics that involves the science and technology challenges of basic and applied materials at high pressures and temperatures. ...

External links

• Particle Physics News and Resources
• ARXIV.ORG preprint server
• The Particle Adventure - educational project sponsored by the Particle Data Group of the Lawrence Berkeley National Laboratory (LBNL)
• History of particle physics
• symmetry magazine
• Introduction to Particle Physics by Matthew Nobes (published on Kuro5hin):
  • Part 1
  • Part 2
  • Part 3a
  • Part 3b
• High-Energy Physics Literature Database
• CERN Courier - International Journal of High-Energy Physics
• Particle physics in 60 seconds

The Berkeley Lab is perched on a hill overlooking the Berkeley central campus and San Francisco Bay. ... Kuro5hin (K5) (pronounced corrosion) is a community discussion website (sometimes known as an example of Commons-based peer production) focused on technology and culture. ...