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Matter

In the classical physics observed in everyday life, matter is any substance that has mass and takes up space by having volume. This includes atoms and anything made up of these, but not other energy phenomena or waves such as light or sound. All the everyday objects that we can bump into, touch or squeeze are ultimately composed of atoms. This ordinary atomic matter is in turn made up of interacting subatomic particles—usually a nucleus of protons and neutrons, and a cloud of orbiting electrons. Typically, science considers these composite particles matter because they have both rest mass and volume. By contrast, massless particles, such as photons, are not considered matter, because they have neither rest mass nor volume. However, not all particles with rest mass have a classical volume, since fundamental particles such as quarks and leptons (sometimes equated with matter) are considered "point particles" with no effective size or volume. Nevertheless, quarks and leptons together make up "ordinary matter", and their interactions contribute to the effective volume of the composite particles that make up ordinary matter. Matter exists in states (or phases): the classical solid, liquid, and gas; as well as the more exotic plasma, Bose–Einstein condensates, fermionic condensates, and quark–gluon plasma. For much of the history of the natural sciences people have contemplated the exact nature of matter. The idea that matter was built of discrete building blocks, the so-called particulate theory of matter, was first put forward by the Greek philosophers Leucippus (~490 BC) and Democritus (~470–380 BC).

Comparison with mass

Matter should not be confused with mass, as the two are not the same in modern physics. Different fields of science use the term matter in different, and sometimes incompatible, ways. Some of these ways are based on loose historical meanings, from a time when there was no reason to distinguish mass from simply a quantity of matter. As such, there is no single universally agreed scientific meaning of the word "matter". Scientifically, the term "mass" is well-defined, but "matter" can be defined in several ways. Sometimes in the field of physics "matter" is simply equated with particles that exhibit rest mass (i.e., that cannot travel at the speed of light), such as quarks and leptons. However, in both physics and chemistry, matter exhibits both wave-like and particle-like properties, the so-called wave–particle duality.

Definition

Based on atoms

A definition of "matter" based on its physical and chemical structure is: matter is made up of atoms.

Based on protons, neutrons and electrons

A definition of "matter" more fine-scale than the atoms and molecules definition is: matter is made up of what atoms and molecules are made of, meaning anything made of positively charged protons, neutral neutrons, and negatively charged electrons.

Based on quarks and leptons

(in purple) and leptons (in green) would be matter—while the gauge bosons (in red) would not be matter. However, interaction energy inherent to composite particles (for example, gluons involved in neutrons and protons) contribute to the mass of ordinary matter.]] As seen in the above discussion, many early definitions of what can be called ordinary matter were based upon its structure or building blocks. On the scale of elementary particles, a definition that follows this tradition can be stated as: ordinary matter is everything that is composed of quarks and leptons, or ordinary matter is everything that is composed of any elementary fermions except antiquarks and antileptons. |journal=International Journal of Modern Physics E |volume=15 |title=WHAT IS A MATTER PARTICLE? |last=Tsan |first=Ung Chan |date=2006 |doi=10.1142/S0218301306003916 |pages=259–272 |url=http://www.worldscientific.com/doi/abs/10.1142/S0218301306003916 |quote="(From Abstract:) Positive baryon numbers (A>0) and positive lepton numbers (L>0) characterize matter particles while negative baryon numbers and negative lepton numbers characterize antimatter particles. Matter particles and antimatter particles belong to two distinct classes of particles. Matter neutral particles are particles characterized by both zero baryon number and zero lepton number. This third class of particles includes mesons formed by a quark and an antiquark pair (a pair of matter particle and antimatter particle) and bosons which are messengers of known interactions (photons for electromagnetism, W and Z bosons for the weak interaction, gluons for the strong interaction). The antiparticle of a matter particle belongs to the class of antimatter particles, the antiparticle of an antimatter particle belongs to the class of matter particles." |bibcode=2006IJMPE..15..259C }} The connection between these formulations follows. Leptons (the most famous being the electron), and quarks (of which baryons, such as protons and neutrons, are made) combine to form atoms, which in turn form molecules. Because atoms and molecules are said to be matter, it is natural to phrase the definition as: ordinary matter is anything that is made of the same things that atoms and molecules are made of. (However, notice that one also can make from these building blocks matter that is not atoms or molecules.) Then, because electrons are leptons, and protons, and neutrons are made of quarks, this definition in turn leads to the definition of matter as being quarks and leptons, which are two of the four types of elementary fermions (the other two being antiquarks and antileptons, which can be considered antimatter as described later). Carithers and Grannis state: Ordinary matter is composed entirely of first-generation particles, namely the up and down quarks, plus the electron and its neutrino.{{cite journal |author1=B. Carithers |author2=P. Grannis |title=Discovery of the Top Quark |url=http://www.slac.stanford.edu/pubs/beamline/pdf/95iii.pdf |publisher= SLAC National Accelerator Laboratory |journal= Beam Line |volume=25 |issue=3 |pages=4–16 |date=1995 }} (Higher generations particles quickly decay into first-generation particles, and thus are not commonly encountered. This definition of ordinary matter is more subtle than it first appears. All the particles that make up ordinary matter (leptons and quarks) are elementary fermions, while all the force carriers are elementary bosons. |author=C. Amsler |collaboration= Particle Data Group |date=2008 |title=Review of Particle Physics: The Mass and Width of the W Boson |url=http://pdg.lbl.gov/2008/reviews/wmass_s043202.pdf |journal= Physics Letters B |volume=667 |page=1 |bibcode = 2008PhLB..667....1A |doi = 10.1016/j.physletb.2008.07.018 }} In other words, mass is not something that is exclusive to ordinary matter. The quark–lepton definition of ordinary matter, however, identifies not only the elementary building blocks of matter, but also includes composites made from the constituents (atoms and molecules, for example). Such composites contain an interaction energy that holds the constituents together, and may constitute the bulk of the mass of the composite. As an example, to a great extent, the mass of an atom is simply the sum of the masses of its constituent protons, neutrons and electrons. However, digging deeper, the protons and neutrons are made up of quarks bound together by gluon fields (see dynamics of quantum chromodynamics) and these gluons fields contribute significantly to the mass of hadrons. The Standard Model groups matter particles into three generations, where each generation consists of two quarks and two leptons. The first generation is the up and down quarks, the electron and the electron neutrino; the second includes the charm and strange quarks, the muon and the muon neutrino; the third generation consists of the top and bottom quarks and the tau and tau neutrino.

Structure

In particle physics, fermions are particles that obey Fermi–Dirac statistics. Fermions can be elementary, like the electron—or composite, like the proton and neutron. In the Standard Model, there are two types of elementary fermions: quarks and leptons, which are discussed next.

Quarks

Quarks are particles of spin-  e (down-type quarks) or + e (up-type quarks). For comparison, an electron has a charge of −1 e. They also carry colour charge, which is the equivalent of the electric charge for the strong interaction. Quarks also undergo radioactive decay, meaning that they are subject to the weak interaction. Quarks are massive particles, and therefore are also subject to gravity.

Baryonic matter

Baryons are strongly interacting fermions, and so are subject to Fermi–Dirac statistics. Amongst the baryons are the protons and neutrons, which occur in atomic nuclei, but many other unstable baryons exist as well. The term baryon usually refers to triquarks—particles made of three quarks. "Exotic" baryons made of four quarks and one antiquark are known as the pentaquarks, but their existence is not generally accepted. Baryonic matter is the part of the universe that is made of baryons (including all atoms). This part of the universe does not include dark energy, dark matter, black holes or various forms of degenerate matter, such as compose white dwarf stars and neutron stars. Microwave light seen by Wilkinson Microwave Anisotropy Probe (WMAP), suggests that only about 4.6% of that part of the universe within range of the best telescopes (that is, matter that may be visible because light could reach us from it), is made of baryonic matter. About 26.8% is dark matter, and about 68.3% is dark energy. As a matter of fact, the great majority of ordinary matter in the universe is unseen, since visible stars and gas inside galaxies and clusters account for less than 10 per cent of the ordinary matter contribution to the mass-energy density of the universe.{{Cite journal | last = Persic | first = Massimo | last2 = Salucci | first2 = Paolo | date = 1992-09-01 | title = The baryon content of the Universe | url = http://mnras.oxfordjournals.org/content/258/1/14P | journal = Monthly Notices of the Royal Astronomical Society | language = en | volume = 258 | issue = 1 | pages = 14P–18P | doi = 10.1093/mnras/258.1.14P | issn = 0035-8711 |arxiv = astro-ph/0502178 |bibcode = 1992MNRAS.258P..14P }} B (center), its A-class companion IK Pegasi A (left) and the Sun (right). This white dwarf has a surface temperature of 35,500 K.]]

Degenerate matter

In physics, degenerate matter refers to the ground state of a gas of fermions at a temperature near absolute zero. Degenerate matter is thought to occur during the evolution of heavy stars. Degenerate matter includes the part of the universe that is made up of neutron stars and white dwarfs.

Strange matter

Strange matter is a particular form of quark matter, usually thought of as a liquid of up, down, and strange quarks. It is contrasted with nuclear matter, which is a liquid of neutrons and protons (which themselves are built out of up and down quarks), and with non-strange quark matter, which is a quark liquid that contains only up and down quarks. At high enough density, strange matter is expected to be color superconducting. Strange matter is hypothesized to occur in the core of neutron stars, or, more speculatively, as isolated droplets that may vary in size from femtometers ( strangelets) to kilometers ( quark stars).

= Two meanings of the term "strange matter"

= In particle physics and astrophysics, the term is used in two ways, one broader and the other more specific.
  1. The broader meaning is just quark matter that contains three flavors of quarks: up, down, and strange. In this definition, there is a critical pressure and an associated critical density, and when nuclear matter (made of protons and neutrons) is compressed beyond this density, the protons and neutrons dissociate into quarks, yielding quark matter (probably strange matter).
  2. The narrower meaning is quark matter that is more stable than nuclear matter. The idea that this could happen is the "strange matter hypothesis" of Bodmer

Leptons

Leptons are particles of spin-{{frac, meaning that they are fermions. They carry an electric charge of −1  e (charged leptons) or 0 e (neutrinos). Unlike quarks, leptons do not carry colour charge, meaning that they do not experience the strong interaction. Leptons also undergo radioactive decay, meaning that they are subject to the weak interaction. Leptons are massive particles, therefore are subject to gravity.

Phases

(above the green line is solid, below it is liquid) and the blue line the boiling point (above it is liquid and below it is gas). So, for example, at higher T, a higher P is necessary to maintain the substance in liquid phase. At the triple point the three phases; liquid, gas and solid; can coexist. Above the critical point there is no detectable difference between the phases. The dotted line shows the anomalous behavior of water: ice melts at constant temperature with increasing pressure. In , matter can exist in several different forms, or states of aggregation, known as phases, Phases are sometimes called states of matter, but this term can lead to confusion with thermodynamic states. For example, two gases maintained at different pressures are in different thermodynamic states (different pressures), but in the same phase (both are gases).

Antimatter

In particle physics and quantum chemistry, antimatter is matter that is composed of the antiparticles of those that constitute ordinary matter. If a particle and its antiparticle come into contact with each other, the two annihilate; that is, they may both be converted into other particles with equal energy in accordance with Einstein's equation . These new particles may be high-energy photons ( gamma rays) or other particle–antiparticle pairs. The resulting particles are endowed with an amount of kinetic energy equal to the difference between the rest mass of the products of the annihilation and the rest mass of the original particle–antiparticle pair, which is often quite large. Depending on which definition of "matter" is adopted, antimatter can be said to be a particular subclass of matter, or the opposite of matter. Antimatter is not found naturally on Earth, except very briefly and in vanishingly small quantities (as the result of radioactive decay, lightning or cosmic rays). This is because antimatter that came to exist on Earth outside the confines of a suitable physics laboratory would almost instantly meet the ordinary matter that Earth is made of, and be annihilated. Antiparticles and some stable antimatter (such as antihydrogen) can be made in tiny amounts, but not in enough quantity to do more than test a few of its theoretical properties. There is considerable speculation both in science and science fiction as to why the observable universe is apparently almost entirely matter (in the sense of quarks and leptons but not antiquarks or antileptons), and whether other places are almost entirely antimatter (antiquarks and antileptons) instead. In the early universe, it is thought that matter and antimatter were equally represented, and the disappearance of antimatter requires an asymmetry in physical laws called CP (charge-parity) symmetry violation, which can be obtained from the Standard Model, Formally, antimatter particles can be defined by their negative baryon number or lepton number, while "normal" (non-antimatter) matter particles have positive baryon or lepton number.{{cite journal |quote="(From Abstract:) Antimatter particles are characterized by negative baryonic number A or/and negative leptonic number L. Materialization and annihilation obey conservation of A and L (associated to all known interactions)" |journal=International Journal of Modern Physics E |volume=21 |number=01 |title=Negative Numbers And Antimatter Particles |last=TSAN |first=U. C. |date=2012 |pages=1250005 |doi=10.1142/S021830131250005X |url=http://www.worldscientific.com/doi/abs/10.1142/S021830131250005X |bibcode=2012IJMPE..2150005T }} These two classes of particles are the antiparticle partners of one another. In October 2017, scientists reported further evidence that matter and antimatter, equally produced at the Big Bang, are identical, should completely annihilate each other and, as a result, the universe should not exist. This implies that there must be something, as yet unknown to scientists, that either stopped the complete mutual destruction of matter and antimatter in the early forming universe, or that gave rise to an imbalance between the two forms.

Conservation of matter

According to CP Symmetry, the two quantities that can define an amount of matter in the quark-lepton sense (and antimatter in an antiquark-antilepton sense), baryon number and lepton number, are conserved—or at least nearly so, considering CP violation. A baryon such as the proton or neutron has a baryon number of one, and a quark, because there are three in a baryon, is given a baryon number of 1/3. So the net amount of matter, as measured by the number of quarks (minus the number of antiquarks, which each have a baryon number of -1/3), which is proportional to baryon number, and number of leptons (minus antileptons), which is called the lepton number, is practically impossible to change in any process. Even in a nuclear bomb, none of the baryons (protons and neutrons of which the atomic nuclei are composed) are destroyed—there are as many baryons after as before the reaction, so none of these matter particles are actually destroyed and none are even converted to non-matter particles (like photons of light or radiation). Instead, nuclear (and perhaps chromodynamic) binding energy is released, as these baryons become bound into mid-size nuclei having less energy (and, equivalently, less mass) per nucleon compared to the original small (hydrogen) and large (plutonium etc.) nuclei. Even in electron–positron annihilation, there is actually no net matter being destroyed, because there was zero net matter (zero total lepton number and baryon number) to begin with before the annihilation—one lepton minus one antilepton equals zero net lepton number—and this net amount matter does not change as it simply remains zero after the annihilation.{{cite journal |quote="(From Abstract:) Matter conservation melans conservation of baryonic number A and leptonic number L, A and L being algebraic numbers. Positive A and L are associated to matter particles, negative A and L are associated to antimatter particles. All known interactions do conserve matter" |journal=International Journal of Modern Physics E |volume=22 |number=05 |title=MASS, MATTER, MATERIALIZATION, MATTERGENESIS AND CONSERVATION OF CHARGE |last=Tsan |first=Ung Chan |date=2013 |pages=1350027 |doi=10.1142/S0218301313500274 |url=http://www.worldscientific.com/doi/abs/10.1142/S0218301313500274 |bibcode=2013IJMPE..2250027T }} So the only way to really "destroy" or "convert" ordinary matter is to pair it with the same amount of antimatter so that their "matterness" cancels out—but in practice there is almost no antimatter generally available in the universe (see baryon asymmetry and leptogenesis) with which to do so.

Other types

[[File:Matter Distribution.JPG|thumb |300px |Pie chart showing the fractions of energy in the universe contributed by different sources. Ordinary matter is divided into luminous matter (the stars and luminous gases and 0.005% radiation) and nonluminous matter (intergalactic gas and about 0.1% neutrinos and 0.04% supermassive black holes). Ordinary matter is uncommon. Modeled after Ostriker and Steinhardt.{{cite journal |author=J.P. Ostriker |author2=P.J. Steinhardt |date=2003 |title=New Light on Dark Matter |doi=10.1126/science.1085976 |journal=Science |volume=300 |issue=5627 |pages=1909–13 |pmid=12817140 |arxiv=astro-ph/0306402 |bibcode = 2003Sci...300.1909O }} For more information, see NASA.]] Ordinary matter, in the quarks and leptons definition, constitutes about 4% of the energy of the observable universe. The remaining energy is theorized to be due to exotic forms, of which 23% is dark matter for the Milky Way. Vertical axis is speed of rotation about the galactic center. Horizontal axis is distance from the galactic center. The sun is marked with a yellow ball. The observed curve of speed of rotation is blue. The predicted curve based upon stellar mass and gas in the Milky Way is red. The difference is due to dark matter or perhaps a modification of the law of gravity.{{cite book |author=P. Schneider |date=2006 |title=Extragalactic Astronomy and Cosmology |url=https://books.google.com/?id=uP1Hz-6sHaMC&pg=PA100 |page=4, Fig. 1.4 |publisher=Springer |isbn=3-540-33174-3 }}{{cite book |author=T. Koupelis |author2=K.F. Kuhn |date=2007 |title=In Quest of the Universe |url=https://books.google.com/?id=6rTttN4ZdyoC&pg=PA491 |page=492; Fig. 16.13 |publisher=Jones & Bartlett Publishers |isbn=0-7637-4387-9 }}{{cite book |author=M. H. Jones |author2=R. J. Lambourne |author3=D. J. Adams |date=2004 |title=An Introduction to Galaxies and Cosmology |url=https://books.google.com/?id=36K1PfetZegC&pg=PA20 |page=21; Fig. 1.13 |publisher=Cambridge University Press |isbn=0-521-54623-0 }} Scatter in observations is indicated roughly by gray bars.]]

Dark matter

In astrophysics and cosmology, dark matter is matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly, but whose presence can be inferred from gravitational effects on visible matter.

Dark energy

In cosmology, dark energy is the name given to source of the repelling influence that is accelerating the rate of expansion of the universe. Its precise nature is currently a mystery, although its effects can reasonably be modeled by assigning matter-like properties such as energy density and pressure to the vacuum itself.

Exotic matter

Exotic matter is a concept of particle physics, which may include dark matter and dark energy but goes further to include any hypothetical material that violates one or more of the properties of known forms of matter. Some such materials might possess hypothetical properties like negative mass.

Historical development

Antiquity (c. 610 BC–c. 322 BC)

The pre-Socratics were among the first recorded speculators about the underlying nature of the visible world. Thales (c. 624 BC–c. 546 BC) regarded water as the fundamental material of the world. Anaximander (c. 610 BC–c. 546 BC) posited that the basic material was wholly characterless or limitless: the Infinite ( apeiron). Anaximenes (flourished 585 BC, d. 528 BC) posited that the basic stuff was pneuma or air. Heraclitus (c. 535–c. 475 BC) seems to say the basic element is fire, though perhaps he means that all is change. Empedocles (c. 490–430 BC) spoke of four elements of which everything was made: earth, water, air, and fire. Aristotle (384 BC – 322 BC) was the first to put the conception on a sound philosophical basis, which he did in his natural philosophy, especially in Physics book I.For a good explanation and elaboration, see {{cite book |author=R.J. Connell |date=1966 |title=Matter and Becoming |publisher=Priory Press |isbn= }} He adopted as reasonable suppositions the four Empedoclean elements, but added a fifth, aether. Nevertheless, these elements are not basic in Aristotle's mind. Rather they, like everything else in the visible world, are composed of the basic principles matter and form. The word Aristotle uses for matter, ὕλη (hyle or hule), can be literally translated as wood or timber, that is, "raw material" for building.

Seventeenth and eighteenth centuries

René Descartes (1596–1650) originated the modern conception of matter. He was primarily a geometer. Instead of, like Aristotle, deducing the existence of matter from the physical reality of change, Descartes arbitrarily postulated matter to be an abstract, mathematical substance that occupies space: For Descartes, matter has only the property of extension, so its only activity aside from locomotion is to exclude other bodies:though even this property seems to be non-essential (René Descartes, Principles of Philosophy II 1644, "On the Principles of Material Things", no. 4.) this is the mechanical philosophy. Descartes makes an absolute distinction between mind, which he defines as unextended, thinking substance, and matter, which he defines as unthinking, extended substance. The continuity and difference between Descartes' and Aristotle's conceptions is noteworthy. In both conceptions, matter is passive or inert. In the respective conceptions matter has different relationships to intelligence. For Aristotle, matter and intelligence (form) exist together in an interdependent relationship, whereas for Descartes, matter and intelligence (mind) are definitionally opposed, independent substances. Descartes' justification for restricting the inherent qualities of matter to extension is its permanence, but his real criterion is not permanence (which equally applied to color and resistance), but his desire to use geometry to explain all material properties.E.A. Burtt, Metaphysical Foundations of Modern Science (Garden City, New York: Doubleday and Company, 1954), 117–118. Like Descartes, Hobbes, Boyle, and Locke argued that the inherent properties of bodies were limited to extension, and that so-called secondary qualities, like color, were only products of human perception.J.E. McGuire and P.M. Heimann, "The Rejection of Newton's Concept of Matter in the Eighteenth Century", The Concept of Matter in Modern Philosophy ed. Ernan McMullin (Notre Dame: University of Notre Dame Press, 1978), 104–118 (105). Isaac Newton (1643–1727) inherited Descartes' mechanical conception of matter. In the third of his "Rules of Reasoning in Philosophy", Newton lists the universal qualities of matter as "extension, hardness, impenetrability, mobility, and inertia".Isaac Newton, ''Mathematical Principles of Natural Philosophy, trans. A. Motte, revised by F. Cajori (Berkeley: University of California Press, 1934), pp. 398–400. Further analyzed by Maurice A. Finocchiaro, "Newton's Third Rule of Philosophizing: A Role for Logic in Historiography", Isis 65:1 (Mar. 1974), pp. 66–73. Similarly in Optics he conjectures that God created matter as "solid, massy, hard, impenetrable, movable particles", which were "...even so very hard as never to wear or break in pieces".Isaac Newton, Optics'', Book III, pt. 1, query 31. The "primary" properties of matter were amenable to mathematical description, unlike "secondary" qualities such as color or taste. Like Descartes, Newton rejected the essential nature of secondary qualities.McGuire and Heimann, 104. Newton developed Descartes' notion of matter by restoring to matter intrinsic properties in addition to extension (at least on a limited basis), such as mass. Newton's use of gravitational force, which worked "at a distance", effectively repudiated Descartes' mechanics, in which interactions happened exclusively by contact. Though Newton's gravity would seem to be a power of bodies, Newton himself did not admit it to be an essential property of matter. Carrying the logic forward more consistently, Joseph Priestley (1733-1804) argued that corporeal properties transcend contact mechanics: chemical properties require the capacity for attraction. He argued matter has other inherent powers besides the so-called primary qualities of Descartes, et al.McGuire and Heimann, 113.

Nineteenth and twentieth centuries

Since Priestley's time, there has been a massive expansion in knowledge of the constituents of the material world (viz., molecules, atoms, subatomic particles), but there has been no further development in the definition of matter. Rather the question has been set aside. Noam Chomsky (born 1928) summarizes the situation that has prevailed since that time: So matter is whatever physics studies and the object of study of physics is matter: there is no independent general definition of matter, apart from its fitting into the methodology of measurement and controlled experimentation. In sum, the boundaries between what constitutes matter and everything else remains as vague as the demarcation problem of delimiting science from everything else.Nevertheless, it remains true that the mathematization regarded as requisite for a modern physical theory carries its own implicit notion of matter, which is very like Descartes', despite the demonstrated vacuity of the latter's notions. In the 19th century, following the development of the periodic table, and of atomic theory, atoms were seen as being the fundamental constituents of matter; atoms formed molecules and compounds. The common definition in terms of occupying space and having mass is in contrast with most physical and chemical definitions of matter, which rely instead upon its structure and upon attributes not necessarily related to volume and mass. At the turn of the nineteenth century, the knowledge of matter began a rapid evolution. Aspects of the Newtonian view still held sway. James Clerk Maxwell discussed matter in his work Matter and Motion. However, the Newtonian picture was not the whole story. In the 19th century, the term "matter" was actively discussed by a host of scientists and philosophers, and a brief outline can be found in Levere. Rather than simply having the attributes of mass and occupying space, matter was held to have chemical and electrical properties. In 1909 the famous physicist J. J. Thomson (1856-1940) wrote about the "constitution of matter" and was concerned with the possible connection between matter and electrical charge. There is an entire literature concerning the "structure of matter", ranging from the "electrical structure" in the early 20th century, In the late 19th century with the discovery of the electron, and in the early 20th century, with the discovery of the atomic nucleus, and the birth of particle physics, matter was seen as made up of electrons, protons and neutrons interacting to form atoms. Today, we know that even protons and neutrons are not indivisible, they can be divided into quarks, while electrons are part of a particle family called leptons. Both quarks and leptons are elementary particles, and are currently seen as being the fundamental constituents of matter. The history of the concept of matter is a history of the fundamental length scales used to define matter. Different building blocks apply depending upon whether one defines matter on an atomic or elementary particle level. One may use a definition that matter is atoms, or that matter is hadrons, or that matter is leptons and quarks depending upon the scale at which one wishes to define matter. These quarks and leptons interact through four fundamental forces: gravity, electromagnetism, weak interactions, and strong interactions. The Standard Model of particle physics is currently the best explanation for all of physics, but despite decades of efforts, gravity cannot yet be accounted for at the quantum level; it is only described by classical physics (see quantum gravity and graviton). |author=B.A. Schumm |date=2004 |title=Deep Down Things: The Breathtaking Beauty of Particle Physics |url=https://books.google.com/?id=htJbAf7xA_oC&pg=PA57 |page=57 |publisher=Johns Hopkins University Press |isbn=0-8018-7971-X }} The force-carrying particles are not themselves building blocks. As one consequence, mass and energy (which cannot be created or destroyed) cannot always be related to matter (which can be created out of non-matter particles such as photons, or even out of pure energy, such as kinetic energy). Force carriers are usually not considered matter: the carriers of the electric force (photons) possess energy (see Planck relation) and the carriers of the weak force ( W and Z bosons) are massive, but neither are considered matter either. See for example, {{cite book |author=M. Jibu |author2=K. Yasue |date=1995 |title=Quantum Brain Dynamics and Consciousness |url=https://books.google.com/?id=iNUvcniwvg0C&pg=PA62 |page=62 |publisher=John Benjamins Publishing Company |isbn=1-55619-183-9 }}, {{cite book |author=B. Martin |date=2009 |title=Nuclear and Particle Physics |url=https://books.google.com/?id=ws8QZ2M5OR8C&pg=PT143 |page=125 |edition=2nd |publisher=John Wiley & Sons |isbn=0-470-74275-5 }} and {{cite book |author=K. W. Plaxco |author2=M. Gross |date=2006 |title=Astrobiology: A Brief Introduction |url=https://books.google.com/?id=2JuGDL144BEC&pg=PA23 |page=23 |publisher=Johns Hopkins University Press |isbn=0-8018-8367-9 }} However, while these particles are not considered matter, they do contribute to the total mass of atoms, subatomic particles, and all systems that contain them.

Summary

The modern conception of matter has been refined many times in history, in light of the improvement in knowledge of just what the basic building blocks are, and in how they interact. The term "matter" is used throughout physics in a bewildering variety of contexts: for example, one refers to " condensed matter physics", The history of the concept of matter is a history of the fundamental length scales used to define matter. Different building blocks apply depending upon whether one defines matter on an atomic or elementary particle level. One may use a definition that matter is atoms, or that matter is hadrons, or that matter is leptons and quarks depending upon the scale at which one wishes to define matter. These quarks and leptons interact through four fundamental forces: gravity, electromagnetism, weak interactions, and strong interactions. The Standard Model of particle physics is currently the best explanation for all of physics, but despite decades of efforts, gravity cannot yet be accounted for at the quantum level; it is only described by classical physics (see quantum gravity and graviton).

See also

Antimatter Cosmology Dark matter Philosophy Other

References

Further reading

  • Stephen Toulmin and June Goodfield, The Architecture of Matter (Chicago: University of Chicago Press, 1962).
  • Richard J. Connell, Matter and Becoming (Chicago: The Priory Press, 1966).
  • Ernan McMullin, The Concept of Matter in Greek and Medieval Philosophy (Notre Dame, Indiana: Univ. of Notre Dame Press, 1965).
  • Ernan McMullin, The Concept of Matter in Modern Philosophy (Notre Dame, Indiana: University of Notre Dame Press, 1978).

External links

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This article based upon the http://en.wikipedia.org/wiki/Matter, the free encyclopaedia Wikipedia and is licensed under the GNU Free Documentation License.
Further informations available on the list of authors and history: http://en.wikipedia.org/w/index.php?title=Matter&action=history
presented by: Ingo Malchow, Mirower Bogen 22, 17235 Neustrelitz, Germany