Revision 1015658 of "Gebruiker:Wordscape/temp30" on afwiki

:''This article is about the concept in astronomy, physics and chemistry. For other uses, see [[Matter (disambiguation)]].''

The term '''matter''' traditionally refers to the substance that objects are made of.<ref name=Penrose>

{{cite book |title=The philosophy of vacuum |chapter=The mass of the classical vacuum |author=Roger Penrose |url=http://books.google.com/books?id=ZU1LL4IbDKcC&pg=PA21 |page=21 |editors= Simon Saunders, Harvey R. Brown |isbn=0198244495 |year=1991 |publisher=Oxford University Press}}

</ref><ref name=mcgrawhill>
{{cite web
 |url=http://www.accessscience.com/abstract.aspx?id=410600&referURL=http%3a%2f%2fwww.accessscience.com%2fcontent.aspx%3fid%3d410600
 |title=Matter (physics) |work=McGraw-Hill's Access Science: Encyclopedia of Science and Technology Online
 |accessdate=2009-05-24
}}</ref> One common way to identify this "substance" is through its properties: for example, ''matter'' is anything that has both [[mass]] and [[volume]].<ref name=Mongillo>
{{cite book
 |author=J. Mongillo
 |title=Nanotechnology 101
 |url=http://books.google.com/books?id=j69lwrrQ4nsC&pg=PA30
 |page=30
 |publisher=Greenwood Publishing Group
 |year=2007
 |isbn=0313338809
}}</ref>

A more general view is that bodies are made of ''several'' substances, and the properties of matter (among them, mass and volume) are determined not only by the substances themselves, but by how they interact. In other words, '''matter''' is made up of interacting ''"building blocks"'',<ref name=Davies2>

{{cite book |title=The new physics: a synthesis |author=Paul Davies |url=http://books.google.com/books?id=akb2FpZSGnMC&pg=PA1 |page=1 |isbn=0521438314 Year=1992 |publisher=Cambridge University Press}}

</ref><ref name=Hooft>

{{cite book |title=In search of the ultimate building blocks |author= G. 't Hooft |page=6 |url=http://books.google.com/books?id=e-7eAp-bVbEC&pg=PA6 |isbn=0521578833 |year=1997 |publisher=Cambridge University Press}}

</ref> the so-called ''particulate theory of matter''.<ref name=particulate>

The particulate theory of matter dates back to Leucippus (≈490 BC) and Democritus (≈470-380 BC). {{cite book |title=Chemistry: the molecular science |author=John Olmsted & GM Williams |url=http://books.google.com/books?id=1vnk6J8knKkC&pg=PA40 |page=40 |isbn=0815184506 |edition=2 |year=1996 |publisher=Jones & Bartlett Publishers}}

</ref>

Underlying the notion of matter are some age-old, seemingly [[simplicity|simple questions]]: "What happens when a substance is cut in half over and over again? Is there a limit to how small a piece of substance you can have?"<ref name=Johnson>

{{cite book |title=Atomic Structure |author=Rebecca L Johnson |url=http://books.google.com/books?id=QScyt5_9NokC&pg=PA6 |page=6 |isbn=0822566028 |publisher=Twenty-First Century Books |year=2007}}

</ref>  "When the pieces of substance are small enough, is there only a small number of different building blocks from which any substance is made?"<ref name= Allday>

{{cite book |title= Quarks leptons and the big bang |author=Jonathan Allday  |page=1 |isbn=0750308060 |year=2001 |publisher=CRC Press |url=http://books.google.com/books?id=kgsBbv3-9xwC&pg=PA1}}

</ref>

Our growing understanding of matter can be seen as an evolution in just ''what'' the basic building blocks are, and in how they interact. For example, for Isaac Newton in the early 18th century, matter was formed "in solid, massy, hard, impenetrable, movable particles", which were "even so very hard as never to wear or break in pieces"<ref name=Newton>

Newton's 31st query, as quoted by {{cite book |title=The arch of knowledge: an introductory study of the history of the philosophy and methodology of science |author=David Roger Oldroyd |url=http://books.google.com/books?id=X78OAAAAQAAJ&pg=PA83 |page= 83|isbn=0416013414 |publisher=Routledge |year=1986}}

</ref> The primary or "real" qualities of matter were amenable to mathematical description (a kind of "billiard ball" model), unlike secondary qualities such as color or taste.<ref name=Newton/> In the 19th century, matter was what is made up of ''atoms'', at that time thought of as irreducible constituents of matter interacting to form [[molecules]].<ref name=Wenham>
{{cite book
 |author=M. Wenham
 |title=Understanding Primary Science: Ideas, Concepts and Explanations
 |edition=2nd
 |url=http://books.google.com/books?id=9vWrbr42VA0C&pg=PA115
 |page=115
 |publisher=Paul Chapman Educational Publishing
 |year=2005
 |isbn=1412901634
}}</ref>{{anchor|note}} Subsequently, matter was seen as made up of electrons, protons and neutrons interacting to form atoms. Today we know even protons and neutrons are not indivisible, but the particulate theory still applies. Just the "building blocks" have changed; matter is constructed of more microscopic building blocks, namely [[#Quarks and leptons definition|quarks and leptons]] interacting to form (among other things) [[nucleons]].<ref name=Povh1>
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 [[hadron]]s, or that matter is leptons and quarks depending upon the scale at which one wishes to define matter.
{{cite book
 |author=B. Povh, K. Rith, C. Scholz, F. Zetsche, M. Lavelle
 |title=Particles and Nuclei: An Introduction to the Physical Concepts
 |edition=4th
 |chapter=Fundamental constituents of matter
 |url=http://books.google.com/books?id=rJe4k8tkq7sC&pg=PA9&dq=povh+%22building+blocks+of+matter%22&lr=&as_brr=0#PPA1,M1
 |publisher=Springer
 |year=2004
 |isbn=3540201688
}}
</ref>

During this evolution of the building blocks over time, each generation has encompassed its predecessor, and so engenders the same properties of matter explored in the earlier epoch. However, the evolution of building blocks has followed probes of the properties of matter to smaller and smaller scales of length, and to higher and higher energies and densities; the new building blocks predict properties in regimes not previously accessible in the days of the earlier building blocks. The change in building blocks means that although matter still may be made up of atoms and molecules (because they are made from leptons and quarks), matter is more general than this, and can be made up of assemblies of leptons and quarks that are ''not'' atoms or molecules, such as a [[quark-gluon plasma]], the form of matter believed to have existed in the first few microseconds of the "[[big bang]]", and to exist in [[neutron star]]s.<ref name=Martin>

See {{cite book  |title=Nuclear and Particle Physics: An Introduction |author=Brian R Martin |page=  |chapter =§5.5 Quark-gluon plasma |url=http://books.google.com/books?id=ws8QZ2M5OR8C&pg=PT178 |page=178 |isbn=0470742755 |publisher=Wiley |edition=2 |year=2009}}; this form of matter is being explored using high energy collisions at the [[Relativistic Heavy Ion Collider]] (RHIC). See {{cite book |title=Structure and dynamics of elementary matter |chapter=Creating bulk QCD matter at RHIC |author=John W Harris |url=http://books.google.com/books?id=lokz2n-9gX0C&pg=PA1 |page=1 |editor=Walter Greiner, Mikhail G. Itkis, Joachim Reinhardt |isbn=1402024460 |publisher=Springer |year=2004}}
</ref>

The quark-lepton building blocks interact through a number of [[fundamental forces]], and are described by the [[Standard Model]] of particle physics (gravity so far included only classically; see [[quantum gravity]] and [[graviton]]).<ref name=Allday2>

{{cite book |title=Quarks, leptons and the big bang |page=12 |author=Jonathan Allday |
|url=http://books.google.com/books?id=kgsBbv3-9xwC&pg=PA12 |isbn=0750308060 |year=2001 |publisher=CRC press}}

</ref> Interactions are mediated by [[field quanta]] or [[force carriers]], of which the [[W-boson]] and the [[photon]] are examples.<ref name=MatterField>

For example, electrons are considered to be excitations of an ''electron field'' that couples to the electromagnetic field through its excitations, which are photons. In general, "a quantum dynamical system comprises a ''matter field'' that couples at every point to an ''interaction field''." The ''quanta'' of matter fields are ''[[fermions]]'' and the quanta of interaction fields are ''[[bosons]]''. The interaction fields are permanently coupled to the matter fields. See {{cite book |title=How is quantum field theory possible? |author=Sunny Y. Auyang |isbn=0195093445 |publisher=Oxford University Press |year=1995 |url=http://books.google.com/books?id=yb-X68WALt4C&pg=PA45 |pages=45-46 & 219}} and {{cite book |title=Deep down things: the breathtaking beauty of particle physics |author=Bruce A. Schumm |page=57 |url=http://books.google.com/books?id=htJbAf7xA_oC&pg=PA57 |isbn=080187971X |publisher=John Hopkins University Press |year=2004}}

</ref>  The interactions are not themselves building blocks, and consequently neither are their quanta. As one consequence, energy cannot always be related to matter: for example, photons possess energy (see [[Planck relation]]); however, photons commonly are distinguished from matter.<ref name=PhotonsMatter>

See for example,{{cite book |title=Quantum brain dynamics and consciousness |url=http://books.google.com/books?id=iNUvcniwvg0C&pg=PA62 |page=62 |author= Mari Jibu, Kunio Yasue |isbn=1556191839 |publisher=John Benjamins Publishing Company |year=1995}}, {{cite book |title=Nuclear and Particle Physics|page=125 |author=Brian Martin |isbn=0470742755 |publisher=Wiley |url=http://books.google.com/books?id=ws8QZ2M5OR8C&pg=PT143 |edition=2 |year=2009}} and {{cite book |title=Astrobiology: A Brief Introduction |author=Kevin W. Plaxco, Michael Gross |url=http://books.google.com/books?id=2JuGDL144BEC&pg=PA23 |page=23 |isbn=0801883679 |year=2006 |publisher=The Johns Hopkins University Press}}.

</ref> Also, mass cannot always be related to matter: certain particles are massive, such as the W-boson, but are not matter. Although the field quanta by themselves are not matter, in conjunction with a complex of building blocks like an atom or a [[hadron]], they contribute to the invariant mass of the combination, for example, through a binding energy. <ref name=Tipler0>

{{cite book |title=Modern Physics |author=PA Tipler & RA Llewellyn |url=http://books.google.com/books?id=tpU18JqcSNkC&pg=PA94 |pages=89-91 & 94-95 |isbn=0716743450 |year=2002 |publisher=Macmillan}}</ref><ref name=Spitzer>

{{cite book |Constituents of Matter |chapter=Particles |author=Peter Schmüser & Hartwig Spitzer |editor=L Bergmann ''et al.'' |url=http://books.google.com/books?id=mGj1y1WYflMC&printsec=frontcover#PPA773,M1  |isbn= 0849312027 |year=2002 |pages=773 ''ff'' |publisher=CRC Press}}

</ref>

Matter is commonly said to exist in four ''[[state of matter|states]]'' (or ''[[phase (matter)|phases]]''): [[solid]], [[liquid]], [[gas]] and [[Plasma (physics)|plasma]]. However, advances in experimental technique have realized other phases, previously only theoretical constructs, such as [[Bose–Einstein condensate]]s and [[Fermionic condensate]]s. A focus on an elementary-particle view of matter also leads to new phases of matter, such as the [[quark-gluon plasma]].<ref name=RHIC>

[http://www.bnl.gov/bnlweb/pubaf/pr/pr_display.asp?prid=05-38 RHIC Scientists Serve Up "Perfect" Liquid]

</ref>

In [[physics]] and [[chemistry]], matter and [[energy]] exhibit both [[wave]]-like and [[Subatomic particle|particle]]-like properties, the so-called [[wave-particle duality]] or [[matter wave]]. In this connection, physicists speak of ''matter fields'', and speak of particles as "quantum excitations of a mode of the matter field".<ref name=Davies>
{{cite book
 |author=P.C.W. Davies
 |title=The Forces of Nature
 |url=http://books.google.com/books?id=Av08AAAAIAAJ&pg=PA116&dq=%22matter+field%22&lr=&as_brr=0
 |page=116
 |publisher=Cambridge University Press
 |year=1979
 |isbn=052122523X
}}</ref><ref name=Weinberg>
{{cite book
 |author=S. Weinberg
 |title=The Quantum Theory of Fields
 |url=http://books.google.com/books?id=2oPZJJerMLsC&pg=PA5&dq=Weinberg+%22matter+field%22&lr=&as_brr=0#PPA5,M1
 |page=2
 |publisher=Cambridge University Press
 |year=1998
 |isbn=0521550025
}}</ref><ref name= Masujima>
{{cite book |title=Path Integral Quantization and Stochastic Quantization |author=Michio Masujima |url=http://books.google.com/books?id=OM15pk3ZHf0C&pg=PA103 |page=103 |isbn=3540878505 |publisher=Springer |year=2008}}
</ref>

In the realm of [[cosmology]], extensions of the term ''matter'' are invoked to include [[#Dark matter|dark matter]] and [[#Dark energy|dark energy]], concepts introduced to explain some odd phenomena of the [[observable universe]], such as the [[galactic rotation curve]]. These exotic forms of "matter" are not formed of the same building blocks that make up ordinary matter.<ref name=Majumdar>

{{cite journal |title=Dark matter&nbsp;— possible candidates and direct detection |author=Debasish Majumdar |url=http://arxiv.org/abs/hep-ph/0703310v1 |journal=ArXive preprint |year=2007 }}

</ref>

== Definitions ==
=== Common definition ===
[[Image:DNA chemical structure.svg|right|thumb|350px|The [[DNA molecule]] is an example of ''matter'' under the "atoms and molecules" definition. [[Hydrogen bond]]s are shown as dotted lines.]]
The common definition of matter is ''anything that has both [[mass]] and [[volume]] (occupies [[space]])''.<ref name=Walker>
{{cite book
 |author=S.M. Walker, A. King
 |title=What is Matter?
 |url=http://books.google.com/books?id=o7EquxOl4MAC&printsec=frontcover&dq=matter&lr=&as_brr=0#PPA7,M1
 |page=7
 |publisher=Lerner Publications
 |year=2005
 |isbn=0822551314
}}</ref><ref name=Hage>
{{cite book
 |author=J.Kenkel, P.B. Kelter, D.S. Hage
 |title=Chemistry: An Industry-based Introduction with CD-ROM
 |url=http://books.google.com/books?id=ADSjPRl_tgoC&pg=PA1&dq=matter+chemistry+properties&lr=&as_brr=0#PPA2,M1
 |page=2
 |publisher=CRC Press
 |isbn=1566703034
 |year=2000
 |quote=All basic science textbooks define ''matter'' as simply the collective aggregate of all material substances that occupy space and have mass or weight.
}}</ref> For example, a car would be said to be made of matter, as it occupies space, and has mass.

The observation that matter occupies space goes back to antiquity. However, an explanation for why matter occupies space is recent, and is argued to be a result of the [[Pauli exclusion principle]].<ref name=Peacock>
{{cite book
 |author=K.A. Peacock
 |title=The Quantum Revolution: A Historical Perspective
 |url=http://books.google.com/books?id=ITqnf5jdE5QC&pg=PA47&dq=%22prevents+matter+from+collapsing%22&lr=&as_brr=0
 |page=47
 |publisher=Greenwood Publishing Group
 |year=2008
 |isbn=031333448X
}}</ref><ref name=Kreiger>
{{cite book
 |author=M.H. Krieger
 |title=Constitutions of Matter: Mathematically Modeling the Most Everyday of Physical Phenomena
 |url=http://books.google.com/books?id=VduHhkzl-aQC&pg=PA22&dq=%22does+not+collapse+into+itself%22&lr=&as_brr=0#PPA22,M1
 |page=22
 |publisher=University of Chicago Press
 |year=1998
 |isbn=0226453057
}}</ref> Two particular examples where the exclusion principle clearly relates matter to the occupation of space are white dwarf stars and neutron stars, discussed further below.

=== Amount of substance ===
The international standards organization ''[[International Bureau of Weights and Measures|Bureau International des Poids et Mesures]]'' (BIPM) uses the terminology "amount of substance", rather than "matter". To quote the SI brochure:<ref>
{{cite web
 |title=SI brochure, Section 2.1.1.6&nbsp;– Mole
 |url=http://www.bipm.org/en/si/base_units/mole.html
 |publisher=[[BIPM]]
 |accessdate=2009-04-30
}}</ref> <blockquote>"Amount of substance is defined to be proportional to the number of specified elementary entities in a sample, the proportionality constant being a universal constant which is the same for all samples. The unit of amount of substance is called the mole, symbol mol, and the mole is defined by specifying the mass of carbon 12 that constitutes one mole of carbon 12 atoms. By international agreement this was fixed at 0.012 kg, i.e. 12 g.
*1. The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is "mol".
*2. When the mole is used, the elementary entities must be specified and may be atoms, molecules, ions, electrons, other particles, or specified groups of such particles."
</blockquote>

=== Atoms and molecules definition ===
A definition of "matter" that is based upon its physical and chemical ''structure'' is: ''matter is made up of [[atom]]s and [[molecule]]s''. This definition is consistent with the BIPM definition of "[[#Amount of substance|amount of substance]]" above, but is more specific about the constituents of matter (and unconcerned about the unit ''mole''). Further discussion appears below in the discussion [[#Discussion and background|section]] and in the description of the [[#Quarks and leptons definition|quarks and leptons definition]]. As an example of matter under this definition, genetic information is carried by a long molecule called [[DNA]], which is copied and inherited across generations. It is matter under this definition because it is made of atoms, not by virtue of having mass or occupying space. This definition can be extended to include charged atoms and molecules, so as to include [[Plasma (physics)|plasma]]s (gases of ions) and [[electrolyte]]s (ionic solutions), which are not obviously included in the atoms and molecules definition. Alternatively, one can adopt the ''protons, neutrons and electrons'' definition below.

=== Protons, neutrons and electrons definition ===
A definition of "matter" more fine-scale than the atoms and molecules definition is: ''matter is made up of what [[atom]]s and [[molecule]]s are made of'', meaning anything made of [[proton]]s, [[neutron]]s, and [[electron]]s.<ref name=DePodesta1>{{cite book |title=Understanding the Properties of Matter |author=Michael De Podesta |page=8 |url=http://books.google.com/books?id=h8BNvnR050cC&pg=PA8 |isbn=0415257883 |edition=2 |year=2002 |publisher=CRC Press}}</ref> This definition goes beyond atoms and molecules, however, to include substances made from these building blocks that are ''not'' simply atoms or molecules, for example [[white dwarf]] matter&nbsp;— typically, carbon and oxygen nuclei in a sea of degenerate electrons. At a microscopic level, the constituent "particles" of matter such as protons, neutrons and electrons obey the laws of quantum mechanics and exhibit wave-particle duality. At an even deeper level, protons and neutrons are made up of [[quarks]] and the force fields ([[gluons]]) that bind them together (see [[#Quarks and leptons definition|Quarks and leptons definition]] below).

=== Quarks and leptons definition ===
[[Image:Standard Model of Elementary Particles.svg|thumb|250px|Under the "quarks and leptons" definition, the elementary and composite particles made of the [[quarks]] (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 may be seen from 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 elementary [[fermions]], namely [[quark]]s and [[lepton]]s.''<ref name=Povh0>
{{cite book
 |author=B. Povh, K. Rith, C. Scholz, F. Zetsche, M. Lavelle
 |title=Particles and Nuclei: An Introduction to the Physical Concepts
 |edition=4th
 |chapter=Part I: Analysis: The building blocks of matter
 |url=http://books.google.com/books?id=rJe4k8tkq7sC&pg=PA9&dq=povh+%22building+blocks+of+matter%22&lr=&as_brr=0#PPA2,M1
 |publisher=Springer
 |year=2004
 |isbn=3540201688
}}</ref><ref>
{{cite journal
 |author=B. Carithers, P. Grannis
 |title=Discovery of the Top Quark
 |url=http://www.slac.stanford.edu/pubs/beamline/pdf/95iii.pdf
 |publisher=[[SLAC]]
 |journal=Beam Line
 |volume=25 |issue=3 |pages=4–16
 |year=1995
}}</ref> 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 the two types of elementary fermions. Carithers and Grannis state: ''Ordinary matter is composed entirely of first-generation particles, namely the ''u'' [up] and ''d'' [down] quarks, plus the electron and its neutrino.''<ref name=Carithers>See p.7 in {{cite journal
 |author=B. Carithers, P. Grannis
 |title=Discovery of the Top Quark
 |url=http://www.slac.stanford.edu/pubs/beamline/pdf/95iii.pdf
 |publisher=[[SLAC]]
 |journal=Beam Line
 |volume=25 |issue=3 |pages=4–16
 |year=1995
}}</ref> (By "first-generation" is meant the stable quarks and leptons. Higher "generations" decay into "first-generation" particles.<ref name=Green>

{{cite book |title=High P<sub>T</sub> (transverse momentum) physics at hadron colliders |author=Dan Green |url=http://books.google.com/books?id=6-7TE5N0vbIC&pg=PA23 |page=23 |isbn=0521835097 |publisher=Cambridge University Press |year=2005 }}

</ref>)

This definition of ordinary matter is more subtle than it first appears. There are two groups of particles. All the particles that make up matter, such as electrons, protons and neutrinos, are fermions. All the [[force carriers]] are bosons.<ref name=Smolin>
{{cite book
 |author=L. Smolin
 |title=The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next
 |url=http://books.google.com/books?id=z5rxrnlcp3sC&pg=PA67&dq=%22all+the+particles+that+make+up+matter%22&lr=&as_brr=0
 |page=67
 |publisher=Mariner Books
 |year=2007
 |isbn=061891868X
}}</ref> See the tabulation in the figure. The [[W and Z bosons]] that mediate the [[weak force]] are not made of quarks and leptons, and so are not ordinary matter, but do have mass.<ref name=Caso>The W boson mass is 80.43 GeV; see Figure 1 in {{cite web
 |author=C. Caso, M.W. Grünewald, A. Gurtu
 |title=The mass and width of the W boson
 |url=http://pdg.lbl.gov/2008/reviews/wmass_s043202.pdf
 |publisher=Particle Data Group
 |date=2008
 |accessdate=10 December 2008
}}</ref> 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 [[Quantum chromodynamics#The dynamics|QCD]]).<ref name=Aitchison>
{{cite book
 |author=I.J.R. Aitchison, A.J.G. Hey
 |title=Gauge Theories in Particle Physics
 |url=http://books.google.com/books?id=vLP7XN2pWlEC&pg=PA48&dq=%22source+particles+of+the+gluon+fields%22&lr=&as_brr=0#PPA48,M1
 |page=48
 |publisher=CRC Press
 |year=2004
 |isbn=0750308648
}}</ref> Basically, much of the mass of hadrons is the interaction energy of bound quarks. Thus, most of what composes the "mass" of ordinary matter is interquark interaction energy.<ref name=Povh>
{{cite book
 |author=B. Povh, K. Rith, C. Scholz, F. Zetsche, M. Lavelle
 |title=''op. cit.''
 |url=http://books.google.com/books?id=rJe4k8tkq7sC&pg=PA103&dq=%22interquark+interaction+energy%22&lr=&as_brr=0
 |page=103
 |publisher=Springer
 |location=Berlin
 |year=2004
 |isbn=3540201688
}}</ref> For example, "the gluonic forces binding three quarks (total mass 12.5 MeV) to make a nucleon contribute most of its mass of 938 MeV".<ref name=Green>
{{cite book
 |author=A.M. Green
 |title=Hadronic Physics from Lattice QCD
 |url=http://books.google.com/books?id=XUGVOJKHgKAC&pg=PA120&dq=%22gluonic+forces+binding%22&lr=&as_brr=0
 |page=120
 |publisher=World Scientific
 |year=2004
 |isbn=981256022X}}
</ref><ref name=Akai>

{{cite book |title=Condensed matter theories |volume=21 |page=296 |author= T Hatsuda |editor=Hisazumi Akai |url=http://books.google.com/books?id=PZdFi145170C&pg=PA296 |isbn=1600215017 |publisher=Nova Publishers |year=2008 |chapter = Quark-gluon plasma and QCD}}

</ref> In a similar vein, the quark gluon plasma is considered to be a state of matter, and obviously includes the gluons. The bottom line here is: in a complex such as an atom or a hadron, the matter in the complex is generally ''not'' the most significant source of the mass belonging to the complex.

=== Smaller building blocks? ===
“In the past, the search for building blocks of matter has led us to more and more 'elementary' entities&nbsp;– from the molecule to the atom, to the nucleus and electrons, to the nucleons, and eventually to the quarks. Have we completed this 'onion peeling' process ... ?”<ref name= Kirsh>

{{cite book |title=The particle hunters |author= Yuval Ne̕eman, Y. Kirsh |url=http://books.google.com/books?id=K4jcfCguj8YC&pg=PA276 |page=276 |isbn=0521476860 |year=1996 |publisher=Cambridge University Press |edition=2}}

</ref>  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''. <ref name=Staley>

{{cite book |url=http://books.google.com/books?id=DLt_fcBYynAC&pg=PA8 |title=The evidence for the top quark |chapter=Origins of the third generation of matter |author=Kent Wade Staley |page =8 |isbn=0521827108 |publisher=Cambridge University Press |year=2004}}

</ref> “... the most natural explanation to the existence of higher generations of quarks and leptons is that they correspond to excited states of the first generation, and experience suggests that excited systems must be composite.”<ref name= Kirsh/>

=== Discussion and background ===
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. [[James Clerk Maxwell]] discussed matter in his work ''Matter and Motion''.<ref name=Maxwell>
{{cite book
 |author=J.C. Maxwell
 |title=Matter and Motion
 |url=http://books.google.com/books?id=MWoOAAAAIAAJ&printsec=frontcover&dq=matter&lr=&as_brr=0#PPA18,M1
 |page=18
 |publisher=Society for Promoting Christian Knowledge
 |year=1876
}}</ref> He carefully separates "matter" from [[space]] and [[time]], and defines it in terms of the object referred to in [[Newton's first law of motion]]. 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.<ref name=Levere>
{{cite book
 |author=T.H. Levere
 |title=Affinity and Matter: Elements of Chemical Philosophy, 1800-1865
 |chapter=Introduction
 |url=http://books.google.com/books?id=gKSDWsE8fZMC&printsec=frontcover&dq=matter&lr=&as_brr=0#PPA11,M1
 |publisher=Taylor & Francis
 |year=1993
 |isbn=2881245838
}}</ref> A textbook discussion from 1870 suggests matter is what is made up of atoms:<ref name=Barker>
{{cite book
 |author=G.F. Barker
 |title=A Text Book of Elementary Chemistry: Theoretical and Inorganic
 |chapter=Introduction
 |url=http://books.google.com/books?id=B6Yz6eW-5joC
 |page=2
 |publisher=John P. Morton and Company
 |year=1870
}}
</ref><blockquote>Three divisions of matter are recognized in science: masses, molecules and atoms. <br />A Mass of matter is any portion of matter appreciable by the senses. <br />A Molecule is the smallest particle of matter into which a body can be divided without losing its identity. <br />An Atom is a still smaller particle produced by division of a molecule. </blockquote>

Rather than simply having the attributes of mass and occupying space, matter was held to have chemical and electrical properties. The famous physicist [[J. J. Thomson]] wrote about the "constitution of matter" and was concerned with the possible connection between matter and electrical charge.<ref name=Thomson>
{{cite book
 |author=J.J. Thomson
 |title=Electricity and Matter
 |chapter=Preface
 |url=http://books.google.com/books?id=2AaToepvKoEC&printsec=titlepage#PPP13,M1
 |publisher=A. Constable
 |year=1909
}}</ref> There is an entire literature concerning the "structure of matter", ranging from the "electrical structure" in the early 20th century,<ref name=Richardson>
{{cite book
 |author=O.W. Richardson
 |title=The Electron Theory of Matter
 |chapter=Chapter 1
 |url=http://books.google.com/books?id=RpdDAAAAIAAJ&printsec=frontcover&dq=matter&lr=&as_brr=0#PPA1,M1
 |publisher=The University Press
 |year=1914
}}</ref> to the more recent "quark structure of matter", introduced today with the remark: ''Understanding the quark structure of matter has been one of the most important advances in contemporary physics.''<ref name=Jacob>
{{cite book
 |url=http://books.google.com/books?id=iQ1e2a9bPikC&printsec=frontcover&dq=matter&lr=&as_brr=0#PPA1,M1
 |title=The Quark Structure of Matter
 |author=M. Jacob
 |publisher=World Scientific
 |year=1992
 |isbn=9810236875
}}<!-- |title=The Quark Structure of Matter: proceedings of a topical European meeting in the Rhine Valley : Strasbourgh-Karlsruhe, 26 September-1 October 1985--></ref>  In this connection, physicists speak of ''matter fields'', and speak of particles as "quantum excitations of a mode of the matter field".<ref name=Davies>
{{cite book
 |author=P.C.W. Davies
 |title=The Forces of Nature
 |url=http://books.google.com/books?id=Av08AAAAIAAJ&pg=PA116&dq=%22matter+field%22&lr=&as_brr=0
 |page=116
 |publisher=Cambridge University Press
 |year=1979
 |isbn=052122523X
}}</ref><ref name=Weinberg>
{{cite book
 |author=S. Weinberg
 |title=The Quantum Theory of Fields
 |url=http://books.google.com/books?id=2oPZJJerMLsC&pg=PA5&dq=Weinberg+%22matter+field%22&lr=&as_brr=0#PPA5,M1
 |page=2
 |publisher=Cambridge University Press
 |year=1998
 |isbn=0521550025
}}</ref> And here is a quote from De Sabbata and Gasperini: "With the word "matter" we denote, in this context, the sources of the interactions, that is [[spinor field]]s (like [[quark]]s and [[lepton]]s), which are believed to be the fundamental components of matter, or [[Bosonic field|scalar field]]s, like the [[Higgs particle]]s, which are used to introduced mass in a [[gauge theory]] (and which, however, could be composed of more fundamental fermion fields)."<ref name=Sabbata>
{{cite book
 |author=V. De Sabbata, M. Gasperini
 |title=Introduction to Gravitation
 |url=http://books.google.com/books?id=7sJ6m8s0_ccC&pg=PA293&dq=Weinberg+%22matter+field%22&lr=&as_brr=0
 |page=293
 |publisher=World Scientific
 |year=1985
 |isbn=9971500493
}}</ref>

The term "matter" is used throughout physics in a bewildering variety of contexts: for example, one refers to "[[condensed matter physics]]",<ref name=Chaikin>
{{cite book
 |author=P.M. Chaikin, T.C. Lubensky
 |title=Principles of Condensed Matter Physics
 |url=http://books.google.com/books?id=P9YjNjzr9OIC&printsec=frontcover&dq=matter&lr=&as_brr=0#PPR17,M1
 |page=xvii
 |publisher=Cambridge University Press
 |year=2000
 |isbn=0521794501
}}</ref> "elementary matter",<ref name=Greiner>
{{cite book
 |author=W. Greiner, M.G. Itkis
 |title=Structure and Dynamics of Elementary Matter: Proceedings of the NATO Asi on Structure and Dynamics of Elementary Matter, Camyuva-Kemer (Antalya), Turkey, from 22 September to 2 October 2003
 |url=http://books.google.com/books?id=ORyJzhAzpUgC&printsec=frontcover&dq=matter&lr=&as_brr=0#PPR12,M1
 |publisher=Springer
 |year=2003
 |isbn=1402024452
}}</ref> "[[parton]]ic" matter, "[[dark matter|dark]]" matter, "[[antimatter|anti]]"-matter, "[[strange matter|strange]]" matter, and "[[nuclear matter|nuclear]]" matter. In discussions of matter and [[antimatter]], normal matter has been referred to by [[Hannes Alfvén|Alfvén]] as ''koinomatter''.<ref>
{{cite book
 |author=P. Sukys
 |title=Lifting the Scientific Veil: Science Appreciation for the Nonscientist
 |url=http://books.google.com/books?id=WEM4hqxJ-xYC&pg=PR23&dq=isbn=0847696006#PPA87,M1
 |page=87
 |publisher=Rowman & Littlefield
 |year=1999
 |isbn=0847696006
}}</ref> It is fair to say that in [[physics]], there is no broad consensus as to an exact definition of matter, and the term "matter" usually is used in conjunction with some modifier.

== Phases of ordinary matter ==
[[Image:Liquid nitrogen dsc04496.jpg|thumb|right|250px| A solid metal cup containing [[liquid nitrogen]] slowly evaporating into [[nitrogen|gaseous nitrogen]]. [[Evaporation]] is the [[phase transition]] from a liquid state to a gas state.]]
[[Image:Phase diagram for pure substance.JPG|thumb|250px||Phase diagram for a typical substance at a fixed volume. Vertical axis is ''P''ressure, horizontal axis is ''T''emperature.  The green line marks the [[freezing point]] (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 (thermodynamics)|critical point]] there is no detectable difference between the phases. The dotted line shows the [[Water (molecule)#Density of water and ice|anomalous behavior of water]]: ice melts at constant temperature with increasing pressure.<ref name=Logan>
{{cite book
 |author=S.R. Logan
 |title=Physical Chemistry for the Biomedical Sciences
 |url=http://books.google.com/books?id=LA_8QzoCNMsC&pg=PA110&dq=water+%22phase++diagram%22&lr=&as_brr=0
 |pages=110–111
 |publisher=CRC Press
 |year=1998
 |isbn=0748407103
}}</ref>]]
{{basis|Phase (matter)}}
{{sienook|Phase diagram|State of matter}}
In [[bulk]], matter can exist in several different forms, or states of aggregation, known as ''[[phase (matter)|phases]]'',<ref name=Collings>
{{cite book
 |author=P.J. Collings
 |title=Liquid Crystals: Nature's Delicate Phase of Matter
 |chapter=Chapter 1: States of Matter
 |url=http://books.google.com/books?id=NE1RWiGXtdUC&printsec=frontcover#PPA1,M1
 |publisher=Princeton University Press
 |year=2002
 |isbn=0691086729
}}</ref> depending on ambient [[pressure]], [[temperature]] and [[volume]].<ref name=Trevena>
{{cite book
 |author=D.H. Trevena
 |title=The Liquid Phase
 |chapter=Chapter 1.2 ''Changes of phase''
 |url=http://books.google.com/books?id=oOkOAAAAQAAJ&pg=PA1&dq=phase+of+matter&lr=&as_brr=0&as_pt=ALLTYPES#PPA1,M1
 |publisher=Taylor & Francis
 |year=1975
}}</ref> A phase is a form of matter that has a relatively uniform chemical composition and physical properties (such as [[density]], [[specific heat]], [[refractive index]], and so forth).  These phases include the three familiar ones ([[solid]]s, [[liquid]]s, and [[gas]]es), as well as more exotic states of matter ( such as [[plasma (physics)|plasma]]s, [[superfluid]]s, [[supersolid]]s, [[Bose-Einstein condensate]]s, ...). A ''[[fluid]]'' may be a liquid, gas or plasma. There are also [[paramagnetism|paramagnetic]] and [[ferromagnetism|ferromagnetic]] phases of [[magnetic material]]s. As conditions change, matter may change from one phase into another. These phenomena are called [[phase transition]]s, and are studied in the field of [[thermodynamics]]. In nanomaterials, the vastly increased ratio of surface area to volume results in matter that can exhibit properties entirely different from those of bulk material, and not well described by any bulk phase (see [[nanomaterials]] for more details).

Phases are sometimes called ''states of matter'', but this term can lead to confusion with [[thermodynamics|thermodynamic states]]. For example, two gases maintained at different pressures are in different ''thermodynamic states'' (different pressures), but in the same ''phase'' (both are solids).

=== Solid ===
{{Basis|Solid}}

Solids are characterized by a tendency to retain their structural integrity; if left on their own, they will not spread in the same way gas or liquids would. Many solids, like rocks and concrete, have very high [[hardness]] and [[rigidity]] and will tend to break or shatter when subject to various forms of [[stress (mechanics)|stress]], but others like [[steel]] and [[paper]] are more [[flexible]] and will bend. Solids are often composed of [[crystal]]s, [[glass]]es, or [[long chain molecule]]s (e.g. [[rubber]] and [[paper]]). Some solids are [[amorphous]] such as [[glass]]. A common example of a solid is the solid form of water, ''ice''.

=== Liquid ===
{{Basis|Liquid}}
In a liquid, the constituents frequently are touching, but able to move around each other. So unlike a gas, it has [[cohesion (chemistry)|cohesion]] and [[viscosity]]. Compared to a solid, the forces holding constituents together are weaker, and it is not rigid, but adapts a shape decided by its container. Liquids are hard to compress. A common example is ''water''.

=== Gas ===
{{Basis|Gas}}
A gas is a state of aggregation without cohesion; a vapor. Thus a gas has no resistance to changing shape (beyond the inertia of its constituents, which have to be knocked aside). The distance between constituent particles is flexible, determined, for example, by the size of a container and the number of particles, not by internal forces. A common example is the vapor form of water, ''steam''.

=== Plasma ===
{{basis|Plasma (physics)|Astrophysical plasma}}
Plasma is a fourth state of matter consisting of an overall charge-neutral mix of electrons, ions and neutral atoms.<ref name=Makabe>
{{cite book
 |author=T. Makabe, Z. Petrović
 |title=Plasma Electronics: Applications in Microelectronic Device Fabrication
 |url=http://books.google.com/books?id=BpRhkONZEdQC&pg=PA1
 |page=1
 |publisher=CRC Press
 |year=2006
 |isbn=0750309768
}}</ref> The plasma exhibits behavior peculiar to long range [[Coulomb's law|Coulomb forces]] in which the particles move in electromagnetic fields generated by and self-consistent with their own motions. The sun and stars are plasmas, as is the Earth's ionosphere, and plasmas occur in neon signs. Plasmas of deuterium and tritium ions are used in [[Fusion power|fusion]] reactions.<ref name=Birdsall>
{{cite book
 |author=C.K. Birdsall, A.B. Langdon
 |title=Plasma Physics via Computer Simulation
 |url=http://books.google.com/books?id=S2lqgDTm6a4C&pg=PAxvii#PPR17,M1
 |page=xvii
 |publisher=CRC Press
 |year=2005
 |isbn=0750310251
}}</ref> The term ''plasma'' was applied for the first time by [[Lewi Tonks|Tonks]] and [[Irving Langmuir|Langmuir]] in 1929, to the inner regions of a glowing ionized gas produced by electric discharge in a tube.<ref name=Bittencourt>
{{cite book
 |author=J.A. Bittencourt
 |title=Fundamentals of Plasma Physics
 |url=http://books.google.com/books?id=qCA64ys-5bUC&pg=PA1
 |page=2
 |publisher=Springer
 |year=2004
 |isbn=0387209751
}}</ref>

=== Bose–Einstein condensate ===
{{Basis|Bose–Einstein condensate}}

This state of matter was first discovered by [[Satyendra Nath Bose]], who sent his work on statistics of photons to [[Albert Einstein]] for comment. Following publication of Bose's paper, Einstein extended his treatment to massive particles fixed in number, and predicted this fifth state of matter in 1925. Bose–Einstein condensates were first realized experimentally by several different scientific groups in 1995 for rubidium, sodium, and lithium, using a combination of laser and evaporative cooling.<ref name=Fraser>
{{cite book
 |author=G. Fraser
 |title=The New Physics for the Twenty-first Century
 |url=http://books.google.com/books?id=0idvEIXwfxsC&pg=PA238&dq=%22Bose-Einstein+condensate%22&lr=&as_brr=0#PPA238,M1
 |page=238
 |publisher=Cambridge University Press
 |year=2006
 |isbn=0521816009
}}</ref>  Bose–Einstein condensation for atomic hydrogen was achieved in 1998.<ref name=Pethick>
{{cite book
 |author=C. Pethick, H. Smith
 |title=Bose–Einstein Condensation in Dilute Gases
 |chapter=Introduction
 |url=http://books.google.com/books?id=K_KPhpTTmkEC&printsec=frontcover&dq=%22Bose-Einstein+condensate%22&lr=&as_brr=0#PPA1,M1
 |publisher=Cambridge University Press
 |year=2002
 |isbn=0521665809
}}</ref>

The Bose–Einstein condensate is a liquid-like [[superfluid]] that occurs in at low temperatures in which all atoms occupy the same quantum state. In low-density systems, it occurs at or below 10<sup>−5</sup>&nbsp;K.<ref name=Pethick/>

=== Fermionic condensate ===
{{basis|Fermionic condensate}}
{{sienook|Superconductor|BCS theory}}
A fermonic condensate is a superfluid phase formed by fermionic particles at low temperatures. It is closely related to the Bose-Einstein condensate under similar conditions. Unlike the Bose-Einstein condensates, fermionic condensates are formed using fermions instead of bosons. The earliest recognized fermionic condensate described the state of electrons in a superconductor; the physics of other examples including recent work with fermionic atoms is analogous. The first atomic fermionic condensate was created by [[Deborah S. Jin]] in 2003.<ref name=Jin>
{{cite arXiv
 |author=M. Greiner, C.A. Regal, D.S. Jin
 |title=A molecular Bose-Einstein condensate emerges from a Fermi sea
 |eprint=cond-mat/0311172v1
 |class=cond-mat.stat-mech
 |year=2003
}}</ref> These atomic fermionic condensates are studied at temperatures in the vicinity of 50-350&nbsp;nK.<ref name=Zwierlein>
{{cite arXiv
 |author=M.W. Zwierlein, C.H. Schunck, A. Schirotzek, W. Ketterle
 |title=Direct Observation of the Superfluid Phase Transition in Ultracold Fermi Gases
 |eprint=cond-mat/0605258v1
 |class=cond-mat.supr-con
 |year=2006
}}</ref>

A hypothetical fermionic condensate that appears in theories of massless fermions with chiral symmetry breaking is the ''chiral condensate'' or the ''quark condensate''.<ref name=Shuryak>
{{cite book
 |author=E.V. Shuryak
 |title=The QCD Vacuum, Hadrons and Superdense Matter
 |url=http://books.google.com/books?id=rbcQMK6a6ekC&pg=PA182&dq=%22chiral+condensate%22&lr=&as_brr=0&as_pt=ALLTYPES#PPA159,M1
 |page=159
 |publisher=World Scientific
 |year=2004
 |isbn=9812385746
}}</ref>

[[Image:Neutron star cross-section.JPG|280px|thumb|A model of a neutron star's internal structure. (Other models exist.<ref name=Haensel> {{cite book |author=P. Haensel, A.Y. Potekhin, A.Û. Potehin, D.G. Yakovlev
 |title=Neutron Stars
 |url=http://books.google.com/books?id=iIrj9nfHnesC&pg=PA52&dq=neutron+star+crystalline+mantle&lr=&as_brr=0#PPA11,M1
 |page=11
 |publisher=Springer
 |year=2007
 |isbn=0387335439
}}</ref>) At a depth of about 10&nbsp;km the core becomes a superfluid liquid primarily of neutrons. The section at the left shows density vs. radius. Data from Luminet ''et al.''<ref name=Luminet0>
{{cite book
 |author=J.-P. Luminet, A. Bullough, A. King
 |title=Black Holes
 |url=http://books.google.com/books?id=WRexJODPq5AC&pg=PA55&dq=isbn=0521409063&lr=&as_brr=0#PPA111,M1
 |page=111, Figure 25
 |publisher=Cambridge University Press
 |year=1992
 |isbn=0521409063
}}</ref>]]

=== Core of a neutron star ===
{{basis|Neutron star|Pulsar}}
{{sienook|Magnetar}}
Because of its extreme density, the core of a neutron star falls under no other state of matter. While a white dwarf is about as massive as the sun (up to 1.4 solar masses, the [[Chandrasekhar limit]]), the Pauli exclusion principle prevents its collapse to smaller radius, and it becomes an example of [[#Degenerate matter|degenerate matter]]. In contrast, neutron stars are between 1.5 and 3 solar masses, and achieve such density that the protons and electrons are crushed to become neutrons. Neutrons are fermions, so further collapse is prevented by the exclusion principle, forming so-called [[Degenerate matter#Neutron degeneracy|neutron degenerate matter]].<ref name=Danielson>
{{cite book
 |author=D.R. Danielson
 |title=The Book of the Cosmos
 |url=http://books.google.com/books?id=zwIN_-rqrL4C&pg=PA453&dq=exclusion+principle+%22neutron+star%22&lr=&as_brr=0#PPA455,M1
 |page=455
 |publisher=Da Capo Press
 |year=2001
 |isbn=0738204986
}}</ref><ref name=Strain>
{{cite book
 |author=M.A. Strain
 |title=Cosmic Entity
 |url=http://books.google.com/books?id=Ic7YLrm0xvAC&pg=PA50&dq=matter+%22exclusion+principle%22&lr=&as_brr=0
 |page=50
 |publisher=iUniverse (self-published)
 |year=2004
 |isbn=0595301258
}}</ref>

[[File:Phases of Nuclear Matter.JPG|thumb|280px|Phases of nuclear matter; Compare with Siemens & Jensen.<ref name=Seimens> {{cite book |title=Elements Of Nuclei: Many-body Physics With The Strong Interaction |url=http://books.google.com/books?id=z-8vuyAqT9MC&pg=PA347 |author=Phillip John Siemens, Aksel S. Jensen |isbn=0201627310 |publisher=Westview Press |year=1994}}</ref> ]]
]

=== Quark-gluon plasma ===
{{basis|Quark-gluon plasma|QCD matter}}
{{sienook|Gluon|Hadron}}
Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei. The quark-gluon plasma is a hypothetical phase of matter, a phase of matter as yet not observed, supposed to exist in the early universe and to have evolved into a hadronic-gas phase.<ref name=Letessier>

{{cite book |title=Hadrons and quark-gluon plasma |author=Jean Letessier, Johann Rafelski |url=http://books.google.com/books?id=vSnFPyQaSTsC&printsec=frontcover#PPR11,M1 |page=xi |isbn=0521385369 |publisher=Cambridge University Press |year=2002}}

</ref> At extremely high energy the [[strong force]] is anticipated to become so weak that the atomic nuclei break down into a bunch of loose quarks, which distinguishes the quark-gluon phase from normal plasma. In collisions of relativistic heavy ions, a phase transition occurs from the nuclear, hadronic phase to a matter phase consisting of quarks and gluons. So far, experimental results have shown that instead of a weakly interacting plasma, an almost ideal liquid is produced.<ref name=RHIC>

[http://www.bnl.gov/bnlweb/pubaf/pr/pr_display.asp?prid=05-38 RHIC Scientists Serve Up "Perfect" Liquid]

</ref><ref name=Zajc>

{{cite journal |title=The fluid nature of quark-gluon plasma |author= WA Zajc |journal=Nuclear Physics A |year=2008 |volume=805 |pages=283c-294c |doi=10.1016/j.nuclphysa.2008.02.285 |url=http://arxiv.org/PS_cache/arxiv/pdf/0802/0802.3552v1.pdf}}

</ref> An animation is found at [http://real.bnl.gov/ramgen/bnl/RHIC_animation.rm Gold ion collision @ RHIC].

=== Transparent Aluminum ===
{{Basis|Transparent aluminum}}

In [[2009]], scientists from [[Oxford University]] led an international team in using the FLASH laser synchrotron in [[Hamburg, Germany]] to create a new state of matter, transparent [[aluminum]]. Using a short pulse from the FLASH laser, they removed a core electron from each aluminium atom, but did not destroy or disrupt the metal’s crystalline structure. What resulted was an aluminum that was almost invisible to [[ultraviolet radiation]]. Scientists involved in the discovery suggest that this will aid in further research concerning [[planetary science]] and [[nuclear fusion]]. The effect on the aluminum lasted for 40 [[femtoseconds]].<ref name=ScienceDaily>
{{cite web
 |url=http://www.sciencedaily.com/releases/2009/07/090727130814.htm
 |title=Transparent Aluminum Is ‘New State Of Matter’
 |accessdate=2009-07-30
}}</ref> 

A concept of transparent aluminum was seen in [[Star Trek IV]].

== Structure of ordinary matter ==

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

=== Quarks ===
{{Basis|Quark}}
Quarks are a particles of [[fermion|spin-{{frac|1|2}}]], implying that they are [[fermion]]s. They carry an [[electric charge]] of −{{frac|1|3}}&nbsp;[[elementary charge|e]] (down-type quarks) or +{{frac|2|3}}&nbsp;e (up-type quarks). For comparison, an electron has a charge of −1&nbsp;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]].

{| class="wikitable" border="1" style="margin:0 auto; text-align:center;"
|+Quark properties<ref>
{{cite journal
 |author=C. Amsler ''et al''. (Particle Data Group)
 |link=http://pdg.lbl.gov/2008/tables/rpp2008-sum-quarks.pdf
 |journal=Physics Letters
 |volume='''B667''' |page=1
 |year=2008
}}</ref>
! Name !! Symbol !! Spin !! Electric charge<br />([[elementary charge|e]]) !! Mass<br />([[electronvolt|MeV]]/[[speed of light|c]]<sup>2</sup>) !! Mass comparable to !! Antiparticle !! Antiparticle<br />symbol
|-
|colspan="7"| Up-type quarks
|-
| Up
| {{SubatomiesePartikel|Up quark}}
| {{frac|1|2}}
| +{{frac|2|3}}
| 1.5 to 3.3
| ~ 5 electrons
| Antiup
| {{SubatomiesePartikel|Up antiquark}}
|-
| Charm
| {{SubatomiesePartikel|Charm quark}}
| {{frac|1|2}}
| +{{frac|2|3}}
| 1160 to 1340
| ~ 1 proton
| Anticharm
| {{SubatomiesePartikel|Charm antiquark}}
|-
| Top
| {{SubatomiesePartikel|Top quark}}
| {{frac|1|2}}
| +{{frac|2|3}}
| 169,100 to 173,300
| ~ 180 protons or<br />~ 1 tungsten atom
| Antitop
| {{SubatomiesePartikel|Top antiquark}}
|-
|colspan="7"| Down-type quarks
|-
| Down
| {{SubatomiesePartikel|Down quark}}
| {{frac|1|2}}
| −{{frac|1|3}}
| 3.5 to 6.0
| ~ 10 electrons
| Antidown
| {{SubatomiesePartikel|Down antiquark}}
|-
| Strange
| {{SubatomiesePartikel|Strange quark}}
| {{frac|1|2}}
| −{{frac|1|3}}
| 70 to 130
| ~ 200 electrons
| Antistrange
| {{SubatomiesePartikel|Strange antiquark}}
|-
| Bottom
| {{SubatomiesePartikel|Bottom quark}}
| {{frac|1|2}}
| −{{frac|1|3}}
| 4130 to 4370
| ~ 5 protons
| Antibottom
| {{SubatomiesePartikel|Bottom antiquark}}
|}

[[Image:Quark structure proton.svg|thumb|120px|Quark structure of a proton: 2 up quarks and 1 down quark.]]
==== Baryonic matter ====
{{basis|Baryon}}
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]] is usually used to refer to triquarks&nbsp;— 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 star]]s. 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 [[telescope]]s (that is, matter that may be visible because light could reach us from it), is made of baryionic matter. About 23% is dark matter, and about 72% is dark energy.<ref name="NASA-WMAP">
{{cite web
 |title=Five Year Results on the Oldest Light in the Universe
 |url=http://map.gsfc.nasa.gov/m_mm.html
 |publisher=NASA
 |year=2008
 |accessdate=2 May 2008
}}</ref>

[[File:Size IK Peg.svg|250px|thumb|A comparison between the white dwarf [[IK Pegasi]] B (center), its A-class companion IK Pegasi A (left) and the Sun (right). This white dwarf has a surface temperature of 35,500&nbsp;K.]]

==== Degenerate matter ====
{{basis|Degenerate matter}}
In physics, '''degenerate matter''' refers to the ground state of a gas of fermions at a temperature near absolute zero.<ref name=Goldberg0>
{{cite book
 |author=H.S. Goldberg, M.D. Scadron
 |title=Physics of stellar evolution and cosmology
 |url=http://books.google.com/books?id=NowVde8kzIoC&pg=PA207&dq=matter+%22exclusion+principle%22&lr=&as_brr=0#PPA202,M1
 |page=202
 |publisher=Taylor & Francis
 |year=1987
 |isbn=0677055404
}}</ref> The [[Pauli exclusion principle]] requires that only two fermions can occupy a quantum state, one spin-up and the other spin-down. Hence, at zero temperature, the fermions fill up sufficient levels to accommodate all the available fermions, and for the case of many fermions the maximum kinetic energy called the [[Fermi energy]] and the pressure of the gas becomes very large and dependent upon the number of fermions rather than the temperature, unlike normal states of matter.

Degenerate matter is thought to occur during the evolution of heavy stars.<ref name=Goldberg1>
{{cite book
 |author=H.S. Goldberg, M.D. Scadron
 |title=''op. cit.''
 |url=http://books.google.com/books?id=NowVde8kzIoC&pg=PA207&dq=matter+%22exclusion+principle%22&lr=&as_brr=0#PPA233,M1
 |page=233
 |publisher=Gordon and Breach
 |location=New York
 |year=1987
 |isbn=0677055404
}}</ref> The demonstration by [[Subrahmanyan Chandrasekhar]] that [[white dwarf star]]s have a maximum allowed mass because of the exclusion principle caused a revolution in the theory of star evolution.<ref name=Luminet>
{{cite book
 |author=J.-P. Luminet, A. Bullough, A. King
 |title=Black Holes
 |url=http://books.google.com/books?id=WRexJODPq5AC&pg=PA72&dq=matter+%22exclusion+principle%22&lr=&as_brr=0#PPA75,M1
 |page=75
 |publisher=Cambridge University Press
 |year=1992
 |isbn=0521409063
}}</ref>

Degenerate matter includes the part of the universe that is made up of neutron stars and white dwarfs.

==== Strange matter ====
{{basis|Strange matter}}
'''Strange matter''' is a particular form of [[quark matter]], usually thought of as a 'liquid' of [[up quark|up]], [[down quark|down]], and [[strange quark|strange]] [[quark]]s. It is to be contrasted with [[nuclear matter]], which is a liquid of [[neutron]]s and [[proton]]s (which themselves are built out of up and down quarks), and with non-strange quark matter, which is a quark liquid containing only up and down quarks. At high enough density, strange matter is expected to be [[color superconductor|color superconducting]]. Strange matter is hypothesized to occur in the core of [[neutron star]]s, or, more speculatively, as isolated droplets that may vary in size from [[femtometer]]s ([[strangelet]]s) to kilometers ([[quark star]]s).

===== 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.
# 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).
# The narrower meaning is quark matter that is <em>more stable than nuclear matter</em>. The idea that this could happen is the "strange matter hypothesis" of Bodmer <ref>A. Bodmer "Collapsed Nuclei" [http://prola.aps.org/abstract/PRD/v4/i6/p1601_1 Phys. Rev. D4, 1601 (1971)]</ref> and Witten <ref>E. Witten, "Cosmic Separation Of Phases" [http://prola.aps.org/abstract/PRD/v30/i2/p272_1 Phys. Rev. D30, 272 (1984)]</ref>. In this definition, the critical pressure is zero: the true ground state of matter is <em>always</em> quark matter. The nuclei that we see in the matter around us, which are droplets of nuclear matter, are actually [[metastable]], and given enough time (or the right external stimulus) would decay into droplets of strange matter, i.e. [[strangelet]]s.

=== Leptons ===
{{Basis|Lepton}}

Leptons are a particles of [[fermion|spin-{{frac|1|2}}]], meaning that they are [[fermion]]s. They carry an [[electric charge]] of −1&nbsp;[[elementary charge|e]] (electron-like leptons) or 0&nbsp;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.

{| class="wikitable" border="1" style="margin:0 auto; text-align:center;"
|+Lepton properties
! Name !! Symbol !! Spin !! Electric charge<br />([[elementary charge|e]]) !! Mass<br />([[electronvolt|MeV]]/[[speed of light|c]]<sup>2</sup>) !! Mass comparable to !!Antiparticle !! Antiparticle<br />symbol
|-
|colspan="7"| Charged leptons<ref>
{{cite journal
 |author=C. Amsler ''et al''. (Particle Data Group)
 |link=http://pdg.lbl.gov/2008/tables/rpp2008-sum-leptons.pdf
 |journal=Physics Letters
 |volume='''B667''' |page=1
 |year=2008
}}</ref>
|-
| Electron
| {{SubatomiesePartikel|electron}}
| {{frac|1|2}}
| −1
| 0.5110
| 1 electron
| Antielectron<br />(positron)
| {{SubatomiesePartikel|antielectron}}
|-
| Muon
| {{SubatomiesePartikel|muon}}
| {{frac|1|2}}
| −1
| 105.7
| ~ 200 electrons
| Antimuon
| {{SubatomiesePartikel|antimuon}}
|-
| Tauon
| {{SubatomiesePartikel|tauon}}
| {{frac|1|2}}
| −1
| 1,777
| ~ 2 protons
| Antitauon
| {{SubatomiesePartikel|antitauon}}
|-
|colspan="7"| Neutrinos<ref>
{{cite journal
 |author=C. Amsler ''et al''. (Particle Data Group)
 |link=http://pdg.lbl.gov/2008/listings/s066.pdf
 |journal=Physics Letters
 |volume='''B667''' |page=1
 |year=2008
}}</ref>
|-
| Electron neutrino
| {{SubatomiesePartikel|Electron neutrino}}
| {{frac|1|2}}
| 0
| < 0.000460
| Less than a thousandth of an electron
| Electron antineutrino
| {{SubatomiesePartikel|Electron antineutrino}}
|-
| Muon neutrino
| {{SubatomiesePartikel|Muon neutrino}}
| {{frac|1|2}}
| 0
| < 0.19
| Less than half of an electron
| Muon antineutrino
| {{SubatomiesePartikel|Muon antineutrino}}
|-
| Tauon neutrino<br />(or tau neutrino)
| {{SubatomiesePartikel|Tau neutrino}}
| {{frac|1|2}}
| 0
| < 18.2
| Less than ~ 40 electrons
| Tauon antineutrino<br />(or tau antineutrino)
| {{SubatomiesePartikel|Tau antineutrino}}
|}

== Antimatter ==
{{basis|Antimatter}}
{{unsolved|physics|[[Baryon asymmetry]]. Why is there far more matter than antimatter in the observable universe? }}
In [[particle physics]] and [[quantum chemistry]], '''antimatter''' is matter that is composed of the [[antiparticle]]s of those that constitute ordinary matter. If a particle and its antiparticle come into contact with each other, the two [[annihilation|annihilate]]; that is, they may both be converted into other particles with equal [[energy]] in accordance with [[Einstein]]'s equation ''{{nowrap|[[E=MC2|E = mc<sup>2</sup>]]}}''. These new particles may be high-energy [[photon]]s ([[gamma ray]]s) 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.

Antimatter is not found naturally on Earth, except very briefly and in vanishingly small quantities (as the result of [[radioactive decay]] or [[cosmic ray]]s). This is because antimatter which 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, and whether other places are almost entirely antimatter 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 the charge parity (or [[CP symmetry]]) violation. CP symmetry violation can be obtained from the Standard Model,<ref name=CP>

{{cite book |title=Revealing the hidden nature of space and time |url=http://books.google.com/books?id=oTedc3rTDr4C&pg=PA46 |page=46 |isbn=0309101948 |year=2006 |author=National Research Council (U.S.)|publisher=National Academies Press }}

</ref> but at this time the apparent [[asymmetry]] of matter and antimatter in the visible universe is one of the great [[unsolved problems in physics]]. Possible processes by which it came about are explored in more detail under [[baryogenesis]].

== Other types of matter ==
[[Image: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.<ref name=Ostriker>
{{cite arXiv
 |author=J.P. Ostriker, P.J. Steinhardt
 |title=New Light on Dark Matter
 |eprint=astro-ph/0306402
 |class=astro-ph
 |year=2003
}}</ref>  For more information, see [http://map.gsfc.nasa.gov/news/index.html NASA].]]

Ordinary matter, in the quarks and leptons definition, constitutes about 4% of the [[mass-energy equivalence|energy]] of the [[observable universe]]. The remaining energy is theorized to be due to exotic forms, of which 23% is [[dark matter]]<ref name=Pretzl>
{{cite book
 |author=K. Pretzl
 |title=Structure and Dynamics of Elementary Matter
 |chapter=Dark Matter, Massive Neutrinos and Susy Particles
 |url=http://books.google.com/books?id=lokz2n-9gX0C&pg=PA289&dq=matter+%22massive+particles%22&lr=&as_brr=0
 |page=289
 |publisher=Walter Greiner
 |year=2004
 |isbn=1402024460
}}</ref><ref name=Freeman>
{{Cite book
 |author=K. Freeman, G. McNamara
 |title=In Search of Dark Matter
 |chapter=What can the matter be?
 |url=http://books.google.com/books?id=C2OS1kmQ8JIC&pg=PA45&dq=isbn=0387276165#PPA105,M1
 |page=105
 |publisher=Birkhäuser
 |year=2006
 |isbn=0387276165
}}</ref> and 73% is [[dark energy]].<ref name=Wheeler0>
{{cite book
 |author=J.C. Wheeler
 |title=Cosmic Catastrophes: Exploding Stars, Black Holes, and Mapping the Universe
 |url=http://books.google.com/books?id=j1ej8d0F8jAC&pg=PA282&dq=%22dark+energy%22+date:2002-2009&lr=&as_brr=0
 |page=282
 |publisher=Cambridge University Press
 |year=2007
 |isbn=0521857147
}}</ref><ref name=Gribbin>
{{cite book
 |author=J. Gribbin
 |title=The Origins of the Future: Ten Questions for the Next Ten Years
 |url=http://books.google.com/books?id=f6AYrZYGig8C&pg=PA151&dq=%22dark+energy%22+date:2002-2009&lr=&as_brr=0
 |page=151
 |publisher=Yale University Press
 |year=2007
 |isbn=0300125968
}}</ref>

[[File:Rotation curve (Milky Way).JPG|thumb |300px |[[Galaxy rotation curve]] 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. Scatter in observations roughly indicated by gray bars. The difference is due to [[dark matter]] or perhaps a modification of the [[MOND|law of gravity]].<ref name=Schneider>
{{cite book
 |author=P. Schneider
 |title=Extragalactic Astronomy and Cosmology
 |url=http://books.google.com/books?id=uP1Hz-6sHaMC&pg=PA100&dq=rotation+Milky+way&lr=&as_brr=0&as_pt=ALLTYPES#PPA5,M1
 |page=4, Figure 1.4
 |publisher=Springer
 |year=2006
 |isbn=3540331743
}}</ref><ref name=Koupelis>
{{cite book
 |title=In Quest of the Universe
 |author=T. Koupelis, K.F. Kuhn
 |page=492; Figure 16-13
 |url=http://books.google.com/books?id=6rTttN4ZdyoC&pg=PA491&dq=Milky+Way+%22rotation+curve%22&lr=&as_brr=0&as_pt=ALLTYPES#PPA492,M1
 |publisher=Jones & Bartlett Publishers
 |year=2007
 |isbn=0763743879
}}</ref><ref name=Jones>
{{cite book
 |author=M.H. Jones, R.J. Lambourne, D.J. Adams
 |title=An Introduction to Galaxies and Cosmology
 |url=http://books.google.com/books?id=36K1PfetZegC&pg=PA20&dq=Milky+Way+%22rotation+curve%22&lr=&as_brr=0&as_pt=ALLTYPES#PPA21,M1
 |page=21; Figure 1.13
 |publisher=Cambridge University Press
 |year=2004
 |isbn=0521546230
}}</ref>]]

=== Dark matter ===
{{basis|Dark matter|Lambda-CDM model|WIMPs}}
{{sienook|Galaxy formation and evolution|Dark matter halo}}

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.<ref name=Majumdar>

{{cite journal |title=Dark matter&nbsp;— possible candidates and direct detection |author=Debasish Majumdar |url=http://arxiv.org/abs/hep-ph/0703310v1 |journal=ArXive preprint |year=2007 }}

</ref><ref name=Olive>

{{cite journal |title=Theoretical Advanced Study Institute lectures on dark matter |journal=ArXive preprint |url=http://arxiv.org/abs/astro-ph/0301505 |author= Keith A Olive |year=2003}}

</ref> Observational evidence of the early universe and the [[big bang]] theory require that this matter have energy and mass, but is not composed of either elementary fermions (as above) OR gauge bosons. The commonly accepted view is that most of the dark-matter is non-baryonic in nature.<ref name=Majumdar/>  As such, it is composed of particles as yet unobserved in the laboratory. Perhaps they are [[supersymmetry|supersymmetric particles]],<ref name=Olive2>{{cite journal |title=Colliders and Cosmology |journal = Eur Phys J |volume=C59 |author=Keith A Olive |pages=269-295 |year=2009 |url=http://arxiv.org/abs/0806.1208v1}}</ref> which are not [[Standard Model]] particles, but relics formed at very high energies in the early phase of the universe and still floating about.<ref name=Majumdar/>

=== Dark energy ===
{{basis|Dark energy}}
{{sienook|Big bang#Dark energy}}
In [[cosmology]], '''dark energy''' is the name given to the antigravitating influence that is accelerating the rate of [[expansion of the universe]]. It is known not to be composed of known particles like protons, neutrons or electrons, nor of the particles of dark matter, because these all gravitate.<ref name=Wheeler1>
{{cite book
 |author=J.C. Wheeler
 |title=Cosmic Catastrophes
 |url=http://books.google.com/books?id=j1ej8d0F8jAC&pg=PA282&dq=%22dark+energy%22&lr=&as_brr=0
 |page=282
 |publisher=Cambridge University Press
 |year=2007
 |isbn=0521857147
}}</ref><ref name=Smolin2>
{{cite book
 |author=L. Smolin
 |title=''op. cit.''
 |url=http://books.google.com/books?id=z5rxrnlcp3sC&pg=PA67&dq=%22all+the+particles+that+make+up+matter%22&lr=&as_brr=0#PPA16,M1
 |page=16
 |publisher=Mariner Books
 |location=Boston
 |year=2007
 |isbn=061891868X
}}</ref>
{{Quotation|Fully 70% of the matter density in the universe appears to be in the form of dark energy. Twenty-six percent is dark matter. Only 4% is ordinary matter. So less than 1 part in 20 is made out of matter we have observed experimentally or described in the [[standard model]] of particle physics. Of the other 96%, apart from the properties just mentioned, we know absolutely nothing.|Lee Smolin: ''The Trouble with Physics'', p. 16}}

=== Exotic matter ===
{{basis|Exotic matter}}

Exotic matter is a hypothetical concept of [[particle physics]]. It covers any material which violates one or more classical conditions or is not made of known [[baryonic particles]]. Such materials would possess qualities like negative mass or being repelled rather than attracted by gravity.

== References ==
{{reflist|2}}

== Further reading ==
*{{cite book |title=The Rise of the Standard Model |editor= Lillian Hoddeson, Michael Riordan |isbn=0521578167 |publisher=Cambridge University Press |year=1997 |url=http://books.google.com/books?id=klLUs2XUmOkC&printsec=frontcover&source=gbs_summary_r&cad=0#PPR5,M1 }}
*{{cite book |title=Hidden Worlds |chapter=The search for quarks in ordinary matter |author=Timothy Paul Smith |page=1 |url=http://books.google.com/books?id=Pc1A0qJio88C&pg=PA1 |isbn=0691057737 |year=2004 |publisher=Princeton University Press}}
*{{cite book |title=Elementary Particles: Building blocks of matter |isbn=9812561412 |year=2005 |publisher=World Scientific |author=Harald Fritzsch |url=http://books.google.com/books?id=KFodZ8oHz2sC&pg=PA1 |page=1}}
*{{cite book |title=A Critical Exposition of the Philosophy of Leibniz |author= Bertrand Russell |url=http://books.google.com/books?id=R7GauFXXedwC&pg=PA88 |page=88 |chapter=The philosophy of matter |isbn=041508296X |year=1992 |edition=Reprint of 1937 2nd |publisher=Routledge}}

== External links ==
* [http://www.visionlearning.com/library/module_viewer.php?mid=49&l=&c3= Visionlearning Module on Matter]
* [http://www.newuniverse.co.uk/Matter.html Matter in the universe] How much Matter is in the Universe?
* [http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970213.html NASA on superfluid core of neutron star]

== See also ==

{{Col-begin}}
{{Kolom-1-van-4}}
'''Dark matter'''
*[[Minimal Supersymmetric Standard Model]]
*[[Neutralino]]
*[[Axion]]
*[[Nonbaryonic dark matter]]
*[[Scalar field dark matter]]
{{Kolom-2-van-4}}
'''Antimatter'''
*[[Ambiplasma]]
*[[Particle accelerator]]
*[[Antiparticle]]
*[[Antihydrogen]]

{{Kolom-3-van-4}}
'''Cosmology'''
*[[Cosmological constant]]
*[[Friedmann equations]]

{{Kolom-4-van-4}}
<!--'''Other'''-->
{{col-end}}

{{commonscat}}
{{Wikipedia-Boeke}}
{{staat van materie}}
{{Partikels}}

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