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In
classical physics Classical physics is a group of physics theories that predate modern, more complete, or more widely applicable theories. If a currently accepted theory is considered to be modern, and its introduction represented a major paradigm shift, then the ...
and general
chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, molecules and i ...
, matter is any substance that has
mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a measure (mathematics), measure of the body's ''inertia'', the resistance to acceleration (change of velocity) when a net force is applied. An object's mass ...
and takes up space by having
volume Volume is a scalar quantity (physics), scalar quantity expressing the amount of three-dimensional space enclosed by a closed surface. For example, the space that a substance (solid, liquid, gas, or Plasma (physics), plasma) or 3D shape occupies ...

volume
. All everyday objects that can be touched are ultimately composed of
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atom ...

atom
s, which are made up of interacting
subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All ...
s, and in everyday as well as scientific usage, "matter" generally includes
atoms An atom is the smallest unit of ordinary matter that forms a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance c ...
and anything made up of them, and any particles (or combination of particles) that act as if they have both
rest mass The word ''mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article ...
and volume. However it does not include
massless particleIn particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the na ...
s such as
photon The photon ( el, φῶς, phōs, light) is a type of elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be eleme ...

photon
s, or other energy phenomena or waves such as
light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 ...

light
. Matter exists in various
states State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, Un ...
(also known as phases). These include classical everyday phases such as
solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

solid
,
liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers to a fluid flow, flow in which the material density is constant within a fluid parc ...

liquid
, and
gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an appl ...

gas
– for example
water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts ...

water
exists as ice, liquid water, and gaseous steam – but other states are possible, including
plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral) or heliotrope, a mineral aggregate * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood plasma ...
,
Bose–Einstein condensate In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter (also called the fifth state of matter) which is typically formed when a gas of bosons at low densities is cooled to temperature Temperature is a ...
s,
fermionic condensate A fermionic condensate or Fermi-Dirac condensate is a superfluid File:Liquid helium Rollin film.jpg, The liquid helium is in the superfluid phase. A thin invisible film creeps up the inside wall of the bowl and down on the outside. A drop forms. ...
s, and
quark–gluon plasma Quark–gluon plasma or QGP is an interacting localized assembly of quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from ...
. Usually atoms can be imagined as a
nucleus ''Nucleus'' (plural nuclei) is a Latin word for the seed inside a fruit. It most often refers to: *Atomic nucleus, the very dense central region of an atom *Cell nucleus, a central organelle of a eukaryotic cell, containing most of the cell's DNA ...
of
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
s and
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

neutron
s, and a surrounding "cloud" of orbiting
electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...
s which "take up space". However this is only somewhat correct, because subatomic particles and their properties are governed by their quantum nature, which means they do not act as everyday objects appear to act – they can act like and they do not have well-defined sizes or positions. In the
Standard Model The Standard Model of particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis ...

Standard Model
of
particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...
, matter is not a fundamental concept because the elementary constituents of atoms are
quantum In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "P ...

quantum
entities which do not have an inherent "size" or "
volume Volume is a scalar quantity (physics), scalar quantity expressing the amount of three-dimensional space enclosed by a closed surface. For example, the space that a substance (solid, liquid, gas, or Plasma (physics), plasma) or 3D shape occupies ...

volume
" in any everyday sense of the word. Due to the exclusion principle and other
fundamental interaction In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through Sp ...
s, some "
point particle A point particle (ideal particle or point-like particle, often spelled pointlike particle) is an idealization of particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, l ...
s" known as
fermion In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
s (
quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge ...

quark
s,
lepton In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is ...

lepton
s), and many composites and atoms, are effectively forced to keep a distance from other particles under everyday conditions; this creates the property of matter which appears to us as matter taking up space. For much of the history of the
natural science Natural science is a Branches of science, branch of science concerned with the description, understanding and prediction of Phenomenon, natural phenomena, based on empirical evidence from observation and experimentation. Mechanisms such as peer r ...

natural science
s 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 In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical property, physical or chemical , chemical properties ...
, independently appeared in
ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era was ...
and
ancient India According to consensus in modern genetics, anatomically modern humans first arrived on the Indian subcontinent from Africa between 73,000 and 55,000 years ago. Quote: "Y-Chromosome and Mt-DNA data support the colonization of South Asia by mode ...

ancient India
among
Buddhists Buddhism (, ) is the world's fourth-largest religion Religion is a social system, social-cultural system of designated religious behaviour, behaviors and practices, morality, morals, beliefs, worldviews, religious text, texts, shrine, ...
,
Hindus Hindus () are persons who regard themselves as culturally, ethnically, or religiously adhering to aspects of Hinduism Hinduism () is an Indian religion and ''dharma'', or way of life. It is the Major religious groups, world's third-l ...

Hindus
and
Jains Jainism (), traditionally known as ''Jain Dharma'', is an ancient Indian religion Indian religions, sometimes also termed Dharmic religions or Indic religions, are the religions that originated in the Indian subcontinent; namely Hinduis ...

Jains
in 1st-millennium BC. Ancient philosophers who proposed the particulate theory of matter include Kanada (c. 6th–century BC or after),
Leucippus Leucippus (; el, Λεύκιππος, ''Leúkippos''; fl. 5th century BCE) is reported in some ancient sources to have been a philosopher A philosopher is someone who practices philosophy. The term ''philosopher'' comes from the grc, φιλό ...
(~490 BC) and
Democritus Democritus (; el, Δημόκριτος, ''Dēmókritos'', meaning "chosen of the people"; – ) was an Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...
(~470–380 BC).


Comparison with mass

Matter should not be confused with mass, as the two are not the same in modern physics. Matter is a general term describing any 'physical substance'. By contrast,
mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a measure (mathematics), measure of the body's ''inertia'', the resistance to acceleration (change of velocity) when a net force is applied. An object's mass ...
is not a substance but rather a quantitative ''property'' of matter and other substances or systems; various types of mass are defined within
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scien ...

physics
– including but not limited to
rest mass The word ''mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article ...
,
inertial mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article, it is one or mo ...
,
relativistic mass The word ''mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article ...
, mass–energy. While there are different views on what should be considered matter, the mass of a substance has exact scientific definitions. Another difference is that matter has an "opposite" called
antimatter In modern physics Modern physics is a branch of physics either developed in the early 20th century and onward or branches greatly influenced by early 20th century physics. Notable branches of modern physics include quantum physics, special ...
, but mass has no opposite—there is no such thing as "anti-mass" or
negative mass In theoretical physics, negative mass is a type of exotic matter whose mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or ...
, so far as is known, although scientists do discuss the concept. Antimatter has the same (i.e. positive) mass property as its normal matter counterpart. 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 Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scien ...

physics
and
chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, molecules and i ...
, matter exhibits both
wave In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...

wave
-like and
particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical property, physical or chemical , chemical properties ...

particle
-like properties, the so-called
wave–particle duality Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be described as either a particle or a wave. It expresses the inability of the classical physics, classical concepts "particle" or "wave" to ful ...
.


Definition


Based on atoms

A definition of "matter" based on its physical and chemical structure is: ''matter is made up of
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atom ...

atom
s''. Such ''atomic matter'' is also sometimes termed ''ordinary matter''. As an example,
deoxyribonucleic acid File:DNA animation.gif, The structure of part of a DNA double helix Deoxyribonucleic acid (; DNA) is a molecule composed of two polynucleotide chains that coil around each other to form a Nucleic acid double helix, double helix carrying genet ...
molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms held together by chemical bo ...

molecule
s (DNA) are matter under this definition because they are made of atoms. This definition can be extended to include charged atoms and molecules, so as to include plasmas (gases of ions) and
electrolyte An electrolyte is a medium containing ions that is conductivity (electrolytic), electrically conducting through the movement of ions, but not conducting Electron, electrons. This includes most soluble Salt (chemistry), salts, acids, and Base (chemi ...
s (ionic solutions), which are not obviously included in the atoms definition. Alternatively, one can adopt the ''protons, neutrons, and electrons'' definition.


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
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atom ...

atom
s and
molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms held together by chemical bo ...

molecule
s are made of'', meaning anything made of positively charged
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
s, neutral
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

neutron
s, and negatively charged
electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...
s. 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 electron beams in an old
cathode ray tube File:CRT monochrome.png, 250px, Cutaway rendering of a monochrome CRT: 1. Deflection coils2. Electron beam3. Focusing coil4. Phosphor layer on the inner side of the screen; emits light when struck by the electron beam5.&nbs ...

cathode ray tube
television, or
white dwarf A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter Degenerate matter is a highly dense state of fermionic matter in which the Pauli exclusion principle exerts significant ...

white dwarf
matter—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
quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge ...

quark
s and the force fields (
gluon A gluon () is an elementary particle that acts as the exchange particle (or gauge boson) for the strong force between quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy ...

gluon
s) that bind them together, leading to the next definition.


Based on quarks and leptons

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
quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge ...

quark
s and
lepton In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is ...

lepton
s", or "ordinary matter is everything that is composed of any elementary fermions except antiquarks and antileptons". The connection between these formulations follows. Leptons (the most famous being the
electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...
), and quarks (of which
baryons In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...
, such as
protons A proton is a subatomic particle, symbol or , with a positive electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric cha ...
and
neutrons The neutron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass ...

neutrons
, are made) combine to form
atoms An atom is the smallest unit of ordinary matter that forms a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance c ...
, which in turn form
molecules A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...

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 and ownquarks, plus the electron and its neutrino." (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. The
W and Z bosons In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles force carrier, mediate the weak interaction; the respective symbol ...
that mediate the
weak force Weak may refer to: Songs * "Weak" (AJR song), 2016 * "Weak" (Melanie C song), 2011 * Weak (SWV song), "Weak" (SWV song), 1993 * Weak (Skunk Anansie song), "Weak" (Skunk Anansie song), 1995 * "Weak", a song by Seether from ''Seether: 2002-2013'' ...

weak force
are not made of quarks or leptons, and so are not ordinary matter, even if they have mass.The W boson mass is 80.398 GeV; see Figure 1 in In other words,
mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a measure (mathematics), measure of the body's ''inertia'', the resistance to acceleration (change of velocity) when a net force is applied. An object's 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 ) and these gluons fields contribute significantly to the mass of hadrons. In other words, most of what composes the "mass" of ordinary matter is due to the
binding energy In physics and chemistry, binding energy is the smallest amount of energy required to remove a particle from a system of particles or to disassemble a system of particles into individual parts. In the former meaning the term is predominantly use ...

binding energy
of quarks within protons and neutrons. For example, the sum of the mass of the three quarks in a
nucleon In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
is approximately , which is low compared to the mass of a nucleon (approximately ). The bottom line is that most of the mass of everyday objects comes from the interaction energy of its elementary components. The Standard Model groups matter particles into three generations, where each generation consists of two quarks and two leptons. The first generation is the '''' and ''
down Down most often refers to: * Down, the relative direction opposed to up * Down (gridiron football), in American/Canadian football, a period when one play takes place * Down feather, a soft bird feather used in bedding and clothing * Downland, a typ ...

down
'' quarks, the ''
electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...
'' and the ''
electron neutrino The electron neutrino () is a subatomic lepton In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowle ...

electron neutrino
''; the second includes the ''
charm Charm may refer to: Social science * Charisma, a person or thing's pronounced ability to attract others * Superficial charm, the tendency to be smooth, engaging, charming, slick and verbally facile Science and technology * Charm quark, a type of e ...

charm
'' and '''' quarks, the ''
muon The muon (; from the Greek letter mu (μ) used to represent it) is an elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπι ...
'' and the ''
muon neutrino The muon neutrino is a lepton, an elementary subatomic particle which has the symbol and no electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Ther ...

muon neutrino
''; the third generation consists of the ''
top A spinning top, or simply a top, is a toy with a squat body and a sharp point at the bottom, designed to be spun on its vertical axis, balancing on the tip due to the gyroscopic effect. Once set in motion, a top will usually wobble for a few ...

top
'' and '''' quarks and the ''
tau Tau (uppercase Τ, lowercase τ; el, ταυ ) is the 19th letter of the Greek alphabet The Greek alphabet has been used to write the Greek language since the late ninth or early eighth century BC. It is derived from the earlier Phoenician ...
'' and ''
tau neutrino The tau neutrino or tauon neutrino is a subatomic elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ ( ...

tau neutrino
''. The most natural explanation for this would be that quarks and leptons of higher generations are
excited state In quantum mechanics Quantum mechanics is a fundamental Scientific theory, theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantu ...
s of the first generations. If this turns out to be the case, it would imply that quarks and leptons are
composite particle This is a list of known and hypothesized particles. Elementary particles Elementary particles are particles with no measurable internal structure; that is, it is unknown whether they are composed of other particles. They are the fundamental obj ...
s, rather than
elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include the fundamental fermions (quarks, leptons, antiquarks, and an ...
s. This quark–lepton definition of matter also leads to what can be described as "conservation of (net) matter" laws—discussed later below. Alternatively, one could return to the mass–volume–space concept of matter, leading to the next definition, in which antimatter becomes included as a subclass of matter.


Based on elementary fermions (mass, volume, and space)

A common or traditional definition of matter is "anything that has
mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a measure (mathematics), measure of the body's ''inertia'', the resistance to acceleration (change of velocity) when a net force is applied. An object's mass ...
and
volume Volume is a scalar quantity (physics), scalar quantity expressing the amount of three-dimensional space enclosed by a closed surface. For example, the space that a substance (solid, liquid, gas, or Plasma (physics), plasma) or 3D shape occupies ...

volume
(occupies
space Space is the boundless three-dimensional Three-dimensional space (also: 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called parameter A parameter (from the Ancient Greek language, Ancient Gree ...

space
)". For example, a car would be said to be made of matter, as it has mass and volume (occupies space). 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 phenomenon described in the
Pauli exclusion principle The Pauli exclusion principle is the quantum mechanical principle which states that two or more identical fermion In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc ...
, which applies to
fermions In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
. 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. Thus, matter can be defined as everything composed of elementary fermions. Although we don't encounter them in everyday life, antiquarks (such as the
antiproton The antiproton, , (pronounced ''p-bar'') is the antiparticle s (left) and antiparticles (right). From top to bottom; electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An ...

antiproton
) and antileptons (such as the
positron The positron or antielectron is the antiparticle s (left) and antiparticles (right). From top to bottom; electron The electron is a subatomic particle, symbol or , whose electric charge Electric charge is the physical property of mat ...

positron
) are the
antiparticle s (left) and antiparticles (right). From top to bottom; electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classica ...
s of the quark and the lepton, are elementary fermions as well, and have essentially the same properties as quarks and leptons, including the applicability of the Pauli exclusion principle which can be said to prevent two particles from being in the same place at the same time (in the same state), i.e. makes each particle "take up space". This particular definition leads to matter being defined to include anything made of these
antimatter In modern physics Modern physics is a branch of physics either developed in the early 20th century and onward or branches greatly influenced by early 20th century physics. Notable branches of modern physics include quantum physics, special ...
particles as well as the ordinary quark and lepton, and thus also anything made of
meson In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...

meson
s, which are unstable particles made up of a quark and an antiquark.


In general relativity and cosmology

In the context of relativity, mass is not an additive quantity, in the sense that one can not add the rest masses of particles in a system to get the total rest mass of the system. Thus, in relativity usually a more general view is that it is not the sum of
rest mass The word ''mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article ...
es, but the
energy–momentum tensorEnergy–momentum may refer to: *Four-momentum *Stress–energy tensor *Energy–momentum relation {{dab ...
that quantifies the amount of matter. This tensor gives the rest mass for the entire system. "Matter" therefore is sometimes considered as anything that contributes to the energy–momentum of a system, that is, anything that is not purely gravity. This view is commonly held in fields that deal with
general relativity General relativity, also known as the general theory of relativity, is the differential geometry, geometric scientific theory, theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern ph ...
such as
cosmology Cosmology (from Ancient Greek, Greek κόσμος, ''kosmos'' "world" and -λογία, ''-logia'' "study of") is a branch of astronomy concerned with the study of the chronology of the universe. Physical cosmology is the study of the universe's ...
. In this view, light and other massless particles and fields are all part of "matter".


Structure

In particle physics, fermions are particles that obey
Fermi–Dirac statistics In quantum statistics, a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physi ...
. Fermions can be elementary, like the electron—or composite, like the proton and neutron. In the
Standard Model The Standard Model of particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis ...

Standard Model
, there are two types of elementary fermions: quarks and leptons, which are discussed next.


Quarks

Quarks are massive particles of spin-, implying that they are
fermion In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
s. They carry an
electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respectively). Like ch ...
of −  e (down-type quarks) or + e (up-type quarks). For comparison, an electron has a charge of −1 e. They also carry
colour charge Color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). The "color charge" of quarks and gluons is completely unrelated to the everyday meaning of color. ...
, which is the equivalent of the electric charge for the
strong interaction In nuclear physics and particle physics, the strong interaction is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation. At the range of 10−15 m (slightly more than ...
. Quarks also undergo
radioactive decay Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

radioactive decay
, meaning that they are subject to the
weak interaction In nuclear physics and particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýs ...
.


Baryonic

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. Also, "exotic" baryons made of four quarks and one antiquark are known as
pentaquark A pentaquark is a human-made subatomic particle, consisting of four quarks and one antiquark bound state, bound together; they are not known to occur naturally, or exist outside of experiments specifically carried out to create them. As quarks hav ...

pentaquark
s, 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 In physical cosmology and astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial eve ...

dark energy
,
dark matter Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained b ...

dark matter
, or various forms of degenerate matter, such as compose
white dwarf A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter Degenerate matter is a highly dense state of fermionic matter in which the Pauli exclusion principle exerts significant ...

white dwarf
stars and
neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes, and some hypothetical objects (e.g. w ...
s. Microwave light seen by
Wilkinson Microwave Anisotropy Probe The Wilkinson Microwave Anisotropy Probe (WMAP), originally known as the Microwave Anisotropy Probe (MAP), is an inactive uncrewed spacecraft operating from 2001 to 2010 which measured temperature differences across the sky in the cosmic micr ...
(WMAP), suggests that only about 4.6% of that part of the universe within range of the best
telescope A telescope is an optical instrument An optical instrument (or "optic" for short) is a device that processes light waves (or photon The photon (Greek: φῶς, phōs, light) is a type of elementary particle. It is the quantum of the ele ...

telescope
s (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. 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.


Hadronic

Hadronic matter can refer to 'ordinary' baryonic matter, made from
hadron In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
s (baryons and
meson In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is th ...

meson
s), or
quark matter Quark matter or QCD matter (quantum chromodynamics, quantum chromodynamic) refers to any of a number of hypothetical phase (matter), phases of matter whose degrees of freedom (physics and chemistry), degrees of freedom include quarks and gluons, of ...
(a generalisation of atomic nuclei), i.e. the 'low' temperature
QCD matter Quark matter or QCD matter ( quantum chromodynamic) refers to any of a number of hypothetical phases of matter whose degrees of freedom include quark A quark () is a type of elementary particle In particle physics Particle physics (als ...
. It includes
degenerate matter Degenerate matter is a highly dense state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a dail ...
and the result of high energy heavy nuclei collisions.


Degenerate

In physics, ''degenerate matter'' refers to the ground state of a gas of fermions at a temperature near absolute zero. The
Pauli exclusion principle The Pauli exclusion principle is the quantum mechanical principle which states that two or more identical fermion In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc ...
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 in the case of many fermions, the maximum kinetic energy (called the ''
Fermi energy The Fermi energy is a concept in quantum mechanics Quantum mechanics is a fundamental Scientific theory, theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is th ...
'') and the pressure of the gas becomes very large, and depends on 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. The demonstration by
Subrahmanyan Chandrasekhar Subrahmanyan Chandrasekhar () (19 October 1910 – 21 August 1995) was an Indian-American astrophysicist who spent his professional life in the United States The United States of America (USA), commonly known as the United States (U ...

Subrahmanyan Chandrasekhar
that white dwarf stars have a maximum allowed mass because of the exclusion principle caused a revolution in the theory of star evolution. Degenerate matter includes the part of the universe that is made up of neutron stars and white dwarfs.


Strange

''Strange matter'' is a particular form of
quark matter Quark matter or QCD matter (quantum chromodynamics, quantum chromodynamic) refers to any of a number of hypothetical phase (matter), phases of matter whose degrees of freedom (physics and chemistry), degrees of freedom include quarks and gluons, of ...
, usually thought of as a ''liquid'' of ,
down Down most often refers to: * Down, the relative direction opposed to up * Down (gridiron football), in American/Canadian football, a period when one play takes place * Down feather, a soft bird feather used in bedding and clothing * Downland, a typ ...

down
, and quarks. It is contrasted with nuclear matter, which is a liquid of
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

neutron
s and
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
s (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 superconductor, color superconducting. Strange matter is hypothesized to occur in the core of
neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes, and some hypothetical objects (e.g. w ...
s, or, more speculatively, as isolated droplets that may vary in size from femtometers (strangelets) to kilometers (quark stars).


= Two meanings

= In
particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...
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 A proton is a subatomic particle, symbol or , with a positive electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric cha ...
and
neutrons The neutron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass ...

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 ''more stable than nuclear matter''. The idea that this could happen is the "strange matter hypothesis" of Bodmer and Witten. In this definition, the critical pressure is zero: the true ground state of matter is ''always'' 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. strangelets.


Leptons

Leptons are particles of spin-, meaning that they are
fermion In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
s. They carry an
electric charge Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respectively). Like ch ...
of −1  e (charged leptons) or 0 e (neutrinos). Unlike quarks, leptons do not carry
colour charge Color charge is a property of quarks and gluons that is related to the particles' strong interactions in the theory of quantum chromodynamics (QCD). The "color charge" of quarks and gluons is completely unrelated to the everyday meaning of color. ...
, meaning that they do not experience the
strong interaction In nuclear physics and particle physics, the strong interaction is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation. At the range of 10−15 m (slightly more than ...
. Leptons also undergo radioactive decay, meaning that they are subject to the
weak interaction In nuclear physics and particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýs ...
. Leptons are massive particles, therefore are subject to gravity.


Phases

In wikt:bulk, bulk, matter can exist in several different forms, or states of aggregation, known as '' phases'', depending on ambient pressure, temperature and
volume Volume is a scalar quantity (physics), scalar quantity expressing the amount of three-dimensional space enclosed by a closed surface. For example, the space that a substance (solid, liquid, gas, or Plasma (physics), plasma) or 3D shape occupies ...

volume
. 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 Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

solid
s,
liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers to a fluid flow, flow in which the material density is constant within a fluid parc ...

liquid
s, and
gas Gas is one of the four fundamental states of matter (the others being solid, liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an appl ...

gas
es), as well as more exotic states of matter (such as plasma (physics), plasmas, superfluids, supersolids,
Bose–Einstein condensate In condensed matter physics, a Bose–Einstein condensate (BEC) is a state of matter (also called the fifth state of matter) which is typically formed when a gas of bosons at low densities is cooled to temperature Temperature is a ...
s, ...). A ''fluid'' may be a liquid, gas or plasma. There are also paramagnetism, paramagnetic and ferromagnetism, ferromagnetic phases of magnetic materials. As conditions change, matter may change from one phase into another. These phenomena are called phase transitions, 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 gases).


Antimatter

''Antimatter'' is matter that is composed of the
antiparticle s (left) and antiparticles (right). From top to bottom; electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classica ...
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 Albert Einstein's equation . These new particles may be high-energy
photon The photon ( el, φῶς, phōs, light) is a type of elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be eleme ...

photon
s (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 The word ''mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or as a component of said thing. In the context of this article ...
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 Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

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 violation, CP (charge-parity) symmetry violation, which can be obtained from the Standard Model, 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. 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. These two classes of particles are the antiparticle partners of one another. In October 2017, scientists reported further evidence that matter and
antimatter In modern physics Modern physics is a branch of physics either developed in the early 20th century and onward or branches greatly influenced by early 20th century physics. Notable branches of modern physics include quantum physics, special ...
, 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

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 conservation law, conserved in the Standard Model. 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 binding energy, nuclear (and perhaps quantum chromodynamics binding energy, chromodynamic) binding energy is released, as these baryons become bound into mid-size nuclei having less energy (and, Mass–energy equivalence, equivalently, less mass per nucleon, mass) per nucleon compared to the original small (hydrogen) and large (plutonium etc.) nuclei. Even in electron–positron annihilation, there is 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. In short, matter, as defined in physics, refers to baryons and leptons. The amount of matter is defined in terms of baryon and lepton number. Baryons and leptons can be created, but their creation is accompanied by antibaryons or antileptons; and they can be destroyed, by annihilating them with antibaryons or antileptons. Since antibaryons/antileptons have negative baryon/lepton numbers, the overall baryon/lepton numbers aren't changed, so matter is conserved. However, baryons/leptons and antibaryons/antileptons all have positive mass, so the total amount of mass is not conserved. Further, outside of natural or artificial nuclear reactions, there is almost no antimatter generally available in the universe (see baryon asymmetry and leptogenesis (physics), leptogenesis), so particle annihilation is rare in normal circumstances.


Dark

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 Dark matter is a hypothetical form of matter thought to account for approximately 85% of the matter in the universe. Its presence is implied in a variety of astrophysical observations, including gravitational effects that cannot be explained b ...

dark matter
and 73% is
dark energy In physical cosmology and astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial eve ...

dark energy
. In astrophysics and
cosmology Cosmology (from Ancient Greek, Greek κόσμος, ''kosmos'' "world" and -λογία, ''-logia'' "study of") is a branch of astronomy concerned with the study of the chronology of the universe. Physical cosmology is the study of the universe's ...
, ''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. Observational evidence of the early universe and the Big Bang theory require that this matter have energy and mass, but not be composed of ordinary baryons (protons and neutrons). The commonly accepted view is that most of the dark matter is nonbaryonic dark matter, non-baryonic in nature. As such, it is composed of particles as yet unobserved in the laboratory. Perhaps they are supersymmetry, supersymmetric particles, which are not
Standard Model The Standard Model of particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis ...

Standard Model
particles but relics formed at very high energies in the early phase of the universe and still floating about.


Energy

In
cosmology Cosmology (from Ancient Greek, Greek κόσμος, ''kosmos'' "world" and -λογία, ''-logia'' "study of") is a branch of astronomy concerned with the study of the chronology of the universe. Physical cosmology is the study of the universe's ...
, ''dark energy'' is the name given to the 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

Exotic matter is a concept of
particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...
, 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 In theoretical physics, negative mass is a type of exotic matter whose mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or with something, whether as an attribute or ...
.


Historical study


Antiquity (c. 600 BC–c. 322 BC)

In
ancient India According to consensus in modern genetics, anatomically modern humans first arrived on the Indian subcontinent from Africa between 73,000 and 55,000 years ago. Quote: "Y-Chromosome and Mt-DNA data support the colonization of South Asia by mode ...

ancient India
, the Buddhists, the Hindus and the Jains each developed a particulate theory of matter, positing that all matter is made of atoms (''paramanu'', ''pudgala'') that are in itself "eternal, indestructible and innumerable" and which associate and dissociate according to certain fundamental natural laws to form more complex matter or change over time. They coupled their ideas of soul, or lack thereof, into their theory of matter. The strongest developers and defenders of this theory were the Nyaya-Vaisheshika school, with the ideas of the philosopher Kanada (c. 6th–century BC) being the most followed. The Buddhists also developed these ideas in late 1st-millennium BCE, ideas that were similar to the Vaishashika Hindu school, but one that did not include any soul or conscience. The Jains included soul (''jiva''), adding qualities such as taste, smell, touch and color to each atom. They extended the ideas found in early literature of the Hindus and Buddhists by adding that atoms are either humid or dry, and this quality cements matter. They also proposed the possibility that atoms combine because of the attraction of opposites, and the soul attaches to these atoms, transforms with karma residue and transmigrates with each rebirth. In Europe, Pre-Socratic philosophy, pre-Socratics speculated 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 (cosmology), apeiron''). Anaximenes of Miletus, 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 Classical element, elements of which everything was made: earth, water, air, and fire. Meanwhile, Parmenides argued that change does not exist, and
Democritus Democritus (; el, Δημόκριτος, ''Dēmókritos'', meaning "chosen of the people"; – ) was an Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient w ...
argued that everything is composed of minuscule, inert bodies of all shapes called atoms, a philosophy called atomism. All of these notions had deep philosophical problems. Aristotle (384–322 BC) was the first to put the conception on a sound philosophical basis, which he did in his natural philosophy, especially in Physics (Aristotle), ''Physics'' book I. He adopted as reasonable suppositions the four Classical element, Empedoclean elements, but added a fifth, Aether (classical element), 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, hyle, ὕλη (''hyle'' or ''hule''), can be literally translated as wood or timber, that is, "raw material" for building. Indeed, Aristotle's conception of matter is intrinsically linked to something being made or composed. In other words, in contrast to the early modern conception of matter as simply occupying space, matter for Aristotle is definitionally linked to process or change: matter is what underlies a change of substance. For example, a horse eats grass: the horse changes the grass into itself; the grass as such does not persist in the horse, but some aspect of it—its matter—does. The matter is not specifically described (e.g., as
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atom ...

atom
s), but consists of whatever persists in the change of substance from grass to horse. Matter in this understanding does not exist independently (i.e., as a Substance theory, substance), but exists interdependently (i.e., as a "principle") with form and only insofar as it underlies change. It can be helpful to conceive of the relationship of matter and form as very similar to that between parts and whole. For Aristotle, matter as such can only ''receive'' actuality from form; it has no activity or actuality in itself, similar to the way that parts as such only have their existence ''in'' a whole (otherwise they would be independent wholes).


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: this is the Mechanism (philosophy), 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. They are independent things. In contrast, Aristotle defines matter and the formal/forming principle as complementary ''principles'' that together compose one independent thing (Substance theory, substance). In short, Aristotle defines matter (roughly speaking) as what things are actually made of (with a ''potential'' independent existence), but Descartes elevates matter to an actual independent thing in itself. 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 Substance theory, 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. 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. 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". 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". 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. 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.


19th and 20th 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). In the 19th century, following the development of the periodic table, and of atomic theory,
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atom ...

atom
s were seen as being the fundamental constituents of matter; atoms formed
molecules A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atom An atom is the smallest unit of ordinary matter In ...

molecules
and compound (chemistry), 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''. 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. 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. A textbook discussion from 1870 suggests matter is what is made up of atoms:
Three divisions of matter are recognized in science: masses, molecules and atoms.
A Mass of matter is any portion of matter appreciable by the senses.
A Molecule is the smallest particle of matter into which a body can be divided without losing its identity.
An Atom is a still smaller particle produced by division of a molecule.
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. In the late 19th century with the Thomson experiment, discovery of the
electron The electron is a subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has ma ...
, and in the early 20th century, with the Geiger–Marsden experiment discovery of the atomic nucleus, and the birth of
particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that ...
, matter was seen as made up of electrons,
proton A proton is a subatomic particle, symbol or , with a positive electric charge of +1''e'' elementary charge and a mass slightly less than that of a neutron. Protons and neutrons, each with masses of approximately one atomic mass unit, are collecti ...

proton
s and
neutron The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the nuclei of atoms. Since protons and neutrons behav ...

neutron
s interacting to form atoms. There then developed an entire literature concerning the "structure of matter", ranging from the "electrical structure" in the early 20th century, to the more recent "quark structure of matter", introduced as early as 1992 by Jacob with the remark: "Understanding the quark structure of matter has been one of the most important advances in contemporary physics." In this connection, physicists speak of ''matter fields'', and speak of particles as "quantum excitations of a mode of the matter field". 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 fields (like
quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge ...

quark
s and
lepton In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is ...

lepton
s), which are believed to be the fundamental components of matter, or Bosonic field, scalar fields, like the Higgs particles, which are used to introduced mass in a gauge theory (and that, however, could be composed of more fundamental
fermion In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
Fermionic field, fields)." Protons and neutrons however are not indivisible: they can be divided into
quark A quark () is a type of elementary particle In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge ...

quark
s. And electrons are part of a particle family called
lepton In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is ...

lepton
s. Both #Quarks and leptons definition, quarks and leptons are
elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be elementary include the fundamental fermions (quarks, leptons, antiquarks, and an ...
s, and were in 2004 seen by authors of an undergraduate text 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
hadron In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
s, 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 interaction In nuclear physics and particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýs ...
s, and
strong interaction In nuclear physics and particle physics, the strong interaction is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation. At the range of 10−15 m (slightly more than ...
s. The
Standard Model The Standard Model of particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis ...

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 Classical physics is a group of physics theories that predate modern, more complete, or more widely applicable theories. If a currently accepted theory is considered to be modern, and its introduction represented a major paradigm shift, then the ...
(see quantum gravity and graviton) to the frustration of theoreticians like Stephen Hawking. Interactions between quarks and leptons are the result of an exchange of force carriers, force-carrying particles such as
photon The photon ( el, φῶς, phōs, light) is a type of elementary particle In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles. Particles currently thought to be eleme ...

photon
s between quarks and leptons. The force-carrying particles are not themselves building blocks. As one consequence, mass and energy (which to our present knowledge 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 mediators are usually not considered matter: the mediators of the electric force (photons) possess energy (see Planck relation) and the mediators of the weak force (
W and Z bosons In particle physics, the W and Z bosons are vector bosons that are together known as the weak bosons or more generally as the intermediate vector bosons. These elementary particles force carrier, mediate the weak interaction; the respective symbol ...
) have mass, but neither are considered matter either. See for example, , and However, while these quanta are not considered matter, they do contribute to the total mass of atoms,
subatomic particle In physical sciences, subatomic particles are smaller than atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All ...
s, 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 wide variety of contexts: for example, one refers to "condensed matter physics", "elementary matter", "parton (particle physics), partonic" matter, "dark matter, dark" matter, "antimatter, anti"-matter, "strange matter, strange" matter, and "nuclear matter, nuclear" matter. In discussions of matter and
antimatter In modern physics Modern physics is a branch of physics either developed in the early 20th century and onward or branches greatly influenced by early 20th century physics. Notable branches of modern physics include quantum physics, special ...
, the former has been referred to by Hannes Alfvén, Alfvén as ''koinomatter'' (Gk. ''common matter''). It is fair to say that in
physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force. "Physical scien ...

physics
, there is no broad consensus as to a general definition of matter, and the term "matter" usually is used in conjunction with a specifying modifier. 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 In particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the ...
s, 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 interaction In nuclear physics and particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýs ...
s, and
strong interaction In nuclear physics and particle physics, the strong interaction is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation. At the range of 10−15 m (slightly more than ...
s. The
Standard Model The Standard Model of particle physics Particle physics (also known as high energy physics) is a branch of physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis ...

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 Classical physics is a group of physics theories that predate modern, more complete, or more widely applicable theories. If a currently accepted theory is considered to be modern, and its introduction represented a major paradigm shift, then the ...
(see quantum gravity and graviton).


See also

Antimatter * Ambiplasma * Antihydrogen * Antiparticle * Particle accelerator Cosmology * Cosmological constant * Friedmann equations * Motion * Physical ontology Dark matter * Axion * Minimal Supersymmetric Standard Model * Neutralino * Nonbaryonic dark matter * Scalar field dark matter Philosophy * Atomism * Materialism * Physicalism * Substance theory Other * Mass–energy equivalence * Hybrid word#English examples, Mattergy * Pattern formation * Periodic Systems of Small Molecules


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


Visionlearning Module on Matter


How much Matter is in the Universe?


Matter and Energy: A False Dichotomy
– Conversations About Science with Theoretical Physicist Matt Strassler {{Authority control Matter,