For these reasons, it appears that there is no easy definition of "matter" that correctly takes into account special relativity while still satisfying most people's intuition.
Colloquially and in , matter is easy to define because it is directly associated with mass. Matter is what ponderable objects are made of, and consists of identifiable . These are made of ,
Christian Louboutin Sale, which are made of , ,
Louboutin Men, and . In this way,
matter is contrasted with
.
Matter is defined as the of which physical objects are composed. In common use, , , and are not usually considered to be "matter."
The same difficulty occurs with the word
particle.
In , there is no broad consensus as to an exact definition of matter. Physicists generally do not use the word when precision is needed, preferring instead to speak of the more clearly defined concepts of , , ,
Louboutin Pas Cher, and .
In , matter can exist in several different , according to and . A phase is a state of a macroscopic physical system that has relatively uniform chemical composition and/or physical properties (i.e., , , , and so forth). These phases include the three familiar ones �� ,
UGG Boots Sale, , and �� as well as , , , , , , and . There are also the and phases of materials. As conditions change, matter may change from one phase into another. These phenomena are called , and their energetics are studied in the field of .
There is considerable speculation both in and as to why the observable universe is apparently almost entirely matter, whether other places are almost entirely antimatter instead, and what might be possible if antimatter could be harnessed, but at this time the apparent of matter and antimatter in the visible universe is one of the great . Possible processes by which it came about are explored in more detail under .
A possible definition of matter which at least some physicists use is that matter is everything that is constituted of truly called . These fermions are spin-1/2 particles, which are thought to have no substructure. They include the (an example of which is the familiar ), and also the , including the up and down quarks of which and are made. Since protons, neutrons and electrons combine to form atoms,
Tods Shoes Sale, the bulk substances which are made of atoms are all "made" of fermionic matter.
As bulk matter
References
Antimatter
In this scheme, matter also includes the various high-mass and short-lived (such as ) which are never seen except in physics experiments, and also the . Things which are not matter include light () and the other massless , such as and . Massive gauge bosons such as the which mediate the are not included in this definition (i.e., because they are not fermions, having a spin of 1, they would not be considered matter).
There is a semantic difficulty with the word
matter, since it has two meanings, once of which includes the other.
Matter may mean either:
Leptons do not feel the strong force and so can exist unbound from other particles. On Earth, electrons are generally bound in atoms, but it is easy to free them, a fact which is exploited in the . may briefly form bound states known as . Neutrinos feel neither the strong nor the . They are never bound to other particles.
In small quantities, matter can exhibit properties that are entirely different from those of bulk material and may not be well described by any phase.
Properties of matter As individual particles
Problems with this definition
Usage note regarding
matter and
anti-matter Antimatter is not found naturally on Earth, except very briefly and in vanishingly small quantities as the result of or . 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 ) can be made in minuscule amounts, but not in enough quantity to do more than test a few of its theoretical properties.
In ,
is matter that is composed of the of those that constitute normal matter. If a particle and its antiparticle come into contact with each other, the two ; that is, they may both be converted into other particles with equal in accordance with 's equation
. These new particles may be high-energy () or other particle�Cantiparticle pairs. The resulting particles are endowed with an amount of kinetic energy equal to the difference between the of the products of the annihilation and the rest mass of the original particle-antiparticle pair, which is often quite large.
Fermion definition
Common definition
From Citizendium, the Citizens' Compendium
Phases are sometimes called
states of matter, but this term can lead to confusion with states. For example, two gases maintained at different pressures are in different thermodynamic states, but the same "state of matter".
Quarks combine to form . Because of the principle of which occurs in the , quarks never exist unbound from other quarks. Among the hadrons are the proton and the neutron. Usually these nuclei are surrounded by a cloud of electrons. A nucleus with as many electrons as protons is thus electrically neutral and is called an , otherwise it is an .
Dark matter
Homogeneous matter has a definite composition and properties and any amount of it has the same composition and properties. It may be a mixture, such as , or elemental, like pure .
Heterogeneous matter, such as , does not have a definite composition.
Moreover, any kind of energy in a closed system is associated with an which has weight, inertia, and in general acts exactly like all other forms of matter. For example, when an object is heated, according to modern physics, it gains mass. Should heat then be considered matter? Even a system of massless particles can have invariant mass. For instance, any two photons which are not moving parallel to each other constitute a massive system. There may even be massive quasi-stable particles called which are made entirely of massless, non-fermionic components. See
.
Phases
In , most models of the early universe and require the existence of so called . This matter would have energy and mass, but would
not be composed of either elementary fermions (as above)
or gauge bosons. As such, it would be composed of particles unknown to present science. Its existence is inferential at this point.
It is recognized in the of particle physics that kinetic energy and force fields contribute most of the of ordinary objects. In the natural sciences, the term "matter" is therefore somewhat loosely defined, largely due the fact that use of "matter," as a term opposed to "energy," linguistically forces an artificial distinction between
matter and
energy which is no longer present in the understanding of modern physics. Ordinary physical objects are mostly composed of fields and kinetic energy by weight, and so exclusion of fields and energy from the term "matter" would require that ordinary physical objects be mostly composed of non-matter.
The fermion definition of matter is not always satisfying when examined closely. In this scheme, elementary massive of the have , but are not considered matter because they are not fermions. Furthermore, only a small fraction of the mass of ordinary such as protons and neutrons can be accounted for by the mass of their constituent fermions (quarks).
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