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number of antiquarks which each have a baryon number of 1 3 which is proportional to baryon number and number of leptons minus antileptons which is called the lepton number is practically impossible to change in any process even in a nuclear bomb none of the baryons protons and neutrons of which the atomic nuclei are composed are destroyed there are as many baryons after as before the reaction so none of these matter particles are actually destroyed and none are even converted to non matter particles like photons of light or radiation instead nuclear and perhaps chromodynamic binding energy is released as these baryons become bound into mid size nuclei having less energy and equivalently less mass per nucleon compared to the original small hydrogen and large plutonium etc nuclei even in electron positron annihilation there is 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 53 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 are not 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 so particle annihilation is rare in normal circumstances dark main articles dark matter lambda cdm model and wimps see also galaxy formation and evolution and dark matter halo pie chart showing the fractions of energy in the universe contributed by different sources ordinary matter is divided into luminous matter the stars and luminous gases and 0 005 radiation and nonluminous matter intergalactic gas and about 0 1 neutrinos and 0 04 supermassive black holes ordinary matter is uncommon modeled after ostriker and steinhardt 54 for more information see nasa dark energy 73 0 dark matter 23 0 non luminous matter 3 60 luminous matter 0 40 ordinary matter in the quarks and leptons definition constitutes about 4 of the energy of the observable universe the remaining energy is theorized to be due to exotic forms of which 23 is dark matter 55 56 and 73 is dark energy 57 58 galaxy rotation curve for the milky way the vertical axis is the rotation speed about the galactic center the horizontal axis is the distance from the galactic center the sun is marked in yellow the observed rotation speed curve is marked by data points the predicted curve based on the stellar mass and gas of the milky way is in black the difference is due to dark matter or possibly a modification of gravity like mond the data shown can be found here 59 60 61 62 63 64 65 66 67 68 in astrophysics and cosmology dark matter is matter of unknown composition that does not emit or reflect enough electromagnetic radiation to be observed directly but whose presence can be inferred from gravitational effects on visible matter 69 70 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 non baryonic in nature 69 as such it is composed of particles as yet unobserved in the laboratory perhaps they are supersymmetric particles 71 which are not standard model particles but relics formed at very high energies in the early phase of the universe and still floating about 69 energy main article dark energy see also big bang dark energy in cosmology 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 72 73 fully 70 of the matter density in the universe appears to be in the form of dark energy twenty six percent is dark matter only 4 is ordinary matter so less than 1 part in 20 is made out of matter we have observed experimentally or described in the standard model of particle physics of the other 96 apart from the properties just mentioned we know absolutely nothing lee smolin 2007 the trouble with physics p 16 exotic main article exotic matter exotic matter is a concept of particle physics which may include dark matter and dark energy but goes further to include any hypothetical material that violates one or more of the properties of known forms of matter some such materials might possess hypothetical properties like negative mass historical and philosophical study 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 74 elementary matter 75 partonic matter dark matter anti matter strange matter and nuclear matter in discussions of matter and antimatter the former has been referred to by alfvén as koinomatter gk common matter 76 in 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 hadrons or that matter is leptons and quarks depending upon the scale at which one wishes to define matter 77 classical antiquity main article atomism further information ancient greek philosophy and indian philosophy in ancient india the buddhist hindu and jain philosophical traditions each posited that matter was made of atoms paramanu pudgala that were eternal indestructible without parts and innumerable and which associated or dissociated to form more complex matter according to the laws of nature 6 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 indian philosopher kanada being the most followed 6 7 buddhist philosophers also developed these ideas in late 1st millennium ce ideas that were similar to the vaisheshika school but ones that did not include any soul or conscience 6 jain philosophers included the soul jiva adding qualities such as taste smell touch and color to each atom 78 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 6 in ancient greece pre socratic philosophers speculated the underlying nature of the visible world thales c 624 bce c 546 bce regarded water as the fundamental material of the world anaximander c 610 bce c 546 bce posited that the basic material was wholly characterless or limitless the infinite apeiron anaximenes flourished 585 bce d 528 bce posited that the basic stuff was pneuma or air heraclitus c 535 bce c 475 bce seems to say the basic element is fire though perhaps he means that all is change empedocles c 490 430 bce spoke of four elements of which everything was made earth water air and fire 79 meanwhile parmenides argued that change does not exist and democritus 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 80 aristotle 384 bce 322 bce was the first to put the conception on a sound philosophical basis which he did in his natural philosophy especially in physics book i 81 he adopted as reasonable suppositions the four empedoclean elements but added a fifth aether nevertheless these elements are not basic in aristotle s mind rather they like everything else in the visible world are composed of the basic principles matter and form for my definition of matter is just this the primary substratum of each thing from which it comes to be without qualification and which persists in the result aristotle physics i 9 192a32 the word aristotle uses for matter ὕλη hyle or hule can be literally translated as wood or timber that is raw material for building 82 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 atoms 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 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 age of enlightenment main article enlightenment philosophy french philosopher rené descartes 1596 1650 originated the modern conception of matter he was primarily a geometer unlike aristotle who deduced the existence of matter from the physical reality of change descartes arbitrarily postulated matter to be an abstract mathematical substance that occupies space so extension in length breadth and depth constitutes the nature of bodily substance and thought constitutes the nature of thinking substance and everything else attributable to body presupposes extension and is only a mode of an extended thing rené descartes principles of philosophy 83 for descartes matter has only the property of extension so its only activity aside from locomotion is to exclude other bodies 84 this is the mechanical philosophy descartes makes an absolute distinction between mind which he defines as unextended thinking substance and matter which he defines as unthinking extended substance 85 they are independent things in contrast aristotle defines matter and the formal forming principle as complementary principles that together compose one independent thing 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 s and aristotle s conceptions is noteworthy in both conceptions matter is passive or inert in the respective conceptions matter has different relationships to intelligence for aristotle matter and intelligence form exist together in an interdependent relationship whereas for descartes matter and intelligence mind are definitionally opposed independent substances 86 descartes s 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 87 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 88 english philosopher isaac newton 1643 1727 inherited descartes s 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 89 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 90 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 91 newton developed descartes s 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 s mechanics in which interactions happened exclusively by contact 92 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 92 he argued matter has other inherent powers besides the so called primary qualities of descartes et al 93 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 atoms were seen as being the fundamental constituents of matter atoms formed molecules and compounds 94 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 95 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 i...