95-517: A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment , is described by its boundaries, structure and purpose and is expressed in its functioning. Systems are the subjects of study of systems theory and other systems sciences . Systems have several common properties and characteristics, including structure, function(s), behavior and interconnectivity. The term system comes from
190-573: A Hubble sphere . Some disputed estimates for the total size of the universe, if finite, reach as high as 10 10 10 122 {\displaystyle 10^{10^{10^{122}}}} megaparsecs, as implied by a suggested resolution of the No-Boundary Proposal . Assuming that the Lambda-CDM model is correct, the measurements of the parameters using a variety of techniques by numerous experiments yield
285-603: A system is the part of the universe that is being studied, while the environment is the remainder of the universe that lies outside the boundaries of the system. It is also known as the surroundings or neighbourhood , and in thermodynamics , as the reservoir . Depending on the type of system, it may interact with the environment by exchanging mass , energy (including heat and work ), linear momentum , angular momentum , electric charge , or other conserved properties . In some disciplines, such as information theory , information may also be exchanged. The environment
380-462: A best value of the age of the universe at 13.799 ± 0.021 billion years, as of 2015. Over time, the universe and its contents have evolved. For example, the relative population of quasars and galaxies has changed and the universe has expanded . This expansion is inferred from the observation that the light from distant galaxies has been redshifted , which implies that the galaxies are receding from us. Analyses of Type Ia supernovae indicate that
475-486: A body of water vapor) in steam engines , in regard to the system's ability to do work when heat is applied to it. The working substance could be put in contact with either a boiler, a cold reservoir (a stream of cold water), or a piston (on which the working body could do work by pushing on it). In 1850, the German physicist Rudolf Clausius generalized this picture to include the concept of the surroundings and began to use
570-606: A car, a coffeemaker , or Earth . A closed system exchanges energy, but not matter, with its environment; like a computer or the project Biosphere 2 . An isolated system exchanges neither matter nor energy with its environment. A theoretical example of such a system is the Universe . An open system can also be viewed as a bounded transformation process, that is, a black box that is a process or collection of processes that transform inputs into outputs. Inputs are consumed; outputs are produced. The concept of input and output here
665-402: A galaxy have planets . At the largest scale , galaxies are distributed uniformly and the same in all directions, meaning that the universe has neither an edge nor a center. At smaller scales, galaxies are distributed in clusters and superclusters which form immense filaments and voids in space, creating a vast foam-like structure. Discoveries in the early 20th century have suggested that
760-443: A major defect: they must be premised on one or more fundamental assumptions upon which additional knowledge is built. This is in strict alignment with Gödel's incompleteness theorems . The Artificial system can be defined as a "consistent formalized system which contains elementary arithmetic". These fundamental assumptions are not inherently deleterious, but they must by definition be assumed as true, and if they are actually false then
855-547: A reasonably good account of various observations about the universe. The initial hot, dense state is called the Planck epoch , a brief period extending from time zero to one Planck time unit of approximately 10 seconds. During the Planck epoch, all types of matter and all types of energy were concentrated into a dense state, and gravity —currently the weakest by far of the four known forces —is believed to have been as strong as
950-442: A set of four coordinates: ( x , y , z , t ) . On average, space is observed to be very nearly flat (with a curvature close to zero), meaning that Euclidean geometry is empirically true with high accuracy throughout most of the universe. Spacetime also appears to have a simply connected topology , in analogy with a sphere, at least on the length scale of the observable universe. However, present observations cannot exclude
1045-456: Is George Boole 's Boolean operators. Other examples relate specifically to philosophy, biology, or cognitive science. Maslow's hierarchy of needs applies psychology to biology by using pure logic. Numerous psychologists, including Carl Jung and Sigmund Freud developed systems that logically organize psychological domains, such as personalities, motivations, or intellect and desire. In 1988, military strategist, John A. Warden III introduced
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#17327659576881140-445: Is a composite particle made of quarks held together by the strong force . Hadrons are categorized into two families: baryons (such as protons and neutrons ) made of three quarks, and mesons (such as pions ) made of one quark and one antiquark . Of the hadrons, protons are stable, and neutrons bound within atomic nuclei are stable. Other hadrons are unstable under ordinary conditions and are thus insignificant constituents of
1235-546: Is a hardware system, software system , or combination, which has components as its structure and observable inter-process communications as its behavior. There are systems of counting, as with Roman numerals , and various systems for filing papers, or catalogs, and various library systems, of which the Dewey Decimal Classification is an example. This still fits with the definition of components that are connected together (in this case to facilitate
1330-417: Is called the observable universe . The proper distance (measured at a fixed time) between Earth and the edge of the observable universe is 46 billion light-years (14 billion parsecs ), making the diameter of the observable universe about 93 billion light-years (28 billion parsecs). Although the distance traveled by light from the edge of the observable universe is close to the age of the universe times
1425-411: Is composed almost completely of dark energy, dark matter, and ordinary matter . Other contents are electromagnetic radiation (estimated to constitute from 0.005% to close to 0.01% of the total mass–energy of the universe) and antimatter . The proportions of all types of matter and energy have changed over the history of the universe. The total amount of electromagnetic radiation generated within
1520-405: Is composed of two types of elementary particles : quarks and leptons . For example, the proton is formed of two up quarks and one down quark ; the neutron is formed of two down quarks and one up quark; and the electron is a kind of lepton. An atom consists of an atomic nucleus , made up of protons and neutrons (both of which are baryons ), and electrons that orbit the nucleus. Soon after
1615-555: Is crucial, and defined natural and designed , i. e. artificial, systems. For example, natural systems include subatomic systems, living systems , the Solar System , galaxies , and the Universe , while artificial systems include man-made physical structures, hybrids of natural and artificial systems, and conceptual knowledge. The human elements of organization and functions are emphasized with their relevant abstract systems and representations. Artificial systems inherently have
1710-660: Is equal to, less than, or greater than 1. These are called, respectively, the flat, open and closed universes. Observations, including the Cosmic Background Explorer (COBE), Wilkinson Microwave Anisotropy Probe (WMAP), and Planck maps of the CMB, suggest that the universe is infinite in extent with a finite age, as described by the Friedmann–Lemaître–Robertson–Walker (FLRW) models. These FLRW models thus support inflationary models and
1805-508: Is ignored in analysis of the system, except in regard to these interactions. This physics -related article is a stub . You can help Misplaced Pages by expanding it . This systems -related article is a stub . You can help Misplaced Pages by expanding it . Universe The universe is all of space and time and their contents. It comprises all of existence , any fundamental interaction , physical process and physical constant , and therefore all forms of matter and energy , and
1900-618: Is in the Local Group of galaxies, which in turn is in the Laniakea Supercluster . This supercluster spans over 500 million light-years, while the Local Group spans over 10 million light-years. The universe also has vast regions of relative emptiness; the largest known void measures 1.8 billion ly (550 Mpc) across. The observable universe is isotropic on scales significantly larger than superclusters, meaning that
1995-523: Is known as dark matter . In the widely accepted ΛCDM cosmological model, dark matter accounts for about 25.8% ± 1.1% of the mass and energy in the universe while about 69.2% ± 1.2% is dark energy , a mysterious form of energy responsible for the acceleration of the expansion of the universe . Ordinary (' baryonic ') matter therefore composes only 4.84% ± 0.1% of the universe. Stars, planets, and visible gas clouds only form about 6% of this ordinary matter. There are many competing hypotheses about
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#17327659576882090-786: Is subject to the Pauli exclusion principle ; no two leptons of the same species can be in exactly the same state at the same time. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons), and neutral leptons (better known as neutrinos ). Electrons are stable and the most common charged lepton in the universe, whereas muons and taus are unstable particles that quickly decay after being produced in high energy collisions, such as those involving cosmic rays or carried out in particle accelerators . Charged leptons can combine with other particles to form various composite particles such as atoms and positronium . The electron governs nearly all of chemistry , as it
2185-487: Is the Standard Model , a theory that is concerned with electromagnetic interactions and the weak and strong nuclear interactions. The Standard Model is supported by the experimental confirmation of the existence of particles that compose matter: quarks and leptons , and their corresponding " antimatter " duals, as well as the force particles that mediate interactions : the photon , the W and Z bosons , and
2280-430: Is unknown whether or not they are composed of smaller and even more fundamental particles. In most contemporary models they are thought of as points in space. All elementary particles are currently best explained by quantum mechanics and exhibit wave–particle duality : their behavior has both particle-like and wave -like aspects, with different features dominating under different circumstances. Of central importance
2375-869: Is unknown. Dark matter, a mysterious form of matter that has not yet been identified, accounts for 26.8% of the cosmic contents. Dark energy, which is the energy of empty space and is causing the expansion of the universe to accelerate, accounts for the remaining 68.3% of the contents. Matter, dark matter, and dark energy are distributed homogeneously throughout the universe over length scales longer than 300 million light-years (ly) or so. However, over shorter length-scales, matter tends to clump hierarchically; many atoms are condensed into stars , most stars into galaxies, most galaxies into clusters, superclusters and, finally, large-scale galactic filaments . The observable universe contains as many as an estimated 2 trillion galaxies and, overall, as many as an estimated 10 stars – more stars (and earth-like planets) than all
2470-448: Is very broad. For example, an output of a passenger ship is the movement of people from departure to destination. A system comprises multiple views . Human-made systems may have such views as concept, analysis , design , implementation , deployment, structure, behavior, input data, and output data views. A system model is required to describe and represent all these views. A systems architecture, using one single integrated model for
2565-581: The Big Bang , primordial protons and neutrons formed from the quark–gluon plasma of the early universe as it cooled below two trillion degrees. A few minutes later, in a process known as Big Bang nucleosynthesis , nuclei formed from the primordial protons and neutrons. This nucleosynthesis formed lighter elements, those with small atomic numbers up to lithium and beryllium , but the abundance of heavier elements dropped off sharply with increasing atomic number. Some boron may have been formed at this time, but
2660-418: The Big Bang , would have completely annihilated each other and left only photons as a result of their interaction. These laws are Gauss's law and the non-divergence of the stress–energy–momentum pseudotensor . Due to the finite speed of light , there is a limit (known as the particle horizon ) to how far light can travel over the age of the universe . The spatial region from which we can receive light
2755-628: The Five Ring System model in his book, The Air Campaign , contending that any complex system could be broken down into five concentric rings. Each ring—leadership, processes, infrastructure, population and action units—could be used to isolate key elements of any system that needed change. The model was used effectively by Air Force planners in the Iran–Iraq War . In the late 1990s, Warden applied his model to business strategy. Environment (systems) In science and engineering ,
2850-541: The German words Das All , Weltall , and Natur for universe . The same synonyms are found in English, such as everything (as in the theory of everything ), the cosmos (as in cosmology ), the world (as in the many-worlds interpretation ), and nature (as in natural laws or natural philosophy ). The prevailing model for the evolution of the universe is the Big Bang theory. The Big Bang model states that
2945-525: The Latin word systēma , in turn from Greek σύστημα systēma : "whole concept made of several parts or members, system", literary "composition". In the 19th century, the French physicist Nicolas Léonard Sadi Carnot , who studied thermodynamics , pioneered the development of the concept of a system in the natural sciences . In 1824, he studied the system which he called the working substance (typically
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3040-635: The Milky Way is roughly 100,000–180,000 light-years in diameter, and the nearest sister galaxy to the Milky Way, the Andromeda Galaxy , is located roughly 2.5 million light-years away. Because humans cannot observe space beyond the edge of the observable universe, it is unknown whether the size of the universe in its totality is finite or infinite. Estimates suggest that the whole universe, if finite, must be more than 250 times larger than
3135-468: The expansion is accelerating . The more matter there is in the universe, the stronger the mutual gravitational pull of the matter. If the universe were too dense then it would re-collapse into a gravitational singularity . However, if the universe contained too little matter then the self-gravity would be too weak for astronomical structures, like galaxies or planets, to form. Since the Big Bang,
3230-404: The general theory of relativity , explains gravity by recognizing that spacetime is not fixed but instead dynamical. In general relativity, gravitational force is reimagined as curvature of spacetime . A curved path like an orbit is not the result of a force deflecting a body from an ideal straight-line path, but rather the body's attempt to fall freely through a background that is itself curved by
3325-560: The gluon . The Standard Model predicted the existence of the recently discovered Higgs boson , a particle that is a manifestation of a field within the universe that can endow particles with mass. Because of its success in explaining a wide variety of experimental results, the Standard Model is sometimes regarded as a "theory of almost everything". The Standard Model does not, however, accommodate gravity. A true force–particle "theory of everything" has not been attained. A hadron
3420-483: The grains of beach sand on planet Earth ; but less than the total number of atoms estimated in the universe as 10 ; and the estimated total number of stars in an inflationary universe (observed and unobserved), as 10 . Typical galaxies range from dwarfs with as few as ten million (10 ) stars up to giants with one trillion (10 ) stars. Between the larger structures are voids , which are typically 10–150 Mpc (33 million–490 million ly) in diameter. The Milky Way
3515-441: The hadron epoch , and the lepton epoch . Together, these epochs encompassed less than 10 seconds of time following the Big Bang. These elementary particles associated stably into ever larger combinations, including stable protons and neutrons , which then formed more complex atomic nuclei through nuclear fusion . This process, known as Big Bang nucleosynthesis , lasted for about 17 minutes and ended about 20 minutes after
3610-404: The large-scale structure of the universe. Other than neutrinos , a form of hot dark matter , dark matter has not been detected directly, making it one of the greatest mysteries in modern astrophysics . Dark matter neither emits nor absorbs light or any other electromagnetic radiation at any significant level. Dark matter is estimated to constitute 26.8% of the total mass–energy and 84.5% of
3705-448: The law of universal gravitation , Isaac Newton built upon Copernicus's work as well as Johannes Kepler 's laws of planetary motion and observations by Tycho Brahe . Further observational improvements led to the realization that the Sun is one of a few hundred billion stars in the Milky Way , which is one of a few hundred billion galaxies in the observable universe. Many of the stars in
3800-421: The observable universe and global geometry . Cosmologists often work with a given space-like slice of spacetime called the comoving coordinates . The section of spacetime which can be observed is the backward light cone , which delimits the cosmological horizon . The cosmological horizon, also called the particle horizon or the light horizon, is the maximum distance from which particles can have traveled to
3895-442: The observer in the age of the universe . This horizon represents the boundary between the observable and the unobservable regions of the universe. An important parameter determining the future evolution of the universe theory is the density parameter , Omega (Ω), defined as the average matter density of the universe divided by a critical value of that density. This selects one of three possible geometries depending on whether Ω
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3990-624: The ultimate fate of the universe and about what, if anything, preceded the Big Bang, while other physicists and philosophers refuse to speculate, doubting that information about prior states will ever be accessible. Some physicists have suggested various multiverse hypotheses, in which the universe might be one among many. The physical universe is defined as all of space and time (collectively referred to as spacetime ) and their contents. Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter , and therefore planets, moons , stars, galaxies, and
4085-480: The weak and strong nuclear forces , decline very rapidly with distance; their effects are confined mainly to sub-atomic length scales. The universe appears to have much more matter than antimatter , an asymmetry possibly related to the CP violation . This imbalance between matter and antimatter is partially responsible for the existence of all matter existing today, since matter and antimatter, if equally produced at
4180-421: The Big Bang, so only the fastest and simplest reactions occurred. About 25% of the protons and all the neutrons in the universe, by mass, were converted to helium , with small amounts of deuterium (a form of hydrogen ) and traces of lithium . Any other element was only formed in very tiny quantities. The other 75% of the protons remained unaffected, as hydrogen nuclei. After nucleosynthesis ended,
4275-659: The ability to interact with local and remote operators. A subsystem description is a system object that contains information defining the characteristics of an operating environment controlled by the system. The data tests are performed to verify the correctness of the individual subsystem configuration data (e.g. MA Length, Static Speed Profile, …) and they are related to a single subsystem in order to test its Specific Application (SA). There are many kinds of systems that can be analyzed both quantitatively and qualitatively . For example, in an analysis of urban systems dynamics , A . W. Steiss defined five intersecting systems, including
4370-462: The allocation and scarcity of resources. The international sphere of interacting states is described and analyzed in systems terms by several international relations scholars, most notably in the neorealist school . This systems mode of international analysis has however been challenged by other schools of international relations thought, most notably the constructivist school , which argues that an over-large focus on systems and structures can obscure
4465-476: The contents of intergalactic space . The universe also includes the physical laws that influence energy and matter, such as conservation laws , classical mechanics , and relativity . The universe is often defined as "the totality of existence", or everything that exists, everything that has existed, and everything that will exist. In fact, some philosophers and scientists support the inclusion of ideas and abstract concepts—such as mathematics and logic—in
4560-459: The definition of the universe. The word universe may also refer to concepts such as the cosmos , the world , and nature . The word universe derives from the Old French word univers , which in turn derives from the Latin word universus , meaning 'combined into one'. The Latin word 'universum' was used by Cicero and later Latin authors in many of the same senses as
4655-546: The density of matter was less than the density of dark energy, marking the beginning of the present dark-energy-dominated era . In this era, the expansion of the universe is accelerating due to dark energy. Of the four fundamental interactions , gravitation is the dominant at astronomical length scales. Gravity's effects are cumulative; by contrast, the effects of positive and negative charges tend to cancel one another, making electromagnetism relatively insignificant on astronomical length scales. The remaining two interactions,
4750-410: The description of multiple views, is a kind of system model. A subsystem is a set of elements, which is a system itself, and a component of a larger system. The IBM Mainframe Job Entry Subsystem family ( JES1 , JES2 , JES3 , and their HASP / ASP predecessors) are examples. The main elements they have in common are the components that handle input, scheduling, spooling and output; they also have
4845-399: The distinction between them is often elusive. An economic system is a social institution which deals with the production , distribution and consumption of goods and services in a particular society . The economic system is composed of people , institutions and their relationships to resources, such as the convention of property . It addresses the problems of economics , like
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#17327659576884940-407: The earliest state of the universe was an extremely hot and dense one, and that the universe subsequently expanded and cooled. The model is based on general relativity and on simplifying assumptions such as the homogeneity and isotropy of space. A version of the model with a cosmological constant (Lambda) and cold dark matter , known as the Lambda-CDM model , is the simplest model that provides
5035-411: The energy of each photon decreases as it is cosmologically redshifted . At around 47,000 years, the energy density of matter became larger than that of photons and neutrinos , and began to dominate the large scale behavior of the universe. This marked the end of the radiation-dominated era and the start of the matter-dominated era . In the earliest stages of the universe, tiny fluctuations within
5130-399: The first 10 seconds. This initial period of inflation would explain why space appears to be very flat . Within the first fraction of a second of the universe's existence, the four fundamental forces had separated. As the universe continued to cool from its inconceivably hot state, various types of subatomic particles were able to form in short periods of time known as the quark epoch ,
5225-476: The first subatomic particles and simple atoms to form. Giant clouds of hydrogen and helium were gradually drawn to the places where matter was most dense , forming the first galaxies, stars, and everything else seen today. From studying the effects of gravity on both matter and light, it has been discovered that the universe contains much more matter than is accounted for by visible objects; stars, galaxies, nebulas and interstellar gas. This unseen matter
5320-430: The first time. Unlike plasma, neutral atoms are transparent to many wavelengths of light, so for the first time the universe also became transparent. The photons released (" decoupled ") when these atoms formed can still be seen today; they form the cosmic microwave background (CMB). As the universe expands, the energy density of electromagnetic radiation decreases more quickly than does that of matter because
5415-403: The flow of information). System can also refer to a framework, aka platform , be it software or hardware, designed to allow software programs to run. A flaw in a component or system can cause the component itself or an entire system to fail to perform its required function, e.g., an incorrect statement or data definition . In engineering and physics , a physical system is the portion of
5510-427: The gradual reionization of the universe between about 200–500 million years and 1 billion years, and also for seeding the universe with elements heavier than helium, through stellar nucleosynthesis . The universe also contains a mysterious energy—possibly a scalar field —called dark energy , the density of which does not change over time. After about 9.8 billion years, the universe had expanded sufficiently so that
5605-548: The modern English word is used. A term for universe among the ancient Greek philosophers from Pythagoras onwards was τὸ πᾶν ( tò pân ) 'the all', defined as all matter and all space, and τὸ ὅλον ( tò hólon ) 'all things', which did not necessarily include the void. Another synonym was ὁ κόσμος ( ho kósmos ) meaning 'the world , the cosmos '. Synonyms are also found in Latin authors ( totum , mundus , natura ) and survive in modern languages, e.g.,
5700-448: The modern universe. From approximately 10 seconds after the Big Bang , during a period known as the hadron epoch , the temperature of the universe had fallen sufficiently to allow quarks to bind together into hadrons, and the mass of the universe was dominated by hadrons . Initially, the temperature was high enough to allow the formation of hadron–anti-hadron pairs, which kept matter and antimatter in thermal equilibrium . However, as
5795-541: The next heavier element, carbon , was not formed in significant amounts. Big Bang nucleosynthesis shut down after about 20 minutes due to the rapid drop in temperature and density of the expanding universe. Subsequent formation of heavier elements resulted from stellar nucleosynthesis and supernova nucleosynthesis . Ordinary matter and the forces that act on matter can be described in terms of elementary particles . These particles are sometimes described as being fundamental, since they have an unknown substructure, and it
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#17327659576885890-462: The notion of organizations as systems in his book The Fifth Discipline . Organizational theorists such as Margaret Wheatley have also described the workings of organizational systems in new metaphoric contexts, such as quantum physics , chaos theory , and the self-organization of systems . There is also such a thing as a logical system . An obvious example is the calculus developed simultaneously by Leibniz and Isaac Newton . Another example
5985-518: The observed rate of expansion. Contributions from scalar fields that are constant in space are usually also included in the cosmological constant. The cosmological constant can be formulated to be equivalent to vacuum energy . Dark matter is a hypothetical kind of matter that is invisible to the entire electromagnetic spectrum , but which accounts for most of the matter in the universe. The existence and properties of dark matter are inferred from its gravitational effects on visible matter, radiation, and
6080-428: The other fundamental forces, and all the forces may have been unified . The physics controlling this very early period (including quantum gravity in the Planck epoch) is not understood, so we cannot say what, if anything, happened before time zero . Since the Planck epoch, the universe has been expanding to its present scale, with a very short but intense period of cosmic inflation speculated to have occurred within
6175-429: The physical subsystem and behavioral system. For sociological models influenced by systems theory, Kenneth D. Bailey defined systems in terms of conceptual , concrete , and abstract systems, either isolated , closed , or open . Walter F. Buckley defined systems in sociology in terms of mechanical , organic , and process models . Bela H. Banathy cautioned that for any inquiry into a system understanding its kind
6270-442: The possibilities that the universe has more dimensions (which is postulated by theories such as string theory) and that its spacetime may have a multiply connected global topology, in analogy with the cylindrical or toroidal topologies of two-dimensional spaces . General relativity describes how spacetime is curved and bent by mass and energy (gravity). The topology or geometry of the universe includes both local geometry in
6365-458: The presence of other masses. A remark by John Archibald Wheeler that has become proverbial among physicists summarizes the theory: "Spacetime tells matter how to move; matter tells spacetime how to curve", and therefore there is no point in considering one without the other. The Newtonian theory of gravity is a good approximation to the predictions of general relativity when gravitational effects are weak and objects are moving slowly compared to
6460-408: The present dark-energy era, it dominates the mass–energy of the universe because it is uniform across space. Two proposed forms for dark energy are the cosmological constant , a constant energy density filling space homogeneously, and scalar fields such as quintessence or moduli , dynamic quantities whose energy density can vary in time and space while still permeating them enough to cause
6555-405: The role of individual agency in social interactions. Systems-based models of international relations also underlie the vision of the international sphere held by the liberal institutionalist school of thought, which places more emphasis on systems generated by rules and interaction governance, particularly economic governance. In computer science and information science , an information system
6650-456: The same from all vantage points and has no center. An explanation for why the expansion of the universe is accelerating remains elusive. It is often attributed to the gravitational influence of "dark energy", an unknown form of energy that is hypothesized to permeate space. On a mass–energy equivalence basis, the density of dark energy (~ 7 × 10 g/cm ) is much less than the density of ordinary matter or dark matter within galaxies. However, in
6745-456: The same time, a second observer who is moving relative to the first will see those events happening at different times. The two observers will disagree on the time T {\displaystyle T} between the events, and they will disagree about the distance D {\displaystyle D} separating the events, but they will agree on the speed of light c {\displaystyle c} , and they will measure
6840-477: The same value for the combination c 2 T 2 − D 2 {\displaystyle c^{2}T^{2}-D^{2}} . The square root of the absolute value of this quantity is called the interval between the two events. The interval expresses how widely separated events are, not just in space or in time, but in the combined setting of spacetime. The special theory of relativity cannot account for gravity . Its successor,
6935-401: The second derivative of the cosmic scale factor a ¨ {\displaystyle {\ddot {a}}} has been positive in the last 5–6 billion years. Modern physics regards events as being organized into spacetime . This idea originated with the special theory of relativity , which predicts that if one observer sees two events happening in different places at
7030-466: The speed of light, 13.8 billion light-years (4.2 × 10 ^ pc), the proper distance is larger because the edge of the observable universe and the Earth have since moved further apart. For comparison, the diameter of a typical galaxy is 30,000 light-years (9,198 parsecs ), and the typical distance between two neighboring galaxies is 3 million light-years (919.8 kiloparsecs). As an example,
7125-454: The speed of light. The relation between matter distribution and spacetime curvature is given by the Einstein field equations , which require tensor calculus to express. The universe appears to be a smooth spacetime continuum consisting of three spatial dimensions and one temporal ( time ) dimension. Therefore, an event in the spacetime of the physical universe can be identified by
7220-483: The standard model of cosmology, describing a flat , homogeneous universe presently dominated by dark matter and dark energy . The fine-tuned universe hypothesis is the proposition that the conditions that allow the existence of observable life in the universe can only occur when certain universal fundamental physical constants lie within a very narrow range of values. According to this hypothesis, if any of several fundamental constants were only slightly different,
7315-433: The statistical properties of the universe are the same in all directions as observed from Earth. The universe is bathed in highly isotropic microwave radiation that corresponds to a thermal equilibrium blackbody spectrum of roughly 2.72548 kelvins . The hypothesis that the large-scale universe is homogeneous and isotropic is known as the cosmological principle . A universe that is both homogeneous and isotropic looks
7410-421: The structures they form, from sub-atomic particles to entire galactic filaments . Since the early 20th century, the field of cosmology establishes that space and time emerged together at the Big Bang 13.787 ± 0.020 billion years ago and that the universe has been expanding since then. The portion of the universe that we can see is approximately 93 billion light-years in diameter at present, but
7505-1205: The system is not as structurally integral as is assumed (i.e. it is evident that if the initial expression is false, then the artificial system is not a "consistent formalized system"). For example, in geometry this is very evident in the postulation of theorems and extrapolation of proofs from them. George J. Klir maintained that no "classification is complete and perfect for all purposes", and defined systems as abstract, real, and conceptual physical systems , bounded and unbounded systems , discrete to continuous, pulse to hybrid systems , etc. The interactions between systems and their environments are categorized as relatively closed and open systems . Important distinctions have also been made between hard systems—–technical in nature and amenable to methods such as systems engineering , operations research, and quantitative systems analysis—and soft systems that involve people and organizations, commonly associated with concepts developed by Peter Checkland and Brian Wilson through soft systems methodology (SSM) involving methods such as action research and emphasis of participatory designs. Where hard systems might be identified as more scientific ,
7600-552: The system. There are natural and human-made (designed) systems. Natural systems may not have an apparent objective but their behavior can be interpreted as purposeful by an observer. Human-made systems are made with various purposes that are achieved by some action performed by or with the system. The parts of a system must be related; they must be "designed to work as a coherent entity"—otherwise they would be two or more distinct systems. Most systems are open systems , exchanging matter and energy with their respective surroundings; like
7695-404: The temperature of the universe continued to fall, hadron–anti-hadron pairs were no longer produced. Most of the hadrons and anti-hadrons were then eliminated in particle–antiparticle annihilation reactions, leaving a small residual of hadrons by the time the universe was about one second old. A lepton is an elementary , half-integer spin particle that does not undergo strong interactions but
7790-461: The term working body when referring to the system. The biologist Ludwig von Bertalanffy became one of the pioneers of the general systems theory . In 1945 he introduced models, principles, and laws that apply to generalized systems or their subclasses, irrespective of their particular kind, the nature of their component elements, and the relation or 'forces' between them. In the late 1940s and mid-50s, Norbert Wiener and Ross Ashby pioneered
7885-476: The total matter in the universe. The remaining 4.9% of the mass–energy of the universe is ordinary matter, that is, atoms , ions , electrons and the objects they form. This matter includes stars , which produce nearly all of the light we see from galaxies, as well as interstellar gas in the interstellar and intergalactic media, planets , and all the objects from everyday life that we can bump into, touch or squeeze. The great majority of ordinary matter in
7980-455: The total size of the universe is not known. Some of the earliest cosmological models of the universe were developed by ancient Greek and Indian philosophers and were geocentric , placing Earth at the center. Over the centuries, more precise astronomical observations led Nicolaus Copernicus to develop the heliocentric model with the Sun at the center of the Solar System . In developing
8075-488: The universe entered a period known as the photon epoch . During this period, the universe was still far too hot for matter to form neutral atoms , so it contained a hot, dense, foggy plasma of negatively charged electrons , neutral neutrinos and positive nuclei. After about 377,000 years, the universe had cooled enough that electrons and nuclei could form the first stable atoms . This is known as recombination for historical reasons; electrons and nuclei were combining for
8170-406: The universe had a beginning and has been expanding since then. According to the Big Bang theory, the energy and matter initially present have become less dense as the universe expanded. After an initial accelerated expansion called the inflationary epoch at around 10 seconds, and the separation of the four known fundamental forces , the universe gradually cooled and continued to expand, allowing
8265-454: The universe has decreased by 1/2 in the past 2 billion years. Today, ordinary matter, which includes atoms, stars, galaxies, and life , accounts for only 4.9% of the contents of the universe. The present overall density of this type of matter is very low, roughly 4.5 × 10 grams per cubic centimeter, corresponding to a density of the order of only one proton for every four cubic meters of volume. The nature of both dark energy and dark matter
8360-406: The universe has expanded monotonically . Perhaps unsurprisingly , our universe has just the right mass–energy density , equivalent to about 5 protons per cubic meter, which has allowed it to expand for the last 13.8 billion years, giving time to form the universe as observed today. There are dynamical forces acting on the particles in the universe which affect the expansion rate. Before 1998, it
8455-482: The universe is unseen, since visible stars and gas inside galaxies and clusters account for less than 10 percent of the ordinary matter contribution to the mass–energy density of the universe. Ordinary matter commonly exists in four states (or phases ): solid , liquid , gas , and plasma . However, advances in experimental techniques have revealed other previously theoretical phases, such as Bose–Einstein condensates and fermionic condensates . Ordinary matter
8550-1002: The universe that is being studied (of which a thermodynamic system is one major example). Engineering also has the concept of a system referring to all of the parts and interactions between parts of a complex project. Systems engineering is the branch of engineering that studies how this type of system should be planned, designed, implemented, built, and maintained. Social and cognitive sciences recognize systems in models of individual humans and in human societies. They include human brain functions and mental processes as well as normative ethics systems and social and cultural behavioral patterns. In management science , operations research and organizational development , human organizations are viewed as management systems of interacting components such as subsystems or system aggregates, which are carriers of numerous complex business processes ( organizational behaviors ) and organizational structures. Organizational development theorist Peter Senge developed
8645-422: The universe would have been unlikely to be conducive to the establishment and development of matter , astronomical structures, elemental diversity, or life as it is understood. Whether this is true, and whether that question is even logically meaningful to ask, are subjects of much debate. The proposition is discussed among philosophers , scientists , theologians , and proponents of creationism . The universe
8740-467: The universe's density led to concentrations of dark matter gradually forming. Ordinary matter, attracted to these by gravity , formed large gas clouds and eventually, stars and galaxies, where the dark matter was most dense, and voids where it was least dense. After around 100–300 million years, the first stars formed, known as Population III stars. These were probably very massive, luminous, non metallic and short-lived. They were responsible for
8835-458: The use of mathematics to study systems of control and communication , calling it cybernetics . In the 1960s, Marshall McLuhan applied general systems theory in an approach that he called a field approach and figure/ground analysis , to the study of media theory . In the 1980s, John Henry Holland , Murray Gell-Mann and others coined the term complex adaptive system at the interdisciplinary Santa Fe Institute . Systems theory views
8930-401: The world as a complex system of interconnected parts. One scopes a system by defining its boundary ; this means choosing which entities are inside the system and which are outside—part of the environment . One can make simplified representations ( models ) of the system in order to understand it and to predict or impact its future behavior. These models may define the structure and behavior of
9025-485: Was expected that the expansion rate would be decreasing as time went on due to the influence of gravitational interactions in the universe; and thus there is an additional observable quantity in the universe called the deceleration parameter , which most cosmologists expected to be positive and related to the matter density of the universe. In 1998, the deceleration parameter was measured by two different groups to be negative, approximately −0.55, which technically implies that
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