The Universe is most commonly defined as everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and constants that govern them. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light The Virgo Supercluster or Local Supercluster is the galactic Supercluster that contains the Local Group, the latter containing in its turn The Local Group is the group of galaxies that includes our galaxy the Milky Way. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The Orion Arm is a minor Spiral arm of the Milky Way galaxy The Solar System and Earth are within the Orion Arm The Gould Belt is a partial ring of Stars about 3000 Light years across tilted toward the Galactic plane by about 16 to 20 degrees The Local Bubble is a cavity in the Interstellar medium (ISM of the Orion Arm of the Milky Way. The Local Interstellar Cloud, casually called the Local Fluff, is the Interstellar cloud (roughly 30 light years across through which our Solar system The Solar System consists of the Sun and those celestial objects bound to it by Gravity. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Everything is the concept of all that exists Every Entity, Physical body, and Abstract object is part of everything Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of Matter is commonly defined as being anything that has mass and that takes up space. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product A physical law or scientific law is a Scientific generalization based on empirical Observations of physical behavior (i A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time However, the term "universe" may be used in slightly different contextual senses, denoting such concepts as the cosmos the world or Nature. In its most general sense a cosmos is an orderly or harmonious system In philosophy the World is everything that makes up Reality. While clarifying the Concept of world has arguably always been among the basic tasks of Western Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe.

Astronomical observations indicate that the universe is 13.73 ± 0.12 billion years old and at least 93 billion light years across. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that The age of the Universe is the time elapsed between the theory of the Big Bang and the present day A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by The event that started the universe is called the Big Bang. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. At this point in time all matter and energy of the observable universe was concentrated in one point of infinite density. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that Infinity (symbolically represented with ∞) comes from the Latin infinitas or "unboundedness After the Big Bang the universe started to expand to its present form. Since special relativity states that matter cannot exceed the speed of light, in a fixed space-time, it may seem paradoxical that two galaxies can be separated by 93 billion light years in 13 billion years; however, this separation is a natural consequence of general relativity. Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Stated simply, space can expand with no intrinsic limit on its rate; thus, two galaxies can separate more quickly than the speed of light if the space between them grows. Experimental measurements such as the redshifts and spatial distribution of distant galaxies, the cosmic microwave background radiation, and the relative percentages of the lighter chemical elements, support this theoretical expansion and, more generally, the Big Bang theory, which proposes that space itself was created ex nihilo at a specific time in the past. In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. The metric expansion of space is the averaged increase of metric (i The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. The Latin phrase ex nihilo means "out of nothing" It often appears in conjunction with the concept of Creation, as in creatio ex nihilo Recent observations have shown that this expansion is accelerating, and that most of the matter and energy in the universe is fundamentally different from that observed on Earth and not directly observable (cf. dark energy). In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe The imprecision of current observations has hindered predictions of the ultimate fate of the universe. The ultimate fate of the universe is a topic in Physical cosmology.

Experiments suggest that the universe has been governed by the same physical laws and constants throughout its extent and history. The dominant force at cosmological distances is gravity, and general relativity is currently the most accurate theory of gravitation. Gravitation is a natural Phenomenon by which objects with Mass attract one another General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 The remaining three fundamental forces and the particles on which they act are described by the Standard Model. In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles The universe has at least three dimensions of space and one of time, although extremely small additional dimensions cannot be ruled out experimentally. In mathematics the dimension of a Space is roughly defined as the minimum number of Coordinates needed to specify every point within it In Physics, compactification means changing a theory with respect to one of its Space-time dimensions Spacetime appears to be smoothly and simply connected, and space has very small mean curvature, so that Euclidean geometry is accurate on the average throughout the universe. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A differentiable manifold is a type of Manifold that is locally similar enough to Euclidean space to allow one to do Calculus. In Topology, a geometrical object or space is called simply connected (or 1-connected) if it is Path-connected and every path between two points can be Three-dimensional space is a geometric model of the physical Universe in which we live In the Mathematical field of Differential geometry, the Riemann curvature tensor or Riemann–Christoffel tensor is the most standard way to express Euclidean geometry is a mathematical system attributed to the Greek Mathematician Euclid of Alexandria.

According to some speculations, this universe may be one of many disconnected universes, which are collectively denoted as the multiverse. The multiverse (or meta-universe) is the hypothetical set of multiple possible Universes (including our universe that together comprise all of Reality. In one theory, there is an infinite variety of universes, each with different physical constants. The Chaotic Inflation theory is a variety of the Inflationary universe model which is itself an outgrowth (or extension of the Big bang theory A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time In another theory, new universes are spawned with every quantum measurement. The many-worlds interpretation or MWI (also known as relative state formulation, theory of the universal wavefunction, parallel universes, The framework of Quantum mechanics requires a careful definition of measurement, and a thorough discussion of its practical and philosophical implications By definition, these speculations cannot currently be tested experimentally.

Throughout recorded history, several cosmologies and cosmogonies have been proposed to account for observations of the universe. Cosmology (from Greek grc κοσμολογία - grc κόσμος kosmos, "universe" and grc -λογία -logia) is study This article discusses scientific theories of creation (cosmogony The earliest quantitative models were developed by the ancient Greeks, who proposed that the universe possesses infinite space and has existed eternally, but contains a single set of concentric spheres of finite size - corresponding to the fixed stars, the Sun and various planets - rotating about a spherical but unmoving Earth. The term ancient Greece refers to the period of Greek history lasting from the Greek Dark Ages ca "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe The Sun (Sol is the Star at the center of the Solar System. A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 Over the centuries, more precise observations and improved theories of gravity led to Copernicus' heliocentric model and the Newtonian model of the solar system, respectively. Gravitation is a natural Phenomenon by which objects with Mass attract one another In Astronomy, heliocentrism is the theory that the Sun is at the center of the Solar System. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements The Solar System consists of the Sun and those celestial objects bound to it by Gravity. Further improvements in astronomy led to the characterization of the Milky Way, and the discovery of other galaxies and the microwave background radiation; careful studies of the distribution of these galaxies and their spectral lines have led to much of modern cosmology. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range compared Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its

Physical cosmology

Universe · Big Bang Age of the universe Timeline of the Big Bang Ultimate fate of the universe

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Etymology, synonyms and definitions

See also: Cosmos, Nature, World (philosophy), and Celestial spheres

The word universe derives from the Old French word univers, which in turn derives from the Latin word universum. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. The age of the Universe is the time elapsed between the theory of the Big Bang and the present day This timeline of the Big Bang describes the events according to the Scientific theory of the Big Bang, using the cosmological time parameter of Comoving coordinates The ultimate fate of the universe is a topic in Physical cosmology. In its most general sense a cosmos is an orderly or harmonious system Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. In philosophy the World is everything that makes up Reality. While clarifying the Concept of world has arguably always been among the basic tasks of Western The celestial spheres or celestial orbs were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle Old French was the Romance Dialect continuum spoken in territories which span roughly the northern half of modern France and parts of modern Belgium Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. ^[1] The Latin word was used by Cicero and later Latin authors in many of the same senses as the modern English word is used. Marcus Tullius Cicero ( Classical Latin ˈkikeroː usually ˈsɪsərəʊ in English January 3, 106 BC &ndash December 7, 43 BC was a Roman English is a West Germanic language originating in England and is the First language for most people in the United Kingdom, the United States ^[2] The Latin word derives from the poetic contraction unvorsum — first used by Lucretius in Book IV (line 262) of his De rerum natura (On the Nature of Things) — which connects un, uni (the combining form of unus, or "one") with vorsum, versum (a noun made from the perfect passive participle of vertere, meaning "something rotated, rolled, changed"). Titus Lucretius Carus (ca 99 BC- ca 55 BC was a Roman Poet and Philosopher. On the Nature of Things (Latin De rerum natura) is a first century BC Poem by the Roman Poet and Philosopher ^[2] Lucretius used the word in the sense "everything rolled into one, everything combined into one".

Artistic rendition of a Foucault pendulum showing that the Earth is not stationary, but rotates. The Foucault pendulum (fuːˈkoʊ "foo-KOH" or Foucault's pendulum, named after the French physicist Léon Foucault, was conceived as

An alternative interpretation of unvorsum is "everything rotated as one" or "everything rotated by one". In this sense, it may be considered a translation of an earlier Greek word for the universe, περιφορα, "something transported in a circle", originally used to describe a course of a meal, the food being carried around the circle of dinner guests. ^[3] This Greek word refers to an early Greek model of the universe, in which all matter was contained within rotating spheres centered on the Earth; according to Aristotle, the rotation of the outermost sphere was responsible for the motion and change of everything within. The celestial spheres or celestial orbs were the fundamental celestial entities of the cosmological celestial mechanics first invented by Eudoxus, and developed by Aristotle Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. In medieval and Renaissance astronomy the Primum Mobile, or "first moved" is the outermost moving sphere in the Geocentric model of the Universe. It was natural for the Greeks to assume that the Earth was stationary and that the heavens rotated about the Earth, since careful astronomical and physical measurements (such as the Foucault pendulum) are required to prove otherwise. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study The Foucault pendulum (fuːˈkoʊ "foo-KOH" or Foucault's pendulum, named after the French physicist Léon Foucault, was conceived as

The most common term for "universe" among the ancient Greek philosophers from Pythagoras onwards was το παν (The All), defined as all matter (το ολον) and all space (το κενον). "Pythagoras of Samos" redirects here For the Samian statuary of the same name see Pythagoras (sculptor. ^[4][5] Other synonyms for the universe among the ancient Greek philosophers included κοσμος (meaning the world, the cosmos) and φυσις (meaning Nature, from which we derive the word physics). In philosophy the World is everything that makes up Reality. While clarifying the Concept of world has arguably always been among the basic tasks of Western In its most general sense a cosmos is an orderly or harmonious system Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. ^[6] The same synonyms are found in Latin authors (totum, mundus, natura)^[7] and survive in modern languages, e. g. , 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 hypothesis), and Nature (as in natural laws or natural philosophy). Everything is the concept of all that exists Every Entity, Physical body, and Abstract object is part of everything A theory of everything ( TOE) is a putative Theory of Theoretical physics that fully explains and links together all known physical phenomena In its most general sense a cosmos is an orderly or harmonious system Cosmology (from Greek grc κοσμολογία - grc κόσμος kosmos, "universe" and grc -λογία -logia) is study In philosophy the World is everything that makes up Reality. While clarifying the Concept of world has arguably always been among the basic tasks of Western The many-worlds interpretation or MWI (also known as relative state formulation, theory of the universal wavefunction, parallel universes, Nature, in the broadest sense is equivalent to the natural world, physical universe, material world or material universe. Natural law or the law of nature ( Latin: lex naturalis) is a theory that posits the existence of a law whose content is set by Nature and that For the current in the 19th century German idealism see Naturphilosophie Natural philosophy or the philosophy of nature (from ^[8]

Broadest definition: reality and probability

See also: Introduction to quantum mechanics, Interpretation of quantum mechanics, and Many-worlds hypothesis

The broadest definition of the universe is found in De divisione naturae by the medieval philosopher Johannes Scotus Eriugena, who defined it as simply everything: everything that exists and everything that does not exist. Quantum mechanics (QM or quantum theory) is a physical science dealing with the behavior of Matter and Energy on the scale of Atoms An interpretation of quantum mechanics is a statement which attempts to explain how Quantum mechanics informs our Understanding of Nature. The many-worlds interpretation or MWI (also known as relative state formulation, theory of the universal wavefunction, parallel universes, De divisione naturae ("The division of nature" also titled Periphyseon) was the Magnum opus of Ninth century theologian Philosophy is the study of general problems concerning matters such as existence knowledge truth beauty justice validity mind and language Time is not considered in Eriugena's definition; thus, his definition includes everything that exists, has existed and will exist, as well as everything that does not exist, has never existed and will never exist. This all-embracing definition was not adopted by most later philosophers, but it is relevant in quantum physics, particularly the path-integral formulation of Feynman. Quantum mechanics is the study of mechanical systems whose dimensions are close to the Atomic scale such as Molecules Atoms Electrons This article is about a formulation of quantum mechanics For integrals along a path also known as line or contour integrals see Line integral. Richard Phillips Feynman (ˈfaɪnmən May 11 1918 – February 15 1988 was an American Physicist known for the Path integral formulation of quantum ^[9] According to that formulation, the probability amplitudes for the various outcomes of an experiment given a perfectly defined initial state of the system are determined by summing over all possible paths by which the system could progress from the initial to final state. In Quantum mechanics, a probability amplitude is a complex -valued function that describes an uncertain or unknown quantity Naturally, an experiment can have only one outcome; in other words, only one possible outcome is made real in this universe, via the mysterious process of quantum measurement, also known as the collapse of the wavefunction (but see the many-worlds hypothesis below in the Multiverse section). The framework of Quantum mechanics requires a careful definition of measurement, and a thorough discussion of its practical and philosophical implications In certain interpretations of quantum mechanics, wave function collapse is one of two processes by which Quantum systems apparently evolve according to the laws of The many-worlds interpretation or MWI (also known as relative state formulation, theory of the universal wavefunction, parallel universes, The multiverse (or meta-universe) is the hypothetical set of multiple possible Universes (including our universe that together comprise all of Reality. In this well-defined mathematical sense, even that which does not exist (all possible paths) can influence that which does finally exist (the experimental measurement). As a specific example, every electron is intrinsically identical to every other; therefore, probability amplitudes must be computed allowing for the possibility that they exchange positions, something known as exchange symmetry. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Exchange symmetry is derived from a fundamental Postulate of Quantum statistics, which states that no observable Physical quantity should change after exchanging This conception of the universe embracing both the existent and the non-existent is loosely related to the Buddhist doctrines of shunyata and interdependent development of reality, and to Gottfried Leibniz's more modern concepts of contingency and the identity of indiscernibles. Buddhism is a family of beliefs and practices The doctrine of pratītyasamutpāda (Sanskrit paticcasamuppāda; rten The identity of indiscernibles is an ontological principle which states that two or more objects or entities are identical (are one and the same entity

Definition as reality

See also: Reality and Physics

More customarily, the universe is defined as everything that exists, has existed and will exist. Reality, in everyday usage means "the state of things as they actually exist" Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. According to this definition and our present understanding, the universe consists of three elements: space and time, collectively known as space-time or the vacuum; matter and various forms of energy and momentum occupying space-time; and the physical laws that govern the first two. Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. Matter is commonly defined as being anything that has mass and that takes up space. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A physical law or scientific law is a Scientific generalization based on empirical Observations of physical behavior (i These elements will be discussed in greater detail below. A related definition of "universe" is everything that exists at a single moment of time, such as the present, as in the sentence "The universe is now bathed uniformly in microwave radiation". The present is the Time that is perceived directly not as a recollection or a speculation

The three elements of the universe (spacetime, matter-energy, and physical law) correspond roughly to the ideas of Aristotle. Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. In his book The Physics (Φυσικης, from which we derive the word "physics"), Aristotle divided το παν (everything) into three roughly analogous elements: matter (the stuff of which the universe is made), form (the arrangement of that matter in space) and change (how matter is created, destroyed or altered in its properties, and similarly, how form is altered). Physics (or "Physica" or "Physicae Auscultationes" meaning "lessons" is a key text in the philosophy of Aristotle. Physical laws were conceived as the rules governing the properties of matter, form and their changes. A physical law or scientific law is a Scientific generalization based on empirical Observations of physical behavior (i Later philosophers such as Lucretius, Averroes, Avicenna and Baruch Spinoza altered or refined these divisions; for example, Averroes and Spinoza discern natura naturans (the active principles governing the universe) from natura naturata, the passive elements upon which the former act. Titus Lucretius Carus (ca 99 BC- ca 55 BC was a Roman Poet and Philosopher. Abū 'l-Walīd Muḥammad ibn Aḥmad ibn Rushd (Arabicأبو الوليد محمد بن احمد بن رشد better known just as Ibn Rushd (ابن رشد and in European TemplateInfobox Muslim scholars --> ( Persian /ابو علی الحسین ابن عبدالله ابن سینا (born Baruch or Benedict de Spinoza (ברוך שפינוזה Bento de Espinosa Benedictus de Spinoza ( November 24, 1632 – February 21, Natura naturans is a Latin term coined during the Middle Ages mainly used by Baruch Spinoza meaning "Nature naturing" or more loosely "nature Natura naturata is a Latin term coined in the Middle Ages mainly used by Baruch Spinoza meaning "Nature natured" or "Nature already created"

Definition as connected space-time

Hubble Ultra Deep Field image of a small region of the observable universe, near the constellation Fornax. The Hubble Ultra Deep Field, or HUDF, is an image of a small region of space in the constellation Fornax, composited from Hubble Space Telescope In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Fornax (ˈfɔrnæks Furnace) is a southern Constellation which was first introduced by Nicolas Louis de Lacaille under the name Fornax Chemica The light from the smallest, most redshifted galaxies originated roughly 13 billion years ago. In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by

See also: Bubble universe theory and Chaotic inflation

It is possible to conceive of disconnected space-times, each existing but unable to interact with one another. The Chaotic Inflation theory is a variety of the Inflationary universe model which is itself an outgrowth (or extension of the Big bang theory The Chaotic Inflation theory is a variety of the Inflationary universe model which is itself an outgrowth (or extension of the Big bang theory SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS An easily visualized metaphor is a group of separate soap bubbles, in which observers living on one soap bubble cannot interact with those on other soap bubbles, even in principle. A soap bubble is a very thin film of Soap water that forms a Sphere with an iridescent Surface. According to one common terminology, each "soap bubble" of space-time is denoted as a universe, whereas our particular space-time is denoted as the Universe, just as we call our moon the Moon. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS The entire collection of these separate space-times is denoted as the multiverse. The multiverse (or meta-universe) is the hypothetical set of multiple possible Universes (including our universe that together comprise all of Reality. ^[10] In principle, the other unconnected universes may have different dimensionalities and topologies of space-time, different forms of matter and energy, and different physical laws and physical constants, although it is impossible to know for sure. In mathematics the dimension of a Space is roughly defined as the minimum number of Coordinates needed to specify every point within it Topology ( Greek topos, "place" and logos, "study" is the branch of Mathematics that studies the properties of SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS Matter is commonly defined as being anything that has mass and that takes up space. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός A physical law or scientific law is a Scientific generalization based on empirical Observations of physical behavior (i A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time These multiverses could also exist within other universes, in the same way that the interior of a black hole is discontinuous with our world; once something goes in it will never come out.

Definition as observable reality

See also: Observable universe and Observational cosmology

According to a still more restrictive definition, the universe is everything within our connected space-time that could ever interact with us and vice versa. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that Observational cosmology is the study of the structure the evolution and the origin of the Universe through Observation, using instruments such as Telescopes SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS According to the general theory of relativity, some regions of space may never interact with ours even in the lifetime of the universe, due to the finite speed of light and the expansion of space. General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another The metric expansion of space is the averaged increase of metric (i For example, radio messages sent from Earth may never reach some regions of space, even if the universe lives forever; space may expand faster than light can cover it. It is worth emphasizing that those distant regions of space are taken to exist and be part of reality as much as we are; yet we can never interact with them. The spatial region within which we can affect and be affected is denoted as the observable universe. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that Strictly speaking, the observable universe depends on the observer. By traveling, an observer can come into contact with a greater region of space-time than an observer who remains still, so that the observable universe for the former is larger than for the latter; nevertheless, even the most rapid traveler may not be able to interact with all of space. Typically, the observable universe is taken to mean the universe observable from our vantage point in the Milky Way galaxy.

Size, age, contents, structure, and laws

Main articles: Observable universe, Age of the universe, Large-scale structure of the universe, and Abundance of the chemical elements

The universe is very large and possibly infinite in volume; the observable matter is spread over a space at least 93 billion light years across. In Big Bang Cosmology, the observable universe is the region of space bounded by a Sphere, centered on the observer that is small enough that The age of the Universe is the time elapsed between the theory of the Big Bang and the present day In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light See also Abundances of the elements (data page The abundance of a Chemical element measures how relatively common the element is or how much of the element A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by ^[11] For comparison, the diameter of a typical galaxy is only 30,000 light-years, and the typical distance between two neighboring galaxies is only 3 million light-years. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by ^[12] As an example, our Milky Way galaxy is roughly 100,000 light years in diameter,^[13] and our nearest sister galaxy, the Andromeda Galaxy, is located roughly 2. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply The Andromeda Galaxy (ænˈdrɒmədə also known as Messier 31, M31, or NGC 224; often referred to as the Great Andromeda 5 million light years away. ^[14]

The universe is believed to be mostly composed of dark energy and dark matter, both of which are poorly understood at present. In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from Only ≈4% of the universe is ordinary matter, a relatively small perturbation.

The observable matter is spread uniformly (homogeneously) throughout the universe, when averaged over distances longer than 300 million light-years. ^[15] However, on smaller length-scales, matter is observed to form "clumps", i. e. , to cluster hierarchically; many atoms are condensed into stars, most stars into galaxies, most galaxies into clusters, superclusters and, finally, the largest-scale structures such as the Great Wall of galaxies. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny A star is a massive luminous ball of plasma. The nearest star to Earth is the Sun, which is the source of most of the Energy on Earth A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light The Great Wall (also called Coma Wall) sometimes specifically referred to as the CfA2 Great Wall, is the second largest known super-structure in the The observable matter of the universe is also spread isotropically, meaning that no direction of observation seems different from any other; each region of the sky has roughly the same content. ^[16] The universe is also bathed in a highly isotropic microwave radiation that corresponds to a thermal equilibrium blackbody spectrum of roughly 2. Microwaves are electromagnetic waves with Wavelengths ranging from 1 mm to 1 m or frequencies between 0 Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. In Thermodynamics, a thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium Mechanical equilibrium, and In Physics, a black body is an object that absorbs all light that falls on it 725 Kelvin. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic ^[17] The hypothesis that the large-scale universe is homogeneous and isotropic is known as the cosmological principle,^[18] which is supported by astronomical observations. The cosmological principle is an assumption invoked in Cosmology that when applied severely restricts the large variety of possible cosmological theories In Physical cosmology, the term large-scale structure refers to the characterization of observable distributions of Matter and Light

The present overall density of the universe is very low, roughly 9. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 9 × 10^-30 grams per cubic centimetre. This mass-energy appears to consist of 73% dark energy, 23% cold dark matter and 4% ordinary matter. In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from Thus the density of atoms is on the order of a single hydrogen atom for every four cubic meters of volume. ^[19] The properties of dark energy and dark matter are largely unknown. Dark matter gravitates as ordinary matter, and thus works to slow the expansion of the universe; by contrast, dark energy accelerates its expansion. Gravitation is a natural Phenomenon by which objects with Mass attract one another The metric expansion of space is the averaged increase of metric (i The accelerating universe is the observation that the universe appears to be expanding at an accelerated rate

The universe is old and evolving. The age of the Universe is the time elapsed between the theory of the Big Bang and the present day The most precise estimate of the universe's age is 13. 73±0. 12 billion years old, based on observations of the cosmic microwave background radiation. ^[20] Independent estimates (based on measurements such as radioactive dating) agree, although they are less precise, ranging from 11-20 billion years^[21] to 13–15 billion years. Radiometric dating (often called radioactive dating) is a technique used to date materials usually based on a comparison between the observed abundance of a naturally occurring ^[22] The universe has not been the same at all times in its history; for example, the relative populations of quasars and galaxies have changed and space itself appears to have expanded. A quasar (contraction of QUASi-stellAR radio source) is an extremely powerful and distant Active galactic nucleus. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another The metric expansion of space is the averaged increase of metric (i This expansion accounts for how Earth-bound scientists can observe the light from a galaxy 30 billion light years away, even if that light has traveled for only 13 billion years; the very space between them has expanded. This expansion is consistent with the observation that the light from distant galaxies has been redshifted; the photons emitted have been stretched to longer wavelengths and lower frequency during their journey. In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Frequency is a measure of the number of occurrences of a repeating event per unit Time. The rate of this spatial expansion is accelerating, based on studies of Type Ia supernovae and corroborated by other data. The accelerating universe is the observation that the universe appears to be expanding at an accelerated rate A Type Ia supernova is a sub-category of cataclysmic Variable

The relative fractions of different chemical elements — particularly the lightest atoms such as hydrogen, deuterium and helium — seem to be identical throughout the universe and throughout its observable history. See also Abundances of the elements (data page The abundance of a Chemical element measures how relatively common the element is or how much of the element A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical ^[23] The universe seems to have much more matter than antimatter, an asymmetry possibly related to the observations of CP violation. Matter is commonly defined as being anything that has mass and that takes up space. In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed In Particle physics, CP violation is a violation of the postulated CP symmetry of the laws of physics ^[24] The universe appears to have no net electric charge, and therefore gravity appears to be the dominant interaction on cosmological length scales. Electric charge is a fundamental conserved property of some Subatomic particles which determines their Electromagnetic interaction. Gravitation is a natural Phenomenon by which objects with Mass attract one another The universe appears to have no net momentum and angular momentum. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position The absence of net charge and momentum would follow from accepted physical laws (Gauss's law and the non-divergence of the stress-energy-momentum pseudotensor, respectively), if the universe were finite. In the theory of General relativity, a stress-energy-momentum pseudotensor, such as the Landau-Lifshitz pseudotensor, is an extension of the non-gravitational ^[25]

The elementary particles from which the universe is constructed. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Six leptons and six quarks comprise most of the matter; for example, the protons and neutrons of atomic nuclei are composed of quarks, and the ubiquitous electron is a lepton. Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. Matter is commonly defined as being anything that has mass and that takes up space. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their These particles interact via the gauge bosons shown in the middle row, each corresponding to a particular type of gauge symmetry. In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations The Higgs boson (as yet unobserved) is believed to confer mass on the particles with which it is connected. The Higgs Boson is a hypothetical massive scalar Elementary particle predicted to exist by the Standard Model of Particle physics Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object The graviton, a supposed gauge boson for gravity, is not shown. In Physics, the graviton is a hypothetical Elementary particle, a Boson to be exact that mediates the force of Gravity in the framework Gravitation is a natural Phenomenon by which objects with Mass attract one another

The universe appears to have a smooth spacetime continuum consisting of three spatial dimensions and one temporal (time) dimension. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another In mathematics the dimension of a Space is roughly defined as the minimum number of Coordinates needed to specify every point within it For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of On the average, space is observed to be very nearly flat (close to zero curvature), meaning that Euclidean geometry is experimentally true with high accuracy throughout most of the universe. Three-dimensional space is a geometric model of the physical Universe in which we live In Mathematics, curvature refers to any of a number of loosely related concepts in different areas of geometry Euclidean geometry is a mathematical system attributed to the Greek Mathematician Euclid of Alexandria. ^[26] Spacetime also appears to have a simply connected topology, at least on the length-scale of the observable universe. In Topology, a geometrical object or space is called simply connected (or 1-connected) if it is Path-connected and every path between two points can be Topology ( Greek topos, "place" and logos, "study" is the branch of Mathematics that studies the properties of However, present observations cannot exclude the possibilities that the universe has more dimensions and that its spacetime may have a multiply connected global topology, in analogy with the cylindrical or toroidal topologies of two-dimensional spaces. Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another ^[27]

The universe appears to be governed throughout by the same physical laws and physical constants. A physical law or scientific law is a Scientific generalization based on empirical Observations of physical behavior (i A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time ^[28] According to the prevailing Standard Model of physics, all matter is composed of three generations of leptons and quarks, both of which are fermions. The Standard Model of Particle physics is a theory that describes three of the four known Fundamental interactions together with the Elementary particles Leptons are a family of fundamental Subatomic particles comprising the Electron, the Muon, and the Tauon (or tau particle as well as their In Physics, a quark (kwɔrk kwɑːk or kwɑːrk is a type of Subatomic particle. In Particle physics, fermions are particles which obey Fermi-Dirac statistics; they are named after Enrico Fermi. These elementary particles interact via at most three fundamental interactions: the electroweak interaction which includes electromagnetism and the weak nuclear force; the strong nuclear force described by quantum chromodynamics; and gravity, which is best described at present by general relativity. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms In Particle physics, the electroweak interaction is the unified description of two of the four Fundamental interactions of nature Electromagnetism and the Electromagnetism is the Physics of the Electromagnetic field: a field which exerts a Force on particles that possess the property of The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and Quantum chromodynamics (abbreviated as QCD is a theory of the Strong interaction ( color force a Fundamental force describing the interactions of the Gravitation is a natural Phenomenon by which objects with Mass attract one another General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 The first two interactions can be described by renormalized quantum field theory, and are mediated by gauge bosons that correspond to a particular type of gauge symmetry. In Quantum field theory, the Statistical mechanics of fields and the theory of self-similar geometric structures renormalization refers to a collection In quantum field theory (QFT the forces between particles are mediated by other particles In Particle physics, gauge bosons are Bosonic particles that act as carriers of the fundamental forces of nature Gauge theory is a peculiar Quantum field theory where the Lagrangian is invariant under certain transformations A renormalized quantum field theory of general relativity has not yet been achieved, although various forms of string theory seem promising. General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 String theory is a still-developing scientific approach to Theoretical physics, whose original building blocks are one-dimensional extended objects called strings The theory of special relativity is believed to hold throughout the universe, provided that the spatial and temporal length scales are sufficiently short; otherwise, the more general theory of general relativity must be applied. Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 There is no explanation for the particular values that physical constants appear to have throughout our universe, such as Planck's constant h or the gravitational constant G. A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time The Planck constant (denoted h\ is a Physical constant used to describe the sizes of quanta. The gravitational constant, denoted G, is a Physical constant involved in the calculation of the gravitational attraction between objects with mass Several conservation laws have been identified, such as the conservation of charge, momentum, angular momentum and energy; in many cases, these conservation laws can be related to symmetries or mathematical identities. In Physics, a conservation law states that a particular measurable property of an isolated Physical system does not change as the system evolves Charge conservation is the principle that Electric charge can neither be created nor destroyed In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product In Physics, the angular momentum of a particle about an origin is a vector quantity equal to the mass of the particle multiplied by the Cross product of the position In Physics, the law of conservation of energy states that the total amount of Energy in an isolated system remains constant and cannot be created although it may Symmetry generally conveys two primary meanings The first is an imprecise sense of harmonious or aesthetically-pleasing proportionality and balance such that it reflects beauty or In Differential geometry, the curvature form describes Curvature of a connection on a Principal bundle.

Historical models

Main article: Timeline of cosmology

Many models of the cosmos (cosmologies) and its origin (cosmogonies) have been proposed, based on the then available data and conceptions of the universe. This timeline of cosmological theories and discoveries is a chronological catalog of the evolution of humankind's understanding of the Cosmos over the last two-plus Initially, cosmologies and cosmogonies were based on narratives of gods acting in various ways. The Greeks were the first to propose theories of an impersonal universe governed by physical laws. Over the centuries, improvements in astronomical observations and theories of motion and gravitation led to ever more accurate descriptions of the universe. The modern era of cosmology began with Albert Einstein's 1915 general theory of relativity, which made it possible to quantitatively predict the origin, evolution and conclusion of the universe as a whole. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 Most accepted theories of cosmology are based on general relativity and, more specifically, the predicted Big Bang; however, still more careful measurements are required to determine which theory is correct. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation.

Creation myths

Main articles: Creation myth and Creator deity

Sumerian account of the creatrix goddess Nammu, the precursor of the Assyrian goddess Tiamat; perhaps the earliest surviving creation myth. A creation myth is a supernatural mytho-[[religion religious]] story or explanation that describes the beginnings of humanity, Earth, life, and A creator deity is a Deity in a Creation myth responsible for the creation of the World (or Universe) Sumer ( Sumerian: sux-Latn [[Ki (earth ki]]-[[EN (cuneiform en]]-'''ĝir15''', Akkadian: Šumeru; possibly Biblical Shinar In Sumerian mythology, Nammu (more properly Namma) is the Sumerian creation goddess In Babylonian mythology, Tiamat is the sea personified as a Goddess, and a monstrous embodiment of Primordial chaos.

Many cultures have stories describing the creation of the world, which may be roughly grouped into common types. A creation myth is a supernatural mytho-[[religion religious]] story or explanation that describes the beginnings of humanity, Earth, life, and In one type of story, the world is born from a world egg; such stories include the Finnish epic poem Kalevala, the Chinese story of Pangu or the Indian Brahmanda Purana. A world egg or cosmic egg is a mythological motif found in the Creation myths of many Cultures and Civilizations Typically The terms Finns and Finnish people ( Finnish: suomalaiset, Swedish: finländare) are used in English to An epic is a lengthy Narrative poem, ordinarily concerning a serious subject containing details of heroic deeds and events significant to a culture or nation The Kalevala is a book and epic poem which the Finn Elias Lönnrot compiled from Finnish and Karelian Folklore in the nineteenth China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National For the 1st century Chinese historian see Ban Gu. For the town in Nepal see Pangu Nepal. This article is about the history of South Asia prior to the Partition of British India in 1947 Brahmanda Purana, one of the major eighteen Puranas, a Hindu religious text is considered as the eighteenth Purana in almost all the lists of the Puranas and it In related stories, the creation is caused by a single god emanating or producing something by themselves, as in Buddhist concept of Adi-Buddha, the ancient Greek story of Gaia (Mother Earth), the Aztec goddess Coatlicue or the ancient Egyptian god Atum. Buddhism is a family of beliefs and practices In Buddhism, the Adi-Buddha is the "Primordial Buddha." The term refers to a self-emanating self-originating Buddha present before The term ancient Greece refers to the period of Greek history lasting from the Greek Dark Ages ca The Aztec civilization recognized a polytheistic mythology which contained the many gods (over 100 and supernatural creatures from their religious beliefs Coatlicue, also known as Teteoinan (also transcribed Teteo Inan) "The Mother of Gods" (Cōhuātlīcue koː Ancient Egyptian religion encompasses the various religious beliefs and rituals practiced in Ancient Egypt from the predynastic period until the adoption of Christianity For the neo-Platonist work by Plotinus see Enneads. For the Latin epic see Aeneid. Atum (alternatively spelled Tem, Temu, Tum, and Atem) is an important Deity in Egyptian mythology, whose cult centred In another type of story, the world is created from the union of male and female deities, as in the Maori story of Rangi and Papa. Māori mythology and Māori traditions are the two major categories into which the Legends of the Māori of New Zealand may usefully be divided Māori mythology the primal couple Rangi and Papa (or Ranginui and Papatuanuku) appear in a Creation myth explaining the origin of the world In other stories, the universe is created by crafting it from pre-existing materials, such as the corpse of a dead god - as from Tiamat in the Babylonian epic Enuma Elish or from the giant Ymir in Norse mythology - or from chaotic materials, as in Izanagi and Izanami in Japanese mythology. In Babylonian mythology, Tiamat is the sea personified as a Goddess, and a monstrous embodiment of Primordial chaos. Babylon was a City-state of ancient Mesopotamia, the remains of which can be found in present-day Al Hillah, Babil Province, Iraq The akk Enûma Eliš is the Babylonian Creation myth (named for its Incipit) In Norse mythology, Ymir, also named Aurgelmir ( Old Norse gravel-yeller) among the giants themselves was the founder of the race of Norse mythology comprises the indigenous pre-Christian religion, beliefs and Legends of the Scandinavian peoples including those who settled on Iceland is a deity born of the seven divine generations in Japanese mythology and Shintoism, and is also referred to in the roughly translated Kojiki as "male who invites" In Japanese mythology, is a Goddess of both creation and death as well as the former wife of the god Izanagi. Japanese mythology is a system of beliefs that embraces Shinto and Buddhist traditions as well as agriculture-based Folk religion. In another type of story, the world is created by the command of a divinity, as in the ancient Egyptian story of Ptah or the Biblical account in Genesis, wherein some Christians believe that the universe was created 6,000-10,000 years ago, while other Christians believe that the Creation account is compatible with modern science. God is the principal or sole Deity in Religions and other belief systems that worship one deity. Ancient Egypt was an Ancient Civilization in eastern North Africa, concentrated along the lower reaches of the Nile River in what is now In Egyptian mythology, Ptah (also spelt Peteh) was the deification of the primordial mound in the Ennead Cosmogony, which was more literally Etymology According to the Online Etymology Dictionary, the word bible is from Latin biblia, traced from the same word through Medieval Latin and Late Latin Creation according to Genesis refers to the Hebrew narrative of the creation of the heavens and the earth as told in chapters 1 and 2 of Genesis In other stories, the universe emanates from fundamental principles, such as Brahman and Prakrti, or the yin and yang of the Tao. Brahman ( bráhman-, Nominative bráhma sa ब्रह्म is a concept of Hinduism. Prakrti or Prakriti (from Sanskrit language प्रकृ्रति prakṛti is according to Vedanta philosophy the basic matter of which the Tao ( 道, Pinyin Dào) is a metaphysical concept found in Taoism, Confucianism, and more generally in ancient Chinese philosophy

Milanese flag (c. Milan (Milano Milan (listen) is one of the largest cities in Italy, located in the plains of Lombardy. A flag is a piece of Cloth, often flown from a pole or mast, generally used Symbolically for signaling or identification 1450) depicting the four classical elements in the outermost ring. Many ancient philosophies used a set of archetypal classical "elements" to explain patterns in Nature. Fire and Air are above, holding red and white spheres, respectively; Water and Earth are below, holding blue and green spheres, respectively. Fire has been an important part of many cultures and religions from pre-history to modern day and was vital to the development of civilization In traditional cultures air is often seen as a universal power or pure substance Water has been important to all peoples of the earth and it is rich in spiritual tradition Earth, home and origin of humanity has often been worshipped in its own right with its own unique spiritual tradition

Philosophical models

Main articles: Pre-Socratic philosophy and Physics (Aristotle)

The first philosophical models of the universe were developed by the pre-Socratic philosophers. The Pre-Socratic Greek philosophers were active before Socrates or contemporaneously but expounding knowledge developed earlier Physics (or "Physica" or "Physicae Auscultationes" meaning "lessons" is a key text in the philosophy of Aristotle. The Pre-Socratic Greek philosophers were active before Socrates or contemporaneously but expounding knowledge developed earlier The earliest Greek philosophers noted that appearances can be deceiving, and sought to understand the underlying reality behind the appearances. In particular, they noted the ability of matter to change forms (e. g. , ice to water to steam) and several philosophers proposed that all the apparently different materials of the world (wood, metal, etc. ) are all different forms of a single material, the arche. In the ancient Greek philosophy, arche (ἀρχή is the beginning or the first principle of the world The first to do so was Thales, who called this material Water. Thales of Miletus According to Bertrand Russell, "Philosophy begins with Thales Water has been important to all peoples of the earth and it is rich in spiritual tradition Following him, Anaximenes called it Air, and posited that there must be attractive and repulsive forces that cause the arche to condense or dissociate into different forms. In traditional cultures air is often seen as a universal power or pure substance In Physics, a force is whatever can cause an object with Mass to Accelerate. Empedocles proposed that multiple fundamental materials were necessary to explain the diversity of the universe, and proposed that all four classical elements (Earth, Air, Fire and Water) existed, albeit in different combinations and forms. Empedocles ( Greek:, ca 490–430 BC was a Greek Pre-Socratic Philosopher and a citizen of Agrigentum, a Greek colony in Many ancient philosophies used a set of archetypal classical "elements" to explain patterns in Nature. This four-element theory was adopted by many of the subsequent philosophers. Some philosophers before Empedocles advocated less material things for the arche; Heraclitus argued for a Logos, Pythagoras believed that all things were composed of numbers, whereas Thales' student, Anaximander, proposed that everything was composed of a chaotic substance known as apeiron, roughly corresponding to the modern concept of a quantum foam. In the ancient Greek philosophy, arche (ἀρχή is the beginning or the first principle of the world Heraclitus of Ephesus ( Ancient Greek: &mdash grc-Latn ''Hērákleitos ho Ephésios'' English Heraclitus the Ephesian) (ca grc-Latn Logos (ˈloʊːgɒs ( Greek, logos) is an important term in Philosophy, Analytical psychology, Rhetoric and Religion "Pythagoras of Samos" redirects here For the Samian statuary of the same name see Pythagoras (sculptor. A number is an Abstract object, tokens of which are Symbols used in Counting and measuring. Anaximander ( Ancient Greek:) (c 610 BC–c 546 BC was a Pre-Socratic Greek philosopher who lived in Miletus Quantum foam, also referred to as spacetime foam, is a concept in Quantum mechanics, devised by John Wheeler in 1955. Various modifications of the apeiron theory were proposed, most notably that of Anaxagoras, which proposed that the various matter in the world was spun off from a rapidly rotating apeiron, set in motion by the principle of Nous (Mind). Anaxagoras ( Greek: Ἀναξαγόρας c 500 BC &ndash 428 BC was a Pre-Socratic Greek philosopher famous for introducing the Cosmological Nous (ˈnuːs Greek: or) is a philosophical term for Mind or Intellect. Still other philosophers — most notably Leucippus and Democritus — proposed that the universe was composed of indivisible atoms moving through empty space, a vacuum; Aristotle opposed this view ("Nature abhors a vacuum") on the grounds that resistance to motion increases with density; hence, empty space should offer no resistance to motion, leading to the possibility of infinite speed. Leucippus or Leukippos ( Greek, first half of 5th century BC was among the earliest philosophers of Atomism, the idea that everything is composed entirely Democritus ( Greek:) was a pre-Socratic Greek Materialist Philosopher (born at Abdera in Thrace ca History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny This vacuum means "absence of matter" or "an empty area or space" for the cleaning appliance see Vacuum cleaner. Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. In Fluid dynamics, drag (sometimes called fluid resistance) is the force that resists the movement of a Solid object through a Fluid (a The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Speed is the rate of motion, or equivalently the rate of change in position often expressed as Distance d traveled per unit of

Although Heraclitus argued for eternal change, his rough contemporary Parmenides made the radical suggestion that all change is an illusion, that the true underlying reality is eternally unchanging and of a single nature. Parmenides of Elea ( Greek:, early 5th century BC was an Ancient Greek Philosopher born in Elea, a Greek city on the southern coast of Parmenides denoted this reality as το εν (The One). Parmenides' theory seemed implausible to many Greeks, but his student Zeno of Elea challenged them with several famous paradoxes. Zeno of Elea (ˈziːnoʊ əv ˈɛliə Greek: Ζήνων ὁ Ἐλεάτης (ca Aristotle resolved these paradoxes by developing the notion of an infinitely divisible continuum, and applying it to space and time. Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of

Astronomical models

Hand-colored version of the Flammarion woodcut, depicting the Aristotelian conception of the universe that preceded the models of Copernicus and Thomas Digges. The Flammarion woodcut is an anonymous Wood engraving (once thought to be a Woodcut) so named because its first documented appearance is in Camille Flammarion Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. Thomas Digges (1546 &ndash 24 August 1595) was an English Astronomer, son of Leonard Digges, and great populariser of Science

Main article: History of astronomy

More practical Greek philosophers were concerned with developing models of the universe that would account for the observed motion of the stars and planets. Astronomy is the oldest of the Natural sciences dating back to antiquity, with its origins in the religious, Mythological, and Astrological The first coherent model was proposed by Eudoxus of Cnidos. Eudoxus of Cnidus ( Greek Εὔδοξος ὁ Κνίδιος (410 or 408 BC &ndash 355 or 347 BC was a Greek Astronomer, Mathematician According to this model, space and time are infinite and eternal, the Earth is spherical and stationary, and all other matter is confined to rotating concentric spheres. This model was refined by Callippus and Aristotle, and brought into nearly perfect agreement with astronomical observations by Ptolemy. Callippus or Calippus ( Greek: Κάλλιπος ca 370 BC&ndashca Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. Claudius Ptolemaeus ( Greek: Klaúdios Ptolemaîos; after 83 &ndash ca The success of this model is largely due to the mathematical fact that any function (such as the position of a planet) can be decomposed into a set of circular functions (the Fourier modes). In Mathematics, a Fourier series decomposes a periodic function into a sum of simple oscillating functions However, not all Greek scientists accepted the geocentric model of the Universe. Aristarchus of Samos was the first astronomer to propose a heliocentric model. Aristarchus (Ἀρίσταρχος 310 BC - ca 230 BC) was a Greek Astronomer and Mathematician, born on the island of Though the original text has been lost, a reference in Archimedes' book The Sand Reckoner describes Aristarchus' heliocentric theory. Archimedes wrote: (translated into English)

You King Gelon are aware the 'universe' is the name given by most astronomers to the sphere the center of which is the center of the Earth, while its radius is equal to the straight line between the center of the Sun and the center of the Earth. Archimedes of Syracuse ( Greek:) ( c. 287 BC – c 212 BC was a Greek mathematician, Physicist, Engineer This is the common account as you have heard from astronomers. But Aristarchus has brought out a book consisting of certain hypotheses, wherein it appears, as a consequence of the assumptions made, that the universe is many times greater than the 'universe' just mentioned. His hypotheses are that the fixed stars and the Sun remain unmoved, that the Earth revolves about the Sun on the circumference of a circle, the Sun lying in the middle of the orbit, and that the sphere of fixed stars, situated about the same center as the Sun, is so great that the circle in which he supposes the Earth to revolve bears such a proportion to the distance of the fixed stars as the center of the sphere bears to its surface.

Aristarchus thus believed the stars to be very far away, and saw this as the reason why there was no visible parallax, that is, an observed movement of the stars relative to each other as the Earth moved around the Sun. The stars are in fact much farther away than the distance that was generally assumed in ancient times, which is why stellar parallax is only detectable with telescopes. The geocentric model, consistent with planetary parallax, was assumed to be an explanation for the unobservability of the parallel phenomenon, stellar parallax. The rejection of the heliocentric view was apparently quite strong, as the following passage from Plutarch suggests (On the Apparent Face in the Orb of the Moon):

Cleanthes [a contemporary of Aristarchus and head of the Stoics] thought it was the duty of the Greeks to indict Aristarchus of Samos on the charge of impiety for putting in motion the Hearth of the universe [i. Cleanthes (Κλέανθης of Assos, lived c 330- c 230 BC was a Stoic Philosopher and the successor to Zeno as the second head ( scholarch e. the earth], . . . supposing the heaven to remain at rest and the earth to revolve in an oblique circle, while it rotates, at the same time, about its own axis. [1]

The only other astronomer from antiquity known by name who supported Aristarchus' heliocentric model was Seleucus of Seleucia, a Greek astronomer who lived a century after Aristarchus.

Model of the Copernican universe by Thomas Digges in 1576, with the amendment that the stars are no longer confined to a sphere, but spread uniformly throughout the space surrounding the planets. Thomas Digges (1546 &ndash 24 August 1595) was an English Astronomer, son of Leonard Digges, and great populariser of Science A planet, as defined by the International Astronomical Union (IAU is a celestial body Orbiting a Star or stellar remnant that is

The Aristotelian model was accepted for roughly two millennia, until Copernicus revived Aristarchus' theory that the astronomical data could be explained more plausibly if the earth rotated on its axis and if the sun were placed at the center of the universe

As noted by Copernicus himself, the suggestion that the Earth rotates was very old, dating at least to Philolaus (c. Philolaus (ca 480 BC &ndash ca 385 BC Φιλόλαος was a Greek Pythagorean and Presocratic. 450 BC), Heraclides Ponticus (c. "Heraclides" redirects here The former Butterfly Genus of the same name is now included in Papilio. 350 BC) and Ecphantus the Pythagorean. Ecphantus ( Ecphantos) is a shadowy Greek Pre-Socratic philosopher Roughly a century before Copernicus, Nicholas of Cusa also proposed that the Earth rotates on its axis in his book, On Learned Ignorance (1440). ^[29] Copernicus' heliocentric model allowed the stars to be placed uniformly through the (infinite) space surrounding the planets, as first proposed by Thomas Digges in his Perfit Description of the Caelestiall Orbes according to the most aunciente doctrine of the Pythagoreans, latelye revived by Copernicus and by Geometricall Demonstrations approved (1576). In Astronomy, heliocentrism is the theory that the Sun is at the center of the Solar System. Thomas Digges (1546 &ndash 24 August 1595) was an English Astronomer, son of Leonard Digges, and great populariser of Science ^[30] Giordano Bruno accepted the idea that space was infinite and filled with solar systems similar to our own; for the publication of this view, he was burned at the stake in the Campo dei Fiori in Rome on 17 February 1600. Giordano Bruno (1548 – February 17, 1600) was an Italian Philosopher best-known as an early proponent of Heliocentrism and Execution by burning has a long history as a method of Punishment for Crimes such as Treason, Heresy and Witchcraft Campo dei Fiori is a rectangular Piazza near Piazza Navona in Rome, on the border of rione Parione and rione Regola ^[30]

This cosmology was accepted provisionally by Isaac Newton, Christiaan Huygens and later scientists,^[30] although it had several paradoxes that were resolved only with the development of general relativity. Sir Isaac Newton, FRS (ˈnjuːtən 4 January 1643 31 March 1727) Biography Early years See also Isaac Newton's early life and achievements Christiaan Huygens (ˈhaɪgənz in English ˈhœyɣəns in Dutch) ( April 14, 1629 &ndash July 8, 1695) was a Dutch General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 The first of these was that it assumed that space and time were infinite, and that the stars in the universe had been burning forever; however, since stars are constantly radiating energy, a finite star seems inconsistent with the radiation of infinite energy. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Secondly, Edmund Halley (1720)^[31] and Jean-Philippe de Cheseaux (1744)^[32] noted independently that the assumption of an infinite space filled uniformly with stars would lead to the prediction that the nighttime sky would be as bright as the sun itself; this became known as Olbers' paradox in the 19th century. Jean-Philippe Loys de Chéseaux (1718&ndash1751 was an astronomer from Lausanne in Switzerland. Olbers' paradox, described by the German Astronomer Heinrich Wilhelm Olbers in 1823 (but not published until 1826 by Bode) and earlier by ^[33] Third, Newton himself showed that an infinite space uniformly filled with matter would cause infinite forces and instabilities causing the matter to be crushed inwards under its own gravity. ^[30] This instability was clarified in 1902 by the Jeans instability criterion. The Jeans instability causes the collapse of interstellar gas clouds and subsequent star formation ^[34] One solution to these latter two paradoxes is the Charlier universe, in which the matter is arranged hierarchically (systems of orbiting bodies that are themselves orbiting in a larger system, ad infinitum) in a fractal way such that the universe has a negligibly small overall density; such a cosmological model had also been proposed earlier in 1761 by Johann Heinrich Lambert. Carl Vilhelm Ludwig Charlier ( April 1 1862 &ndash November 5 1934) was a Swedish Astronomer. A fractal is generally "a rough or fragmented geometric shape that can be split into parts each of which is (at least approximately a reduced-size copy of the whole" Johann Heinrich Lambert ( August 26, 1728 &ndash September 25 1777) was a Swiss Mathematician, Physicist and ^[35] A significant astronomical advance of the 18th century was the realization by Thomas Wright, Immanuel Kant and others that stars are not distributed uniformly throughout space; rather, they are grouped into galaxies. Thomas Wright ( 21 April, 1810 &ndash 23 December, 1877) was an English Antiquarian and writer Immanuel Kant (ɪmanuəl kant 22 April 1724 12 February 1804 was an 18th-century German Philosopher from the Prussian city of Königsberg A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter ^[36]

The modern era of physical cosmology began in 1917, when Albert Einstein first applied his general theory of relativity to model the structure and dynamics of the universe. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its Year 1917 ( MCMXVII) was a Common year starting on Monday (link will display the full calendar of the Gregorian calendar (or a Common year Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 ^[37] This theory and its implications will be discussed in more detail in the following section.

Theoretical models

High-precision test of general relativity by the Cassini space probe (artist's impression): radio signals sent between the Earth and the probe (green wave) are delayed by the warping of space and time (blue lines) due to the Sun's mass. Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. The Shapiro time delay effect or gravitational time delay effect is one of the four classic solar system Tests of general relativity. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS The Sun (Sol is the Star at the center of the Solar System.

Of the four fundamental interactions, gravitation is dominant at cosmological length scales; that is, the other three forces are believed to play a negligible role in determining structures at the level of planets, stars, galaxies and larger-scale structures. In Physics, a fundamental interaction or fundamental force is a mechanism by which particles interact with each other and which cannot be explained in terms Gravitation is a natural Phenomenon by which objects with Mass attract one another Since all matter and energy gravitate, gravity's effects are cumulative; by contrast, the effects of positive and negative charges tend to cancel one another, making electromagnetism relatively insignificant on cosmological length scales. The remaining two interactions, the weak and strong nuclear forces, decline very rapidly with distance; their effects are confined mainly to sub-atomic length scales. The weak interaction (often called the weak force or sometimes the weak nuclear force) is one of the four Fundamental interactions of nature In particle physics the strong interaction, or strong force, or color force, holds Quarks and Gluons together to form Protons and

General theory of relativity

Main articles: Introduction to general relativity, General relativity, and Einstein's field equations

Given gravitation's predominance in shaping cosmological structures, accurate predictions of the universe's past and future require an accurate theory of gravitation. General relativity (GR is a Theory of Gravitation that was developed by Albert Einstein between 1907 and 1915 General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 The Einstein field equations ( EFE) or Einstein's equations are a set of ten equations in Einstein 's theory of General relativity in which the The best theory available is Albert Einstein's general theory of relativity, which has passed all experimental tests hitherto. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 However, since rigorous experiments have not been carried out on cosmological length scales, general relativity could conceivably be inaccurate. Nevertheless, its cosmological predictions appear to be consistent with observations, so there is no compelling reason to adopt another theory.

General relativity provides of a set of ten nonlinear partial differential equations for the spacetime metric (Einstein's field equations) that must be solved from the distribution of mass-energy and momentum throughout the universe. This article discusses metrics in General relativity, for a discussion of metrics in general see Metric tensor. The Einstein field equations ( EFE) or Einstein's equations are a set of ten equations in Einstein 's theory of General relativity in which the In Physics, mass–energy equivalence is the concept that for particles slower than light any Mass has an associated Energy and vice versa. In Classical mechanics, momentum ( pl momenta SI unit kg · m/s, or equivalently N · s) is the product Since these are unknown in exact detail, cosmological models have been based on the cosmological principle, which states that the universe is homogeneous and isotropic. The cosmological principle is an assumption invoked in Cosmology that when applied severely restricts the large variety of possible cosmological theories In effect, this principle asserts that the gravitational effects of the various galaxies making up the universe are equivalent to those of a fine dust distributed uniformly throughout the universe with the same average density. The assumption of a uniform dust makes it easy to solve Einstein's field equations and predict the past and future of the universe on cosmological time scales.

Einstein's field equations include a cosmological constant Λ,^[37][38] that corresponds to an energy density of empty space. In Physical cosmology, the cosmological constant (usually denoted by the Greek capital letter Lambda: Λ was proposed by Albert Einstein as a modification ^[39] Depending on its sign, the cosmological constant can either slow (negative Λ) or accelerate (positive Λ) the expansion of the universe. The metric expansion of space is the averaged increase of metric (i Although many scientists, including Einstein, had speculated that Λ was zero,^[40] recent astronomical observations of type Ia supernovae have detected a large amount of "dark energy" that is accelerating the universe's expansion. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical A Type Ia supernova is a sub-category of cataclysmic Variable In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe ^[41] Preliminary studies suggest that this dark energy corresponds to a positive Λ, although alternative theories cannot be ruled out as yet. ^[42] Russian physicist Zel'dovich suggested that Λ is a measure of the zero-point energy associated with virtual particles of quantum field theory, a pervasive vacuum energy that exists everywhere, even in empty space. Physics (Greek Physis - φύσις in everyday terms is the Science of Matter and its motion. Yakov Borisovich Zel'dovich (Яков Борисович Зельдович ( March 8, 1914 &ndash December 2, 1987) was a prolific Soviet In Physics, the zero-point energy is the lowest possible Energy that a Quantum mechanical Physical system may possess and is the energy of the In Physics, a virtual particle is a particle that exists for a limited time and space introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty In quantum field theory (QFT the forces between particles are mediated by other particles Vacuum energy is an underlying background Energy that exists in Space even when devoid of Matter (known as Free space) ^[43] Evidence for such zero-point energy is observed in the Casimir effect. In Physics, the Casimir effect and the Casimir-Polder force are physical forces arising from a quantized field.

Special relativity and space-time

Main articles: Introduction to special relativity and Special relativity

Only its length L is intrinsic to the rod (shown in black); coordinate differences between its endpoints (such as Δx, Δy or Δξ, Δη) depend on their frame of reference (depicted in blue and red, respectively). In Physics, special relativity is a fundamental Theory about Space and Time, developed by Albert Einstein in 1905 as a modification Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial

The universe has at least three spatial and one temporal (time) dimension. Space is the extent within which Matter is physically extended and objects and Events have positions relative to one another For other uses see Time (disambiguation Time is a component of a measuring system used to sequence events to compare the durations of It was long thought that the spatial and temporal dimensions were different in nature and independent of one another. However, according to the special theory of relativity, spatial and temporal separations are interconvertible (within limits) by changing one's motion. Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial

To understand this interconversion, it is helpful to consider the analogous interconversion of spatial separations along the three spatial dimensions. Consider the two endpoints of a rod of length L. The length can be determined from the differences in the three coordinates Δx, Δy and Δz of the two endpoints in a given reference frame

L² = Δx² + Δy² + Δz²

using the Pythagorean theorem. In Mathematics, the Pythagorean theorem ( American English) or Pythagoras' theorem ( British English) is a relation in Euclidean geometry In a rotated reference frame, the coordinate differences differ, but they give the same length

L² = Δξ² + Δη² + Δζ²

Thus, the coordinates differences (Δx, Δy, Δz) and (Δξ, Δη, Δζ) are not intrinsic to the rod, but merely reflect the reference frame used to describe it; by contrast, the length L is an intrinsic property of the rod. The coordinate differences can be changed without affecting the rod, by rotating one's reference frame.

The analogy in spacetime is called the interval between two events; an event is defined as a point in spacetime, a specific position in space and a specific moment in time. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS The spacetime interval between two events is given by

where c is the speed of light. According to special relativity, one can change a spatial and time separation (L₁, Δt₁) into another (L₂, Δt₂) by changing one's reference frame, as long as the change maintains the spacetime interval s. Special relativity (SR (also known as the special theory of relativity or STR) is the Physical theory of Measurement in Inertial Such a change in reference frame corresponds to changing one's motion; in a moving frame, lengths and times are different from their counterparts in a stationary reference frame. The precise manner in which the coordinate and time differences change with motion is described by the Lorentz transformation. In Physics, the Lorentz transformation converts between two different observers' measurements of space and time where one observer is in constant motion with respect to

Solving Einstein's field equations

See also: Big Bang and Ultimate fate of the universe

In non-Cartesian (non-square) or curved coordinate systems, the Pythagorean theorem holds only on infinitesimal length scales and must be augmented with a more general metric tensor g_μν, which can vary from place to place and which describes the local geometry in the particular coordinate system. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. The ultimate fate of the universe is a topic in Physical cosmology. In the mathematical field of Differential geometry, a metric tensor is a type of function defined on a Manifold (such as a Surface in space However, assuming the cosmological principle that the universe is homogeneous and isotropic everywhere, every point in space is like every other point; hence, the metric tensor must be the same everywhere. The cosmological principle is an assumption invoked in Cosmology that when applied severely restricts the large variety of possible cosmological theories That leads to a single form for the metric tensor, called the Friedmann-Lemaître-Robertson-Walker metric

where (r, θ, φ) correspond to a spherical coordinate system. In Mathematics, the spherical coordinate system is a Coordinate system for representing geometric figures in three dimensions using three coordinates the radial This metric has only two undetermined parameters: an overall length scale R that can vary with time, and a curvature index k that can be only 0, 1 or -1, corresponding to flat Euclidean geometry, or spaces of positive or negative curvature. In Mathematics, a metric or distance function is a function which defines a Distance between elements of a set. Euclidean geometry is a mathematical system attributed to the Greek Mathematician Euclid of Alexandria. In Mathematics, curvature refers to any of a number of loosely related concepts in different areas of geometry In cosmology, solving for the history of the universe is done by calculating R as a function of time, given k and the value of the cosmological constant Λ, which is a (small) parameter in Einstein's field equations. In Physical cosmology, the cosmological constant (usually denoted by the Greek capital letter Lambda: Λ was proposed by Albert Einstein as a modification The equation describing how R varies with time is known as the Friedmann equation, after its inventor, Alexander Friedmann. The Friedmann equations are a set of Equations in cosmology that govern the expansion of space in homogeneous and isotropic models Alexander Alexandrovich Friedman or Friedmann (Александр Александрович Фридман ( June 16 1888, Saint Petersburg, Imperial ^[44]

Prevailing model of the creation and expansion of spacetime and all that it contains. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS

The solutions for R(t) depend on k and Λ, but some qualitative features of such solutions are general. First and most importantly, the length scale R of the universe can remain constant only if the universe is perfectly isotropic with positive curvature (k=1) and has one precise value of density everywhere, as first noted by Albert Einstein. Albert Einstein ( German: ˈalbɐt ˈaɪ̯nʃtaɪ̯n; English: ˈælbɝt ˈaɪnstaɪn (14 March 1879 – 18 April 1955 was a German -born theoretical However, this equilibrium is unstable and since the universe is known to be inhomogeneous on smaller scales, R must change, according to general relativity. General relativity or the general theory of relativity is the geometric theory of Gravitation published by Albert Einstein in 1916 When R changes, all the spatial distances in the universe change in tandem; there is an overall expansion or contraction of space itself. The accounts for the observation that galaxies appear to be flying apart; the space between them is stretching. The stretching of space also accounts for the apparent paradox that two galaxies can be 40 billion light years apart, although they started from the same point 13. 7 billion years ago and never moved faster than the speed of light.

Second, all solutions suggest that there was a gravitational singularity in the past, when R goes to zero and matter and energy became infinitely dense. A gravitational singularity (sometimes spacetime singularity) is approximately a place where quantities which are used to measure the Gravitational field become It may seem that this conclusion is uncertain since it is based on the questionable assumptions of perfect homogeneity and isotropy (the cosmological principle) and that only the gravitational interaction is significant. The cosmological principle is an assumption invoked in Cosmology that when applied severely restricts the large variety of possible cosmological theories However, the Penrose-Hawking singularity theorems show that a singularity should exist for very general conditions. The Penrose-Hawking singularity theorems are a set of results in General relativity which attempt to answer the question of whether gravity is necessarily singular Hence, according to Einstein's field equations, R grew rapidly from an unimaginably hot, dense state that existed immediately following this singularity (when R had a small, finite value); this is the essence of the Big Bang model of the universe. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. A common misconception is that the Big Bang model predicts that matter and energy exploded from a single point in space and time; that is false. Rather, space itself was created in the Big Bang and imbued with a fixed amount of energy and matter distributed uniformly throughout; as space expands (i. e. , as R(t) increases), the density of that matter and energy decreases.

Third, the curvature index k determines the sign of the mean spatial curvature of spacetime averaged over length scales greater than a billion light years. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by If k=1, the curvature is positive and the universe has a finite volume. Such universes are often visualized as a three-dimensional sphere S³ embedded in a four-dimensional space. In Mathematics, a 3-sphere is a higher-dimensional analogue of a Sphere. Conversely, if k is zero or negative, the universe may have infinite volume, depending on its overall topology. Topology ( Greek topos, "place" and logos, "study" is the branch of Mathematics that studies the properties of It may seem counter-intuitive that an infinite and yet infinitely dense universe could be created in a single instant at the Big Bang when R=0, but exactly that is predicted mathematically when k does not equal 1. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. For comparison, an infinite plane has zero curvature but infinite area, whereas an infinite cylinder is finite in one direction and a torus is finite in both. In Geometry, a torus (pl tori) is a Surface of revolution generated by revolving a Circle in three dimensional space about an axis Coplanar A toroidal universe could behave like a normal universe with periodic boundary conditions, as seen in "wrap-around" video games such as Asteroids; a traveler crossing an outer "boundary" of space going outwards would reappear instantly at another point on the boundary moving inwards. In Molecular dynamics, periodic boundary conditions (PBC are a set of Boundary conditions used to simulate an effectively infinitely tiled system usually applied A video game is a Game that involves interaction with a User interface to generate visual feedback on a video device. Asteroids is a video Arcade game released in 1979 by Atari Inc

The ultimate fate of the universe is still unknown, since it depends critically on the curvature index k and the cosmological constant Λ. The ultimate fate of the universe is a topic in Physical cosmology. In Physical cosmology, the cosmological constant (usually denoted by the Greek capital letter Lambda: Λ was proposed by Albert Einstein as a modification If the universe is sufficiently dense, k equals +1, meaning that its average curvature throughout is positive and the universe will eventually recollapse in a Big Crunch, possibly starting a new universe in a Big Bounce. In Physical cosmology, the Big Crunch is one possible scenario for the Ultimate fate of the universe, in which the Metric expansion of space eventually The Big Bounce is a theorized Scientific model related to the creation of the known Universe. Conversely, if the universe is insufficiently dense, k equals 0 or -1 and the universe will expand forever, cooling off and eventually becoming inhospitable for all life, as the stars die and all matter coalesces into black holes (the Big Freeze and the heat death of the universe). The heat death is a possible final state of the universe, in which it has " run down " to a state of no Thermodynamic free energy to sustain The heat death is a possible final state of the universe, in which it has " run down " to a state of no Thermodynamic free energy to sustain As noted above, recent data suggests that the expansion of the universe is not decreasing as originally expected, but accelerating; if this continues indefinitely, the universe will eventually rip itself to shreds (the Big Rip). The Big Rip is a cosmological Hypothesis first published in 2003 about the Ultimate fate of the universe, in which the matter of the universe Experimentally, the universe has an overall density that is very close to the critical value between recollapse and eternal expansion; more careful astronomical observations are needed to decide the question.

Big Bang model

Main articles: Big Bang, Timeline of the Big Bang, Nucleosynthesis, and Lambda-CDM model

The prevailing Big Bang model accounts for many of the experimental observations described above, such as the correlation of distance and redshift of galaxies, the universal ratio of hydrogen:helium atoms, and the ubiquitous, isotropic microwave radiation background. The Big Bang is the cosmological model of the Universe that is best supported by all lines of scientific evidence and Observation. This timeline of the Big Bang describes the events according to the Scientific theory of the Big Bang, using the cosmological time parameter of Comoving coordinates Nucleosynthesis is the process of creating new atomic nuclei from preexisting Nucleons (protons and neutrons &LambdaCDM or Lambda-CDM is an abbreviation for Lambda-Cold Dark Matter. In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by As noted above, the redshift arises from the metric expansion of space; as the space itself expands, the wavelength of a photon traveling through space likewise increases, decreasing its energy. The metric expansion of space is the averaged increase of metric (i In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena The longer a photon has been traveling, the more expansion it has undergone; hence, older photons from more distant galaxies are the most red-shifted. Determining the correlation between distance and redshift is an important problem in experimental physical cosmology. Physical cosmology, as a branch of Astronomy, is the study of the large-scale structure of the Universe and is concerned with fundamental questions about its

Chief nuclear reactions responsible for the relative abundances of light atomic nuclei observed throughout the universe. See also Abundances of the elements (data page The abundance of a Chemical element measures how relatively common the element is or how much of the element The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom

Other experimental observations can be explained by combining the overall expansion of space with nuclear and atomic physics. Nuclear physics is the field of Physics that studies the building blocks and interactions of Atomic nuclei. Atomic physics (or atom physics) is the field of Physics that studies atoms as an isolated system of Electrons and an atomic nucleus. As the universe expands, the energy density of the electromagnetic radiation decreases more quickly than does that of matter, since the energy of a photon decreases with its wavelength. Electromagnetic radiation takes the form of self-propagating Waves in a Vacuum or in Matter. Matter is commonly defined as being anything that has mass and that takes up space. Thus, although the energy density of the universe is now dominated by matter, it was once dominated by radiation; poetically speaking, all was light. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 As the universe expanded, its energy density decreased and it became cooler; as it did so, the elementary particles of matter could associate stably into ever larger combinations. In Particle physics, an elementary particle or fundamental particle is a particle not known to have substructure that is it is not known to be made Thus, in the early part of the matter-dominated era, stable protons and neutrons formed, which then associated into atomic nuclei. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. The nucleus of an Atom is the very dense region consisting of Nucleons ( Protons and Neutrons, at the center of an atom At this stage, the matter in the universe was mainly a hot, dense plasma of negative electrons, neutral neutrinos and positive nuclei. The electron is a fundamental Subatomic particle that was identified and assigned the negative charge in 1897 by J Neutrinos are Elementary particles that travel close to the Speed of light, lack an Electric charge, are able to pass through ordinary matter almost Nuclear reactions among the nuclei led to the present abundances of the lighter nuclei, particularly hydrogen, deuterium, and helium. In Nuclear physics, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products different from the initial particles Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical Eventually, the electrons and nuclei combined to form stable atoms, which are transparent to most wavelengths of radiation; at this point, the radiation decoupled from the matter, forming the ubiquitous, isotropic background of microwave radiation observed today. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny

Other observations are not answered definitively by known physics. According to the prevailing theory, a slight imbalance of matter over antimatter was present in the universe's creation, or developed very shortly thereafter, possibly due to the CP violation that has been observed by particle physicists. Matter is commonly defined as being anything that has mass and that takes up space. In Particle physics and Quantum chemistry, antimatter is the extension of the concept of the Antiparticle to Matter, where antimatter is composed In Particle physics, CP violation is a violation of the postulated CP symmetry of the laws of physics Particle physics is a branch of Physics that studies the elementary constituents of Matter and Radiation, and the interactions between them Although the matter and antimatter mostly annihilated one another, producing photons, a small residue of matter survived, giving the present matter-dominated universe. In Physics, the photon is the Elementary particle responsible for electromagnetic phenomena Several lines of evidence also suggest that a rapid cosmic inflation of the universe occurred very early in its history (roughly 10^-35 seconds after its creation). In Physical cosmology, cosmic inflation is the idea that the nascent Universe passed through a phase of exponential expansion that Recent observations also suggest that the cosmological constant Λ is not zero and that the net mass-energy content of the universe is dominated by a dark energy and dark matter that have not been characterized scientifically. In Physical cosmology, the cosmological constant (usually denoted by the Greek capital letter Lambda: Λ was proposed by Albert Einstein as a modification In Physics, mass–energy equivalence is the concept that for particles slower than light any Mass has an associated Energy and vice versa. In Physical cosmology, dark energy is a hypothetical exotic form of Energy that permeates all of space and tends to increase the rate of expansion of the universe In Physics and cosmology, dark matter is hypothetical Matter that does not interact with the electromagnetic force but whose presence can be inferred from They differ in their gravitational effects. Dark matter gravitates as ordinary matter does, and thus slows the expansion of the universe; by contrast, dark energy serves to accelerate the universe's expansion.

Multiverse

Main articles: Multiverse, Many-worlds hypothesis, Bubble universe theory, and Parallel universe (fiction)

Artistic depiction of a multiverse of seven "bubble" universes, which are separate spacetime continua, each having different physical laws, physical constants, and perhaps even different numbers of dimensions or topologies. The multiverse (or meta-universe) is the hypothetical set of multiple possible Universes (including our universe that together comprise all of Reality. The many-worlds interpretation or MWI (also known as relative state formulation, theory of the universal wavefunction, parallel universes, The Chaotic Inflation theory is a variety of the Inflationary universe model which is itself an outgrowth (or extension of the Big bang theory Parallel universe or alternative reality is a self-contained separate reality coexisting with one's own The multiverse (or meta-universe) is the hypothetical set of multiple possible Universes (including our universe that together comprise all of Reality. The Chaotic Inflation theory is a variety of the Inflationary universe model which is itself an outgrowth (or extension of the Big bang theory SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS A physical law or scientific law is a Scientific generalization based on empirical Observations of physical behavior (i A physical Constant is a Physical quantity that is generally believed to be both universal in nature and constant in time In mathematics the dimension of a Space is roughly defined as the minimum number of Coordinates needed to specify every point within it Topology ( Greek topos, "place" and logos, "study" is the branch of Mathematics that studies the properties of

Some speculative theories have proposed that this universe is but one of a set of disconnected universes, collectively denoted as the multiverse. The multiverse (or meta-universe) is the hypothetical set of multiple possible Universes (including our universe that together comprise all of Reality. ^[10][45] By definition, there is no possible way for anything in one universe to affect another; if two "universes" could affect one another, they would be part of a single universe. Thus, although some fictional characters travel between parallel fictional "universes", this is, strictly speaking, an incorrect usage of the term "universe". Parallel universe or alternative reality is a self-contained separate reality coexisting with one's own The disconnected universes are conceived as being physical, in the sense that each should have its own space and time, its own matter and energy, and its own physical laws. Thus such physical disconnected universes should be distinguished from the metaphysical conception of alternate planes of consciousness, which are not thought to be physical places. Metaphysics is the branch of Philosophy investigating principles of reality transcending those of any particular science In Metaphysics and Esoteric cosmology, a plane, other than the Physical plane, is conceived as a subtle state of Consciousness that transcends The concept of a multiverse of disconnected universes is very old; for example, Bishop Étienne Tempier of Paris ruled in 1277 that God could create as many universes as he saw fit, a question that was being hotly debated by the French theologians. Étienne (Stephen Tempier (also known as Stephanus of Orleans) (died September 3 1279 was a French Bishop of Paris during the thirteenth century ^[46]

There are two scientific senses in which multiple universes can occur. First, disconnected spacetime continua may exist; presumably, all forms of matter and energy are confined to one universe and cannot "tunnel" between them. SpaceTime is a patent-pending three dimensional graphical user interface that allows end users to search their content such as Google Google Images Yahoo! YouTube eBay Amazon and RSS An example of such a theory is the chaotic inflation model of the early universe. The Chaotic Inflation theory is a variety of the Inflationary universe model which is itself an outgrowth (or extension of the Big bang theory ^[47] Second, according to the many-worlds hypothesis, a parallel universe is born with every quantum measurement; the universe "forks" into parallel copies, each one corresponding to a different outcome of the quantum measurement. The many-worlds interpretation or MWI (also known as relative state formulation, theory of the universal wavefunction, parallel universes, The framework of Quantum mechanics requires a careful definition of measurement, and a thorough discussion of its practical and philosophical implications Authors have explored this concept in some fiction, most notably Jorge Borges' short story The Garden of Forking Paths. "The Garden of Forking Paths" (original Spanish title "El Jardín de senderos que se bifurcan") is a 1941 Short story However, both senses of the term "multiverse" are speculative and may be considered unscientific; the fact that universes cannot interact makes it impossible to test experimentally in this universe whether another universe exists.

See also

Notes and references

Further reading

• Weinberg S (1993). Steven Weinberg (born May 3, 1933) is an American Physicist, and Nobel laureate in Physics for his contributions with Abdus Salam The First Three Minutes: A Modern View of the Origin of the Universe, 2nd updated edition, New York: Basic Books. ISBN 978-0465024377.  

• Rindler W (1977). Essential Relativity: Special, General, and Cosmological. New York: Springer Verlag, pp. 193–244. ISBN 0-387-10090-3.  

• Landau LD, Lifshitz EM (1975). Lev Davidovich Landau ( Russian language: Ле́в Дави́дович Ланда́у ( January 22, 1908 &ndash April 1, 1968 Evgeny Mikhailovich Lifshitz (Евгений Михайлович Лифшиц February 21 1915 &ndash October 29 1985) was a leading Soviet The Classical Theory of Fields (Course of Theoretical Physics, Vol. 2), revised 4th English ed. , New York: Pergamon Press, pp. 358–397. ISBN 978-0-08-018176-9.  

• Misner CW,Thorne K, Wheeler JA (1973). Charles W Misner is an American physicist and one of the authors of " Gravitation " Kip Stephen Thorne (born June 1, 1940) is an American theoretical physicist, known for his prolific contributions in gravitation physics John Archibald Wheeler ( July 9, 1911 &ndash April 13, 2008) was an eminent American Theoretical physicist. Gravitation. San Francisco: W. H. Freeman, pp. 703–816. ISBN 978-0-7167-0344-0.   (See Gravitation (book). In Physics, Gravitation is a very important reference book on Einstein 's theory of gravity by Charles W )

• Weinberg S (1972). Steven Weinberg (born May 3, 1933) is an American Physicist, and Nobel laureate in Physics for his contributions with Abdus Salam Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity. New York: John Wiley and Sons, pp. 407–633. ISBN 0-471-92567-5.  

External links

Is there a hole in the universe? at HowStuffWorks

• Age of the Universe at Space. Com
• Cosmology FAQ
• Cosmos - an "illustrated dimensional journey from microcosmos to macrocosmos"
• Illustration comparing the sizes of the planets, the sun, and other stars
• Logarithmic Maps of the Universe
• My So-Called Universe arguments for and against an infinite and parallel universes
• Parallel Universes by Max Tegmark
• The Dark Side and the Bright Side of the Universe Princeton University, Shirley Ho
• Richard Powell: An Atlas of the Universe - images at various scales, with explanations
• Size of the Universe at Space. Com
• Stephen Hawking's Universe - why is the universe the way it is?
• Universe - Space Information Centre by Exploreuniverse. com