In statistical mechanics, entropy is an extensive property of a thermodynamic system. It is related to the number Ω of microscopic configurations that are consistent with the macroscopic quantities that characterize the system. Under the assumption that each microstate is probable, the entropy S is the natural logarithm of the number of microstates, multiplied by the Boltzmann constant kB. Formally, S = k B ln Ω. Macroscopic systems have a large number Ω of possible microscopic configurations. For example, the entropy of an ideal gas is proportional to the number of gas molecules N. Twenty liters of gas at room temperature and atmospheric pressure has N ≈ 6×1023. At equilibrium, each of the Ω ≈ eN configurations can be regarded as random and likely; the second law of thermodynamics states. Such systems spontaneously evolve towards the state with maximum entropy. Non-isolated systems may lose entropy, provided their environment's entropy increases by at least that amount so that the total entropy increases.
Entropy is a function of the state of the system, so the change in entropy of a system is determined by its initial and final states. In the idealization that a process is reversible, the entropy does not change, while irreversible processes always increase the total entropy; because it is determined by the number of random microstates, entropy is related to the amount of additional information needed to specify the exact physical state of a system, given its macroscopic specification. For this reason, it is said that entropy is an expression of the disorder, or randomness of a system, or of the lack of information about it; the concept of entropy plays a central role in information theory. Boltzmann's constant, therefore entropy, have dimensions of energy divided by temperature, which has a unit of joules per kelvin in the International System of Units; the entropy of a substance is given as an intensive property—either entropy per unit mass or entropy per unit amount of substance. The French mathematician Lazare Carnot proposed in his 1803 paper Fundamental Principles of Equilibrium and Movement that in any machine the accelerations and shocks of the moving parts represent losses of moment of activity.
In other words, in any natural process there exists an inherent tendency towards the dissipation of useful energy. Building on this work, in 1824 Lazare's son Sadi Carnot published Reflections on the Motive Power of Fire which posited that in all heat-engines, whenever "caloric" falls through a temperature difference, work or motive power can be produced from the actions of its fall from a hot to cold body, he made the analogy with that of. This was an early insight into the second law of thermodynamics. Carnot based his views of heat on the early 18th century "Newtonian hypothesis" that both heat and light were types of indestructible forms of matter, which are attracted and repelled by other matter, on the contemporary views of Count Rumford who showed that heat could be created by friction as when cannon bores are machined. Carnot reasoned that if the body of the working substance, such as a body of steam, is returned to its original state at the end of a complete engine cycle, that "no change occurs in the condition of the working body".
The first law of thermodynamics, deduced from the heat-friction experiments of James Joule in 1843, expresses the concept of energy, its conservation in all processes. In the 1850s and 1860s, German physicist Rudolf Clausius objected to the supposition that no change occurs in the working body, gave this "change" a mathematical interpretation by questioning the nature of the inherent loss of usable heat when work is done, e.g. heat produced by friction. Clausius described entropy as the transformation-content, i.e. dissipative energy use, of a thermodynamic system or working body of chemical species during a change of state. This was in contrast to earlier views, based on the theories of Isaac Newton, that heat was an indestructible particle that had mass. Scientists such as Ludwig Boltzmann, Josiah Willard Gibbs, James Clerk Maxwell gave entropy a statistical basis. In 1877 Boltzmann visualized a probabilistic way to measure the entropy of an ensemble of ideal gas particles, in which he defined entropy to be proportional to the natural logarithm of the number of microstates such a gas could occupy.
Henceforth, the essential problem in statistical thermodynamics, i.e. according to Erwin Schrödinger, has been to determine the distribution of a given amount of energy E over N identical systems. Carathéodory linked entropy with a mathematical definition of irreversibility, in terms of trajectories and integrability. There are two related definitions of entropy: the thermodynamic definition and the statistical mechanics definition; the classical thermodynamics definition developed first. In the classical thermodynamics viewpoint, the system is composed of large numbers of constituents and the state of the system is described by the average thermodynamic properties of those constituents.
Thomas Archer Hirst
Thomas Archer Hirst FRS was a 19th-century mathematician, specialising in geometry. He was awarded the Royal Society's Royal Medal in 1883. Thomas Hirst was born in Heckmondwike, England, where both his parents came from families in the wool trade, he was the youngest of four sons. The family moved to Wakefield. Thomas attended Wakefield Proprietary School for four years from 1841. Of these days, he said "... I could obtain the most necessary instruction. I remember, that here mathematics was my favourite study..." He left the school at fifteen to work as an apprentice engineer in Halifax, surveying for proposed railway lines. It was there that he met John Tyndall, ten years older than Hirst and working as an engineer in the same firm. In his late teens, at the instigation of Tyndall, Hirst decided to go to Germany for education in chemistry, he received a doctorate in mathematics from the University of Marburg in 1852. In 1853, he attended. Hirst married Anna Martin in 1854, spent much of the decade of the 1850s on the European continent, where he socialised with many mathematicians, used his inherited wealth to support himself.
From 1860 to 1864, Hirst taught at University College School, but resigned because he wanted more time for his mathematical research. He was appointed Professor of Physics at University College London in 1865, he succeeded Augustus de Morgan to the Chair of Mathematics at UCL in 1867. In 1873 he was appointed as the first Director of Studies at Greenwich, he retired from that post in 1882. From the 1860s onwards, Hirst allocated much of his time in England to the administrative committees of British science, he was an active member of the governing councils of the Royal Society, the British Association for the Advancement of Science, the London Mathematical Society. He was the founding president of an association to reform school mathematics curricula and worked to promote the education of women. Alongside his old friend Tyndall, Hirst was a member of T. H. Huxley's London X-Club, he died in London in 1892. In his early days, Hirst wrote extensively in his notebooks, recording everything he read and much of what he was thinking about.
This extraordinary record of about fifty years is preserved in the library of the Royal Institution. As a result, we know much about the development of his mind before he became a professional mathematician. We know, for example, what the effect was of his reading the Vestiges of the Natural History of Creation, that epoch-making book authored anonymously by Robert Chambers which promoted the idea of evolution in 1844. "Almost no-one reads like this anymore. It is the reading practice of a self-improving autodidact, shaped by Bible-reading amongst denominations of learned liberal Dissent... Hirst copied large chunks into his journal... the journal shows that Hirst moved between Vestiges and other related works such as Paley's Natural Theology and John Arthur Phillips' Geology of Yorkshire..." Both Hirst and Tyndall left in their journals and letters evidence that Vestiges made a good case against the story of Genesis and the case for divine intervention. They came to the conclusion that parts of the Old Testament were allegorical.
Hirst was a projective geometer in the style of Steiner. He was not an adherent of the algebraic geometry approach of Cayley and Sylvester, despite being a friend of theirs, his speciality was Cremona transformations. Ueber conjugirte Diameter im dreiaxigen Ellipsoid. Inaugural-Dissertation, welche mit Genehmigung der philosophischen Facultät zu Marburg zur Erlangung der Doctorwürde einreicht Thomas Archer Hirst aus England. Marburg, Druck und Papier von Joh. Aug. Koch. 1852.. O'Connor, John J..
History of thermodynamics
The history of thermodynamics is a fundamental strand in the history of physics, the history of chemistry, the history of science in general. Owing to the relevance of thermodynamics in much of science and technology, its history is finely woven with the developments of classical mechanics, quantum mechanics and chemical kinetics, to more distant applied fields such as meteorology, information theory, biology, to technological developments such as the steam engine, internal combustion engine and electricity generation; the development of thermodynamics both was driven by atomic theory. It albeit in a subtle manner, motivated new directions in probability and statistics; the ancients viewed heat as that related to fire. In 3000 BC, the ancient Egyptians viewed heat as related to origin mythologies. In the Western philosophical tradition, after much debate about the primal element among earlier pre-Socratic philosophers, Empedocles proposed a four-element theory, in which all substances derive from earth, water and fire.
The Empedoclean element of fire is the principal ancestor of concepts such as phlogin and caloric. Around 500 BC, the Greek philosopher Heraclitus became famous as the "flux and fire" philosopher for his proverbial utterance: "All things are flowing." Heraclitus argued that the three principal elements in nature were fire and water. Atomism is a central part of today's relationship between statistical mechanics. Ancient thinkers such as Leucippus and Democritus, the Epicureans, by advancing atomism, laid the foundations for the atomic theory; until experimental proof of atoms was provided in the 20th century, the atomic theory was driven by philosophical considerations and scientific intuition. The 5th century BC Greek philosopher Parmenides, in his only known work, a poem conventionally titled On Nature, uses verbal reasoning to postulate that a void what is now known as a vacuum, in nature could not occur; this view was supported by the arguments of Aristotle, but was criticized by Leucippus and Hero of Alexandria.
From antiquity to the Middle Ages various arguments were put forward to prove or disapprove the existence of a vacuum and several attempts were made to construct a vacuum but all proved unsuccessful. The European scientists Cornelius Drebbel, Robert Fludd, Galileo Galilei and Santorio Santorio in the 16th and 17th centuries were able to gauge the relative "coldness" or "hotness" of air, using a rudimentary air thermometer; this may have been influenced by an earlier device which could expand and contract the air constructed by Philo of Byzantium and Hero of Alexandria. Around 1600, the English philosopher and scientist Francis Bacon surmised: "Heat itself, its essence and quiddity is motion and nothing else." In 1643, Galileo Galilei, while accepting the'sucking' explanation of horror vacui proposed by Aristotle, believed that nature's vacuum-abhorrence is limited. Pumps operating in mines had proven that nature would only fill a vacuum with water up to a height of ~30 feet. Knowing this curious fact, Galileo encouraged his former pupil Evangelista Torricelli to investigate these supposed limitations.
Torricelli did not believe that vacuum-abhorrence in the sense of Aristotle's'sucking' perspective, was responsible for raising the water. Rather, he reasoned, it was the result of the pressure exerted on the liquid by the surrounding air. To prove this theory, he filled a long glass tube with mercury and upended it into a dish containing mercury. Only a portion of the tube emptied; as the mercury emptied, a partial vacuum was created at the top of the tube. The gravitational force on the heavy element Mercury prevented it from filling the vacuum; the theory of phlogiston arose in the 17th century, late in the period of alchemy. Its replacement by caloric theory in the 18th century is one of the historical markers of the transition from alchemy to chemistry. Phlogiston was a hypothetical substance, presumed to be liberated from combustible substances during burning, from metals during the process of rusting. Caloric, like phlogiston, was presumed to be the "substance" of heat that would flow from a hotter body to a cooler body, thus warming it.
The first substantial experimental challenges to caloric theory arose in Rumford's 1798 work, when he showed that boring cast iron cannons produced great amounts of heat which he ascribed to friction, his work was among the first to undermine the caloric theory. The development of the steam engine focused attention on calorimetry and the amount of heat produced from different types of coal; the first quantitative research on the heat changes during chemical reactions was initiated by Lavoisier using an ice calorimeter following research by Joseph Black on the latent heat of water. More quantitative studies by James Prescott Joule in 1843 onwards provided soundly reproducible phenomena, helped to place the subject of thermodynamics on a solid footing. William Thomson, for example, was still trying to explain Joule's observations within a caloric framework as late as 1850; the utility and explanatory power of kinetic theory, soon started to displace caloric and it was obsolete by the end of the 19th century.
Joseph Black and Lavoisier made important contributions in the precise measurement of heat changes using the calorimeter, a subject which became known as thermochemistry. Boyle's law Charles's law was first published by Joseph Louis Gay-Lussac in 1802, but he referenced unpublished work by Jacques Charles from around
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz was a German physician and physicist who made significant contributions in several scientific fields. The largest German association of research institutions, the Helmholtz Association, is named after him. In physiology and psychology, he is known for his mathematics of the eye, theories of vision, ideas on the visual perception of space, color vision research, on the sensation of tone, perception of sound, empiricism in the physiology of perception. In physics, he is known for his theories on the conservation of energy, work in electrodynamics, chemical thermodynamics, on a mechanical foundation of thermodynamics; as a philosopher, he is known for his philosophy of science, ideas on the relation between the laws of perception and the laws of nature, the science of aesthetics, ideas on the civilizing power of science. Helmholtz was born in Potsdam the son of the local Gymnasium headmaster, Ferdinand Helmholtz, who had studied classical philology and philosophy, and, a close friend of the publisher and philosopher Immanuel Hermann Fichte.
Helmholtz's work was influenced by the philosophy of Johann Gottlieb Immanuel Kant. He tried to trace their theories in empirical matters like physiology; as a young man, Helmholtz was interested in natural science, but his father wanted him to study medicine at the Charité because there was financial support for medical students. Trained in physiology, Helmholtz wrote on many other topics, ranging from theoretical physics, to the age of the Earth, to the origin of the Solar System. Helmholtz's first academic position was as a teacher of Anatomy at the Academy of Arts in Berlin in 1848, he moved to take a post of associate professor of physiology at the Prussian University of Königsberg, where he was appointed in 1849. In 1855 he accepted a full professorship of physiology at the University of Bonn, he was not happy in Bonn and three years he transferred to the University of Heidelberg, in Baden, where he served as professor of physiology. In 1871 he accepted his final university position, as professor of physics at the Humboldt University in Berlin.
His first important scientific achievement, an 1847 treatise on the conservation of energy, was written in the context of his medical studies and philosophical background. His work on energy conservation came about while studying muscle metabolism, he tried to demonstrate that no energy is lost in muscle movement, motivated by the implication that there were no vital forces necessary to move a muscle. This was a rejection of the speculative tradition of Naturphilosophie, at that time a dominant philosophical paradigm in German physiology. Drawing on the earlier work of Sadi Carnot, Benoît Paul Émile Clapeyron and James Prescott Joule, he postulated a relationship between mechanics, light and magnetism by treating them all as manifestations of a single force, or energy in today's terminology, he published his theories in his book Über die Erhaltung der Kraft. In the 1850s and 60s, building on the publications of William Thomson and William Rankine popularized the idea of the heat death of the universe.
In fluid dynamics, Helmholtz made several contributions, including Helmholtz's theorems for vortex dynamics in inviscid fluids. Helmholtz was a pioneer in the scientific study of human audition. Inspired by psychophysics, he was interested in the relationships between measurable physical stimuli and their correspondent human perceptions. For example, the amplitude of a sound wave can be varied, causing the sound to appear louder or softer, but a linear step in sound pressure amplitude does not result in a linear step in perceived loudness; the physical sound needs to be increased exponentially in order for equal steps to seem linear, a fact, used in current electronic devices to control volume. Helmholtz paved the way in experimental studies on the relationship between the physical energy and its appreciation, with the goal in mind to develop "psychophysical laws." The sensory physiology of Helmholtz was the basis of the work of Wilhelm Wundt, a student of Helmholtz, considered one of the founders of experimental psychology.
More explicitly than Helmholtz, Wundt described his research as a form of empirical philosophy and as a study of the mind as something separate. Helmholtz had, in his early repudiation of Naturphilosophie, stressed the importance of materialism, was focusing more on the unity of "mind" and body. In 1851, Helmholtz revolutionized the field of ophthalmology with the invention of the ophthalmoscope; this made. Helmholtz's interests at that time were focused on the physiology of the senses, his main publication, titled Handbuch der Physiologischen Optik, provided empirical theories on depth perception, color vision, motion perception, became the fundamental reference work in his field during the second half of the nineteenth century. In the third and final volume, published in 1867, Helmholtz described the importance of unconscious inferences for perception; the Handbuch was first translated into English under the editorship of James P. C. Southall on behalf of the Optical Society of America in 1924-5.
His theory of accommodation went unchallenged until the final decade of the 20th century. Helmholtz continued to work for several decades on several editions of the handbook updating his work because of his dispute with Ewald Hering who held opposite views on spatial and color vision; this dispute divided the discipline
In thermodynamics, work performed by a system is energy transferred by the system to its surroundings, due to macroscopic forces exerted by the system on its surroundings, where those forces, their external effects, can be measured. Such work is the only kind; the externally measured forces and external effects may be electromagnetic, gravitational, or pressure/volume or other macroscopically mechanical variables. Thermodynamic work is defined to be measurable from knowledge of such external macroscopic factors. For thermodynamic work, these external factors are matched by values of or contributions to changes in macroscopic internal state variables of the system, which always occur in conjugate pairs, for example pressure and volume or magnetic flux density and magnetization. In the SI system of measurement, work is measured in joules; the rate at which work is performed is power. In the surroundings of a thermodynamic system, external to it, all the various mechanical and non-mechanical macroscopic forms of work can be converted into each other with no limitation in principle due to the laws of thermodynamics, so that the energy conversion efficiency can approach 100% in some cases.
Work sometimes is said to be done on a system of interest by an external system that lies in the surroundings, not a thermodynamic system as defined by the usual thermodynamic state variables. The paddle stirring experiments of Joule provide an example, illustrating the concept of isochoric mechanical work; such work is not adiabatic, because it occurs through friction on the system of interest. Though the external system does macroscopic mechanical work, described by its own macroscopic mechanical variables, the thermodynamic work, as defined here, such as pressure–volume work, done by the system of interest, is zero; the external system generates friction on and in the system of interest. Another form of isochoric work is Joule heating, not adiabatic, because it occurs through friction as the electric current passes through the system of interest; because no thermodynamic work is done by the system of interest, no matter is transferred, such an energy transfer is regarded as a heat transfer into the system of interest.
A system of interest cannot raise a weight by such work. It is a consequence of the second law of thermodynamics that a thermodynamic system in its own state of internal thermodynamic equilibrium cannot do isochoric mechanical work on an external system. Thermodynamic work is a version of the concept of work in physics. Work, i.e. "weight lifted through a height", was defined in 1824 by Sadi Carnot in his famous paper Reflections on the Motive Power of Fire, where he used the term motive power for work. According to Carnot: We use here motive power to express the useful effect that a motor is capable of producing; this effect can always be likened to the elevation of a weight to a certain height. It has, as we know, as a measure, the product of the weight multiplied by the height to which it is raised. In 1845, the English physicist James Joule wrote a paper On the mechanical equivalent of heat for the British Association meeting in Cambridge. In this paper, he reported his best-known experiment, in which the mechanical power released through the action of a "weight falling through a height" was used to turn a paddle-wheel in an insulated barrel of water.
In this experiment, the friction and agitation of the paddle-wheel on the body of water caused heat to be generated which, in turn, increased the temperature of water. Both the temperature change ∆T of the water and the height of the fall ∆h of the weight mg were recorded. Using these values, Joule was able to determine the mechanical equivalent of heat. Joule estimated a mechanical equivalent of heat to be 819 ft•lbf/Btu; the modern day definitions of heat, work and energy all have connection to this experiment. In this arrangement of apparatus, it never happens that the process runs in reverse, with the water driving the paddles so as to raise the weight, not slightly; the doing of such isochoric mechanical work by the device, which lies external to the water, while the energy supplied by the fall of the weight becomes heat passing into the water, is irreversible. A pre-supposed guiding principle of thermodynamics is the conservation of energy; the total energy of a system is the sum of its internal energy, of its potential energy as a whole system in an external force field, such as gravity, of its kinetic energy as a whole system in motion.
Thermodynamics is concerned with transfers of energy. Transfer of energy by work has been given logical priority in thermodynamics since the end of the nineteenth century. Besides transfer of energy by work, thermodynamics admits transfer of energy as heat. For a process in a closed thermodynamic system, the first law of thermodynamics relates changes in the internal energy of the system to those two forms of energy transfer, by work, as heat. Adiabatic work is done without heat transfer. In principle, in thermodynamics, for a process in a closed system, quantity of heat transferred is defined by the amount of adiabatic work that would be needed to effect the change in the system, occasioned by the heat transfer. In experimental practice, heat transfer is estimated calorimetrically, through change of temperature of a known quantity of calorimetric material substance. In the surroundings
Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force exhibits electromagnetic fields such as electric fields, magnetic fields, light, is one of the four fundamental interactions in nature; the other three fundamental interactions are the strong interaction, the weak interaction, gravitation. At high energy the weak force and electromagnetic force are unified as a single electroweak force. Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force, which includes both electricity and magnetism as different manifestations of the same phenomenon; the electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. Ordinary matter takes its form as a result of intermolecular forces between individual atoms and molecules in matter, is a manifestation of the electromagnetic force.
Electrons are bound by the electromagnetic force to atomic nuclei, their orbital shapes and their influence on nearby atoms with their electrons is described by quantum mechanics. The electromagnetic force governs all chemical processes, which arise from interactions between the electrons of neighboring atoms. There are numerous mathematical descriptions of the electromagnetic field. In classical electrodynamics, electric fields are described as electric potential and electric current. In Faraday's law, magnetic fields are associated with electromagnetic induction and magnetism, Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents; the theoretical implications of electromagnetism the establishment of the speed of light based on properties of the "medium" of propagation, led to the development of special relativity by Albert Einstein in 1905. Electricity and magnetism were considered to be two separate forces; this view changed, with the publication of James Clerk Maxwell's 1873 A Treatise on Electricity and Magnetism in which the interactions of positive and negative charges were shown to be mediated by one force.
There are four main effects resulting from these interactions, all of which have been demonstrated by experiments: Electric charges attract or repel one another with a force inversely proportional to the square of the distance between them: unlike charges attract, like ones repel. Magnetic poles attract or repel one another in a manner similar to positive and negative charges and always exist as pairs: every north pole is yoked to a south pole. An electric current inside a wire creates a corresponding circumferential magnetic field outside the wire, its direction depends on the direction of the current in the wire. A current is induced in a loop of wire when it is moved toward or away from a magnetic field, or a magnet is moved towards or away from it. While preparing for an evening lecture on 21 April 1820, Hans Christian Ørsted made a surprising observation; as he was setting up his materials, he noticed a compass needle deflected away from magnetic north when the electric current from the battery he was using was switched on and off.
This deflection convinced him that magnetic fields radiate from all sides of a wire carrying an electric current, just as light and heat do, that it confirmed a direct relationship between electricity and magnetism. At the time of discovery, Ørsted did not suggest any satisfactory explanation of the phenomenon, nor did he try to represent the phenomenon in a mathematical framework. However, three months he began more intensive investigations. Soon thereafter he published his findings, proving that an electric current produces a magnetic field as it flows through a wire; the CGS unit of magnetic induction is named in honor of his contributions to the field of electromagnetism. His findings resulted in intensive research throughout the scientific community in electrodynamics, they influenced French physicist André-Marie Ampère's developments of a single mathematical form to represent the magnetic forces between current-carrying conductors. Ørsted's discovery represented a major step toward a unified concept of energy.
This unification, observed by Michael Faraday, extended by James Clerk Maxwell, reformulated by Oliver Heaviside and Heinrich Hertz, is one of the key accomplishments of 19th century mathematical physics. It has had far-reaching consequences, one of, the understanding of the nature of light. Unlike what was proposed by the electromagnetic theory of that time and other electromagnetic waves are at present seen as taking the form of quantized, self-propagating oscillatory electromagnetic field disturbances called photons. Different frequencies of oscillation give rise to the different forms of electromagnetic radiation, from radio waves at the lowest frequencies, to visible light at intermediate frequencies, to gamma rays at the highest frequencies. Ørsted was not the only person to examine the relationship between magnetism. In 1802, Gian Domenico Romagnosi, an Italian legal scholar, deflected a magnetic needle using a Voltaic pile; the factual setup of the experiment is not clear, so if current flew across the needle or not.
An account of the discovery was published in 1802 in an Italian newspaper, but it was overlooked by the contemporary scientific community, because Romagnosi did not belong to this community. An earlier, neglected, connec
The world is the planet Earth and all life upon it, including human civilization. In a philosophical context, the "world" is the whole of the physical Universe, or an ontological world. In a theological context, the world is the material or the profane sphere, as opposed to the celestial, transcendent or sacred spheres. "End of the world" scenarios refer to the end of human history in religious contexts. The history of the world is understood as spanning the major geopolitical developments of about five millennia, from the first civilizations to the present. In terms such as world religion, world language, world government, world war, the term world suggests an international or intercontinental scope without implying participation of every part of the world; the world population is the sum of all human populations at any time. Terms such as "world championship", "gross world product", "world flags" imply the sum or combination of all sovereign states; the English word world comes from the Old English weorold, worold, a compound of wer "man" and eld "age," which thus means "Age of Man."
The Old English is a reflex of the Common Germanic *wira-alđiz reflected in Old Saxon werold, Old Dutch werilt, Old High German weralt, Old Frisian warld and Old Norse verǫld. The corresponding word in Latin is mundus "clean, elegant", itself a loan translation of Greek cosmos "orderly arrangement." While the Germanic word thus reflects a mythological notion of a "domain of Man" as opposed to the divine sphere on the one hand and the chthonic sphere of the underworld on the other, the Greco-Latin term expresses a notion of creation as an act of establishing order out of chaos. "World" distinguishes the entire planet or population from any particular country or region: world affairs pertain not just to one place but to the whole world, world history is a field of history that examines events from a global perspective. Earth, on the other hand, refers to the planet as a physical entity, distinguishes it from other planets and physical objects. "World" was classically used to mean the material universe, or the cosmos: "The worlde is an apte frame of heauen and earthe, all other naturall thinges contained in them."
The earth was described as "the center of the world". The term can be used attributively, to mean "global", or "relating to the whole world", forming usages such as world community or world canonical texts. By extension, a world may refer to any planet or heavenly body when it is thought of as inhabited in the context of science fiction or futurology. World, in its original sense, when qualified, can refer to a particular domain of human experience; the world of work describes paid work and the pursuit of a career, in all its social aspects, to distinguish it from home life and academic study. The fashion world describes the environment of the designers, fashion houses and consumers that make up the fashion industry. Historically, the New World vs. the Old World, referring to the parts of the world colonized in the wake of the age of discovery. Now used in zoology and botany, as in New World monkey. In philosophy, the term world has several possible meanings. In some contexts, it refers to everything that makes up the physical universe.
In others, it can mean have a specific ontological sense. While clarifying the concept of world has arguably always been among the basic tasks of Western philosophy, this theme appears to have been raised explicitly only at the start of the twentieth century and has been the subject of continuous debate; the question of what the world is has by no means been settled. The traditional interpretation of Parmenides' work is that he argued that the everyday perception of reality of the physical world is mistaken, that the reality of the world is'One Being': an unchanging, indestructible whole. In his Allegory of the Cave, Plato distinguishes between forms and ideas and imagines two distinct worlds: the sensible world and the intelligible world. In Georg Wilhelm Friedrich Hegel's philosophy of history, the expression Weltgeschichte ist Weltgericht is used to assert the view that History is what judges men, their actions and their opinions. Science is born from the desire to transform the World in relation to Man.
The World as Will and Representation is the central work of Arthur Schopenhauer. Schopenhauer saw the human will as our one window to the world behind the representation, he believed, that we could gain knowledge about the thing-in-itself, something Kant said was impossible, since the rest of the relationship between representation and thing-in-itself could be understood by analogy to the relationship between human will and human body. Two definitions that were both put forward in the 1920s, suggest the range of available opinion. "The world is everything, the case," wrote Ludwig Wittgenstein in his influential Tractatus Logico-Philosophicus, first published in 1921. This definition would serve as the basis of logical positivism, with its assumption that there is one world, consisting of the totality of facts, regardless of the interpretations that individual people may make of them. Martin Heidegger, argued that "the surrounding world is different for each of us, notwithstanding t