This article is about the general framework of distance and direction. For the space beyond Earth's atmosphere, seeOuter space. For the writing separator, seeSpace (punctuation). For other uses, seeSpace (disambiguation).
Debates concerning the nature, essence and the mode of existence of space date back to antiquity; namely, to treatises like theTimaeus ofPlato, orSocrates in his reflections on what the Greeks calledkhôra (i.e. "space"), or in thePhysics ofAristotle (Book IV, Delta) in the definition oftopos (i.e. place), or in the later "geometrical conception of place" as "spacequa extension" in theDiscourse on Place (Qawl fi al-Makan) of the 11th-century ArabpolymathAlhazen.[4] Many of these classical philosophical questions were discussed in theRenaissance and then reformulated in the 17th century, particularly during the early development ofclassical mechanics.
Isaac Newton viewed space as absolute, existing permanently and independently of whether there was any matter in it.[5] In contrast, othernatural philosophers, notablyGottfried Leibniz, thought that space was in fact a collection of relations between objects, given by theirdistance anddirection from one another. In the 18th century, the philosopher and theologianGeorge Berkeley attempted to refute the "visibility of spatial depth" in hisEssay Towards a New Theory of Vision. Later, themetaphysicianImmanuel Kant said that the concepts of space and time are not empirical ones derived from experiences of the outside world—they are elements of an already given systematic framework that humans possess and use to structure all experiences. Kant referred to the experience of "space" in hisCritique of Pure Reason as being a subjective "purea priori form of intuition".
Galileo
Galilean andCartesian theories about space, matter, and motion are at the foundation of theScientific Revolution, which is understood to have culminated with the publication ofNewton'sPrincipia Mathematica in 1687.[6] Newton's theories about space and time helped him explain the movement of objects. While his theory of space is considered the most influential in physics, it emerged from his predecessors' ideas about the same.[7]
As one of the pioneers ofmodern science, Galileo revised the establishedAristotelian andPtolemaic ideas about ageocentric cosmos. He backed theCopernican theory that the universe washeliocentric, with a stationary Sun at the center and the planets—including the Earth—revolving around the Sun. If the Earth moved, the Aristotelian belief that its natural tendency was to remain at rest was in question. Galileo wanted to prove instead that the Sun moved around its axis, that motion was as natural to an object as the state of rest. In other words, for Galileo, celestial bodies, including the Earth, were naturally inclined to move in circles. This view displaced another Aristotelian idea—that all objects gravitated towards their designated natural place-of-belonging.[8]
René Descartes
Descartes set out to replace the Aristotelian worldview with a theory about space and motion as determined bynatural laws. In other words, he sought ametaphysical foundation or amechanical explanation for his theories about matter and motion.Cartesian space wasEuclidean in structure—infinite, uniform and flat.[9] It was defined as that which contained matter; conversely, matter by definition had a spatial extension so that there was no such thing as empty space.[6]
The Cartesian notion of space is closely linked to his theories about the nature of the body, mind and matter. He is famously known for his "cogito ergo sum" (I think therefore I am), or the idea that we can only be certain of the fact that we can doubt, and therefore think and therefore exist. His theories belong to therationalist tradition, which attributes knowledge about the world to our ability to think rather than to our experiences, as theempiricists believe.[10] He posited a clear distinction between the body and mind, which is referred to as theCartesian dualism.
Following Galileo and Descartes, during the seventeenth century thephilosophy of space and time revolved around the ideas ofGottfried Leibniz, a German philosopher–mathematician, andIsaac Newton, who set out two opposing theories of what space is. Rather than being an entity that independently exists over and above other matter, Leibniz held that space is no more than the collection of spatial relations between objects in the world: "space is that which results from places taken together".[11] Unoccupied regions are those thatcould have objects in them, and thus spatial relations with other places. For Leibniz, then, space was an idealisedabstraction from the relations between individual entities or their possible locations and therefore could not becontinuous but must bediscrete.[12]Space could be thought of in a similar way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people.[13]Leibniz argued that space could not exist independently of objects in the world because that implies a difference between two universes exactly alike except for the location of the material world in each universe. But since there would be no observational way of telling these universes apart then, according to theidentity of indiscernibles, there would be no real difference between them. According to theprinciple of sufficient reason, any theory of space that implied that there could be these two possible universes must therefore be wrong.[14]
Newton took space to be more than relations between material objects and based his position onobservation and experimentation. For arelationist there can be no real difference betweeninertial motion, in which the object travels with constantvelocity, andnon-inertial motion, in which the velocity changes with time, since all spatial measurements are relative to other objects and their motions. But Newton argued that since non-inertial motion generatesforces, it must be absolute.[15] He used the example ofwater in a spinning bucket to demonstrate his argument. Water in abucket is hung from a rope and set to spin, starts with a flat surface. After a while, as the bucket continues to spin, the surface of the water becomes concave. If the bucket's spinning is stopped then the surface of the water remains concave as it continues to spin. The concave surface is therefore apparently not the result of relative motion between the bucket and the water.[16] Instead, Newton argued, it must be a result of non-inertial motion relative to space itself. For several centuries the bucket argument was considered decisive in showing that space must exist independently of matter.
In the eighteenth century the German philosopherImmanuel Kant published his theory of space as "a property of our mind" by which "we represent to ourselves objects as outside us, and all as in space" in theCritique of Pure Reason[17] On his view the nature of spatial predicates are "relations that only attach to the form of intuition alone, and thus to the subjective constitution of our mind, without which these predicates could not be attached to anything at all."[18] This develops his theory ofknowledge in which knowledge about space itself can be botha priori andsynthetic.[19]According to Kant, knowledge about space issynthetic because any proposition about space cannot be truemerely in virtue of the meaning of the terms contained in the proposition. In the counter-example, the proposition "all unmarried men are bachelors"is true by virtue of each term's meaning. Further, space isa priori because it is the form of our receptive abilities to receive information about the external world. For example, someone without sight can still perceive spatial attributes via touch, hearing, and smell. Knowledge of space itself isa priori because it belongs to the subjective constitution of our mind as the form or manner of our intuition of external objects.
Euclid'sElements contained five postulates that form the basis for Euclidean geometry. One of these, theparallel postulate, has been the subject of debate among mathematicians for many centuries. It states that on anyplane on which there is a straight lineL1 and a pointP not onL1, there is exactly one straight lineL2 on the plane that passes through the pointP and is parallel to the straight lineL1. Until the 19th century, few doubted the truth of the postulate; instead debate centered over whether it was necessary as an axiom, or whether it was a theory that could be derived from the other axioms.[20] Around 1830 though, the HungarianJános Bolyai and the RussianNikolai Ivanovich Lobachevsky separately published treatises on a type of geometry that does not include the parallel postulate, calledhyperbolic geometry. In this geometry, aninfinite number of parallel lines pass through the pointP. Consequently, the sum of angles in a triangle is less than 180° and the ratio of acircle'scircumference to itsdiameter is greater thanpi. In the 1850s,Bernhard Riemann developed an equivalent theory ofelliptical geometry, in which no parallel lines pass throughP. In this geometry, triangles have more than 180° and circles have a ratio of circumference-to-diameter that is less thanpi.
Although there was a prevailing Kantian consensus at the time, once non-Euclidean geometries had been formalised, some began to wonder whether or not physical space is curved.Carl Friedrich Gauss, a German mathematician, was the first to consider an empirical investigation of the geometrical structure of space. He thought of making a test of the sum of the angles of an enormous stellar triangle, and there are reports that he actually carried out a test, on a small scale, bytriangulating mountain tops in Germany.[21]
Henri Poincaré, a French mathematician and physicist of the late 19th century, introduced an important insight in which he attempted to demonstrate the futility of any attempt to discover which geometry applies to space by experiment.[22] He considered the predicament that would face scientists if they were confined to the surface of an imaginary large sphere with particular properties, known as asphere-world. In this world, the temperature is taken to vary in such a way that all objects expand and contract in similar proportions in different places on the sphere. With a suitable falloff in temperature, if the scientists try to use measuring rods to determine the sum of the angles in a triangle, they can be deceived into thinking that they inhabit a plane, rather than a spherical surface.[23] In fact, the scientists cannot in principle determine whether they inhabit a plane or sphere and, Poincaré argued, the same is true for the debate over whether real space is Euclidean or not. For him, which geometry was used to describe space was a matter ofconvention.[24] SinceEuclidean geometry is simpler than non-Euclidean geometry, he assumed the former would always be used to describe the 'true' geometry of the world.[25]
In 1905,Albert Einstein published hisspecial theory of relativity, which led to the concept that space and time can be viewed as a single construct known asspacetime. In this theory, thespeed of light invacuum is the same for all observers—which hasthe result that two events that appear simultaneous to one particular observer will not be simultaneous to another observer if the observers are moving with respect to one another. Moreover, an observer will measure a moving clock totick more slowly than one that is stationary with respect to them; and objects are measuredto be shortened in the direction that they are moving with respect to the observer.
Subsequently, Einstein worked on ageneral theory of relativity, which is a theory of howgravity interacts with spacetime. Instead of viewing gravity as aforce field acting in spacetime, Einstein suggested that it modifies the geometric structure of spacetime itself.[26] According to the general theory, timegoes more slowly at places with lower gravitational potentials and rays of light bend in the presence of a gravitational field. Scientists have studied the behaviour ofbinary pulsars, confirming the predictions of Einstein's theories.[citation needed] Non-Euclidean geometry is usually used to describe spacetime.[citation needed]
Space is one of the fewfundamental quantities inphysics, meaning that it cannot be defined via other quantities because nothing more fundamental is known at the present. On the other hand, it can be related to other fundamental quantities. Thus, similar to other fundamental quantities (like time andmass), space can be explored viameasurement and experiment.
BeforeAlbert Einstein's work on relativistic physics, time and space were viewed as independent dimensions. Einstein's discoveries showed that due to relativity of motion our space and time can be mathematically combined into one object–spacetime. It turns out that distances inspace or intime separately are not invariant with respect to Lorentz coordinate transformations, but distances in Minkowski space alongspacetime intervals are—which justifies the name.
In addition, time and space dimensions should not be viewed as exactly equivalent in Minkowski space. One can freely move in space but not in time. Thus, time and space coordinates are treated differently both inspecial relativity (where time is sometimes considered animaginary coordinate) and ingeneral relativity (where different signs are assigned to time and space components ofspacetimemetric).
Furthermore, inEinstein's general theory of relativity, it is postulated that spacetime is geometrically distorted –curved – near to gravitationally significant masses.[27]
One consequence of this postulate, which follows from the equations of general relativity, is the prediction of moving ripples of spacetime, calledgravitational waves. While indirect evidence for these waves has been found (in the motions of theHulse–Taylor binary system, for example) experiments attempting to directly measure these waves are ongoing at theLIGO andVirgo collaborations. LIGO scientists reported thefirst such direct observation of gravitational waves on 14 September 2015.[28][29]
Relativity theory leads to thecosmological question of what shape the universe is, and where space came from. It appears that space was created in theBig Bang, 13.8 billion years ago[30] and has been expanding ever since. The overall shape of space is not known, but space is known to be expanding very rapidly due to thecosmic inflation.
The measurement ofphysical space has long been important. Although earlier societies had developed measuring systems, theInternational System of Units, (SI), is now the most common system of units used in the measuring of space, and is almost universally used.
Currently, the standard space interval, called a standard meter or simply meter, is defined as thedistance traveled by light in vacuum during a time interval of exactly 1/299,792,458 of a second. This definition coupled with present definition of the second is based on thespecial theory of relativity in which thespeed of light plays the role of a fundamental constant of nature.
Geography is the branch of science concerned with identifying and describing places onEarth, utilizing spatial awareness to try to understand why things exist in specific locations.Cartography is the mapping of spaces to allow better navigation, for visualization purposes and to act as a locational device.Geostatistics apply statistical concepts to collected spatial data of Earth to create an estimate for unobserved phenomena.
Geographical space is often considered as land, and can have a relation toownership usage (in which space is seen asproperty or territory). While some cultures assert the rights of the individual in terms of ownership, other cultures will identify with a communal approach to land ownership, while still other cultures such asAustralian Aboriginals, rather than asserting ownership rights to land, invert the relationship and consider that they are in fact owned by the land.Spatial planning is a method of regulating the use of space at land-level, with decisions made at regional, national and international levels. Space can also impact on human and cultural behavior, being an important factor in architecture, where it will impact on the design of buildings and structures, and on farming.
Ownership of space is not restricted to land. Ownership ofairspace and ofwaters is decided internationally. Other forms of ownership have been recently asserted to other spaces—for example to the radio bands of theelectromagnetic spectrum or tocyberspace.
Public space is a term used to define areas of land as collectively owned by the community, and managed in their name by delegated bodies; such spaces are open to all, whileprivate property is the land culturally owned by an individual or company, for their own use and pleasure.
Abstract space is a term used ingeography to refer to a hypothetical space characterized by complete homogeneity. When modeling activity or behavior, it is a conceptual tool used to limitextraneous variables such as terrain.
Psychologists first began to study the way space is perceived in the middle of the 19th century. Those now concerned with such studies regard it as a distinct branch ofpsychology. Psychologists analyzing the perception of space are concerned with how recognition of an object's physical appearance or its interactions are perceived, see, for example,visual space.
Several space-relatedphobias have been identified, includingagoraphobia (the fear of open spaces),astrophobia (the fear of celestial space) andclaustrophobia (the fear of enclosed spaces).
The understanding of three-dimensional space in humans is thought to be learned during infancy usingunconscious inference, and is closely related tohand-eye coordination. The visual ability to perceive the world in three dimensions is calleddepth perception.
In the social sciences
Space has been studied in the social sciences from the perspectives ofMarxism,feminism,postmodernism,postcolonialism,urban theory andcritical geography. These theories account for the effect of the history of colonialism, transatlantic slavery and globalization on our understanding and experience of space and place. The topic has garnered attention since the 1980s, after the publication ofHenri Lefebvre'sThe Production of Space . In this book, Lefebvre applies Marxist ideas about the production of commodities and accumulation of capital to discuss space as a social product. His focus is on the multiple and overlapping social processes that produce space.[31]
In his bookThe Condition of Postmodernity,David Harvey describes what he terms the "time-space compression." This is the effect of technological advances and capitalism on our perception of time, space and distance.[32] Changes in the modes of production and consumption of capital affect and are affected by developments in transportation and technology. These advances create relationships across time and space, new markets and groups of wealthy elites in urban centers, all of which annihilate distances and affect our perception of linearity and distance.[33]
In his bookThirdspace,Edward Soja describes space and spatiality as an integral and neglected aspect of what he calls the "trialectics of being," the three modes that determine how we inhabit, experience and understand the world. He argues that critical theories in the Humanities and Social Sciences study the historical and social dimensions of our lived experience, neglecting the spatial dimension.[34] He builds on Henri Lefebvre's work to address the dualistic way in which humans understand space—as either material/physical or as represented/imagined. Lefebvre's "lived space"[35] and Soja's "thirdspace" are terms that account for the complex ways in which humans understand and navigate place, which "firstspace" and "Secondspace" (Soja's terms for material and imagined spaces respectively) do not fully encompass.
Postcolonial theoristHomi Bhabha's concept ofThird Space is different from Soja's Thirdspace, even though both terms offer a way to think outside the terms of abinary logic. Bhabha's Third Space is the space in which hybrid cultural forms and identities exist. In his theories, the termhybrid describes new cultural forms that emerge through the interaction between colonizer and colonized.[36]
^Carnap, R. (1995).An Introduction to the Philosophy of Science. New York: Dove. (Original edition:Philosophical Foundations of Physics. New York: Basic books, 1966).
^Refer to Plato'sTimaeus in the Loeb Classical Library,Harvard University, and to his reflections onkhora. See also Aristotle'sPhysics, Book IV, Chapter 5, on the definition oftopos. Concerning Ibn al-Haytham's 11th century conception of "geometrical place" as "spatial extension", which is akin toDescartes' and Leibniz's 17th century notions ofextensio andanalysis situs, and his own mathematical refutation of Aristotle's definition oftopos in natural philosophy, refer to:Nader El-Bizri, "In Defence of the Sovereignty of Philosophy: al-Baghdadi's Critique of Ibn al-Haytham's Geometrisation of Place",Arabic Sciences and Philosophy (Cambridge University Press), Vol. 17 (2007), pp. 57–80.
^French, A.J.; Ebison, M.G. (1986).Introduction to Classical Mechanics. Dordrecht: Springer, p. 1.
^Leibniz, Fifth letter to Samuel Clarke. By H.G. Alexander (1956).The Leibniz-Clarke Correspondence. Manchester: Manchester University Press, pp. 55–96.
^Vailati, E. (1997).Leibniz & Clarke: A Study of Their Correspondence. New York: Oxford University Press, p. 115.
^Sklar, L. (1992).Philosophy of Physics. Boulder: Westview Press, p. 20.
^Allison, Henry E. (2004).Kant's Transcendental Idealism: An Interpretation and Defense; Revised and Enlarged Edition. Yale University Press. p. 97-132.ISBN978-0300102666.
^Kant, Immanuel (1999).Critique of Pure Reason (The Cambridge Edition of the Works of Immanuel Kant). Cambridge University Press. p. A3/B37-38.ISBN978-0-5216-5729-7.
^Carnap, R.An Introduction to the Philosophy of Science. pp. 177–178.
^Carnap, R.An Introduction to the Philosophy of Science. p. 126.
^Carnap, R.An Introduction to the Philosophy of Science. pp. 134–136.
^Jammer, Max (1954).Concepts of Space. The History of Theories of Space in Physics. Cambridge: Harvard University Press, p. 165.
^A medium with a variableindex of refraction could also be used to bend the path of light and again deceive the scientists if they attempt to use light to map out their geometry.
^Carnap, R.An Introduction to the Philosophy of Science. p. 148.
^Harvey, David (2001).Spaces of Capital: Towards a Critical Geography. Edinburgh University Press. pp. 244–246.
^W., Soja, Edward (1996).Thirdspace: journeys to Los Angeles and other real-and-imagined places. Cambridge, Mass.: Blackwell.ISBN978-1-55786-674-5.OCLC33863376.{{cite book}}: CS1 maint: multiple names: authors list (link)
