Space is the boundless, three-dimensional extent in which
objectsIn physics, a physical body or physical object is a collection of masses, taken to be one...
and events occur and have relative position and direction. Physical space is often conceived in three
linearThe word linear comes from the Latin word linearis, which means created by lines.In mathematics, a linear map or function f is a function which satisfies the following two properties......
dimensionIn mathematics and physics, the dimension of a space or object is informally defined as the minimum number of coordinates needed to specify each point within it. Thus a line has a dimension of one because only one coordinate is needed to specify a point on it...
s, although modern
physicistsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
usually consider it, with
timeTime is a component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects...
, to be part of the boundless four-dimensional continuum known as
spacetimeIn physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort than the spatial dimensions...
. In
mathematicsMathematics is the science and study of quantity, structure, space, and change. Mathematicians seek out patterns, formulate new conjectures, and establish truth by rigorous deduction from appropriately chosen axioms and definitions....
one examines 'spaces' with different numbers of dimensions and with different underlying structures. The concept of space is considered to be of fundamental importance to an understanding of the physical
universeThe Universe comprises everything that physically exists, the entirety of space and time, all forms of matter and energy, and the physical laws and constants that govern them...
although disagreement continues between
philosophersPhilosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing these questions by its critical, generally systematic approach and its reliance on reasoned...
over whether it is itself an entity, a relationship between entities, or part of a
conceptual frameworkA conceptual framework is used in research to outline possible courses of action or to present a preferred approach to an idea or thought. For example, the philosopher Isaiah Berlin used the 'hedgehogs' versus 'foxes' approach; a 'hedgehog' might approach the world in terms of a single organizing...
.
Many of the philosophical questions arose in the 17th century, during the early development of
classical mechanicsIn the fields of physics, classical mechanics is one of the two major sub-fields of study in the science of mechanics, which is concerned with the set of physical laws governing and mathematically describing the motions of bodies and aggregates of bodies geometrically distributed within a certain...
. In
Isaac Newton'sSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
view, space was absolute - in the sense that it existed permanently and independently of whether there were any matter in the space. Other
natural philosophersNatural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...
, notably
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, thought instead that space was a collection of relations between objects, given by their
distanceDistance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, a period of time, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical...
and direction from one another. In the 18th century,
Immanuel KantImmanuel Kant was an 18th-century German philosopher from the Prussian city of Königsberg...
described space and time as elements of a systematic framework which humans use to structure their experience.
In the 19th and 20th centuries mathematicians began to examine
non-Euclidean geometriesA non-Euclidean geometry is characterized by a non-vanishing Riemann curvature tensor. Examples of non-Euclidean geometries include the hyperbolic and elliptic geometry, which are contrasted with a Euclidean geometry. The essential difference between Euclidean and non-Euclidean geometry is the...
, in which space can be said to be
curved, rather than
flat. According to
Albert EinsteinAlbert Einstein was a theoretical physicist. His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, explaining the perihelion advance of Mercury, prediction of the deflection of...
's theory of general relativity, space around
gravitational fieldA gravitational field is a model used within physics to explain how gravity exists in the universe. In its original concept, gravity was a force between point masses...
s deviates from Euclidean space. Experimental
tests of general relativityAt its introduction in 1915, the general theory of relativity did not have a solid empirical foundation. It was known that it correctly accounted for the "anomalous" precession of the perihelion of Mercury and on philosophical grounds it was considered satisfying that it was able to unify Newton's...
have confirmed that non-Euclidean space provides a better model for explaining the existing laws of
mechanicsMechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces or displacements, and the subsequent effect of the bodies on their environment....
and
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
.
Leibniz and Newton
In the seventeenth century, the
philosophy of space and timePhilosophy of space and time is the branch of philosophy concerned with the issues surrounding the ontology, epistemology, and character of space and time. While such ideas have been central to philosophy from its inception, the philosophy of space and time was both an inspiration for and a...
emerged as a central issue in
epistemologyEpistemology or theory of knowledge is the branch of philosophy concerned with the nature and scope of knowledge...
and
metaphysicsMetaphysics investigates principles of reality transcending those of any particular science. Cosmology and ontology are traditional branches of metaphysics. It is concerned with explaining the fundamental nature of being and the world...
. At its heart,
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, the German philosopher-mathematician, and
Isaac NewtonSir Isaac Newton FRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian who is perceived and considered by a substantial number of scholars and the general public as one of the most influential men in history...
, the English physicist-mathematician, set out two opposing theories of what space is. Rather than being an entity which 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". Unoccupied regions are those which
could have objects in them and thus spatial relations with other places. For Leibniz, then, space was an idealised
abstractionAbstraction is the process or result of generalization by reducing the information content of a concept or an observable phenomenon, typically to retain only information which is relevant for a particular purpose. For example, abstracting a leather soccer ball to a ball retains only the information...
from the relations between individual entities or their possible locations and therefore could not be
continuousIn probability theory, a probability distribution is called continuous if its cumulative distribution function is continuous . This is equivalent to saying that for random variables X with the distribution in question, Pr[X = a] = 0 for all real numbers a, i.e.: the probability that X attains the...
but must be
discreteDiscrete probability distributions arise in the mathematical description of probabilistic and statistical problems in which the values that might be observed are restricted to being within a pre-defined list of possible values...
.
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.
Leibniz argued that space could not exist independently of objects in the world because that would imply that there would be 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 the
identity of indiscerniblesThe identity of indiscernibles is an ontological principle which states that two or more objects or entities are identical , if they have all their properties in common. That is, entities x and y are identical if any predicate possessed by x is also possessed by y and vice versa...
, there would be no real difference between them. According to the
principle of sufficient reasonThe principle of sufficient reason states that anything that happens does so for a definite reason. In virtue of which no fact can be real or no statement true unless it has sufficient reason why it should not be otherwise...
, any theory of space which implied that there could be these two possible universes, must therefore be wrong.
Newton took space to be more than relations between material objects and based his position on
observationObservation is either an activity of a living being , consisting of receiving knowledge of the outside world through the senses, or the recording of data using scientific instruments. The term may also refer to any datum collected during this activity.-Observation in science:A scientific method...
and
experimentIn scientific research, an experiment is a method of investigating causal relationships among variables, or to test a hypothesis. An experiment is a cornerstone of the empirical approach to acquiring data about the world and is used in both natural sciences and social sciences...
ation. For a
relationistRelationism can refer to a framework of social thought governing political, economic and social behaviour; or to a particular philosophical position on the ontology of fundamental quantities of physics.- Relationism in social thought :...
there can be no real difference between
inertial motionIn physics, an inertial frame of reference is a member of the subset of reference frames with the property that every physical law takes the same form in each such frame. In contrast, in the set of non-inertial frames the laws of physics are frame-dependent, and the usual physical forces must be...
, in which the object travels with constant
velocityIn physics, velocity is the rate of change of position. It is a vector physical quantity; both speed and direction are required to define it. In the SI system, it is measured in meters per second: or ms-1. The scalar absolute value of velocity is speed...
, and
non-inertial motionA non-inertial reference frame is a reference frame that is not an inertial reference frame. As such, the laws of physics in such a frame do not take on their most simple form, as required by the special principle of relativity...
, 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 generates
forceIn physics, a force is any agent that causes a change in the motion of a free body, or that causes stress in a fixed body. It can also be described by intuitive concepts such as a push or pull that can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a...
s, it must be absolute. He used the example of
water in a spinning bucketIsaac Newton's rotating bucket argument was designed to demonstrate that true rotational motion cannot be defined as the relative rotation of the body with respect to the immediately surrounding bodies...
to demonstrate his argument.
WaterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
in a
bucketA bucket, also called a pail, is a watertight, vertical cylinder or truncated cone, with an open top and a flat bottom, usually attached to a semicircular carrying handle called the bail. Their main purpose is the carrying of water, but they may also have other purposes...
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. Instead, Newton argued, it must be a result of non-inertial motion relative to space itself. For several centuries the bucket argument was decisive in showing that space must exist independently of matter.
Kant
In the eighteenth century the German philosopher
Immanuel KantImmanuel Kant was an 18th-century German philosopher from the Prussian city of Königsberg...
developed a theory of
knowledgeKnowledge is defined by the Oxford English Dictionary as expertise, and skills acquired by a person through experience or education; the theoretical or practical understanding of a subject, what is known in a particular field or in total; facts and information or awareness or familiarity gained...
in which knowledge about space can be both
a prioriThe terms "a priori" and "a posteriori" are used in philosophy to distinguish two types of knowledge, justifications or arguments...
and
synthetic. According to Kant, knowledge about space is
synthetic, in that statements about space are not simply true by virtue of the meaning of the words in the statement. In his work, Kant rejected the view that space must be either a substance or relation. Instead he came to the conclusion that space and time are not discovered by humans to be objective features of the world, but are part of an unavoidable systematic framework for organizing our experiences.
Non-Euclidean geometry
Euclid's
Elements contained five postulates which form the basis for Euclidean geometry. One of these, the
parallel postulateIn geometry, the parallel postulate, also called Euclid's fifth postulate because it is the fifth postulate in Euclid's Elements, is a distinctive axiom in Euclidean geometry...
has been the subject of debate among mathematicians for many centuries. It states that on any
planeIn mathematics, a plane is a flat surface. Planes can arise as subspaces of some higher dimensional space, as with the walls of a room, or they may enjoy an independent existence in their own right, as in the setting of Euclidean geometry....
on which there is a straight line
L1 and a point
P not on
L1, there is only one straight line
L2 on the plane which passes through the point
P and is parallel to the straight line
L1. 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 which could be derived from the other axioms. Around 1830 though, the
HungarianHungary , in English officially the Republic of Hungary , is a landlocked country in the Carpathian Basin of Central Europe, bordered by Austria, Slovakia, Ukraine, Romania, Serbia, Croatia, and Slovenia. Its capital is Budapest. Hungary is a member of OECD, NATO, EU, V4 and is a Schengen state...
János BolyaiJános Bolyai was a Hungarian mathematician, known for his work in non-Euclidean geometry.Bolyai was born in Kolozsvár, Transylvania, Kingdom of Hungary, Habsburg Empire , the son of a well-known mathematician, Farkas Bolyai.- Life :By the age of 13, he had mastered calculus and other forms of...
and the
RussiaRussia , officially known as both Russia and the Russian Federation , is a country in northern Eurasia . It is a semi-presidential republic, comprising 83 federal subjects...
n
Nikolai Ivanovich LobachevskyNikolai Ivanovich Lobachevsky was a Russian mathematician, often called the Copernicus of Geometry.-Biography:...
separately published treatises on a type of geometry which does not include the parallel postulate, called
hyperbolic geometryIn mathematics, hyperbolic geometry is a non-Euclidean geometry, meaning that the parallel postulate of Euclidean geometry is replaced...
. In this geometry, there are an infinite number of parallel lines which pass through the point
P. Consequently the sum of angles in a triangle is less than 180
o and the ratio of a
circleA circle is a simple shape of Euclidean geometry consisting of those points in a plane which are equidistant from a given point called the centre. The common distance of the points of a circle from its center is called its radius....
's
circumferenceThe circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....
to its
diameterIn geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
is greater than
piPi or π is a mathematical constant whose value is the ratio of any circle's circumference to its diameter in Euclidean space; this is the same value as the ratio of a circle's area to the square of its radius. The symbol π was first proposed by the Welsh mathematician William Jones in 1706...
. In the 1850s,
Bernhard Riemannwas an influential German mathematician who made contributions to analysis and differential geometry, some of them enabling the later development of general relativity.-Early life:...
developed an equivalent theory of elliptical geometry, in which there are no parallel lines which pass through
P. In this geometry, triangles have more than 180
o and circles have a ratio of circumference to diameter which is less than pi.
| Type of geometry |
Number of parallels |
Sum of angles in a triangle |
Ratio of circumference to diameter of circle |
Measure of curvature |
| Hyperbolic |
Infinite |
< 180o |
> π |
< 0 |
| Euclidean |
1 |
180o |
π |
0 |
| Elliptical |
0 |
> 180o |
< π |
> 0 |
Gauss and Poincaré
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 GaussJohann Carl Friedrich Gauss was a German mathematician and scientist who contributed significantly to many fields, including number theory, statistics, analysis, differential geometry, geodesy, geophysics, electrostatics, astronomy and optics...
, the 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 he actually carried out a test, on a small scale, by
triangulatingIn trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly...
mountain tops in Germany.
Henri PoincaréJules Henri Poincaré was a French mathematician and theoretical physicist, and a philosopher of science...
, a French mathematician and physicist of the late 19th century introduced an important insight which attempted to demonstrate the futility of any attempt to discover by experiment which geometry applies to space. He considered the predicament which would face scientists if they were confined to the surface of an imaginary large sphere with particular properties, known as a
sphere-worldThe idea of a sphere-world was constructed by Henri Poincaré while pursuing his argument for conventionalism , offered a thought experiment about a sphere with strange properties....
. In this world, the
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
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. 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, it was a matter of
conventionConventionalism is the philosophical attitude that fundamental principles of a certain kind are grounded on agreements in society, rather than on external reality...
which geometry was used to describe space. Since
Euclidean geometryEuclidean geometry is a mathematical system attributed to the Greek mathematician Euclid of Alexandria. Euclid's Elements is the earliest known systematic discussion of geometry. It has been one of the most influential books in history, as much for its method as for its mathematical content...
is simpler than non-Euclidean geometry, he assumed the former would always be used to describe the 'true' geometry of the world.
Einstein
In 1905,
Albert EinsteinAlbert Einstein was a theoretical physicist. His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, explaining the perihelion advance of Mercury, prediction of the deflection of...
published a paper on a special theory of relativity, in which he proposed that space and time be combined into a single construct known as
spacetime. In this theory, the
speed of lightIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
in a
vacuumIn everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty," but in reality, no volume of space can ever be perfectly empty...
is the same for all observers - which has
the resultThe relativity of simultaneity is the concept that simultaneity is not absolute, but dependent on the observer . That is, according to the special theory of relativity, it is impossible to say in an absolute sense whether two events occur at the same time if those events are separated in space...
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 to
tick more slowlyTime dilation is a phenomenon described by the theory of relativity. It can be illustrated by supposing that two observers are in motion relative to each other, and/or differently situated with regard to nearby gravitational masses. They each carry a clock of identically similar construction and...
than one which is stationary with respect to them; and objects are measured
to be shortenedLength contraction, according to Hendrik Lorentz, is the physical phenomenon of a decrease in length detected by an observer in objects that travel at any non-zero velocity relative to that observer...
in the direction that they are moving with respect to the observer.
Over the following ten years Einstein worked on a general theory of relativity, which is a theory of how gravity interacts with spacetime. Instead of viewing gravity as a
force fieldA force field, sometimes known as an energy shield, force shield, or deflector shield is a barrier, typically made of energy or charged particles, that protects a person, area or object from attacks or intrusions...
acting in spacetime, Einstein suggested that it modifies the geometric structure of spacetime itself. According to the general theory, time
goes more slowlyGravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential , the more slowly clocks run...
at places with lower gravitational potentials and rays of light bend in the presence of a gravitational field. Scientists have studied the behaviour of
binary pulsarA binary pulsar is a pulsar with a binary companion, often another pulsar, white dwarf or neutron star. They are one of the few objects which allow physicists to test general relativity in the case of a strong gravitational field...
s, confirming the predictions of Einstein's theories and Non-Euclidean geometry is usually used to describe spacetime.
Mathematics
In modern mathematics
spacesIn mathematics, a space is a set with some added structure.Mathematical spaces often form a hierarchy, i.e., one space may inherit all the characteristics of a parent space...
are defined as sets with some added structure. They are frequently described as different types of
manifoldIn mathematics, more specifically in differential geometry and topology, a manifold is a mathematical space that on a small enough scale resembles the Euclidean space of a certain dimension, called the dimension of the manifold....
s which are spaces that locally approximate to Euclidean space and where the properties are defined largely on local connectedness of points that lie on the manifold. There are however, many diverse mathematical objects that are called spaces. For example, function spaces in general have no close relation to Euclidean space.
Classical mechanics
Space is one of the few
fundamentalFundamental may refer to:* Foundation of reality.* Fundamental frequency, as in music or phonetics, often referred to as simply a "fundamental"....
quantities in
physicsPhysics is a natural science; it is the study of matter and its motion through spacetime and all that derives from these, such as energy and force...
, 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
timeTime is a component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects...
and
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
), space can be explored via
measurementIn science, measurement is the process of obtaining the magnitude of a quantity, such as length or mass, relative to a unit of measurement, such as a meter or a kilogram...
and experiment.
Astronomy
AstronomyAstronomy is the scientific study of celestial objects and phenomena that originate outside the Earth's atmosphere...
is the science involved with the observation, explanation and measuring of objects in
outer spaceOuter space comprises the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace and terrestrial locations....
.
Relativity
Before 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 —
spacetimeIn physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort than the spatial dimensions...
. It turns out that distances in space or in time separately are not invariant with respect to Lorentz coordinate transformations, but distances in Minkowski space-time along space-time intervals are — which justifies the name.
In addition, time and space dimensions should not be viewed as exactly equivalent in Minkowski space-time. One can freely move in space but not in time. Thus, time and space coordinates are treated differently both in
special relativitySpecial relativity is the physical theory of measurement in inertial frames of reference proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies"...
(where time is sometimes considered an
imaginaryfrom blue area)|-||-||-||-| style="background:#cedff2;" | |-|style="background:#cedff2;" | |-|style="background:#cedff2;" | |-|style="background:#cedff2;" | |-||-||-||-| |-|}...
coordinate) and in
general relativityGeneral relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics. It unifies special relativity and Newton's law of universal gravitation, and describes gravity as a...
(where different signs are assigned to time and space components of
spacetimeIn physics, spacetime is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space being three-dimensional and time playing the role of a fourth dimension that is of a different sort than the spatial dimensions...
metricIn the mathematical field of differential geometry, a metric tensor is a type of function defined on a manifold which takes as input a pair of tangent vectors v and w and produces a real number g in a way that generalizes many of the familiar properties of the dot product of vectors in Euclidean...
).
Furthermore, in Einstein's general theory of relativity, it is postulated that space-time is geometrically distorted-
curved -near to gravitationally significant masses.
Experiments are ongoing to attempt to directly measure
gravitational waveIn physics, a gravitational wave is a fluctuation in the curvature of spacetime which propagates as a wave, traveling outward from the source. Predicted by Einstein's theory of general relativity, the waves transport energy known as gravitational radiation...
s. This is essentially solutions to the equations of general relativity which describe moving ripples of spacetime. Indirect evidence for this has been found in the motions of the Hulse-Taylor binary system.
Cosmology
Relativity theory leads to the
cosmologicalCosmology is the study of the Universe in its totality, and by extension, humanity's place in it...
question of what shape the universe is, and where space came from. It appears that space was created in the
Big BangThe Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation...
and has been expanding ever since. The overall shape of space is not known, but space is known to be expanding very rapidly which is evident due to the Hubble expansion.
Spatial measurement
The measurement of
physical space has long been important. Although earlier societies had developed measuring systems, the
International System of UnitsSi, si, or SI may refer to :- Places :* Mount Si, a mountain in state of Washington* Si County, county in Anhui, China* Si River, a river in China* Slovenia, a European nation Si, si, or SI may refer to (all SI unless otherwise stated):- Places :* Mount Si, a mountain in state of Washington* Si...
, (SI), is now the most common system of units used in the measuring of space, and is almost universally used within
scienceScience is in its broadest sense to any systematic knowledge-base or prescriptive practice that is capable of resulting in a prediction or predictable type of outcome...
.
Currently, the standard space interval, called a standard meter or simply meter, is defined as the
distance traveled by light in a vacuumIn physics, the speed of light is a physical constant, the speed at which electromagnetic radiation, such as light, travels in free space . Its value is 299,792,458 metres per second...
during a time interval of exactly 1/299,792,458 of a second. This definition coupled with present definition of the
secondThe second , sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units base unit of time...
is based on the special theory of relativity, that our space-time is a
Minkowski spaceIn physics and mathematics, Minkowski space is the mathematical setting in which Einstein's theory of special relativity is most conveniently formulated. In this setting the three ordinary dimensions of space are combined with a single dimension of time to form a four-dimensional manifold for...
.
Geography
GeographyGeography is the study of the Earth and its lands, features, inhabitants, and phenomena. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...
is the branch of science concerned with identifying and describing the
EarthEarth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density...
, utilizing spatial awareness to try and understand why things exist in specific locations.
CartographyCartography is the study and practice of making geographical maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.The fundamental problems of cartography are to:*Set the map's...
is the mapping of spaces to allow better navigation, for visualization purposes and to act as a locational device.
GeostatisticsGeostatistics is a branch of statistics focusing on spatiotemporal datasets. Developed originally to predict probable distributions for mining operations, it is currently applied in diverse disciplines including petroleum geology, hydrogeology, hydrology, meteorology, oceanography, geochemistry,...
apply statistical concepts to collected spatial data in order to create an estimate for unobserved phenomena.
Geographical space is often considered as land, and can have a relation to
ownershipOwnership is the state or fact of exclusive rights and control over property, which may be an object, land/real estate or intellectual property. An ownership right is also referred to as title. The concept of ownership has existed for thousands of years and in all cultures...
usage (in which space is seen as
propertyProperty is any physical or intangible entity that is owned by a person or jointly by a group of persons. Depending on the nature of the property, an owner of property has the right to consume, sell, rent, mortgage, transfer, exchange or destroy his or her property, and/or to exclude others from...
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 as Australian Aboriginals, rather than asserting ownership rights to land, invert the relationship and consider that they are in fact owned by the land.
Spatial planningSpatial planning refers to the methods used by the public sector to influence the distribution of people and activities in spaces of various scales...
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
architectureFor a topical guide to this subject, see Outline of architecture. Architecture is the art and science of designing and constructing buildings and other physical structures for human shelter or use....
, where it will impact on the design of buildings and structures, and on farming.
Ownership of space is not restricted to land. Ownership of
airspaceAirspace means the portion of the atmosphere controlled by a particular country on top of its territory and territorial waters or, more generally, any specific three-dimensional portion of the atmosphere....
and of
watersThe terms international waters or trans-boundary waters apply where any of the following types of bodies of water transcend international boundaries: oceans, large marine ecosystems, enclosed or semi-enclosed regional seas and estuaries, rivers, lakes, groundwater systems , and wetlands...
is decided internationally. Other forms of ownership have been recently asserted to other spaces — for example to the
radioRadio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
bands of the electromagnetic
spectrumA spectrum is a condition that is not limited to a specific set of values but can vary infinitely within a continuum. The word saw its first scientific use within the field of optics to describe the rainbow of colors in visible light when separated using a prism; it has since been applied by...
or to
cyberspaceCyberspace is the global domain of electromagnetics as accessed and exploited through electronic technology and the modulation of electromagnetic energy to achieve a wide range of communication and control system capabilities...
.
Public spaceA public space refers to an area or place that is open and accessible to all citizens, regardless of gender, race, ethnicity, age or socio-economic level. One of the earliest examples of public spaces are commons. For example, no fees or paid tickets are required for entry, nor are the entrants...
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. While
private propertyPrivate property is the tangible and intangible things owned by individuals or firms over which their owners have exclusive and absolute legal rights, and can only be transferred with the owner's consent. Private property can take the form of real estate, homes, factories, automobiles, capital,...
is the land culturally owned by an individual or company, for their own use and pleasure.
Abstract spaceAbstract space, in geography, refers to a hypothetical space characterized by equal and consistent properties; a geographic space that is completely homogenous. All movement and activity would be equally easy or difficult in all directions and all locations within this space...
is a term used in
geographyGeography is the study of the Earth and its lands, features, inhabitants, and phenomena. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...
to refer to a hypothetical space characterized by complete homogeneity. When modeling activity or behavior, it is a conceptual tool used to limit extraneous variables such as terrain.
In psychology
The way in which space is perceived is an area which psychologists first began to study in the middle of the 19th century, and it is now thought by those concerned with such studies to be a distinct branch within
psychologyPsychology is an academic and applied discipline involving the systematic, and sometimes scientific, study of human or animal mental functions and behavior...
. Psychologists analyzing the perception of space are concerned with how recognition of an object's physical appearance or its interactions are perceived.
Other, more specialized topics studied include
amodal perceptionAmodal perception is the term used to describe the full perception of a physical structure when it is only partially perceived. For example, a table will be perceived as a complete volumetric structure even if only part of it is visible; the internal volumes and hidden rear surfaces are perceived...
and
object permanenceObject permanence is the understanding that objects continue to exist even when they cannot be seen, heard, or touched. Jean Piaget argued that object permanence is one of an infant's most important accomplishments, as without this concept, objects would have no separate, permanent existence...
. The
perceptionIn philosophy, psychology, and the cognitive sciences, perception is the process of attaining awareness or understanding of sensory information. It is a task far more complex than was imagined in the 1950s and 1960s, when it was predicted that building perceiving machines would take about a decade,...
of surroundings is important due to its necessary relevance to survival, especially with regards to
huntingHunting is the practice of pursuing living animals for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...
and
self preservationSelf-preservation is behaviour that ensures the survival of an organism. It is universal among living organisms. In some vertebrates, pain and fear are parts of this mechanism. Pain causes discomfort so that the organism is inclined to stop the pain...
as well as simply one's idea of
personal spacePersonal space is the region surrounding a person that affects them psychologically in terms of it being their domain or territory, or about which they feel uncomfortable if entered by another. The idea comes from Edward T. Hall...
.
Several space-related
phobiaA phobia , is an irrational, intense, persistent fear of certain situations, activities, things, or people. The main symptom of this disorder is the excessive, unreasonable desire to avoid the feared subject...
s have been identified, including
agoraphobiaAgoraphobia is an anxiety disorder, often precipitated by the fear of having a panic attack in a setting from which there is no easy means of escape. As a result, sufferers of agoraphobia avoid public and/or unfamiliar places, especially large, open, spaces such as shopping malls or airports...
(the fear of open spaces),
astrophobiaAstraphobia, also known as Brontophobia, Keraunophobia, or Tonitrophobia, is an abnormal fear of thunder and lightning, a type of specific phobia. It is a treatable phobia that both humans and animals can develop...
(the fear of
celestialCelestial may refer to:*Sky*Heaven*Astronomical objects*Supernatural beings living in heaven, such as divinities and angels*Celestial Kingdom, the highest of three heavens or heavenly kingdoms in Mormon theology....
space) and
claustrophobiaClaustrophobia is the fear of having no escape, and being closed in. It is typically classified as an anxiety disorder and often results in panic attack...
(the fear of enclosed spaces).
See also
- Aether theories
Alchemy, natural philosophy, and early modern physics proposed the existence of a medium of the æther , a space-filling substance or field, thought to be necessary as a transmission medium...
- Cosmology
Cosmology is the study of the Universe in its totality, and by extension, humanity's place in it...
- Curvature of space
- Personal space
Personal space is the region surrounding a person that affects them psychologically in terms of it being their domain or territory, or about which they feel uncomfortable if entered by another. The idea comes from Edward T. Hall...
- Shape of the universe
The shape of the Universe is an informal name for a subject of investigation within physical cosmology which describes the geometry of the universe including both local geometry and global geometry. It is loosely divided into curvature and topology, even though strictly speaking, it goes beyond both...
- Space exploration
Space exploration is the use of astronomy and space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
- Spatial analysis
In statistics, spatial analysis or spatial statistics includes any of the formal techniques which study entities using their topological, geometric, or geographic properties...