Space (Physics)

Physical space. It is the area where objects are located and in which the events that occur have a relative position and direction. Physical space is usually conceived with three linear dimensions, although modern physicists usually consider it, over time, to be four-dimensional and call it spacetime.


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  • 1 Definitions
  • 2 Space-time
  • 3 Evolution of the concept of space
  • 4 Psychological aspects related to space
  • 5 Spatial measurement
  • 6 Sources


The space was already defined by Aristotle , as that which is implied by the bodies, that is, the place that they occupy, their immobile limit, being the sum of the spaces occupied by the bodies, the total space, eliminating the concept of emptiness . Every space contained a body. It was one of the a priori Kantian categories along with time, which shaped sensible matter. Newton approached the concept of space as immaterial, immobile and infinite substance where material objects floated.

The observable physical bodies are then located in a universal environment that is called space.

Space is often referred to as the outer universe, outside the Earth’s atmosphere , as infinite. Thus when speaking of astronauts traveling into space, this meaning is alluded to.

The term is also used in astronomy to consider the distance between galaxies ( intergalactic space ) or between stars ( interstellar space ).

The spatial geometry is a branch of geometry which studies are geometrical figures, in terms of its dimensions and properties in three dimensional space. The branch of mathematics that studies vector or linear space is called linear algebra.

  • Airspaceis called the place in the atmosphere, where the aircraft circulate, belonging to the state that they fly.
  • Urban spaceis called the one occupied by cities, and rural space where agricultural work is carried out.
  • Public spaceincludes the places that all the inhabitants can use, since they belong to the populus or town, like a plaza.
  • Radiographic or television space is what communicators have to express their ideas.
  • In physics, space-timeis called the four dimensions, three of them spatial, and a temporal one, in which events are considered mathematically, event being called a point in space-time.

Space time

Main article: Space-time

Eisnten space-time

According to the Theory of Relativity , space-time is the geometric entity in which all the physical events of the Universe take place. Part of the supposed state of movement of the observer and its consequences, which translates into the relative difference between spatial and temporal components.

In three-dimensional space , three spatial coordinates are required, that is, each of its points can be located by specifying three numbers within a certain range (width, length and depth).

Three-dimensional plane

For classical physics (Newton) time is an independent coordinate of the spatial coordinates and is an identical magnitude for any observer. This concept was questioned at the beginning of the 20th century and Einstein proposed as a solution to consider the constancy of the speed of light as a postulate and to dispense with the notion of time as an independent coordinate.

In the Theory of Relativity , space and time are relative or conventional, depending on the state of movement of the observer. Several verifications have been made of the Theory, one of them was carried out using two initially highly synchronized atomic clocks , one of which was kept fixed while the other was transported in an airplane. Upon returning from the trip it was found that they showed a slight difference of 184 nanoseconds, “time” having elapsed more slowly for the clock in motion.

Evolution of the concept of space

Euclid tracing geometric figures

Classical space is homogeneous, continuous, indefinitely divisible, physically inactive, independent of time, matter and movement, and has three dimensions. The fact of supposing it infinite gave rise, in the 19th century , to the Olbers paradox according to which night cannot exist. The solution to this paradox was given by Einstein’s Finite Universe . The classical space is called Euclidean because it corresponds to the Geometry of Euclid , which until the 19th century was believed to be the only possible geometry.

Two very important qualities of this space is that it is capable of expanding and contracting without changing its shape or leaving it, something that does not happen, for example, to a spherical surface. The other quality is what could be called isotopy, which consists in that space is seen in the same way, whatever the position of the observer in space.

Classical time is homogeneous, uniform, continuous and indefinitely divisible, independent of space and matter, has a single dimension and is distinguished from the space in which it is oriented. Before the Theory of Relativity arose , since radioactivity was discovered , a random microscopic time appeared, the time interval between the decays of two radioactive atoms is random, but the uncertainty of time reappears microscopically, due to a mathematical process called probability convergence, and thus the decay of half of a radioactive body does not take a random time, but, a certain time, for greater accuracy, the sum of a certain time and an infinitesimal random time, is practically equal to zero .

With Einstein these old conceptual schemes are broken and one can rightly speak of space and time before and after Einstein. In the Restricted Theory of Relativity , the first simplest, space and time are not independent, but form a four-dimensional continuum, so that the points (“atoms” of space) and the instants (“atoms” of time) ) merge into events, formed by the association of a point and an instant. The classic concepts of past and future are abandoned for new ones and a third concept, without a classical counterpart, which is the time that passes in another place in space. Space and time are still physically inactive and its metric structure is called pseudoeuclidean, which is the most similar to all non-Euclideans.

The Theory of Restricted Relativity is the bridge between Classical Science and General Relativity, mathematically and conceptually more complicated. In the latter, space, time and matter are no longer independent, the first two are physically active. Matter configures the structure of space-time, the universe is no longer flat or infinite but curved and finite, its geometry is no longer Euclidean. New physical phenomena arise, not conceivable for the classics, among them the space is no longer static, but is dynamic, it is expanding, and since this expansion cannot be carried out without leaving it, it must be immersed in a fictitious Euclidean space of four dimensions.

Psychological aspects related to space

Psychologists first began to study how space is perceived in the middle of the 19th century. Everything concerning those studies is now a branch of psychology . Psychologists analyze the perception of space in relation to how a physical object is recognized or its interactions are perceived.

More specialized studies include amodal perception and object permanence. The perception of the surroundings is important due to its relevance necessary for survival, especially with regard to hunting and self-preservation as well as for the idea of ​​personal space.

Space-related phobias have been found, including agoraphobia (fear of open space), astrophobia (fear of heavenly space), and claustrophobia (fear of closed space).

Spatial measurement

The measurement of physical space has been important for a long time. Although previous societies had developed measurement systems, the International System of Units , (SI), is now the most commonly used in space measurement, and is almost universally used within science .

Currently, the standard space interval, called the standard meter or simply meter, is defined as the distance traveled by light in a vacuum during an interval of exactly 1 / 299,792,458 of a second.

This definition, along with the current definition of second, is based on the Theory of Special Relativity in which the speed of light plays the role of a fundamental constant of nature.


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