Space-time . Geometric entity in which all the physical events of the Universe take place, according to the theory of relativity and other physical theories. The name alludes to the need to consider the geometric location in time and space in a unified way, since the difference between spatial and temporal components is relative according to the state of movement of the observer. In this way, we speak of the space-time continuum. Because the universe has three observable physical spatial dimensions, it is common to refer to time as the “fourth dimension” and space-time as “four-dimensional space” to emphasize the inevitability of considering time as just one more geometric dimension.in 1905 .
Summary
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- 1 History
- 2 Space-time topology
- 3 Eisntein’s spacetime
- 4 Source
History
In general, a specific event can be described by one or more spatial coordinates, and a temporal one. For example, to uniquely identify a car accident, you can give the longitude and latitude of the point where it occurred (two spatial coordinates), and when it occurred (a time coordinate). In three-dimensional space, three spatial coordinates are required. However, the traditional vision on which Classical mechanics is based , whose fundamental principles were established by Isaac Newton, is that time is an independent coordinate of the spatial coordinates and is an identical magnitude for any observer. This view agrees with experience: if an event occurs at 10 meters, it is natural to ask 10 meters from what, but if we are informed that an accident occurred at 10 in the morning in our country, that time is absolute.
However, results such as the Michelson and Morley experiment, and Maxwell’s equations for electrodynamics , suggested, at the beginning of the 20th century , that the Speed of light is constant, independent of the speed of the emitter or observer, in contradiction with the postulated by classical mechanics.
Albert Einstein proposed as a solution to this and other problems of classical mechanics 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. This is reflected, for example, in that the coordinate transformations between inertial observers (the Lorentz Transformations), involve a combination of spatial and temporal coordinates. The same fact is reflected in the measurement of an electromagnetic field, which is formed by an electrical part and another magnetic part, because depending on the state of movement of the observer the electromagnetic field is seen differently between its magnetic and electrical part by different observers. in relative motion.
The expression space-time then picks up the notion that space and time can no longer be considered independent or absolute entities.
The consequences of this relativity of time have had various experimental verifications. One of them was made using two high-precision atomic clocks, initially synchronized, 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.
Space-time topology
The topology of space time has to do with its causal structure. For example, it is interesting to know SI in a space-time:
- There is the closed time curve; that kind of occurrence would allow a particle to influence its own past. Some exact solutions of Einstein’s equations such as the Gödel Universe , which describes a universe filled with a perfect fluid in rotation, allow such closed time curves.
- There are Cauchy hypersurfaces, which allows, in principle, to know the state of the system on one of these surfaces, to know the state at a future moment. As long as the quantum effects have limited effects, the existence of hypersurfaces involves deterministic evolution.
There are incomplete geodesics, which is related to the occurrence of spatio-temporal singularities in which black holes are found .
Eisntein space time
Einstein argued that it is impossible to distinguish between an accelerated reference system and a reference system subjected to a gravitational force. Secondly, from this indistinguishability, and from the consequences of all kinds that this entails, the equality between inertia and gravitation is inferred. Thirdly, according to his interpretation of the Lorentz transformations , space and time cease to be separate entities to appear interconnected. Fourth, this interconnection will force us to abandon, as a scenario in which physical phenomena unfold, space and time as separate entities to replace them with a single entity that will be called space-time.
Fifth, that gravitation affects the space-time of each “place” and dictates how to curve. Finally, since movement is under the action of a gravitational field independent of the mass of the moving object, it is legitimate to think that this movement is linked to “place” and that the geodesic line trajectories are marked by the structure of the space tissue. storm in which they slide.
The gravitational force would end, thus, becoming a manifestation of the curvature of space-time. Hence it follows that in this scheme there is no action at a distance or mysterious tendencies to move towards strange centers, nor absolute spaces that contain, or absolute times that run outside of, matter.
The mass tells space-time how to curve and it dictates to the mass how to move. It is the material content that creates space and time.
