In physics, the term space is understood mainly in two senses:
- 1) the so-called ordinary space , also called the physical space [1] - the three-dimensional space of our everyday world and / or the direct development of this concept in physics (development, perhaps, sometimes quite sophisticated, but direct, so we can say: our usual space on indeed it is). This is the space in which the position of physical bodies is determined, in which mechanical movement occurs, the geometric movement of various physical bodies and objects.
- 2) various abstract spaces in the sense that they are understood in mathematics, which do not have any relation to ordinary (“physical”) space, except for the relation of a more or less distant formal analogy (sometimes, in some simple cases, however, a genetic connection is also seen For example, for velocity space, impulse space). Usually these are some abstract vector or linear spaces, however, often equipped with various additional mathematical structures. As a rule, in physics, the term space is used in this sense with the necessary definition or addition (velocity space, color space, state space, Hilbert space, spinor space), or, in extreme cases, the abstract space in the form of an inseparable phrase. Such spaces are used, however, for the formulation and solution of completely “earthly” problems in ordinary three-dimensional space.
Physics also considers a number of spaces that occupy, as it were, an intermediate position in this simple classification, that is, those that in the particular case may coincide with the usual physical space, but in the general case - differ from it (as, for example, the configuration space) or contain the usual space as a subspace (as phase space, space-time or Kaluza space).
In the theory of relativity, in its standard interpretation, space [2] turns out to be one of the manifestations of a single space-time, and the choice of coordinates in space-time, including their separation into spatial and time , depends on the choice of a specific reference system. [3]
In most branches of physics, the properties of physical space themselves (dimension, unboundedness, etc.) are in no way dependent on the presence or absence of material bodies. In the general theory of relativity, it turns out that material bodies modify the properties of space, and more precisely, space-time, “bend” space-time.
One of the postulates of any physical theory (Newton, GTR, etc.) is a postulate about the reality of a particular mathematical space (for example, Newton's Euclidean).
see also
Notes
- ↑ Physical space is a clarifying term used to distinguish this concept from a more abstract (referred to as abstract space in this opposition), and to distinguish real space from its too simplified mathematical models.
- ↑ Here we have in mind the three-dimensional “ordinary space”, that is, the space in the sense of (1), as described at the beginning of the article. In the traditional framework of the theory of relativity, it is the standard use of the term (and for the four-dimensional Minkowski space or the four-dimensional pseudo-Riemannian manifold of the general theory of relativity, the corresponding term space-time is used ). However, in newer works, especially if this cannot cause confusion, the term space is also used in relation to space-time as a whole. For example, if one speaks of a space of dimension 3 + 1, it is the space-time that is meant (and the representation of dimension as a sum designates the metric signature, which is just the defining number of spatial and temporal coordinates of this space; in many theories the number of spatial coordinates differs from three ; there are also theories with several time coordinates, but the latter are very rare). Similarly, they say "Minkowski space", "Schwarzschild space", "Kerr space", etc.
- ↑ The possibility of choosing different systems of space-time coordinates and moving from one such coordinate system to another is similar to the possibility of choosing different (with different axis directions) Cartesian coordinate systems in the usual three-dimensional space, and from one such coordinate system you can go to another by rotating the axes and the corresponding transformation of the coordinates themselves - the numbers characterizing the position of a point in space relative to the data of specific Cartesian axes. However, it should be noted that Lorentz transformations that serve as analogs of turns for space-time do not allow continuous rotation of the time axis to an arbitrary direction, for example, the time axis cannot be turned to the opposite direction and even to the perpendicular one (the latter would correspond to the motion of the reference system at the speed of light) .
Comments
To leave a comment
Introduction to Physics, Fundamentals
Terms: Introduction to Physics, Fundamentals