Space (physics)

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The room is a kind of "container" for matter and fields , take place in which all physical processes. This deliberately somewhat imprecise understanding of the term “space” has been widespread since Isaac Newton and was only questioned by Einstein .

This corresponds to the fact that in human experience one “always knows what the room is”, e.g. B. that it is determined by the three mutually orthogonal dimensions of length, width and height . Space enables all material objects to expand; it itself exists as a basic order model “a priori in front of the objects it contains”, but according to today's understanding only in relation to them. If the concept of space is formed in this sense, there is no point in speaking of an “empty” space. The problem in physics when determining the size of space is that you can only measure spaces whose limits you know. If one assumes that space is limitless or infinite, it is very likely that the given means for measuring are not sufficient. The same must be assumed while maintaining scientific caution for the eventual discovery of ever smaller elementary particles and their interstices.

For the physical description, formal properties of different mathematical spaces , mostly Euclidean space , are used. The concept of space has changed significantly in the history of physics .

The concept of space in ancient times

In the Middle East, the formation of length, area and volume terms was always dependent on anthropocentric aspects such as the amount of seeds for an area to be tilled or the work done for an area to be worked. The Pythagoreans first recognize the existence of a void between neighboring things, but still confuse this void with air ( pneuma apeiron ). Archytas von Taranto was probably the first to differentiate between space or place ( topos ) on the one hand and matter on the other. The space is therefore independent of the body; however, he has certain powers. With the early atomists such as Leukippus and Democritus , space is pure expansion without any influence on the movement of matter. However, it only includes the spaces between the atoms. Only Lucretius clearly formulates that the bodies have a place in space that represents an infinite vessel for bodies. For Plato , space is inhomogeneous because of its local geometric differences. For Aristotle the place of a body is its outer limit; There are no gaps that are not filled by bodies and there is no penetration of bodies. (This, however, contradicts his theory of the continuous “fifth body” from which the sky is formed; this would be disturbed by the spheres of the planets.) The causes of the movements of the bodies are to be sought in the geometric structure of space alone (today this would be called a “dynamic field structure”), which has a center (the earth), an above and a below. According to Aristotle, the movements of the elementary particles depend only on the spatial conditions, not on what we now call mass. The space is only the sum of all the places of the bodies; therefore it is not infinite. Until the 14th century, Aristotle's conception remained the model for most space theories.

However, there was always criticism: For Aristotle's pupil Theophrastus von Eresos , space is not real, it is a pure order relationship between the bodies. For the Stoics , the material world, which rests in an empty space, is held together by an inner cohesion; there is no preferred direction in space.

In ancient times, space and time were completely heterogeneous, unrelated entities. Zeno was probably the first to recognize that they are related to each other in the concept of speed . In contrast to the geometry of the plane, the geometry of space was also only very poorly developed and had little fixed technical terms, probably also no idea of ​​space coordinates, for which ultimately the incompatibility of Euclidean geometry with the finite, anisotropic (in its properties of the Direction dependent) universe of Aristotle was responsible.

Space in classical mechanics

In classical mechanics , Isaac Newton's definition of space applies :

  • The space is absolute, unchangeable and unaffected by the physical processes that take place in it.
  • The space is Euclidean and three-dimensional .

This infinite, immobile, penetrable space for all bodies, showing no qualities or forms, cannot be separated by any force, is for the 18th century the measure of all distances and speeds, indeed as the work of God .

The dimensions of a room correspond to the Cartesian coordinates implemented by it , usually given in the x, y and z directions. These are called spatial coordinates and the dimensions spanned by them are called spatial dimensions , with no spatial dimension corresponding to a point , one spatial dimension corresponding to a straight line or curve and two spatial dimensions corresponding to a surface . The determination of the reference point of a coordinate system requires real objects. Usually the center of gravity of a large mass such as the earth or the sun is taken for this purpose.

space and time

Modifications of the concept of space

The discovery that the speed of light is the same for all observers required a modification of the concept of space. Albert Einstein did the preparatory work in his special theory of relativity , so that Hermann Minkowski could combine space and time into a common structure, space-time. This means that the space is no longer absolute, but dependent on the observer (more precisely: the inertial system ). This manifests itself, for example, in the Lorentz contraction , according to which observers moving relative to one another measure a different length for the same object .

In the special theory of relativity, space is dependent on the observer, but not on the physical processes in him. He is still Euclidean to any observer. That changes in the general theory of relativity . In this the gravity is described by the curvature of space-time, which also means a curvature of space. The geometry of spacetime depends on the energy-momentum tensor , i.e. on the particles and fields present in space. The space is therefore only locally Euclidean.

Modern theories on spacetime

The Kaluza-Klein theories and string theories , which aim to unite gravity with the other basic forces, add additional dimensions to spacetime. These additional dimensions are not, however, like the known 4 space-time dimensions, extended into (almost) infinite; rather, they are less than the diameter of an atomic nucleus . In addition, it is assumed that they are periodically "rolled up" or that they "flow into" the existing space-time as additional degrees of freedom (e.g. the so-called quintessence ).

One goal of these theories is not to postulate space with its properties as something given, but to justify it in a comprehensive theory together with the known basic forces and elementary particles.

A different opinion is represented by the constructivist protophysics , in which geometry and chronometry are determined by standards for the measuring instruments.

See also

literature

classic
  • Ulf Heuner (ed.): Classical texts on space. Berlin: Parados 2006, ISBN 3-938880-05-8 .
  • Nick Huggett (ed.): Space from Zeno to Einstein , MIT Press 1999 Selection of short classical texts in English. Trans.
  • Jörg Dünne , Stephan Günzel (Ed.): Space theory - basic texts from philosophy and cultural studies . Frankfurt a. M .: Suhrkamp, ​​2006. ISBN 3-518-29400-8 .
  • Stephan Günzel (ed.): Texts on the theory of space . Reclam 2013.
History of science
  • Max Jammer : The problem of space  : the development of space theories, Darmstadt: Wiss. Buchges. 1960. (German edition of the 1st edition of Concepts of Space .)
  • Max Jammer: Concepts of Space  : the history of theories of space in physics, foreword by Albert Einstein , 3rd A., New York: Dover Publ. 1993.
  • Sendker, Werner Bernhard: The so different theories of space and time : The transcendental idealism of Kant in relation to Einstein's theory of relativity, Osnabrück, 2000 ISBN 3-934366-33-3 .
Systematic representations

see also the general literature under: Philosophy of Physics , Philosophy of Science

Individual evidence

  1. ^ Albert Einstein, foreword to Max Jammer, Das Problem des Raumes , Darmstadt 1960, pp. XIII ff.
  2. ↑ “What is infinity?” From the alpha-Centauri TV series (approx. 15 minutes). First broadcast on May 26, 2002. https://www.br.de/mediathek/video/sendung/alpha-centauri/alpha-centauri-unendlichkeit-2002_x100.html#tab=bcastInfo&jump=tab
  3. ↑ Lucretius: De rerum natura , I, 963-976.
  4. ↑ Max Jammer 1960, pp. 12-22.
  5. ↑ Max Jammer 1960, p. 26.
  6. ↑ Max Jammer 1960, p. 139.