# What is the space-time continuum 3

## Space-time continuum

(R.), in modern physics designates the continuous multiplicity of space-time points, i.e. of events that are characterized by space and time coordinates. In a broader sense, one can also speak of an R. in relation to Newtonian physics, but in a narrower sense the term describes the so-called. "Minkowski world", i.e. that space-time that corresponds to the special theory of relativity (sp.R.). The space and time coordinates in classical Newtonian physics and in sp.R. different metric properties. According to Newton's conception of an absolute space and an absolute time, space and time are independent, absolute quantities. According to this, the time interval between two events can be clearly determined, and this time is always the same regardless of the observers who measure the time interval. After that, it can be objectively determined at any time, namely measurable with standard clocks, whether two events take place at the same time and whether they take place in the same place. If one understands the term R. in a broader sense, then within the framework of Newtonian physics the three-dimensional Euclidean (absolute) space and the (absolute) time form an R. The metric is determined by the reference to a rigid body set. - In the sp.R., in which Einstein formulates the spatiotemporal relationships between inertial systems moving relative to one another, the idea of ​​an absolute time is abandoned. Einstein supports himself in the development of the sp.R. on two assumptions: the special principle of relativity (R.p.) and the constancy of the speed of light in a vacuum. According to the classic R.p. In Newton's mechanics there is no inertial system that has empirical priority over others: The same laws of mechanics apply in all inertial systems that are at rest relative to one another or move in a straight-line uniform manner. The classic R.p. is in the sp.R. still expanded. According to the special R.p. the equality of inertial systems affects all physical laws. The speed of light is an invariant; it is the same in all inertial systems. An essential consequence of the sp. R. is now the relativity of simultaneity. Due to the invariance of the speed of light, two events can be considered to be simultaneous if a light signal that is emitted in the middle between these two events reaches both. If one considers the relations of simultaneity in relative to one another according to this criterion moved Judged in inertial systems, it turns out that observers in different inertial systems perceive different pairs of events as simultaneous, i.e. different simultaneity conditions prevail in the inertial systems. Since the different simultaneity ratios according to the sp.R. are empirically equal, the decisions about simultaneity always relate to the respective inertial system in which they are made. Instead of space and time as mutually independent quantities, sp.R. the unified space-time, which H. Minkowski represented four-dimensionally. This four-dimensional space-time structure forms the R., on which the sp.R. refer to the descriptions of events in modern physics. The corresponding »Minkowski world« is made up of individual events, each of which is described by the three spatial coordinates x, y, z and the time coordinate t. The talk of the continuum is to be understood in such a way that for every event E1 there are any further events whose coordinates differ from E1 differentiate as little as possible In contrast to Newtonian physics, space-time can only be derived from the causal relationships between the events.

Literature:

• J. Audretsch / K. Mainzer (ed.): Philosophical problems of space-time. Mannheim et al. 1988
• A. Einstein: Fundamentals of the theory of relativity. Braunschweig 1956
• S. W. Hawking: A Brief History of Time. The search for the primal force of the universe. Reinbek 1988
• E. Schrödinger: The structure of space-time. Darmstadt 1993.

JH