Time&Eternity

144 chapter 3
by which nature is recognized are nothing other than parts of precisely this
nature.” 153 Physics can therefore no longer be understood as natural philosophy
in the sense of a theory of nature “as it is.” Rather, one is dealing with
a theory of nature “as it appears when it is tested using real standards and
clocks.” 154 Time can no longer be understood as a “container” for nature.
Nature is not in time, but rather, time is in nature.
Space-Time Curvature—The General Theory of Relativity
The restricted application of the special theory of relativity to uniformly
moving systems called attention to the fact “that the previous theory of relativity
needed to be generalized so that the seemingly unjust preference for
uniform translation, as contrasted to relative movements of a different type,
vanishes from the theory.” 155 The general theory of relativity 156 solved this
problem of formulating physical laws for all systems. It contains the special
theory of relativity as a limiting case. The great achievement of the general
theory of relativity was the inclusion of gravity, which occurred by expanding
the principle of relativity to coordinate systems accelerated relative to
one another and by considering the gravitational fields that were caused
thereby. The recognition of the invariance 157 of the speed of light made the
idea of instant gravitational effects impossible and required the mathematical
treatment of gravity according to a field theory. This is achieved by the
general theory of relativity. The difference from the concepts of space and
time in classical mechanics is obvious. In Newton, space and time were
defined in advance as the solid stage on which the development of physical
systems takes place, but space-time in the general theory of relativity is an
essential part of this very development. 158
The general theory of relativity makes use of the Gaussian method for
the mathematical treatment of any continuum. In a four-dimensional continuum,
it attributes four coordinates (x 1 , x 2 , x 3 , and x 4 ) to each event,
whereby no distinction is made between space and time coordinates. This
method replaces descriptions that use a reference body and is therefore not
limited to describing a continuum with a Euclidean character. 159
The connection of local space and time coordinates, as is known by the
special theory of relativity, is replaced by a more general relationship that
contains a so-called metric tensor g ik (x, y, z, t). The space-time continuum
of the general theory of relativity corresponds to the shape of a four-dimensional
curved space. The expression “curved space” implies that the spatial
arrangement of material bodies does not agree with the laws of threedimensional
Euclidian geometry. 160 Instead, the theory uses Riemannian
geometry, 161 the simplest illustration of which can draw upon the geometry
of a spherical surface. The two-dimensional surface of a sphere is finite and