خمیدگی ِ فضا-زمان xamidegi-ye fazâ-zamân (#)
*Fr.: courbure de l'espace-temps*
According to → *general relativity*,
→ *space-time* is curved by the
presence of → *matter*. The curvature is described in terms of
→ *Riemann's geometry*. In
→ *cosmological model*s three types of curvature are considered:
positive (spherical, → *closed Universe*), zero
(Euclidean, → *flat Universe*), and negative (hyperbolic,
→ *open Universe*). See also
→ *curvature constant*. → *curvature*; → *space-time*. |

فضا-زمان ِ مینکوفسکی fazâ-zamân-e Minkowski (#)
*Fr.: espace-temps de Minkowski*
A completely flat four-dimensional space, which contains no gravitating matter, used in the
theory of special relativity. → *Minkowski metric*; → *space-time*. |

فضا-زمان fazâ-zamân (#)
*Fr.: espace-temps*
A physical entity resulting from the union of space and time concepts. In its most simple
version space-time is the four-dimensional continuum, having three spatial coordinates and
one temporal coordinate, in which any → *event*
or physical object is located.
In → *special relativity* it is Minkowski's flat space-time.
In → *general relativity*, it is
described by a curved entity characterized by a → *metric*.
Free-fall motion describes the → *geodesic*
of this curved space-time. It may have additional dimensions in
the context of speculative theories, such as → *string theory*. → *space*; → *time*. |

خمیدگی ِ فضا-زمان xamidegi-ye fazâ-zamân
*Fr.: courbure de l'espace-temps*
→ *curvature of space-time*. → *space*; → *time*;
→ *curvature*. |

نمودار ِ فضا-زمان nemudâr-e fazâ-zamân (#)
*Fr.: diagramme espace-temps*
A simple way of representing the → *space-time* continuum,
usually including time and only one spatial dimension. The curve of a particle's
equation of motion on a space-time diagram is called a → *world line*.
Same as → *Minkowski diagram*. → *space*; → *time*;
→ *diagram*. |

اندروار ِ فضا-زمان andarvâr-e fazâ-zamân
*Fr.: intervalle espace-temps*
1) In Einstein's → *theory of relativity*,
*ds*^{2} = *c*^{2}*dt*^{2} -
*dx*^{2} - *dy*^{2} - *dz*^{2}.
2) In → *Newtonian mechanics*,
time interval: *dt*; space interval at fixed time:
*dl*^{2} = *dx*^{2} + *dy*^{2} +
*dz*^{2}. → *space-time*; → *interval*. |