Definition : relativistic (or not) hyperplane

[Richard Hachel]

A hyperplane of simultaneity is a geometric concept used mainly in
relativistic physics.
In a four-dimensional orthonormal framework (three dimensions of space and
one dimension of time), it represents the set of points in space-time that
are considered simultaneous for a given observer; the hypersurface that
contains all the events that, for him, occur at the same time.
This "hyperplane of the present", which is represented as a horizontal
sheet, therefore actually represents a three-dimensional space.

R.H.

[Mikko]

Post by Richard Hachel
A hyperplane of simultaneity is a geometric concept used mainly in
relativistic physics.
In a four-dimensional orthonormal framework (three dimensions of space
and one dimension of time), it represents the set of points in
space-time that are considered simultaneous for a given observer; the
hypersurface that contains all the events that, for him, occur at the
same time.
This "hyperplane of the present", which is represented as a horizontal
sheet, therefore actually represents a three-dimensional space.

A hyperplane is a subspace of a multi-dimensional space that fully
contains those straight lines that have at least two pints in common
with the subspace. Often but not always the term is used only for
subspaces that are at least three-dimensional.