If the Minkowski 4-vector components for displacement in 4D space-time
(1)
are alternatively written in Euclidean form (see also [1]) they read:
(2)
Equations 1 and 2 both contain the same information but the essential difference is that the roles of the variables have switched. In Eq. 1,
is the Lorentz invariant. In Eq. 2,
is the Lorentz invariant. The mathematics for such a switch remain consistent with special relativity if it is assumed that the vectorsum of velocities in all 4 Euclidean dimensions has constant magnitude
. That means that the speed in the Euclidean time dimension, which is now actually formed by the proper time
must be:
(3)
The displacement in the proper time dimension for a moving object in an interval
(according to an observer at rest) then equals:
(4)
So as a result of the assumption that was made about the universal speed
in 4D Euclidean space-time,
is now no longer the invariant Minkowski displacement but the displacement in the proper time dimension. The factor
that played an equivalent role in the Minkowski 4-vector has become the invariant 4D displacement in Euclidean space-time.
Figure 1:
Geometric visualization of Minkowski and Euclidean displacement 4-vectors. Spatial displacement is represented as
.
This is visualized in Fig. 1. Here the spatial displacement
is written as a single variable
. The 'Minkowski triangle' (left) then is:
(5)
and the 'Euclidean triangle' (right) is:
(6)
The dotted lines in Fig. 1 represent the values for
and
that would result from a Lorentz transformation.