The special theory of relativity is defined by the Lorentz transformation between two systems of of space-time coordinates and defined by (normalizing the speed of light to 1):
- , , .
This transformation is supposed to connect observations in two coordinate systems with space-axes moving with velocity with respect to each other as indicated in the above figure typically presented in a book on the special theory of relativity.
However, the figure is misleading: The -axis defined by is not parallel to the -axis, since it is given by the line which is tilted with respect to the -axis.
The Lorentz transformation thus does not describe the physics of two observers moving with constant velocity with respect to each other, each equipped with a space axis, but is instead a non-physical coordinate transformation mixing space and time with the sole purpose of conserving the same speed of light.
Einstein viewed the Lorentz transformation both as a definition and as a physical reality, and physicists have followed in his footsteps with a firm belief that the constancy of the speed of light in vacuum is both a definition (in operation today since now the length unit is defined as a certain fraction of a lightsecond) and a true physical fact.
But this is against the first principle of real science of not viewing a definition (which is true by its construction) as a statement about reality which may be true or false. In other words, physicists of today are not making a clear distinction between science (which may be true or false) and pseudo-science (true by definition). This means a collapse into irrationality and mysticism, in full glory present in the theory of relativity.
In general relativity the principle of equivalence (of heavy and inertial mass) is similarly used both as a definition and physical fact.