Traditional clock synchronisation on a rotating platform is shown to be incompatible with the experimentally established transformation of time. The latter transformation leads directly to solve this problem through noninvariant one-way speed of light. The conventionality of some features of relativity theory allows full compatibility with existing experimental evidence.

The derivation of the transformations between inertial frames made by Mansouri and Sexl is generalised to three dimensions for an arbitrary direction of the velocity. Assuming length contraction and time dilation to have their relativistic values, a set of transformations kinematically equivalent to special relativity is obtained. The "clock hypothesis" allows the derivation to be extended to accelerated systems. A theory of inertial transformations maintaining absolute simultaneity is shown to be the only one logically consistent with accelerated movements. Algebraic properties of these transformations are discussed.

In the last two decades, theories explaining the same experiments as well as special relativity does, were developed by using different synchronization procedures. All of them are ether-like theories. Most authors believe these theories to be equivalent to special relativity, but no general proof was ever brought. By means of a Gedankenexperiment on light aberration, we produce strong evidence that this is the case for experiments made in inertial systems.