Year: 1999

Transformations of space and time between inertial systems are set up by starting from two empirically based assumptions: (1) The two-way velocity of light is the same in all inertial systems; (2) Clock retardation takes place with the usual velocity-dependent factor when clocks move with respect to an isotropic reference frame. The transformations thus obtained contain a free parameter *e _{1}*, the coefficient of

*x*in the transformation of time. The Theory of Special Relativity is recovered for a particular choice of

*e*. Different values of

_{1}*e*correspond to different theories of space and time, which are to a large extent empirically equivalent. We show that Michelson type experiments, aberration, occultation of Jupiter\'s satellites, and radar ranging of planets are insensitive to the choice of

_{1}*e*. Several other experiments lead to the same conclusion. An exception is discussed in Part II.

_{1}