  Some of the well-known experiments: the ''muon'' experiment, the
Michelson-Morley type experiments, the Kennedy-Thorndike type experiments and
the Ives-Stilwell type experiments are analyzed using the nonrelativistic
theory, the ''apparent transformations (AT) relativity'' and the ''true
transformations (TT) relativity.'' It is shown that all the experiments (when
they are complete from the ''TT relativity'' viewpoint) are in agreement with
the ''TT relativity'' in which the special relativity is understood as the
theory of a four-dimensional spacetime with the pseudo-Euclidean geometry. It
is also explicitly shown that, in contrast to the usual opinion, the commonly
used ''AT relativity'' does not always agree with experiments. The concept of
sameness of a physical quantity is essential for the distinction between the
two forms of relativity both in the theory and in experiments. The difference
in this concept causes the agreement of the ''TT relativity'' with the
experiments and the disagreement of the ''AT relativity.''
