Science Forums 2

[sanctus]

There is plenty of evidence of time dilatation. For example in accelerators you can "see" particles which have a half-life of a few microseconds in their proper time, but when they are moving quick enough it seems to us that they live much much longer.

The cause is I would say the fact that in special relativity there is the axiom that there is a maximum velocity (c) and that all massive particles can never move at that velocity.
Like any other theory special relativity is based on axioms. In case of special relativity the first is the one above and the second that there is no preferred system of reference.