It seemed to offer little potential for experimental test, as most of its assertions were on an astronomical scale.
Its mathematics of general relativity seemed difficult and fully understandable only by a small number of people.
Special relativity applies to elementary particles and their interactions, describing all their physical phenomena except gravity.
General relativity explains the law of gravitation and its relation to other forces of nature.
With relativity, cosmology and astrophysics predicted extraordinary astronomical phenomena such as neutron stars, black holes, and gravitational waves.