Science fiction is just another word for...thought experiments, and 'thought experiments' is just another word for ...science fiction.
Relativity...is 'just a theory', a thought experirment..science fiction.
Relativity is science fiction, is it not? It's still a ...theory.
Relativity, possibly true but that is not known or proven to be true, ...a theory, just a theory.
To put it simply...
all theories are science fiction, because all science fiction are thought experiments, and
thought experiments is just another word for science fiction.
It's a loop you cannot get out of.