Children grow up and discover that the world is not as it seemed within the four walls of their homes. Humankind as a whole does the same. - Carlo Rovelli

While non-relativistic time is the observable quantity measured (or approximated) by physical clocks, in general relativity clocks measure s along their worldline, not t. The relativistic... t is a freely chosen label with no direct physical interpretation. ...The physical content of a solution of Einstein's equations is not in its dependence on t, but ...in what remains once the dependence on t (and x) has been factored away.

... theoretical physics is less clean than the way it's usually solved. You can always change parameters and save yourself. ... it's very rare that theories are ruled out by just an experiment or a group of experiments. Theories usually come with flexibility. Theoreticians can add flexibility. And so new experiments — you can just patch up your theory.

Don't trust your teachers.