One could write a very long essay on this, but basically: regardless of what the underlying truth out there in the universe is, all we can get at is an interpretation of the evidence to determine what we think is the truth. To the extent that truth is based on evidence it changes when new evidence is introduced.

To say otherwise is to say that people on death row should never be acquitted because it was true they were a murderer at the time of the trial, and that truth is unchangeable.

(or to use an example from cinema, at one point it "wasn't true" that cigarettes were harmful)