The same applies to evolution although as in astrophysics and many other sciences, there
is limited opportunity for experiments.
Bert: I disagree the same validation can occur about theories such as "what might the universe
look like if this were true?", or concerning events which occurred in the
past, "how might this have happened?". Until you can provide a measurement
and definitions upon which all can agree, such speculations will remain
speculations, regardless of how much their advocates like the theories, or
how many people believe the evidence supports them.
And as such they are not much different from any other scientific theory.