[Dimensio]

Yes. That does not make them the same field.

Oh, I'm sorry, you're right. Astrophysics is not biology.

Correct. Both are sciences and both share aspects in common because they are sciences, but they are still not the same fields of study. Expertise in one area does not translate to expertise in another.

[Dimensio]

Both use math, eh? Both use logic, experimental technique, rationality, eh?

Oops. Forgot to quote this before the first sentence of my reply. Yes, both use logical, experimental technique, rationality and math. But this does not make them the same field of study.