All hard sciences have sufficient evidence to back them up. Whether it is mathematical proofs, experimental evidence, etc. There is no hard evidence for the social sciences. Astronomers can predict orbits with incredible accuracy millions of years into the future. Social sciences haven't been able to create a single useful model.

Also, you said, "However, we seem to have made huge strides in our understanding of the cosmos." That is very different from the social sciences. I don't think we know anything more about human nature today than Shakespeare did in the 1500s.