Out of curiosity, I wonder why some have referred to biology as a "soft" science. Maybe the intro course is, but as you move into higher levels, you need to understand and work with a good deal of chemistry. It isn't just memorizing a book.
Well, physicists, or at least those I know (like my Dad), think anything that isn't physics is "soft."
They have this attitude because only physics attempts to understand the fundamental physical laws that underlie everything. In principle, therefore, if we perfectly understood everything there is to know about physics, we would be able to explain all of biology, chemistry, geology, etc. by simply applying the laws of physics to different contexts. Thus to a physicist, every other science is just applied physics.
The hardness is related to math, not difficulty. Physics, and astronomy, cosmology are all math. Maybe a few datapoints and then a pile of differential equations and tensor matrices relating those few datapoints.