Natural science doesn't simply mirror nature and tell us how 'it' is. We create the concepts and the theories that science uses. 

Philosophers of science no longer believe that science builds its theories out of facts and tests each statement against 'the facts.' 'The facts' are partly our construction. They are always partly determined by the theory we are constructing. And furthermore, we can adjust our theories in lots of ways to make facts fit or not fit.

I'm not saying that natural science is an arbitrary construction, but I am saying that it cannot be so starkly contrasted with morals as you suggest.