I am an actually qualified mathematician. My understanding of a variety of scientific fields mainly comes from the application of mathematical principles. I use differential equations, topology, geometry, etc to understand physics. My main area of expertise is graph theory. I use graph theory to understand the relationships in complex systems, for example, chemical graph theory describes the relationships between atoms in molecules (there is a molecular graph in my profile picture), dataflow graphs describe distributed computation (I mention one of these in the rebel against science blogpost), social graphs describe social relationships such as friendships, etc.