 This view contrasts sharply with the status of the constants from the perspective of fundamental physics. Particle physicists typically regard their theories as effective field theories, which suffice for describing interactions at some specified energy scale. These theories include various constants, characterizing the relative strength of the interactions they describe, that cannot be further explained by the effective field theory. The constants can be fixed by experimental results, but are not derivable from fundamental physical principles. (If the effective field theory can be derived from a more fundamental theory, the value of the constants can in principle be determined by integrating out higher-energy degrees of freedom. But this merely pushes the question back one step: the constants appearing in the more fundamental theory are determined experimentally.) Similarly, the constants appearing in the SM are treated as contingent features of the universe. There is no underlying physical principle that sets, for example, the cosmological densities of different kinds of matter, or the value of the Hubble constant.