Note : Dark Energy can also be added to OP title. Is it good or acceptable science to define the DM as it is? Isn't it quite close to saying that God exists but it cannot interact in general, it somehow manifests itself in miracles. Science does not accept God, so how come it accepts DM, the way it is theorized in mainstream? Let me push it further, gravity and light speed are interlinked, we are attempting to unify EM with gravity. So conceptualizing DM as interacting gravitationally but not electromagnetically will contradict any success on unification. So DM definition appears to be ad hoc. Isn't it?