The Abraham–Minkowski controversy is a physics debate concerning electromagnetic momentum within dielectric media. Two equations were first suggested by Hermann Minkowski (1908) and Max Abraham (1909) for this momentum. They predict different values, from which the name of the controversy derives. Experimental support has been claimed for both. The two points of view have different physical interpretations and thus neither need be more correct than the other. David J. Griffiths argues that, in the presence of matter, only the total stress–energy tensor carries unambiguous physical significance; how one apportions it between an "electromagnetic" part and a "matter" part depends on context and convenience. Several papers have claimed to have resolved this controversy. The controversy is still claimed to have importance in physics beyond the Standard Model where electrodynamics gets modifications, like in the presence of axions.