I don't have a quick explanation, but rather a quick anectode. The incompatibility of MOND with relativity used to be called "Bekenstein's Theorem", based on th

I don't have a quick explanation, but rather a quick anectode. The incompatibility of MOND with relativity used to be called "Bekenstein's Theorem", based on the idea that Bekenstein had tried to write down such a theory but failed to do so. Since Bekenstein was a very smart guy, if he couldn't do it, it couldn't be done. When he heard about this, he proceeded to write down an incredibly ugly theory called TeVeS, but, well, that theory's got fields too (Tensor, Vector, Scalar), so in the end it's just dark matter all the way down.