> we have more observations that Newton's law is wrong No, we don't. We have observations that show that the motion of stars in galaxies is not what we would p

> we have more observations that Newton's law is wrong No, we don't. We have observations that show that the motion of stars in galaxies is not what we would predict if we used our current laws of gravity with a distribution of matter that matches just what is visible to us. There are two possible hypotheses to explain these observations: (1) There is matter present that is not visible to us; (2) Our current laws of gravity are wrong and need to be modified. "Dark matter" is basically a name for #1; "MOND" and similar models are in category #2.