> If objects at large distances from the galaxy center have these large relative velocities induced by external objects they wouldn't be bound to the galaxy. R

> If objects at large distances from the galaxy center have these large relative velocities induced by external objects they wouldn't be bound to the galaxy. Right. Tides must be caused by something other than the Moon because it's just too far away. No, wait, large masses have do have an effect across large distances. There are no isolated reference frames without gravity. Galaxy clusters do orbit around their center of gravity. Would you like to know how many theories in theoretical physics been proven? Precisely none of them, including Dark Matter Theory. This dubiousness is specious and, fwiw, a bandwagon argument.