Friend and reader Rob Dodson sends in a link to an interesting story on some astronomers proposing a new model of gravity, prompted by the anamoly of that orbital speed of many stars is much greater than the currently accepted theory predicts, the same puzzle I described several posts back.
I suggest that this story nicely illustrates the point I was making: it often is not obvious whether to regard some observation(s) out of line with a particular theory as refuting it, or as simply indicating the presence of some as yet undetected factor influencing the situation(s) that will be seen to fit the theory once it is recognized. There is no automatic procedure for correctly deciding between devoting one's (limited) time and energy to searching for a way to explain the anamoly within the current theory and the alternative of attempting to supplant it. When faced with such a situation, a scientist is always forced to rely on her intuition as to which course is more promising. In doing so, I think it is quite sensible to take into account the extent to which the existing model is supported by other evidence -- in other words, positive results should lend a theory added weight.