>, why do we assume that there's additional matter rather than question whether our models are correct at that scale?
There are also physicists that question the models. Some scientists follow a path of inquiry based on assumptions that Einstein's theory is mostly correct -- hence a postulation of "dark matter" which leads to searching for the existence of it(1). But there are other physicists that assume there's something missing in the accepted equations that would explain the galaxy rotation speeds without any need for "dark matter".
Each competing theory tries to accumulate more and more evidence for their case until one "wins" (scientific consensus)(2). Right now, the "dark matter" line of inquiry has more scientists, more papers, and more press coverage.
(1)direct instead of indirect observation
(2)Some might say Dark Matter theory has already "won" in the marketplace of ideas
There are also physicists that question the models. Some scientists follow a path of inquiry based on assumptions that Einstein's theory is mostly correct -- hence a postulation of "dark matter" which leads to searching for the existence of it(1). But there are other physicists that assume there's something missing in the accepted equations that would explain the galaxy rotation speeds without any need for "dark matter".
Each competing theory tries to accumulate more and more evidence for their case until one "wins" (scientific consensus)(2). Right now, the "dark matter" line of inquiry has more scientists, more papers, and more press coverage.
(1)direct instead of indirect observation
(2)Some might say Dark Matter theory has already "won" in the marketplace of ideas