 Cosmological physics extending beyond the physics horizon faces an underdetermination threat due to the lack of independent lines of relevant evidence. The case of dark matter illustrates the value of such independent evidence. Dark matter was first proposed to account for the dynamical behavior of galaxy clusters and galaxies, which could not be explained using Newtonian gravitational theory with only the luminous matter observed. Dark matter also plays a crucial role in accounts of structure formation, as it provides the scaffolding necessary for baryonic matter to clump, without conflicting with the uniformity of the  CMB.[24]  Both inferences to the existence of dark matter rely on gravitational physics, raising the question of whether we should take these phenomena as evidence that our gravitational theory fails, rather than as evidence for a new type of matter. There is an active research program (MOND, for Modified Newtonian Dynamics) devoted to accounting for the relevant phenomena by modifying gravity. Regardless of one’s stance on the relative merits of MOND vs. dark matter (obviously MOND needs to be extended to a relativistic theory), direct evidence of existence of dark matter, or indirect evidence via decay products, would certainly reshape the debate. Efforts have been underway for some time to find dark matter particles through direct interactions with a detector, mediated by the weak force. A positive outcome of these experiments would provide evidence of the existence of dark matter that does not depend upon gravitational  theory.[25] 