Continental Hotspot

I want to call this debate organised by Phil Harper out because it is exactly the kind of discourse that we need more of. Both sides agree on a set of observations and continually affirm that they agree with each others statements even when some disagreements eventually arises. This is how scientific debate should be done between esteemed members of their fields.

There is a lively back-and-forth between, Stacy McGaugh, advocate for MOND, and Simon White, CDM proponent. McGaugh emphasizes MOND’s success in predicting galaxy rotation curves and the tight radial acceleration relation, especially in low surface brightness systems—phenomena that CDM struggles to reproduce without invoking complex baryonic feedback processes. He argues that MOND’s predictive power rests on known baryonic mass distributions without tuning free parameters, contrasting sharply with the parameter-rich galaxy formation models of ΛCDM. White counters that CDM’s flexibility, plus halo structure modifications through stellar feedback, can largely reproduce those same observations—even though the underlying mechanisms are messy and model-dependent.

When the topic turns cosmological, particularly the Cosmic Microwave Background (CMB), the tone shifts. White notes that CDM naturally explains the full acoustic peak spectrum of the CMB—including the crucial third peak—while MOND, in its pure form, does not. He points to CDM’s success in matching lensing profiles and large-scale structure growth as further evidence . McGaugh concedes that MOND lacks a complete relativistic cosmological theory and that hybrid approaches, involving sterile neutrinos or modified inertia, could help close the gap. Yet he emphasizes the scientific value in MOND consistently hitting galactic-scale observations it was never tuned to match—prompting deeper questions about whether dark matter is simply a placeholder for unknown gravitational physics.