“Faced with the choice between changing one’s mind and proving that there is no need to do so, almost everybody gets busy on the proof.” -J. K. Galbraith
Last month, tensions between dark matter simulations and galactic rotation observations reached a new high. Despite all the successes of dark matter on the largest scales — for the CMB, for large-scale structure, for gravitational lensing and for galaxy clusters, among others — the simplest dark matter simulations reproduced unrealistic results for how individual galaxies ought to rotate. Moreover, a team of scientists uncovered a surprising relationship: between the normal (baryonic) matter alone and the observed acceleration in galaxies.
If dark matter were real, then the simulations needed to reproduce that result as well, which appeared to be a tremendous challenge. Yet in a new paper, two scientists from McMaster University, Ben Keller and James Wadsley, did exactly this. Even more impressively, they didn’t make new simulations, they simply took pre-existing ones and showed that this relation does, in fact, get reproduced among all their galaxies.