In 2010, astrophysics professor Pavel Kroupa at the University of Bonn – he of the stellar Initial Mass Function - published a paper in which he highlighted problems with the Standard Model of Cosmology (the so-called ΛCDM model, of which cold dark matter is a crucial ingredient), particularly in its predictions related to environments of large spiral galaxies. In a provocative move, he cited the discrepancies between the model’s predictions and observations as evidence that ΛCDM “doesn’t work”, and that we should explore alternative theories. One of these alternatives is Modified Newtonian Dynamics, or MOND.
In the months after the publication, the University of Bonn hosted a debate on this thorny subject between Kroupa and one of the architects of the ΛCDM framework, Simon White, Director of the Max Planck Institute for Astrophysics in Garching. I thought this was an excellent idea, wrote a few blog posts about the matter and posted the live blog and video of the debate.
To those that read or watched the debate, it was clear that the two scientists don’t disagree in a fundamental way - ΛCDM has proved an extremely successful framework for cosmological structure formation, but the dwarf satellite problem is generally acknowledged. Kroupa’s most important point is that the community should not ignore those observables that don’t match the predictions of ΛCDM, and he encourages scientists not to get locked into a “cold dark matter” mindset, but to explore entirely novel theories, of which MOND is one example. This discussion has been expanded and illustrated further in a blog run by Marcel Pawlowski, a member of Kroupa’s group in Bonn, the Dark Matter Crisis, now hosted on SciLogs.com, which is run by Nature and the German edition of Scientific American.