## Emergent gravity in galaxies and in the Solar System [GA]

I’ve been meaning to do a blog post about Erik Verlinde’s very interesting “Emergent Gravity” theory since it was first aired in November 2016, but never got round to it. However, this recent paper suggests that the new theory fails badly on scales of the Solar System. And when I say “badly”, I mean by seven orders of magnitude. That’s pretty bad.

Unless there’s something wrong with this analysis, this looks pretty terminal …

http://arxiv.org/abs/1702.04358

It was recently proposed that the effects usually attributed to particle dark matter on galaxy scales are due to the displacement of dark energy by baryonic matter, a paradigm known as emergent gravity. This formalism leads to predictions similar to Modified Newtonian Dynamics (MOND) in spherical symmetry, but not quite identical. In particular, it leads to a well defined transition between the Newtonian and the modified gravitational regimes, a transition depending on both the Newtonian acceleration and its first derivative with respect to radius. Under the hypothesis of the applicability of this transition to aspherical systems, we investigate whether it can reproduce observed galaxy rotation curves. We conclude that the formula leads to marginally acceptable fits with strikingly low best-fit distances, low stellar mass-to-light ratios, and a low Hubble constant. In particular, some unobserved wiggles are produced in rotation curves because of the dependence of the transition on the…

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February 19, 2017 at 4:43 am

Its also nice to see a MOND proponent and a dark matter proponent collaborating on this work.

February 19, 2017 at 4:43 am

Peter, I am still waiting for your thoughts on mass acceleration discrepancy relation.