A strange and interesting aspect of MOND is the External Field Effect (EFE). If physics is strictly local, it doesn’t matter what happens outside of an experimental apparatus, only inside it. Examples of gravitational experiments include an Eötvös-style apparatus in a laboratory or a dwarf galaxy in space: in each case, test masses/stars respond to each other’s gravity. The MOND force depends on the acceleration from all sources;

My colleague Jim Schombert pointed out a nifty new result published in Nature Astronomy which you probably can’t access so here is a link to what looks to be the preliminary version.

Currently, English is the lingua franca of science. It wasn’t always that way, and there’s no reason to expect it always will be. A century ago, all the great physicists who wanted to be part of the quantum revolution went to study in Germany.

There are many tensions in the era of precision cosmology. The most prominent, at present, is the Hubble tension – the difference between traditional measurements, which consistently obtain H ₀ = 73 km/s/Mpc, and best fit* to the acoustic power spectrum of the cosmic microwave background (CMB) observed by Planck, H ₀ = 67 km/s/Mpc. There are others of varying severity that are less widely discussed.

I set out last time to discuss some of the tensions that persist in afflicting cosmic concordance, but didn’t get past the Hubble tension. Since then, I’ve come across more of that, e.g., Boubel et al (2024a), who use a variant of Tully-Fisher to obtain H ₀ = 73.3 ± 2.1(stat) ± 3.5(sys) km/s/Mpc.

I took the occasion of the NEIU debate to refresh my knowledge of the status of some of the persistent tensions in cosmology. There wasn’t enough time to discuss those, so I thought I’d go through a few of them here. These issues tend to get downplayed or outright ignored when we hype LCDM’s successes.

As promised, the folks at NEIU have posted the video of my discussion with Scott Dodelson last week, so here you go: I am in the midst of writing a related post on cosmic tensions, so hopefully I can post that soon as well.

This is a quick post to announce that on Monday, April 7 there will be a virtual panel discussion about dark matter and MOND involving Scott Dodelson and myself. It will be moderated by Orin Harris at Northeastern Illinois University starting at 3pm US Central time*. I asked Orin if I should advertise it more widely, and he said yes – apparently their Zoom set up has a capacity for a thousand attendees.

I’ve been busy, and a bit exhausted, since the long series of posts on structure formation in the early universe. The thing I like about MOND is that it helps me understand – and successfully predict – the dynamics of galaxies. Specific galaxies that are real objects: one can observe this particular galaxy and predict that it should have this rotation speed or velocity dispersion.

This is what I hope will be the final installment in a series of posts describing the results published in McGaugh et al. (2024). I started by discussing the timescale for galaxy formation in LCDM and MOND which leads to different and distinct predictions. I then discussed the observations that constrain the growth of stellar mass over cosmic time and the related observation of stellar populations that are mature for the age of the universe.

As discussed in recent posts, the appearance of massive galaxies in the early universe was predicted a priori by MOND (Sanders 1998, Sanders 2008, Eappen et al. 2022). This is problematic for LCDM. How problematic? That’s always the rub. The problem that JWST observations pose for LCDM is that there is a population of galaxies in the high redshift universe that appear to evolve as giant monoliths rather than assembling hierarchically.