Casertano et al. have used Gaia to provide a small but important update in the debate over the value of the Hubble Constant. The ESA Gaia mission is measuring parallaxes for billions of stars. This is fundamental data that will advance astronomy in many ways, no doubt settling long standing problems but also raising new ones – or complicating existing ones.

It has been proposal season for the Hubble Space Telescope, so many astronomers have been busy with that. I am no exception. Talking to others, it is clear that there remain many more excellent Hubble projects than available observing time. So I haven’t written here for a bit, and I have other tasks to get on with. I did get requests for a report on the last conference I went to, Beyond WIMPs: from Theory to Detection.

Note: this is a guest post by David Merritt, following on from his paper on the philosophy of science as applied to aspects of modern cosmology. Stacy kindly invited me to write a guest post, expanding on some of the arguments in my paper . I’ll start out by saying that I certainly don’t think of my paper as a final word on anything.

A recent paper in Nature by Genzel et al. reports declining rotation curves for high redshift galaxies. I have been getting a lot of questions about this result, which would be very important if true. So I thought I’d share a few thoughts here. Nature is a highly reputable journal – in most fields of science. In Astronomy, it has a well earned reputation as the place to publish sexy but incorrect results.

There is a new article in Science on the expansion rate of the universe, very much along the lines of my recent post. It is a good read that I recommend. It includes some of the human elements that influence the science. When I started this blog, I recalled my experience in the ’80s moving from a theory-infused institution to a more observationally and empirically oriented one.

In 1984, I heard Hans Bethe give a talk in which he suggested the dark matter might be neutrinos. This sounded outlandish – from what I had just been taught about the Standard Model, neutrinos were massless. Worse, I had been given the clear impression that it would screw everything up if they did have mass. This was the pervasive attitude, even though the solar neutrino problem was known at the time. This did not compute!

David Merritt recently published the article “Cosmology and convention” in Studies in History and Philosophy of Science . This article is remarkable in many respects. For starters, it is rare that a practicing scientist reads a paper on the philosophy of science, much less publishes one in a philosophy journal.

I wrote my own recollection of Vera Rubin recently. Her long time home institution, the Department of Terrestrial Magnetism (DTM) of the Carnegie Institution of Washington recently held a lunch in her honor. Unfortunately my travel schedule precluded me from attending. However, they have put together a wonderful website that I recommend to everyone.

There has been some hand-wringing of late about the tension between the value of the expansion rate of the universe – the famous Hubble constant, H ₀ , measured directly from observed redshifts and distances, and that obtained by multi-parameter fits to the cosmic microwave background.

We have in MOND a formula that has had repeated predictive successes. Many of these have been true a priori predictions, like the absolute nature of the baryonic Tully-Fisher relation, the large mass discrepancies evinced by low surface brightness galaxies, and the velocity dispersions of  many individual dwarf Spheroidal galaxies like Crater 2. I don’t see how these can be an accident.

One Law to rule them all, One Law to guide them, One Law to form them all and in the dark halo bind them. Galaxies appear to obey a single universal effective force law. Early indications of this have been around for some time.