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.
Vera Rubin passed away a few weeks ago. This was not surprising: she had lived a long, positive, and fruitful life, but had faced the usual health problems of those of us who make it to the upper 80s. Though news of her death was not surprising , it was deeply saddening. It affected me more than I had anticipated, even armed with the intellectual awareness that the inevitable must be approaching.
Recently I have been complaining about the low standards to which science has sunk. It has become normal to be surprised by an observation, express doubt about the data, blame the observers, slowly let it sink in, bicker and argue for a while, construct an unsatisfactory model that sort-of, kind-of explains the surprising data but not really, call it natural, then pretend like that’s what we expected all along.
The arXiv brought an early Xmas gift in the form of a measurement of the velocity dispersion of Crater 2. Crater 2 is an extremely diffuse dwarf satellite of the Milky Way. Upon its discovery, I realized there was an opportunity to predict its velocity dispersion based on the reported photometry. The fact that it is very large (half light radius a bit over 1 kpc) and relatively far from the Milky Way (120 kpc) make it a unique and critical case.
There has been another attempt to explain away the radial acceleration relation as being fine in ΛCDM. That’s good; I’m glad people are finally starting to address this issue. But lets be clear: this is a beginning, not a solution. Indeed, it seems more like a rush to create truth by assertion than an honest scientific investigation.
