At www.bbc.co.uk/news/science-environment-43543195 … (see also https://tallbloke.wordpress.com/2018/03/28/ghost-galaxy-prompts-cosmic-m… ) … a transparent galaxy about the size of our Milky Way is causing problems for cosmologists. The study is published by Nature journal and the researchers seem to have discovered a galaxy that is dark matter free. Oh dear. The galaxy is not abundant with stars which makes it even more mysterious – but those that can be seen are banded in bright clusters. We are assured that in most galaxies there is five times more dark matter than visible matter – also a dark matter halo. So, did the same galaxy form in a defferent way to the others? There follows a sermon on the nature of dark matter. That is of course the BBC way but a more nuanced take can be found at the second link, Tall Bloke's talk shop. The comments are also good with some further links such as https://www.nature.com/articles/nature25767 and https://arstechnica.com/science/2018/03/galaxy-seems-to-lack-dark-matter… … but the main thrust is that if dark matter is absent from one galaxy it is also probably absent from all the other galaxies. Astrophysicists have a different take it would seem – as dark matter is absent from one galaxy this proves it is present in other galaxies. Such thinking may indicate how the idea evolved in the first place – cosmologists unable to divorce themselves from red shift distances. Back to square one perhaps – and Halton Arp.