Thank you, Fresco. Although my understanding of dark matter is limited, I think it is meant to explain how gas clouds collapsed to form galaxies faster than the amount of visible matter within them can account for. A large amount of unseen mass probably accounts for it. In most of the articles I read, physicists are searching for hitherto unknown particles to be that mass. When I read such articles, I often find myself doing lateral thinking to create more parsimonious explanations. This post is one such. It is a very simple idea, quite different from what I normally see in Science News, and probably wrong. But don't have the means to test it. I hope to find an appropriate forum for doing that. An ideal forum would be a large list of frequently asked physics questions with answers like, "such-and-such person tried to model that, once, and it didn't work." Can anyone suggest a forum or searchable database for me to try?