Dark matter cropped up in the news again recently (scientists think they might have detected something which may or may not be produced by dark matter; this happens every four or five years or so with no conclusive result so I wouldn’t hold your breath), so I thought now might be a good time to write something about it on the blog. This is particularly difficult — or easy, depending on how you look at it — since we currently know next to sod-all about dark matter and its even more mysterious counterpart, dark energy. It’s even been said that our calling it dark matter reflects more on our total and utter lack of understanding of what it actually is than any intrinsic properties on the part of the dark matter itself. Still, while we’ve never been able to directly observe dark matter (indeed, this may not ever be possible depending on what the dark matter eventually turns out to be) we have been able to infer its existence from certain odd phenomena that don’t make any sense without something that fits the rather broad description we have of it, so we can at least have an interesting discussion about that.