Are they not the most fabulous/adorable group of little witches you have ever seen?
Galaxies That Are Too Big To Fail, But Fail Anyway
Dark matter exists, but there is still a lot we don’t know about it. Presumably it’s some kind of particle, but we don’t know how massive it is, what forces it interacts with, or how it was produced. On the other hand, there’s actually a lot we do know about the dark matter. We know how much of it there is; we know roughly where it is; we know that it’s “cold,” meaning that the average particle’s velocity is much less than the speed of light; and we know that dark matter particles don’t interact very strongly with each other. Which is quite a bit of knowledge, when you think about it.
Fortunately, astronomers are pushing forward to study how dark matter behaves as it’s scattered through the universe, and the results are interesting. We start with a very basic idea: that dark matter is cold and completely non-interacting, or at least has interactions (the strength with which dark matter particles scatter off of each other) that are too small to make any noticeable difference. This is a well-defined and predictive model: ΛCDM, which includes the cosmological constant (Λ) as well as the cold dark matter (CDM). We can compare astronomical observations to ΛCDM predictions to see if we’re on the right track.
1. a supernatural force believed to dwell in a person or sacred object.
2. power; authority.
3. (Anthropology - Polynesia & Melanesia): a concept of a life force, believed to be seated in the head, and associated with high social status and ritual power; any power achieved by ritual means; prestige; authority.