alt Hacker News> Such behavior could require dark matter to be more complicated than just a single new type of particle. For example, the dark matter particle might have some internal structure, like an ordinary atom, so it would only interact if hit hard enough to excite it to a higher energy internal state
I get a little shiver imagining that the dark matter might be something like ordinary atoms. Imagine that other 85% of the universe could have its own parallel atomic table, chemistry, even some kind of life utterly alien to us?
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It's possible that there could be an entirely different charge mechanism that works exactly like ours but they don't interact at all; but the whole premise of dark matter is that it doesn't seem to have any self-interaction outside of gravity.
You might like this old paper then:
I've heard this referred to as a "dark sector", or "hidden sector":
https://en.wikipedia.org/wiki/Hidden_sector
The scary thought is that, were it true that there is voluminous richly-interacting dark matter, we would be the actual dark sector.