It's obvious why though: most of the things in the universe can be observed using the electromagnetic spectrum, but dark matter doesn't interact with that. Inst

It's obvious why though: most of the things in the universe can be observed using the electromagnetic spectrum, but dark matter doesn't interact with that. Instead we have to use gravitation, a force some 36 orders of magnitude weaker. That means we pretty much only observe it when the scale is large enough that we can notice its effects, which means it'll be very hard to observe on any kind of local scale.