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Well, it's a placeholder, but a very specific kind of placeholder: it fits exactly everywhere. It's not like it's special-cased to one of the problems. It actua
by scarejunba 7y ago
Well, it's a placeholder, but a very specific kind of placeholder: it fits exactly everywhere. It's not like it's special-cased to one of the problems. It actually works in all of them.
- LoSboccacc 7y agoyeah but you'd get consistent results whether is actual mass or a wrong value somewhere in a fundamental constant, the fact that the dark matter proportions comes out always in the same ballpark, alone, tells us not very much.
- denton-scratch 7y agoThe reason it "fits exactly everywhere" is that the only definition we have is that it's the exactly gap between observation and theory.
- DiogenesKynikos 7y agoNo, the definition is cold, gravitationally interacting matter. It just so happens that adding that one extra ingredient reconciles a whole number of different observations with theory. That didn't have to be the case. For example, if the dark matter is hot, structure formation doesn't match observations, or if dark matter is composed of massive, compact objects, we would observe a lot more microlensing events. But putting in just the right amount of cold dark matter makes everything we can test so far work. That could be a giant coincidence, but most cosmologists think it's because cold dark matter really exists.