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I think the argument is that you can put exactly as much dark matter anywhere you want to explain whatever you want. Sure it has to be "a particle that feels gr
by vadansky 6y ago
I think the argument is that you can put exactly as much dark matter anywhere you want to explain whatever you want. Sure it has to be "a particle that feels gravity but not electromagnetism", but that just means it's invisible and the only effect it has is the exact effect you want.
So it's basically being able to add whatever number you want to one side of an equation to get it to balance out.
- dnautics 6y agoalso "constraints" on DM values can be misleading. When you say "a DM particle cannot be more clumpy than X" given an average density of DM particles in the universe, you are saying "we must LOOSEN a constraint on the types of things that DM can explain", because for that particular parameter, there is an inverse relationship between constraint tightness and explanatory power.
- h2odragon 6y agoNicely expressed. Put that way, it becomes obvious the problem isn't that we have a class of unknowns gathered under the label "dark matter", its that the label comes to imply things unrelated to the real use. I take the "faith in human ignorance" view that there are many things extant that we have no inkling of. Its easy to mistake quantified and classified ignorance for knowledge, especially when it is all we have.
- magicalhippo 6y agoSure if your model is complicated enough you can add unicorns and Santa Claus. But those models aren't interesting, precisely because of that. The interesting models have as few parameters as possible, allowing them to be constrained in their behavior.
- jjk166 6y agoYes, and you can put exactly as much invisible air as you want to explain why branches move the way they do. If the branch is moving twice as much, isn't it so convenient to claim that there just happens to be twice as strong a wind?