“Science is almost entirely inferential. No one has ever seen an electron, or a gravitational field, but we take their existence completely for granted.”
Not seeing something and something not being observable are two entirely different things. We can detect electrons. We can detect gravitational fields (heck, we can even feel those things). We can also construct sensible equations describing their behavior, and make testable predictions about them.
On the other hand, the way scientists decide if “dark matter” is somewhere is if their equations’ predictions don’t match the observations. They can’t construct an equation describing dark matter, or make any testable predictions about it. All they can say is “well our equations don’t work, so something must be there”. That’s not science.
No, see http://www.freerepublic.com/focus/chat/3280367/posts?page=27#27
The problem is more than 80 years old, and no one claims to have all the answers.
http://www.learner.org/courses/physics/unit/text.html?unit=10&secNum=2