QUOTE : Given that they’ve never seen (or felt or smelled) it, many people I’ve spoken to are surprised at the existence of dark matter and find it quite mysterious—or even wonder if it’s some sort of mistake. People ask how it can possibly be that most matter—about five times the amount of ordinary matter—cannot be detected with conventional telescopes. Personally, I would expect quite the opposite (though admittedly not everyone sees it this way). It would be even more mysterious to me if the matter we can see with our eyes is all the matter that exists. Why should we have perfect senses that can directly perceive everything? The big lesson of physics over the centuries is how much is hidden from our view. From this perspective, the question is really why the stuff we do know about should constitute as much of the energy density of the Universe as it does.