11ac1064_ions___Astronomy___Black_Holes__Question
[Date Answered] April 3, 1998 [Questioner (age, location)] Michael (Denmark) [Answer] The reason it is a theory is that it hasn't been proved yet. Since we are unable to see dark matter, we can only see its effects on other objects, such as gravitational pull. Based on calculations involving things like gravity, it seems very likely that dark matter does exist. [Question] 
How come the theory about dark matter is that common, when nobody has ever proved the excistance of it?
Quickie Questions - Astronomy - Black Holes