[trhway]

:) imagine say 2 objects in space moving toward each other like 2 cars in the opposite direction lanes. Imagine there is a long metal bar across the road such that these 2 cars hit it simultaneously from their respective directions - the bar will rotate - i.e. the combined system of these 2 cars has angular moment. In space there is no bar, instead there is gravitation - these 2 cars would get clumped together (on the "divider" between the "lanes") due to gravitation pull between them. The resulting clump will rotate as result of the angular moment preservation. Now if we expand the model to billions of billions of rocks and gas clouds which form the filament ... :)