I have once heard a TED Talk about Dark Matter, Einstein Rings and gravitation lenses. http://ed.ted.com/lessons/patricia-burchat-sheds-light-on-dark-matter
I don't think I understood the talk well. Thus I have three questions: It was said that the stars of a galaxy revolve around their center. It was also said, that one could expect stars to move more slowly the farther they are away from their center. However I have two different view points on this: First I remember Merry-go-rounds in which the out parts move faster than the inner parts, I think this view point is not applicable, because the parts are moved mechanically and their movement are fixed circles etc. Secondly I remember Kerbal's Space Program which emulates our solar system to some degree and the movement of objects in it. I don't think that stars, solar systems etc. move in a circle around the center of galaxy, maybe in a ellipse or if you are closer to the center in some other weird way. There are some effects of gravitation working, I don't know which, but well I guess there the path of the objects wouldn't be an ellipse anymore. However I can be clearly seen in KSP that objects slow down, if they move away from the center and then are pulled back and accelerated, if they have passed the turning point and this repeats again and again. However it was said in the TED talk that all objects move at the same speed... and I kinda find that hard to believe, because this would shatter my second view point. So I guess either statement in the talk is wrong or I just misunderstood it.
2th question: Dark matter was shown to surround galaxies in the form of a sphere. Why the hell, should it be a sphere!? I try to imagine a scenario after Big bang, when dark matter had the chance to form "planets" , round objects. The only thing I could imagine is, that those sphere are in facts planets of dark matter and they belong to a solar system of dark matters objects and a galaxy of dark matter objects etc. etc. So intriguing that looks, the less likely I hold it.
3th Question, I would also think, that giant bubbles of dark matter distort Einstein Rings, however it seems that they can be completely explained with the standard viewpoint of gravitation etc.
I didn't find that talk too informative or intuitive, however interesting and I would like to understand the things better, so if someone has information on those topics or source he/she can provide, I would be very happy, if that persons shares them.