[qam1]

Thank you for the links but I am still going to disagree because as of now there is no way of knowing if you re-did those measurements on the same galaxy 1 million or 10 million years, etc down the road they would still be the same. In a spiral galaxy there probaby are way to many intangables (i.e. the way stars interact with each other) to determine if our "snapshot" measurement will always hold true. Another anology (albiet a weak one) would be taking one measurement of the wind speeds in a huricane and expecting them to always remain unchanged.

I think they just don't fully understand the rotational physics of (for lack of a better word)"Chaotic" Spiral galaxies so they are inserting dark matter as a cure all.

One reason is because in more uniform and understandable (in regards to rotation) elliptical galaxies they do not find any of this dark matter

So why would there be dark matter in one type of galaxy but not the other? I could be wrong but I have heard that Spiral galaxies eventually turn into elliptical galaxies. If that's true then where does this dark matter go?

[PatrickHenry]

I am still going to disagree because as of now there is no way of knowing if you re-did those measurements on the same galaxy 1 million or 10 million years, etc down the road they would still be the same. In a spiral galaxy there probaby are way to many intangables (i.e. the way stars interact with each other) to determine if our "snapshot" measurement will always hold true.

Right. A million years from now, all those galaxies might even turn into pork chops or something. We don't really know. However ...

I believe that many galaxies, of various ages (judged by the composition of their stars) have been observed. There seems to be none of the rotational disparity you suggest. Thus the assumption that such things remain somewhat steady over time. But you're right. We don't really know.