[swilhelm73]

Minor quibble -- but how can you "know" about something you've not detected? You can theorize about it, sure -- but that's not "knowing."

The gravitational effects of dark matter on a galactic scale has, IIRC, been pretty well established.

Basically, we can look at two galaxies in close proximity and establish the rough mass of both of them. We can then calculate, again roughly, the amount of 'light' matter, ie stars in them.

Those numbers are *way* off, by a factor of about 10 to 1. So, this seems to be proof that there is something with mass, and quite a bit of it, that we can't see.

[r9etb]

Those numbers are *way* off, by a factor of about 10 to 1. So, this seems to be proof that there is something with mass, and quite a bit of it, that we can't see.

But that's not the same as "knowing" it's some sort of exotic stuff of the sort being talked about in this article.

[Jeff Gordon]

seems to be proof

Proof? Not hardly. "Suggestion" would be a better word.