Dark Matter

So, this shows us what dark matter is about.

dark matter
Name given to the amount of mass whose existence is deduced from the analysis of galaxy rotation curves but which until now, has escaped all detections. There are many theories on what dark matter could be. Not one, at the moment is convincing enough and the question is still a mystery.

http://imagine.gsfc.nasa.gov/docs/dict_ad.html#dark_matter

And this is from NASA too. The big astronomy organization. So, something this mysterious could easily have a big effect if humans mess with it too much.