(I'm desperately trying to get involved with EVC again, but feel hopelessly out of my league lol... I'll take a stab at a minor contribution here)
It doesn't seem to me to be too much of a stretch to accept the notion that, in the vastness of space, there would me matter which is not visible to us. If matter does not emit radiation (visible or not) of its own accord, and has no nearby light source to illuminate it (which would describe the vast majority of the universe), then it would be for all intents and purposes undetectable to us... EXCEPT by observing its gravitational influence on other matter that is observed. If one limits oneself to accepting only that which is
directly observed, one must throw out a great deal of subsequently firmly established science.
As an aside - I'd be curious if someone could point to an article detailing "direct observation" (whatever that might be) of dark matter - I am struggling to locate any sort of "smoking gun" in this respect - I see several plausible studies, but they all rely on indirect observation to some extent. In fact, I don't see how one could "directly" observe dark matter unless you capture it in a test tube and and shine a light on it.
Edited by Briterican, : Added request for info regarding possible "direct" observation of dark matter.