Dark Matter exists, it holds galaxies together, but why can't we see it?
That answer isn't accurate, kissmysoul.
The term "dark matter" is a little bit misleading, as it calls to mind something a ball of something that you can carry around in your hand that just happens to be dark. What scientists talk about when they talk about dark matter and dark energy is a little more elusive than that, and it isn't anything that's "holding galaxies together" exactly.
When scientists started working out how much mass the universe contained, they came up with one number, but when they worked out how much mass it SHOULD contain based on gravitational effects on the thing they could see, they saw the original number was off by, oh, 96% or so. That means that the matter and energy that we can see accounts for only 4% of the stuff in the universe. Since the other 96% was invisible, they coined "dark matter" to account for the rest.
But the thing is, "dark matter" could be anything, from particles the size of neutrinos or even smaller. Hell, it could be interference from a fourth or fifth or sixth dimension that we have no way of detecting. All we know is that there's a lot of it and it doesn't interact with anything that we can measure.other than gravity.
So dark matter isn't dark because of its interaction with light. It's dark in the sense that we have no idea what it is. Many scientists think we're going in the completely wrong direction trying to find it and that there are other explanations for the universe's missing mass, but we'll let them worry about it.
Oh, and many people suspect there's also something called dark energy, which is even more mystifying, so have fun with that.
I do not think that the 4th dimension, time, is interfering with us detecting the contents of dark matter and energy.
Perhaps dark matter and energy is the hand of god. No worries, I am not a religious freak, actually I hate religion, but it is tempting to interpret dark matter/energy as the reminiscent force that disrupted the singularity that led to the inflationary universe. Just like there is a cosmic echo that points to the big bang, dark matter/energy may be the clue of what the force that disrupted the singularity. Since the force that disrupted the singularity resides outside space-time, the echo of this force cannot be detected in the material universe, but its echo dominates 95% of the universe. Also, perhaps it is the force that distrupted the universe that should be called god. Not the bearded fellow in the bible that hates humanity.
magnus you really dont know the concept of the real 4th dimension known as hyperspace or tetraspace not hyperbolic time space. you should do some research guy and quit looking like a dumb. but what mikeh said is pretty much it. yes I know what you are saying when you say god not God. and neutrinos are small enough to be undermined in calculations. but other particles as well. plus black holes alter space and calculations. they have singularities but other things go into calculations like the giants in space known as quasars. stuff like that can go into effect due to the high gravitational forces they have. also the bearded fellow known as jesus doesnt hate humanity. maybe do some more research there too buddy. its humanity that hates humanity.
Because it's dark.. as in a lack of light. Our eyes are designed to intercept light reflected off of different objects. Iight contains every colour, but most light passes through most objects, reflecting only a few colours. Absolutely no light passes through dark matter(hence the name: dark matter), therefor, it can't be seen.