According to a show I just watched the atoms that makes up the visible universe actually consists of only about 5% of the universe. Dark matter makes up about 23% of the universe, and the remaining 72% is made up of dark energy. Dark matter apparently is what made galaxy development possible, whereas dark energy is responsible for the inflation that is expanding the universe at ever quicker speeds.
Somewhere else I once heard these same things, but on top of all that they said that because the universe is expanding at faster and faster rates, eventually it will reach the point where other galaxies are so far away that light from them can never reach us because the rate of expansion is actually faster than the speed of light.
In the show it talked about two galaxies colliding and how the visible matter reacted in a predictable way given physics as we know it, but that the dark matter, which they likened to scaffolding around visible matter several times through out the show, continued on moving in a straight line as though nothing had happened.
Now here is my problem. From several sources I hear that the universe is expanding, and that it causes all other galaxies to be moving away from our own, and yet its possible for these other two galaxies to collide and for scientist to study them? An analogy they used a few times for the expansion of the universe was dots on the surface of a balloon getting farther apart as you blow air into the balloon. If that is true how do galaxies collide? Why aren't they constantly moving away from each other?
I'm not an astrophysicist. I don't really understand any of this stuff. I was once really interested in all of this stuff but as much as I like math, I don't enjoy it that much. If dark matter is what is helping keep matter together, and dark energy is what is pushing everything apart, and there is so much more dark energy than everything else, how are we still together? It seems to me that every time a scientist gets an answer to a question then suddenly just have a dozen new questions to answer based on what they just learned to answer the last question.