One fact that always humbles me is that the universe is made up 68% dark matter, 27% dark energy, and less than 5% matter. That means that all the current knowledge that we have as of February 2016 is only about < 5% of the universe. When we say matter we are talking about stars, planets, moons, nebulas, and all the atoms in the universe. That makes up about 5%. This fact is just mind boggling and you should take a second to let that sink in. Now, that leaves us with dark matter and dark energy?
Dark energy is what we believe is causing the universe to expand. Beyond on that we don’t know much about it. Dark matter on the other hand is interesting. We can say the things that are not dark matter but actually don’t know what it is either. Scientists know that dark matter is not in the form of stars and planets. It’s also not in the form of dark clouds or matter. Dark matter is also not anti-matter. Lastly, we can rule out that dark matter is not a black hole. Which leaves us with the fact that dark matter could possibly be baryonic matter or possibly tied up in heavy elements or brown dwarfs.
Dark Matter in the Milky Way
Scientists believe that throw observations of our own galaxy and studying the mass to light ratio in our galaxy that they believe the Milky Way is made up of more than 90% of dark matter. That is incredible if that is the case! It means that everything you thought makes up the Milk Way or at least the mass of it is not even making a dent. It’s facts like these that challenge humans and brilliant minds of today to make sense of the universe.
If you’re interested in reading more about dark matter and dark energy I’ll leave some of the sources I used as well as some articles that will explain a little more.