A lot of what makes up the universe cannot be seen with a telescope because it doesn't emit or absorb light. Not to be confused with dark energy, dark matter is a type of matter that is said to account for a large portion of our universe's total mass.
Since dark matter can't be detected, you may ask why we even think it exists. Well, we can infer its existence from things that we CAN detect, like light and other forms of radiation; plus all the things that it bounces off of to let us see them. The first clues to dark matter's existence came in the 1930's, when astronomers realized they could weigh a far away galaxy by by plotting the way massive objects inside it moved in relation to each other. This gravitational action could tell you how much mass there was in the galaxy. The galaxies seemed to be weighing a lot more than the stuff inside of them would account for. There just simply wasn't enough stuff in the galaxies to make the stars and such act the way they were acting. There had to be something massive, yet undetectable inside of them that explained how they moved and also what was keeping them together. It took decades of brilliant people to build amazing instruments like the Hubble Space Telescope to re-think the whole enchilada. But today, physicists figure that dark matter accounts for about 23 percent of the known universe.
So what is dark matter? Unfortunately, nobody knows. We're pretty sure that it's not just regular, everyday matter (also called baryonic matter, like protons and neutrons). The most commonly held view is that it's made up of exotic subatomic particles that were created in a fraction of a fraction of a fraction of a second by the big bang. It might be all around us. We could be swimming in dark matter and we would have no idea because it's particles don't interact with ordinary matter.
Now, the Higgs boson might hold the key to dark matter. The Higgs, remember, is a particle that was predicted by the standard model of particle physics, the theory that helps us understand the behavior of matter in the universe. The discovery of the Higgs would mean that there was something larger... the Higgs field; and invisible field that basically gives particles mass when they interact with it.
So even though dark matter and ordinary matter probably can't interact, some scientists think that the Higgs might be a connection between the two. Because it gives mass to ordinary particles in the universe, it would probably also be giving mass to whatever makes up dark matter, seeing that dark matter is also... well, massive. So unlocking the secrets of the Higgs, could end up making dark matter a lot less mysterious.
So as of now, scientists are figuring ways to detect dark matter. But until then, dark matter will be just as mysterious as the Easter Island's moai.
