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Physicists estimate that dark matter accounts for about twenty three percent of the known universe - the only problem is that no one really knows what it is...

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Hank: The universe has a bunch of stuff in it. It's got the planets, the stars, the galaxies, the gas, the dust, all the regular space stuff you hear about, but a lot of what makes up the universe cannot be seen with a telescope because it doesn't emit or absorb light. It's called dark matter and surprise, surprise, it's very mysterious.

[Intro]

Since dark matter can't be detected, you might wonder, like, why we even think that 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 they bounce off of that lets us see them.

The first clues of dark matter's existence came in the 1930s, when astronomers realized that they could weigh a far away galaxy by clocking the rate at which all the massive objects inside it move in relation to each other. This gravitational action could tell you how much mass there was in the galaxy.

The galaxies appear to be weighing a lot more than the stuff inside of them would account for. There simply weren't enough stars and other stuff to make the galaxies act the way they were acting. the ought to be something massive yet undetectable inside of them that explained how they moved and also what was keeping them hanging together.

It took decades of brilliant people and amazing instruments like the Hubble space telescope to rethink the whole enchilada but today physicists figure that dark matter accounts for about 23 percent of the known universe.

So now comes the part where we tell you what dark matter is, what it's made of and tell you all about it. Unfortunately, nobody knows.

We're pretty sure that its not just like everyday matter, also called baryonic matter, like protons and neutrons. The most commonly held view is that it's made up of exotic sub atomic particles that were created a fraction of a fraction of a fraction of second after the big bang, and it might be all around us. We could be swimming in dark matter, and we would have no idea because its particles don't interact with ordinary matter so we can't detect it.

So what's got astrophysicists all hot and bothered these days is the possibility that the newly discovered Higgs-Boson might hold the key to dark matter. The Higgs, remember, is a particle that is predicted by the standard model of particle physics: the theory that helps us understand the behavior of matter in the universe. Verifying the existence of the Higgs is a huge deal because it's an indicator of a larger phenomenon known as the Higgs field: an invisible field that basically gives particles mass when they interact with it.

So even though dark matter and ordinary matter probably can't interact with each other, some scientists think that the Higgs might be able to kind of translate for us. Since it gives mass to ordinary particles in the universe, it probably would also be giving mass to whatever makes up dark matter, seeing as dark matter is also massive.

So unlocking the secrets of the Higgs could end up making dark matter a lot less mysterious. In the meantime scientists are doing their darndest to actually detect dark matter. Most of these experiments are happening deep underground because if we're surrounded by the stuff, which we probably are, then it's likely passing right through our planet all the time.

Thanks for watching this episode of SciShow. If you want to keep up to date on all the latest research into dark matter and the Higgs and other kinds of amazing stuff like this, you can go to youtube.com/scishow and subscribe and if you want to ask us any questions or comments or anything, we're in the comments below. We're also on facebook and twitter. We'll see you next time.