First and perhaps most perplexingly, researchers remain unsure about what exactly dark matter is. Originally, some scientists conjectured that the missing mass in the universe was made up of small faint stars and black holes, though detailed observations have not turned up nearly enough such objects to account for dark matter's influence.
Astrophysicist Paul Sutter explains what #darkmatter is and how physicists can determine the invisible substance exists.
Astrophysicist Paul Sutter explains what #darkmatter is and how physicists can determine the invisible substance exists.
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00:00What is dark matter? Dark matter should be called invisible matter. It's matter
00:08that doesn't interact with light or with any other charged particles. It's matter
00:13that has nothing to do with light. That's the point. I'm Paul Sutter and this is
00:20Paul Explains, the show where I, you know, explain. How do we know that dark matter
00:27exists? Well, we don't see it in Earth or the solar system. You have to look at big
00:34scales before dark matter really starts to reveal itself. And we saw first in the
00:411930s with the motions of galaxies inside of galaxy clusters. The galaxies
00:47were just moving way too fast. The galaxy cluster should have ripped itself apart
00:52billions of years ago, but there was still existing. So something
00:57had to be gluing all those galaxies. Even our own galaxy, the Milky Way, just
01:02shouldn't be here. Then in the 1970s, we discovered that stars are again moving way
01:11too fast. There has to be an extra source of gravity to hold the stars in. And the
01:19source of gravity can't come from something we see like stars or nebula or
01:24anything else that glows. Otherwise we would have seen it. We would have
01:29accounted for it. There is something inside of galaxies. There is something
01:33inside of galaxy clusters that has mass, that has gravity, but isn't emitting any
01:39light. Since the 1970s, we've gone even further to solidify our understanding of
01:46dark matter or that we know it exists. From the earliest moments of the universe, we have
01:52the cosmic microwave background. This is leftover light from when the universe was
01:57just 380,000 years old. And by studying tiny little variations in that light, we can get
02:03a picture, a map of what the universe was like back then. And guess what? There was a lot
02:08of matter back then that didn't interact with light. So we have all these different pieces of evidence
02:14that all fit together and all point to dark matter. Very likely dark matter or
02:22invisible matter is streaming through the room you're in right now. But it doesn't
02:27interact with light, doesn't interact with charged particles, it doesn't interact
02:30with normal matter. So you just don't see it. You just don't care about it. It's
02:34invisible to you. But at the very largest scales, it affects how things move. What we
02:41do know for sure is that the dark matter does exist.