Physics has a bit of a messy problem: There's matter missing in our universe. Something is there that we can't see but can detect! What could this mysterious substance be? A lot of astronomers are searching for the answer. And some, like theoretical particle physicist Chanda Prescod-Weinstein, think a hypothetical particle called the axion may make this problem a little ... tidier. That's right: hypothetical. Scientists have never seen one, and don't know if they exist. So today, we point our cosmic magnifying glasses towards the axion and ask how scientists could find one — and if it could be the neat solution physicists have been searching for. Help shape the future of Short Wave by taking our survey: npr.org/shortwavesurveyListen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
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Just go to npr.org slash shortwave survey. We'll also put a link in our show notes. Thank you. Okay, on to our show. You're listening to Shortwave from NPR. Physics has a bit of a messy problem. There's matter missing in our universe. Something's there that we can't see, but we can detect it. This mysterious substance behaves a lot like the matter we know.
You know, the matter that makes up you, me, the sun, the planets, and the stars. At least in the way that matter attracts other matter. Stars can orbit other stars, galaxies, collections of billions of stars can orbit other galaxies, And looking at those orbits or the way things move around other things in space can tell us how massive the object in the center is.
But sometimes we can't see what is really causing that movement.
When we look at how stars move in galaxies, they move as if there is a lot of matter there that we can't see.
That's Chanda Prescott-Weinstein. She's a theoretical particle physicist at the University of New Hampshire.
And she says that this missing matter... It's actually most of the matter in the universe. And it is not visible. And when we say it's not visible, we mean it doesn't interact with light in any way that we've so far detected.
That's why it's often called dark matter. It makes up over a quarter of the entire universe. Scientists don't know what it is, but they do know whatever it is has to have a few key components.
We want it to be something that doesn't interact very strongly with light, if at all. So we want it to be effectively transparent, effectively invisible. And we also want it to be relatively slow moving. So if it's fast moving, then it won't clump together under gravity. It will escape gravity and then you won't form galaxies.
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