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Uploaded:2019-08-16
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A new study provides mathematical evidence that dark matter could be much older than we thought and we've found a weird glitch in a neutron star.

Host: Hank Green

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Sources:
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.061302
https://arxiv.org/pdf/1905.01214.pdf
https://www.eurekalert.org/pub_releases/2019-08/jhu-dmm080719.php
https://gizmodo.com/this-theory-could-breathe-new-life-into-the-hunt-for-da-1837110948
https://profmattstrassler.com/articles-and-posts/the-higgs-particle/why-is-it-hard-to-find-the-higgs-particle/a-lightweight-standard-model-higgs-particle/
https://www.forbes.com/sites/startswithabang/2018/04/12/how-come-cosmic-inflation-doesnt-break-the-speed-of-light/
https://wmap.gsfc.nasa.gov/universe/bb_cosmo_infl.html
https://blogs.scientificamerican.com/critical-opalescence/gravitational-waves-reveal-the-universe-before-the-big-bang-an-interview-with-physicist-gabriele-veneziano/

https://www.nature.com/articles/s41550-019-0844-6
https://www.eurekalert.org/emb_releases/2019-08/mu-gin080719.php
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Images:
https://www.eso.org/public/videos/eso1709c/
https://svs.gsfc.nasa.gov/12656
https://svs.gsfc.nasa.gov/12314
https://www.spacetelescope.org/videos/astro_bu/
https://svs.gsfc.nasa.gov/10118
https://svs.gsfc.nasa.gov/20267
http://chandra.si.edu/photo/2013/vela/
https://www.eso.org/public/videos/eso1810b/
[♪ INTRO].

For thousands of years, people have been trying to understand why the universe looks the way it does. Why, because we’re humans and that’s what we do.

In the last several decades, one way scientists have been approaching this question is by studying dark matter. This is a mysterious substance that’s needed to explain the observed distributions and motions of galaxies. We can’t see it, smell it, or detect it with any of the techniques available to us, but whatever it is, evidence suggests it exerts a gravitational force on visible matter.

Evidence also suggests that there’s a lot of it, and that it might make up about 80% of the universe’s mass. Of course, if we can’t actually detect this stuff, it’s kind of hard to know anything beyond that, like where dark matter came from, for example. But a new study, published last week in Physical Review Letters, may have just opened the door to a startling possibility.

It provides mathematical evidence suggesting that dark matter might be so hard to find because it formed before the Big Bang. Alright, if that last sentence made you freak out, it’s fine. I understand.

This hypothesis doesn’t break everything you thought you knew about the Big

Bang:. It just depends on your definition of that term. Normally, we talk about the Big Bang as the very beginning of the universe. But some scientists actually use a different definition.

This paper treats the Big Bang as the beginning of the expanding universe as we know it, the time where things started to cool down after a period of rapid growth. That growth period was called cosmic inflation, and that’s when this paper argues that dark matter may have formed. During this short period, the universe expanded much faster than it does today, like, trillions of trillions of times faster.

It was an alien, quantum world, so it’s not weird to think that something like dark matter could have formed during this time. Besides, some scientists already believe that certain particles called scalars might have formed during cosmic inflation. Scalar particles have a pretty technical definition, they’re bosons with a zero spin, if that means anything to you.

But the important thing to know here is that they can also be notoriously difficult to detect. In fact, the only fundamental one we’ve managed to pin down with any certainty is the famous Higgs Boson, and that took decades. So if dark matter formed along with scalars, or is made of scalar particles, well, it’s not surprising we haven’t been able to find it.

Now, it is worth noting that this idea about dark matter isn’t entirely new. But for the first time, this study has done the math to show that it could be true. This work already fits with what we know dark matter can and can’t be, based on previous measurements.

It also gives parameters that could help us test the new model to find out more about dark matter with astronomical observations, rather than with particle physics. That investigation will likely take a while. But in the meantime, we at least have a framework for a testable hypothesis, something that is rare in the speculation-heavy field of dark matter physics.

It’s big, complicated research, but in the end, if this hypothesis is confirmed, it could launch us into an entirely new era of dark matter research. Of course, dark matter isn’t the only thing in the universe we’re still not sure about. I don’t even know what I had for breakfast this morning.

There are all kinds of objects keeping their secrets close to their chests, like my avocado toast and like neutron stars. Neutron stars are small, incredibly dense, rapidly-rotating objects. They’re made almost entirely of neutrons, and they form after a star explodes at the end of its life.

Most neutron stars spin many times per second, but occasionally they glitch, and their rotation can speed up even more. In a study published Monday in Nature Astronomy, scientists have used a glitch like this to study the heart of a neutron star for the first time. And while they were able to confirm some previous ideas, they also uncovered a shiny new mystery.

The team’s observations focused on the Vela pulsar, a neutron star a thousand light-years away that’s known to glitch about once every three years. During its last glitch in 2016, a radio telescope in Australia took some great data, and in this new study, the authors analyzed that data to figure out what was going on in the star’s interior. According to their results, the star is composed of a rigid crust that surrounds layers of spinning, superfluid neutrons.

These neutrons so cold and dense that they can keep flowing without losing any kinetic energy. But sometimes, complex processes can cause that flow to change, and that leads to a glitch. First, the outermost layer of superfluid neutrons starts to move outwards, where it hits the star’s rigid outer crust and causes it to spin faster.

Then, the innermost layer of superfluid neutrons moves outward, too. It catches up with the first layer and ultimately causes the star to slow down again. Although this kind of behavior has been predicted, these analyses were able to confirm it for the first time, but that wasn’t the only important thing they did.

The data also turned up another surprising phenomenon:. Before the glitch, the star’s rotation actually appeared to slow down. Scientists have never seen something like this in a neutron star before, and the researchers admit that right now, they have no idea why it happens.

It’s something they’re going to have to keep checking out, once they’re done celebrating these new findings, at least. Because regardless of what comes next, this study has given us amazing insight into a mysterious cosmic object. And with every paper like this, we’re getting a better understanding of how our universe works as a whole.

Which, honestly, is pretty amazing. So whether it’s from new data or new hypotheses, these papers have opened doors to new research paths. And it’s going to be exciting to see where they lead!

As always, we’ll keep you updated. Thanks for watching this episode of SciShow Space News! If you enjoyed this, there’s a good chance you would also like our podcast.

It’s called SciShow Tangents. It’s part science podcast, part game show, and just generally a very good time. I host it along with three really smart, funny people, and I always learn something new and ridiculous.

You can listen wherever you get your podcasts. And if you want to ask us a question for our next episode, you can find us on Twitter @SciShowTangents. [♪ OUTRO].