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  • [♪ 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]

[♪ INTRO]

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ダークマターはビッグバンの前に来ていたかもしれない!?| サイショウニュース (Dark Matter May Have Come Before the Big Bang?! | SciShow News)

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    林宜悉 に公開 2021 年 01 月 14 日
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