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  • You may think the greatest, most perplexing mysteries of the universe exist way way out

  • there, at the edge of a black hole, or inside an exploding star.

  • But some of them surround us, all the time.

  • I can show you.

  • In this container, we're going to catch some super-fast subatomic particles that are

  • raining down on us from space.

  • They're called cosmic rays.

  • And exactly where some of them come from is part of this 100-year-old mystery in physics.

  • Cosmic rays are a form of radiation.

  • Raysis a misnomerthey're actually little bits of atoms whizzing by us, even

  • through us, all the time.

  • Every square centimeter of Earth at sea level, including the space at the top of your head,

  • gets hit by one of these particles every minute.

  • We can't feel them, and they don't cause our bodies any harm,

  • But they can, sometimes, do weird things: Like make computers malfunction by messing

  • with their memory.

  • Scientists have been studying cosmic rays since the early 1900s, when a physicist went

  • up in a hot air balloon and discovered the radiation increases the higher you gomeaning

  • that it comes from somewhere in space.

  • Since then, they've found out ways to make these little bits of atoms visiblelike

  • we're gonna do here.

  • We've built something called a cloud chamber.

  • Up here is felt that we've soaked with a super-concentrated solution of rubbing alcohol.

  • And at the bottom here is dry ice which is super cold.

  • So when the alcohol vapor goes down to the bottom and gets really coldit condenses

  • and forms a cloud.

  • And when the cosmic rays come shooting in from spacethe alcohol vapor forms into

  • little droplets and you can actually trace their path through the cloud.

  • Hopefully.

  • Okay, let's look.

  • Wait!

  • I saw one!

  • Yeah!

  • The particles in our cloud chamber are traveling from space at nearly the speed of light, as

  • are the untold others passing by you and through you right now.

  • When they hit our atmosphere, the impact is so powerful that the atoms of radiation burst

  • opentearing apart in violent, cascading collisions.

  • That's what we see in the cloud chamber: atomic shrapnel that has reached the ground.

  • Scientists have determined that some of these rays come from the sun's atmosphere, in

  • the form of solar wind, and others from exploding stars.

  • But the most powerful rays are the most puzzlingthey don't even come from our own galaxy.

  • They come from some unknown source out in the universe.

  • The energy from the very most powerful ray recorded had enough power to turn on a light

  • bulb for a second or more.

  • That force is comparable to a top tennis pro hitting a ball with all their strength.

  • It doesn't sound that impressive, but think of this: all that energy is squeezed into

  • an area smaller than an atom.

  • To try to figure out what entity could be shooting these incredibly powerful rays at

  • us, scientists use massive cosmic ray observatories, with detectors not too different from our

  • cloud chamber.

  • Wellyou know, they're on a higher budget and they're more advanced.

  • One in the South Pole uses a block of ice, a whole cubic kilometer, to track the rays

  • instead of vapor.

  • Another one in Argentina has 1,600 huge water tanks, spread out over 1,000 square miles.

  • But instead of just observing cosmic rays as they shoot by, scientists use sophisticated

  • technology to trace the atomic shrapnel backward.

  • There, they can reconstruct the original cosmic ray that hit at the top of the atmosphere.

  • But confirming their source in the deep reaches of space isn't so easy, because these cosmic

  • rays don't always travel in a straight line.

  • Instead, the various magnetic fields of the universe and the galaxy, put them on

  • bendy paths.

  • Scientists have a few suggestions.

  • The cosmic rays could be created in the violent hearts of galaxies far away.

  • Another leading hypothesis is that they're not produced by exploding stars, per se, but

  • by bouncing around the shockwaves produced by those explosions.

  • There is also the possibility that some of the rays are produced by forces and objects

  • we don't know aboutor interact with things like dark matter, in ways we don't

  • yet understand.

  • Or they could come from strange objects left over from the big bang.

  • I mean aliens could be shooting these at usbut I doubt it.

  • What scientists need is more data, more observations to be able to pinpoint the sources in the

  • sky these particles are coming from.

  • If scientists can figure out where the most

  • powerful cosmic rays come from, it means they're discovering one of the most powerful things

  • in the entire universe.

  • Perhaps the most powerful thing in the entire universe.

  • That might open up an entirely new branch of physics, teaching us about how the universe

  • was formed, and about how matter can be pushed to the extreme.

  • But until their origin is discovered, we can think of cosmic rays as messengers from the

  • broader universe.

  • A reminder we're a part of it, and that there's still a great deal of mystery out

  • there.

You may think the greatest, most perplexing mysteries of the universe exist way way out

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The mysterious rays shooting at us from space

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    林宜悉 posted on 2020/08/18
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