what happens to cosmic ray when it hits the atmosphere

Javier Zarracina/Vox

Extremely powerful cosmic rays are raining down on us. No one knows where they come up from.

Simply with large-scale experiments, scientists around the world are determined to find out.

Past Updated Jul 25, 2019, 7:17am EDT

Graphics: Javier Zarracina/Vocalism

You lot may call up the greatest, nigh perplexing mysteries of the universe exist way out in that location, at the edge of a black pigsty, or inside an exploding star.

No, keen mysteries of the universe environment u.s.a., all the time. They even permeate us, sailing straight through our bodies. I such mystery is cosmic rays, made of tiny bits of atoms. These rays, which are passing through us at this very moment, are non harmful to us or whatsoever other life on the surface of Earth.

Simply some carry so much energy that physicists are baffled past what object in the universe could take created them. Many are much too powerful to accept originated from our dominicus. Many are much too powerful to have originated from an exploding star. Because catholic rays don't often travel in a straight line, we don't even know where in the night sky they are coming from.

The answer to the mystery of cosmic rays could involve objects and physical phenomena in the universe that no one has always seen or recorded before. And physicists have several enormous experiments around the world underway at present devoted to cracking the example.

Though we don't know where they come from, or how they get here, we tin can see what happens when these cosmic rays hit our planet'south atmosphere at nearly the speed of light.

Cosmic rays are messengers from the broader universe; a reminder we're a function of it, and a reminder that at that place'due south however a peachy deal of mystery out at that place. Permit's take a close look at these amazing particles, raining on Globe from afar.

Smashing into our temper

When the particles in cosmic rays collide with the atoms in at the top of the atmosphere, they burst, vehement apart atoms in a violent collision. The particles from that explosion and so go on bursting apart other bits of matter, in a snowballing concatenation reaction. Some of this atomic shrapnel even hits the ground.

Javier Zarracina/Voice

Javier Zarracina/Vox; NASA

It's possible to come across this in action by building what's chosen a cloud chamber out of a drinking glass jar, felt, dry out ice, and isopropyl alcohol (i.e. rubbing booze). You soak the felt in the alcohol, and the dry ice (which is super-cold solid carbon dioxide) cools down the alcohol vapor, which is streaming downwardly from the felt. That creates a cloud of booze vapor.

In this chamber, yous can see the cosmic rays, particularly those from a particle called a muon. Muons are like electrons, but a fleck heavier. Every square centimeter of Earth at bounding main level, including the space at the top of your head, gets hitting by one muon every minute.

Like electrons, muons acquit a negative charge. When the muons nix through the alcohol deject, they ionize (charge) the air they pass through. The accuse in the air attracts the alcohol vapor, and it condenses into droplets. And those droplets then trace the path the cosmic rays made through the bedchamber.

When you see the paths these muons make, call back virtually this: These subatomic particles rocket down to World at 98 percent the speed of light.

They motion then fast, they feel the time dilation predicted past Einstein'due south theory of special relativity. They're supposed to disuse — i.e. pause apart into smaller components, electrons, and neutrinos — in simply 2.2 microseconds, which would mean they'd barely get 2,000 feet downwardly from the superlative of the atmosphere earlier dying. But because they're moving so fast, relative to us, they age 22 times more than slowly. (A similar thing happened to Matthew McConaughey'due south character in the movie Interstellar, every bit he sped up his relative speed nearing a blackness hole.)

If Einstein's theory weren't true, we wouldn't come across any muons in the deject chamber. Luckily, they are harmless, moving and so fast that they don't take the time to land an impactful punch in your body. Scientists can do some cool things with muons, like utilize them to photo the inside of the Corking Pyramid in Egypt.

Recall that these rays were potentially propelled past forces from beyond our solar system, by forces no physicist understands. That's plainly awesome.

"Our theoretical physicist colleagues are perplexed" about how these particles are energized, says Charles Jui, a physicist at the University of Utah on the hunt for cosmic rays. "Nosotros likewise can't figure out where they are coming from."

Cosmic rays, explained

The mystery of cosmic rays began with their discovery in 1912. That'due south when the physicist Victor Hess took a ride on a hot air airship and discovered the corporeality of radiation in the temper increases the in a higher place yous go.

He was on the balloon to isolate his experiment from radiation. But it was only noisier higher upwardly. That led him to conclude that the radiation was coming from space, and not radioactive decay from rocks in the globe.

He also took this balloon ride during a total solar eclipse. With the moon blocking the sunday, cosmic radiations coming from the lord's day ought to have been filtered out. But he still recorded some. That led him to the insight that the radiations was not coming from the sun, but from deeper in space. His discovery of catholic rays won him the 1936 Nobel prize in physics.

The highest-energy cosmic ray particle ever recorded, chosen the "Oh-My-God" particle, was some ii meg times more energetic than the most souped-up proton propelled by the Large Hadron Collider, the globe's most powerful particle accelerator.

That free energy, Antonella Castellina, an Italian astrophysicist with the Pierre Auger Observatory, explains, is similar to a top tennis pro hitting a ball with all their strength. Now, that doesn't audio like a lot. Simply imagine all that free energy squeezed into an area smaller than an cantlet — that's extreme. It'due south enough power to plow on a light seedling for a 2d or more. "Nobody knows what in the universe is able to give a subatomic particle such an energy," she says.

More than that, scientists are baffled to how such a particle tin can even achieve Earth. Particles with such crazy-high energies are thought to interact with the radiations leftover from the Big Bang and the creation of the universe, which ought to put the breaks on them before they reach us.

What created the "Oh-My-God" particle and similarly powerful cosmic rays is a complete, inexplainable mystery. (Yous might be thinking, why are we calling these particles "rays"? It'southward a bit of a misnomer that stuck effectually from when they were discovered a century ago. They're also chosen "astroparticles." Simply cosmic rays audio libation, then we'll stick with that.)

Cosmic rays were discovered 100 years ago. Then you might exist thinking: Why can't we figure out what'south shooting these catholic rays at united states?

Well, we do know some catholic rays come from the sun. But the strongest ones, the most mysterious ones, come from the neat way-out-there in the galaxy and universe.

The trouble with looking for the sources of these very high energy catholic rays is that the rays don't always travel in a direct line. The various magnetic fields of the galaxy and universe deflect them, and put them on bendy paths.

Many of the cosmic rays that hit Earth — especially the ones that come from our sun — get deflected to the poles due to Earth's magnetic field. That'due south why we take the Northern and Southern Lights near the poles.

In that location are a few huge projects underway to ameliorate understand where these catholic rays come from. One involves a truly enormous block of water ice at the South Pole.

An enormous block of ice at the South Pole is a giant cosmic-ray detector

There's not much alive at the bottom of the world, except for the physicists. There, at the south pole, they've built the IceCube Neutrino Observatory, forged directly into the ice beneath the surface of the South Pole.

Information technology is a i-cubic kilometer (nearly 1.3 billion cubic yards) cake of crystal-clear ice surrounded past sensors. These sensors are gear up to discover when subatomic particles called neutrinos — which travel along with other subatomic particles in cosmic rays — crash into Globe.

Javier Zarracina/Vox

How it works is not so different from the cloud chamber experiment we showed you above. It's trying to trace the path a very special blazon of cosmic ray — called a neutrino — makes through the observatory.

Neutrinos are different from the other components of cosmic rays in one actually of import way: They don't interact with other forms of matter much at all. They don't have any electrical accuse. That ways they travel through the universe in a relatively straight line, and we tin trace them dorsum to a source.

"If I smoothen a flashlight through a wall, the low-cal won't go through," Naoko Kurahashi Neilson, a particle physicist at Drexel University, told me. "That'south because the light particles, the photons, collaborate with the particles in the wall and they can't penetrate. If I had a neutrino flashlight, that stream of neutrinos would become through the wall."

Simply every one time in a while a neutrino — maybe every 1 in 100,000 — will hit an cantlet in the ice at the observatory and interruption the atom apart.

Then something spectacular happens: The standoff produces other subatomic particles, which are and so propelled to a speed faster than the speed of light as they laissez passer through the ice.

You might take heard that nada tin can travel faster than light. That'south true, but only in a vacuum. The photons that make upwardly light (a subatomic particle in their own right) really slow down a bit when they enter a dense substance like ice. But other subatomic particles, similar muons and electrons, do not ho-hum down.

When particles are moving faster than light through a medium like water ice, they glow. It's called Cherenkov radiations. And the phenomenon is similar to that of a sonic boom. (When you lot go faster than the speed of audio, you produce a blast of noise.) When particles move faster than lite, they leave wakes of an eerie blue lite like a speedboat leaves wakes in the h2o. Here's an artist's depiction of what this all looks like. The neutrino is the tear-drop shape in gray.

NASA's Goddard Space Flight Heart/CI Lab/Nicolle R. Fuller/NSF/IceCube

Other observatories looking for cosmic rays are similarly enormous

The Pierre Auger Observatory, where Castellina works, uses an array of one,600 tanks, each filled with 3,000 gallons of water. The tanks are spread across more than than 1,000 square miles in Mendoza, Argentina.

Javier Zarracina/Vox

The tanks piece of work like the block of water ice at the Southward Pole. But instead of using ice to record cosmic rays, they utilize water. The tanks are completely pitch black inside. Simply when cosmic rays — more than but neutrinos — enter the tanks, they cause little bursts of lite, via Cherenkov radiation, as they exceed the speed of low-cal in h2o.

Javier Zarracina/Phonation

If many of the tanks record a burst of catholic rays at the same time, the scientists tin then piece of work backward and figure out the free energy of the particle that striking at the elevation of the atmosphere. They tin also make a rough guess on where in the sky the particle was shot from.

In the Northern Hemisphere, there's a similar experiment in Utah called the telescope array. Like the tanks in Due south America, the assortment in Utah has a series of detectors spread out over an enormous area. Currently, it takes upwardly about 300 foursquare miles, only there's an upgrade in the works expanding information technology upwardly to 1,200 square miles. (The larger the area, the greater the hazard to spot the nearly elusive and powerful cosmic rays.)

The detectors in Utah are made upwardly of super-clear acrylic plastic, and are housed in units that kind of wait similar hospital beds.

Javier Zarracina/Vox

If many of the detectors tape a hit in sequence (think of the particles all hitting the footing around the same time like shotgun pellets on a target board), "you can reconstruct the direction" from which they came, says Jui, the University of Utah physicist who works on the array.

Javier Zarracina/Vox

The observatory can also exercise something cool. On very clear, night nights in the Utah desert, it can actually see the faint trails of catholic rays lighting upward in our temper.

"The idea is that y'all can see the air shower develop in the temper using ultraviolet cameras," Jui says. "These are cameras that are taking videos, over a few microseconds, x frames a microsecond [that's extreme slow motion], and so you lot can actually see the extended line in the sky, and mensurate the [catholic ray's] free energy from that."

You lot tin can help the search for cosmic rays

With enough data on these loftier-energy catholic rays, scientists hope to one mean solar day meliorate pinpoint where in the heaven they come from.

The problem is that right now, they just don't have enough observations of the most powerful cosmic rays.

Information technology's going to have some time because the most powerful catholic rays don't pass through detectors all too frequently: Every square kilometer of Earth merely sees about 1 of these particles per century. And to account for the fact that these rays don't often travel in a directly line, information technology's going to take a mountain of data.

But already, nosotros have some clues. The Pierre Auger observatory has some (not nonetheless conclusive) data that some of these high-energy particles come from starburst galaxies, which are galaxies that are forming stars at a very fast rate. Jui'south group has ended that nearly a quarter of the virtually powerful cosmic rays observed come up from a circle almost 6 percent the size of the nighttime sky, near the Big Dipper constellation. But that's an enormous surface area of infinite, and there's no obvious smoking gun in the region.

More clues go along to trickle in. Final summer, scientists at the IceCube observatory published exciting show that galaxies called blazars generate some of these high-free energy particles. Blazars have supermassive black holes at the eye of them that rip apart matter into its constituent parts, and and so boom subatomic particles off similar a laser cannon into space.

Here's an artist'due south depiction that is very, very non to scale, showing a blazar shooting a axle of cosmic rays at Earth.

IceCube/NASA

The current results can't even so explain the most powerful catholic rays detected on record. They also need to be repeated.

There is too the possibility that some of the rays are produced by forces and objects we currently don't know about — or collaborate with mysterious things like nighttime matter, in ways we don't even so sympathize. Information technology could be aliens, but I uncertainty it.

What scientists demand is more than data, more than observations to be able to pinpoint the sources in the sky these particles are coming from.

And soon, you lot tin can get in on the search. Your phone tin can exist turned into a cosmic ray detector. Daniel Whiteson is a physicist at the Academy of California Irvine who has been working on a crowd-sourced catholic ray project. It's called Crayfis (Cosmic RAYs Constitute In Smartphones).

"The number of particles that are hit the temper with crazy energies, is really large. It's in the millions [per year]," Whiteson says. But observatories like the Pierre Auger — though huge — aren't large plenty to spot nigh of them. "If we could build a big plenty telescope covering huge swaths of land, nosotros could collect a lot of data actually quickly."

That's where the smartphones come in. The photographic camera in your phone works because photons — the subatomic particle that constitute low-cal — activates a sensor at the back of the lens. Catholic rays tin activate the sensor also. (Every once in a while, too, a cosmic ray can interfere with a microprocessor and crusade a computer to crash.)

"If you lot put your telephone camera face downwards, about of the [light] is blocked, and y'all'd get a black movie," he explains. "But particles from space, volition laissez passer right through your phone, ceiling, or wall, and hit the [camera sensor], and will leave a trace."

The hope is that millions of users can turn the app on at dark while they are asleep, and it will look for these catholic rays. With enough phones, Whiteson hopes, he and his colleagues tin get a better picture of where cosmic rays come up from. The project isn't quite off the footing yet. Only you tin can sign upwardly now to become a beta tester when the app is ready.

Physicists aren't going to give up anytime presently. The being of high-energy cosmic rays tells united states of america our understanding of the universe is woefully incomplete.

"This is some of the most fierce phenomena" in the universe, Jui says. Don't you want to find out what causes it?

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Source: https://www.vox.com/the-highlight/2019/7/16/17690740/cosmic-rays-universe-theory-science

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