Catching the Fastest Particles in the Universe | Miguel Mostafá | TEDxPSU

Translator: kitty bian
Reviewer: Xinyi He Around the clock the sky is raining silver and gold and all kinds of other elements carbon, copper, hydrogen, oxygen, etc. Luckily we don’t get soaked with these rain particles because we have a protective umbrella that we call atmosphere. These particles travel near the speed of light toward us from all directions constantly Then, once in a very long, long while, one of the fastest bits of matter hits the top of the atmosphere. We call these very rare particles ultra high energy cosmic rays. Let’s start with the lowest energy cosmic rays. The lowest energy cosmic rays are thrown at us by the Sun in a stream of charged particles known as the solar wind. Some of us have actually seen these particles and we call them the Northern Light. The rate at which these particles arrive to the top of the atmosphere falls very very rapidly with increasing energy. This makes sense because what it says is that the faster you wanna accelerate these particles, the harder it is. And therefore, they are more and more rare to reach us. So for example, these lowest energy particles hit every square meter of the atmosphere 10,000 of them every second we know even higher energy particles for example we know of sources of high energy cosmic rays in our own galaxy, the Milky Way for example this is how rapidly this rate falls. If you look at a particle with a thousand times higher energy the rate of arrival at the atmosphere is a billion times lower a billion with a bs in bernie This means that that same square meter of atmosphere, instead of being heated by 10,000 particles per second, now at the center she’s heated by 10 particles every hour. So that’s how steep this is. And this is…I stopped at the center intentionally because this is the energy range we have mastered for example here we know how to produce irons. Here you have a very young and handsome despite the short hair, playing with his vibes source of negative ions We also know how to accelerate sub-atomic particles. This is a ? posing for a photo next to the Tevatron this circular particle accelerator accelerated protons and antiprotons along this 4-mile-long ring at the energy of 1 trillion electron volts which means that these protons were travelling along the 4-mile-ring at a speed of 99.99995% of the speed of light. This was the highest energy particle accelerator until the large Hadron Collider was built near Geneva, Illinois. Near Geneva Switzerland. In this machine, this machine is 17 miles long, is the largest single machine in the world, the most powerful accelerator. Here, portons go through this 17-mile run at 7 trillion electron volts, or 99.999999% of the speed of light. So many nines, which means that in one second, these protons go around the 17 miles more that 10 thousand times. Ok? This is the most impressive machine most complex experimental facility that we can build. And particles of the same energy bombard thisconstantly so there are sources out there that can accelerate these particles to this energy, and for my pretty graph you can already tell that there are sources that can go to even higher energies. In fact, some cosmic rays there are sources of cosmic rays that can accelerate these cosmic rays to a power that we cannot even explain yet. Some of the sources may lie in other galaxies, where some very exotic objects live, like supermassive blackholes, which may be the drivers of this acceleration mechanism. We have actually detected cosmic rays with energies 100 millions times higher that what we can do on earth with the most powerful machine. This energy is so huge, this acceleration so big that these particles are extremely rare So the rate of arrival of these particle to the top of the atmosphere is one per square kilometer every century. That is very rare. So we want to detect these particle the direct observation of cosmic rays can only happen on top of our protective umbrella, so on top of the atmosphere, and these high energy cosmic rays are so rare that it’s impossible to leave the detector in the space big enough to capture significant number of these cosmic rays. So we have to do it on the ground. And for that we put detectors on the ground and we use the fact that when these cosmic rays hit the top of the atmosphere, the collisions with air molecules create a large cascade of secondary particles. These extensive showers have billions of secondary particles that fall and reach to the ground, covering a huge area of many square miles. So we put detectorsand we cover a large area on the ground. This is a particle detector. I know it looks a lot like a water tank, but it’s actually a big water tank, because 12 tons of ultra pure water and instruments that can detect the secondary particles when they reach the ground at that point. So we deploit 1600 of these detectors in western Argentina, and each detector is one mile apart in a triangular grid covering a total area of 3000 square kilometers This is 10 times the size of Paris This is the size of the whole state of Rhode Island. So just to give you and idea I will compare these two huge areas we cover with detectors with the two largest cities in the world This is New York metro area Her you have Manhattan, Manhattan is only like 60 square kilometers This is Tokyo, so if you recognize the Yamanote line, it’s this one right here And for the local people in the audience, we have put detectors from Lewis Town to Huntingdon, Tyrone, Philisburg, Lock Haven There is one detector every single mile covering that whole area. This is in the provice of Mendoza in Argentina This is the provice where all the good ? come from. And I know what you are thinking there’s no correlation between that and being located there. This is the footprint, this is actual data from publicly available from the observatory. This is the footprint of one sub-atomic particle, say a proton for example, that hit the top of the atmosphere with ultra high energy. It collided within the atmosphere and it created these extensive secondary particles that spread and left signals on the ground on each one of these detectors covering the whole area of more that 20 square miles. One single proton hitting the top of the atmosphere And I know what you are thinking right now at this point, is that this is cool, I don’t know about sexy, but this is cool, and but why is this important? What are you hoping to learn from this? And more importantly, why should you be intersted in the study of cosmic rays? These are all excellent questions, and they are all related. Cosmic rays are messengers from space. They are real samples of the star stuff that have travelled millions of years before reaching us. We use cosmic rays to infer useful properties about our galaxy such as its composition, its basic structure. In fact, cosmic rays are one of the very few handles we have in which we can sample real matter from protons all the way to the heaviest elements, coming from beyond our solar system. By identifying these diverse nuclei, we are hoping to unravel the mechanism that can actually produce those nuclei. We want to know how they are produced, we want to know how these nuclei can reach near the speed of light, we want to know what these nuclear collisions that occur in super ? Just to think about this. The iron in your blood came from a supernova billions of years ago in our own solar neighborhood. Cosmic rays also opened the world of sub-atomic particles. We discover the positron, the first particle of anti-matter, the positron was discovered in the cosmic rays. We learn that when energy is converted into mass, it shows up as matter and anti matter in equal parts. This is just a cartoon of a shower from a cosmic ray. These are actual tracks from my electrons and anti-electrons, aka a positrons. Before we learned how to build our own particle accelerators, this natural radiation was the only way of studying the sub-atomic world. And again this is pretty cool, but you could still say ‘you haven’t touch my reality.’ And I’ll give you one example, that ‘P’ in PET scan stands for positron. Not only we discover anti matter, we learn how to use it. We learned that when anti-matter meets with matter, they annihilate, and they emit energy. So a PET scan is a nuclear medicine imaging that by detecting these energy can show the structure and function of organs and tissues. So this is what we do. Fundamental research is what drives our reality. So we helped unravel new laws of physics, we helped to discover new particles, and ou can always say so ok, how about my reality and, you know, Can you harness this sort of high energy. That’s a typical question. Can you get all this ultra high energy. How can you improve my quality of life with this cosmic rays ?I don’t know. I guess I’m like a character in Winnie the Pooh, I’m not smart enough. In my defense, though, when Anderson discovered positrons, he was not thinking about PET scans. When Faraday discovered electromagnetic induction he was not thinking about generating electricity. When Einstein figured out General Relativity he was certainly not thinking about the GPS in your smart phones. They are all doing fundamental research. They were all trying to figure out how the universe works. So my fundamental question is how do these cosmic rays reach these ultra high energies. We will discover new laws of physics, we will find super heavy particles that we cannot possibly recreate on earth. I don’t know. But what I do know is that this acceleration mechanism is truly impressive. If we want to build a machine to accelerate protons to ultra high energies this ring, instead of 17 miles, there are clear conference on the rings for ultra high energy protons would be comparable to the orbit of Mars. So that’s something not even Hollywood can make. So that’s why for the past twenty years my reality has been driven by the hunt of the fastest particle in the universe. Thank you. (Applause)

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