YouTube Deep Summary

If you’re going back to school, bring kurzgesagt with you! Students save 10% on our Back to School Collection – only until August 15 on the kurzgesagt shop. You might be unkillable, impossible to delete  out of existence ideas about physics, quantum immortality, is  true. To test this idea, we will put a nuclear bomb in your living room. But more on that  later. This is real science happening around one of the most successful theories of physics. To understand why, we need to tell you a story. The story of the smallest parts in the universe, atoms and fundamental particles. With everyday objects things intuitively  make sense – if you kick a marble ten times with the same force and at the same  angle, it always lands in the same spot. But if you kick an electron ten times exactly the same way, it shows up in different places. On the most fundamental  level of reality, randomness is the rule. The story that solves this is called quantum  mechanics. Simplified it goes something like this: A particle like an electron is not like a tiny  marble but like a shapeshifter – a diffuse thing we call a wave, that ebbs and flows. But to make  it much weirder: It’s not a wave of matter or energy, but a wave of probability – an immaterial  essence that has values between 0% and 100%. What does this even mean? Quantum mechanics doesn't really  tell us much about the electron. It only tells us how this entity that  we call an electron behaves on average. Say you shoot an electron gun at your  apartment. You shoot it 100 times – 80 times the electron shows up in your living  room, and 20 times in your kitchen. So the probability wave of our electron is 80%  in the living room and 20% in the kitchen. What is deeply annoying is that this story of probability waves works insanely well in reality. It's not just some brainchild that only works on paper. Scientists have tested it in countless  experiments and it works every single time. It explains how a lot of real things  work, from information passing through microchips to the atoms fusing in the center of  stars. And yet how can this story make sense? All of our other scientific stories give us a mental picture of the things they are describing – a sphere of iron at the center of  earth, an elastic fabric of space. But a wave of probability? What’s that even supposed to look like? Quantum mechanics doesn’t tell us  anything about the electron itself – what it looks like, how it moves, or how it tastes. But if our story doesn’t describe the electrons  themselves, what does it describe and how does it potentially make you immortal? What Is the Quantum Story Really About? Scientists have been debating this for a  century. They’ve come up with tons of ideas we can’t cover here, but there are two popular  schools of thought. We’ll call them linguists and literary critics. They are screaming and arguing over what the quantum story really means. The position of the linguists is “shut up and  calculate”. They basically claim that quantum mechanics is not a story about reality, but  just a kind of grammar for the theoretical language of the universe. With this language  we can predict experiments. Nothing else. If there is no story, there is no point in asking what the story says about the electron. Whether electrons are tiny marbles or  clouds, waves of negative charge or Detective Pikachu is missing the point. Quantum mechanics  doesn’t enable you to visualize any electrons. All you can do is to run experiments.  And physics is all about experiments, not about creating mental pictures for us.  So shut up, stop imagining fairy tales, and just use the probability wave to calculate  things. Follow the grammar, ignore the plot. “Nooooo!” scream the literary critics: Read  between the lines, there’s a hidden meaning here! They are “many-worldians” and they  are convinced that quantum mechanics is a story about reality. And they want to interpret the story. The many-worlds interpretation of quantum mechanics is not the same as the multiverse by the way, which is a whole different can of worms,  but we’ll get to that another time. The many-worldians think that the universe  is an infinitely complex quantum state, where all physically possible outcomes  coexist simultaneously. If the probability wave of your electron is split 80% to 20%  between your living room and the kitchen, that means that the electron is split in  a similar way. That there are 5 versions of the electron – 4 of them are going to  the living room, and 1 to the kitchen. But it isn’t just the electron that  splits. You are observing the electron, so there are five versions of you, too! Four of them see the electron in  the living room, and one in the kitchen. Each of these different versions of you and the electron are equally real, equally true. And all of them exist at this moment, in your house. But they can’t communicate or interact in any way, so they are totally  invisible to each other. Which means that, whoever “you” are right now, you  are just one of your versions, experiencing just one thing – either seeing the  electron in the living room, or in the kitchen. Many-worlds means that all physically possible  worlds are coexisting right here, right now, but independently of each other, like the  branches of a tree. And there are a lot of them. Every possible quantum process  means there are other possible worlds. A radioactive atom decays? Another world exists  where it didn’t. A cosmic ray hits one of your cells? Another world exists where the ray just passed through. Each second, bazillions upon bazillions of new worlds exist on top of each other. “Stop it!”, shout the linguists. “If these  worlds can’t interact with each other, we can't check whether they exist! This is  not science. So please shut up and calculate…” Wait! There is a way to find out. But to do it, you’ll have to die a few hundred times.  And maybe prove that you are immortal! The Ultimate Experiment All we need are two electron detectors  connected to a nuclear bomb in your living room. If the detector in your living room  is activated the nuke explodes. If the one in the kitchen is activated you are safe.  Now sit on the nuke and have your brave assistant shoot the electron gun. There are  two ways this can go. There is a 20% chance the electron lands in the kitchen and  you survive, and an 80% chance you die. Ok, let’s shoot! Beep. Oh, lucky you! The electron landed  in the kitchen. Let’s try once more: Beep. And once again: Beep. And another 100 times! Beep, Beep, Beep, Beep, Beep, Beep, Beep… If there is only one universe, you’ll die fairly soon. Sooner rather than later the electron will trigger  the nuke and you’ll be instantly vaporized. But if the many worlds interpretation is true,  then every time your assistant shoots the gun, there are five versions of you and four  instantly die. Only one of your versions is alive and there’s only one thing  you can experience – your survival. It doesn’t matter how many times you try. From  your perspective, you will survive every time. At first it will seem like luck. But at some  point your “luck” will become near-impossible. In a universe with just one reality,  your odds of surviving 100 times in a row are about 1 in ten duovigintillion  – a 1 followed by 70 zeroes. So if you did the experiment 100 times and you  are still here, the universe just whispered its deepest secret to you. Yes, you killed  hundreds of versions of yourself. But you now know for sure that the many worlds are true.  Because you are still here experiencing things. And that you are kind of immortal! Okay, well, all that might be a bit  overwhelming - let’s break it down again. The Cosmic Secret If every possible quantum process  always happens in some branch, then this doesn’t only mean that  there are almost, but not quite, infinite versions of you – but there  is always a “you” that gets insanely lucky. A tumor starts, but a cosmic ray kills it before  it spreads. A bolt of lightning strikes at you, but a quantum fluke makes it miss  by a meter. A washing machine falls from a roof, but all its atoms  quantum-tunnel through your body. No matter how extremely high the  likelihood is that you will die, there may always be a branch in which you survive. So should you start wingsuit-flying today?  Well, not so fast. For every version of you that survives, bazillions don’t. And all those versions  of you are just as real as you are right now, watching this video. So if you care about the  current version of yourself, you should care just as much about all the versions still waiting  to be and their loved ones. In other words – if you see a washing machine falling, better move  away and save as many of your versions as you can. The more universes exist with you in them the  better, your existence makes the universe richer. And there is another good reason to move. While the many-worlds interpretation of quantum mechanics feels beautiful and elegant, that doesn’t make it true. We don’t know if  it’s true and so far no literary critic sat on a nuke to risk being wrong. If the “shut  up and calculate” people are right, there is just one world. Just one version of you. And if  the washing machine hits you, you are done for. But wouldn’t this be nice to know? If the many worlds idea is true,  then no matter how unlucky you get, you will always know that somewhere, you are lucky. Quantum mechanics is an amazing tool to explore  different realities. But what about this reality? Ground News, the sponsor of this video,  can help you navigate our media universe, where every news outlet has their  own perspective on the world. In a nutshell, Ground News is a website and  app designed to make reading the news easier and more data-driven. Every day, they  collect articles from around the world and break each story down visually. You see  reporting bias, reliability and ownership; all backed by three independent  media monitoring organizations. Take this story about a new concept for a quantum  computer. Right away you can see that over 90 news outlets reported on it. Then, you can see where  these outlets lean politically and how reliable they generally are - you can even compare  headlines to see how these potential biases might affect framing. Some media outlets frame  it as a major leap forward for IBM as a business, and highlight the commercial potential for  quantum computing. Others focus more on the science itself, and use precise language  to emphasize the technical challenges that were overcome. This way you get to  see how headlines alone can affect your perception and decide for yourself if  this finding is the future or just a fad. If you’d like to give them a try, go to  ground.news/KIN, or scan the QR code on the screen. Using this link saves  you 40% off an unlimited access subscription, and directly supports our channel. We  think the people at Ground News do a really important job - if you can never  know all quantum versions of yourself, better make sure this version  has the full view of the horizon. New school year, new goals: The kurzgesagt shop  has everything you need to turn your workspace into a hub of inspiration – from study posters  like the Periodic Table or World Map to epic art that will spark your curiosity. Plus, cosmic  desk essentials to remind you of the immense beauty of the universe (and your next deadline). Students save 10% on our Back to School Collection with code STUDENTBIRB10 until August 15. Step 1: study. Step 2: conquer the universe.