String Theory Explained – What is The True Nature of Reality?
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String Theory Explained – What is The True Nature of Reality?


What is the true nature of the universe? To answer this question, humans come up with stories to describe the world. We test our stories and learn what to keep and what to throw away. But the more we learn, the more complicated and weird our stories become. Some of them so much so, that it’s really hard to know what they’re actually about. Like string theory. A famous, controversial and often misunderstood story, about the nature of everything. Why did we come up with it and is it correct? Or just an idea we should chuck out? To understand the true nature of reality, we looked at things up close and were amazed. Wonderous landscapes in the dust, zoos of bizarre creatures, complex protein robots. All of them made from structures of molecules made up of countless even smaller things: Atoms. We thought they were the final layer of reality, until we smashed them together really hard and discovered things that can’t be divided anymore: Elementary particles. But now, we had a problem: They are so small that we could no longer look at them. Think about it: what is seeing? To see something, we need light, an electromagnetic wave. This wave hits the surface of the thing and gets reflected back from it into your eye. The wave carries information from the object that your brain uses to create an image. So you can’t see something without somehow interacting with it. Seeing is touching, an active process, not a passive one. This is not a problem with most things. But particles are But particles are very, But particles are very, very, But particles are very, very, very small. So small that the electromagnetic waves we used to see are too big to touch them. Visible light just passes over them. We can try to solve this by creating electromagnetic waves with more and much smaller wavelengths. But more wavelengths, means more energy. So, when we touch a particle with a wave that has a lot of energy it alters it. By looking at a particle, we change it. So, we can’t measure elementary particles precisely. This fact is so important that it has a name: The Heisenberg uncertainty principle. The basis of all quantum physics. So, what does a particle look like then? What is its nature? We don’t know. If we look really hard, we can see a blurry sphere of influence, but not the particles themselves. We just know they exist. But if that’s the case, how can we do any science with them? We did what humans do and invented a new story: A mathematical fiction. The story of the point particle. We decided that we would pretend that a particle is a point in space. Any electron is a point with a certain electric charge and a certain mass. All indistinguishable from each other. This way physicists could define them and calculate all of their interactions. This is called Quantum Field Theory, and solved a lot of problems. All of the standard model of particle physics is built on it and it predicts lots of things very well. Some quantum properties of the electron for example have been tested and are accurate up to 0, 0,00 0,0000 0,000000 0,00000000 0,0000000000 0,000000000000 0,0000000000002 %. So, while particles are not really points, by treating them as if they were, we get a pretty good picture of the universe. Not only did this idea advance science, it also led to a lot of real-world technology we use everyday. But there’s a huge problem: Gravity. In quantum mechanics, all physical forces are carried by certain particles. But according to Einstein’s general relativity, gravity is not a force like the others in the universe. If the universe is a play, particles are the actors, but gravity is the stage. To put it simply, gravity is a theory of geometry. The geometry of space-time itself. Of distances, which we need to describe with absolute precision. But since there is no way to precisely measure things in the quantum world, our story of gravity doesn’t work with our story of quantum physics. When physicists tried to add gravity to the story by inventing a new particle, their mathematics broke down and this is a big problem. If we could marry gravity to quantum physics and the standard model, we would have the theory of everything. So, very smart people came up with a new story. They asked: What is more complex than a point? A line- A line or a string. String theory was born. What makes string theory so elegant, is that it describes many different elementary particles as different modes of vibration of the string. Just like a violin string vibrating differently can give you a lot of different notes, a string can give you different particles Most importantly, this includes gravity. String theory promised to unify all fundamental forces of the universe. This caused enormous excitement and hype. String theory quickly graduated to a possible theory of everything Unfortunately, string theory comes with a lot of strings attached. Much of the maths involving a consistent string theory does not work in our universe with its three spatial and one temporal dimensions. String theory requires ten dimensions to work out. So, string theorists did calculations in model universes. And then try to get rid of the six additional dimensions and describe our own universe But so far, nobody has succeeded and no prediction of string theory has been proven in an experiment So, string theory did not reveal the nature of our universe. One could argue that in this case string theory really isn’t useful at all. Science is all about experiments and predictions. If we can’t do those, why should we bother with strings? It really is all about how we use it. Physics is based on maths. Two plus two makes four. This is true no matter how you feel about it. And the maths in string theory does work out. That’s why string theory is still useful. Imagine that you want to build a cruise ship, but you only have blueprints for a small rowing boat. There are plenty of differences: the engine, the engine, the materials, the engine, the materials, the scale. But both things are fundamentally the same: Things that float. So, by studying the rowing boat blueprints, you might still learn something about how to build a cruise ship eventually. With string theory, we can try to answer some questions about quantum gravity that have been puzzling physicists for decades. Such as how black holes work or the information paradox. String theory may point us in the right direction. When used in this spirit, string theory becomes a precious tool for theoretical physicists and help them discover new aspects of the quantum world and some beautiful mathematics. So, maybe the story of string theory is not the theory of everything. But just like the story of the point particle, it may be an extremely useful story. We don’t yet know what the true nature of reality is but we’ll keep coming up with stories to try and find out. Until one day, Until one day, hopefully Until one day, hopefully, we do know. This video was supported by the Swiss National Science Foundation and realized with the scientific advice of Alessandro Sfondrini.

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92 thoughts on “String Theory Explained – What is The True Nature of Reality?

  1. Perhaps we first need to invent a new language before we can describe the whole universe? I mean, if our current mathematical models don't jive, maybe we need new mathematical languages? Everything from the human perspective is relative. There's always a point of reference for anything we perceive.

    Perhaps that's why we chose to define space/time in relative terms. We perceive the universe in 3, or 4 dimensions, however you choose to look at it. Space/time is perceivable to us in relative terms, so it is describable in relative terms. Gravity and mass too are perceivable and describable in relative terms.

    What do you do if there are more than 3 or 4 dimensions and there's no way to perceive anything outside of those limits? What do you do if there IS a way to perceive them in some way? Is it even possible to create a language to describe such things with so little information? Will we EVER be able to describe the universe in such detail?

    Admiring math is like admiring poetry, it has aesthetic value, it is art by definition. Science is something more though. It has to be able to predict and describe and be testable. If we can't either bring two theories together or eliminate one or both to replace it with a new one, we may still have something useful, but we won't have a theory of everything. We won't truly understand how these things are connected. We need to be able to relate them to each other in some way.

    The funny thing about math is you can pretty much make it do what you want, you simply need to define the rules. Einstein's breakthrough came from not manipulating math, but using only empirical data and ruminating on the possibilities of what that data meant. The math came after. String theorists are doing art, not science. Use Empirical data to figure it out first THEN do the mathematics, you might even have to create a language to do that….

  2. Percussion and String Theory! Heisenberg and the Quantum World are Amazing. The Penguin trying to Play Zelda on SNES is neat too. The turtle is a spin off from Discworld.

  3. We cant imagine 4th dimension.and string theory has 10 dimension.

  4. So bassically we made some kind of quasi religious belief/doctrine to explain the universe and everything? Who said sceience and religion can’t marry?

  5. Great video, just one thing. "True nature of reality", please stop using this sentence. It is a very dangerous one and it has doomed thinkers to run in circles until Wittgenstein finally solved the problem writing his Tractatus. When you say "true nature of reality" you mean just "that makes sense to us humans". How can the true nature of reality be so limited? It will never be contained into our human rules (math & language) and it will never be understable for us. Sad yes, maybe a bit too much philosophical, but it's key. Hawking was wrong, you cannot underestimate philosophy when thinking so big.

  6. String theory is nothing but a foolish answer to explain the theory of everything. Its like when you are under attack in a chess game, for example your bishop moves away from a danger square and it becomes safe but the bigger problem is that you left a gap for your king to be attacked. What Im saying basically is that we need to look at every theory so far, look at the bigger picture, the whole chessboard, not only one piece. What the person behind this theory deosn't realise is that he solved the problem between quantum physics and theory of relativity, but he introduced a bigger problem where he has to change every theory we found so far. There is a solution but we need to open our field of view wider. Look at the picture that is bigger than the big picture.

  7. At 2:07 you said with more wavelength more energy… It should be more frequency results in more energy. E = hc/wavelength

  8. If gravity could be unified with the other forces then what would that mean for us? As imperfect as our understanding of physics is many technologies and sciences have been developed from what little we know. So if we could enlarge our understanding by unifying gravity what exactly can we develop from that breakthrough? What machine, medicine, or chemistry could be possible if the unified field theory was complete?

  9. This video was somewhat poorly done, because it left out some very fundamental pieces of string theory, which led to an incorrect explanation.

    Of the 10 dimensions of space, 9 of them are considered to be sub-dimensions, of the larger one known as "The Bulk." In the bulk, theoretical "branes" exist and on each brain, different types of universes, each with unique physics could exist. It is for this reason, that string theory cannot simply explain our universe. In order for the math in string theory to work, the multiverse would need to exist, thus the showing of more than 3 dimensions of space, which would not explain our universe as the end all, be all of everything.

  10. Hi!! I just wanted to say that I loved watching this video. Oh, I also wanted to ask that since you've done a video on string theory, could you guys do one on loop quantum gravity?? Besides that question just good job overall and i hope you guys keep up the good work👍

  11. Holy fuck my brain hurts just watching this…how do these fucking nerds do this for a living? Like wtf…why would anyone wanna do shit like these? Just get a regular jobs u nerd losers.

  12. Wow! Like einsten…bhor …rutherford…NASA…gravity…space..string…quantum…i guess i have to update my ouija board with these info….

  13. Why should gravity be defined as a force? Isn't gravity the bending of space time by mass and not exactly a force?

  14. Perhaps we're trying to look at and study something that we are actually apart of? How do you see something when you're inside of it?

  15. When the day comes where Scientist have finally solved this mystery – we will finally have scientific proof of the existence of God.. Then they'll spend the next hundred years trying to disprove what they themselves have already proven.

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