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

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.

95 Comments

  • Kurzgesagt – In a Nutshell says:

    There's brand new stuff in the Kurzgesagt Merch Shop. Check it out here: shop.kurzgesagt.org

  • TheOrange with. 100 subs says:

    Carry the 1

  • the annointed one says:

    The world is not a problem to solve for socialagists and scientists. The world is a living mystery. Our births our deaths our being in the moment these are mysteries they are door ways opening on to unimaginable vistas of self exploration, empowerment and hope for the human Enterprise.

  • Noah Jimenez says:

    Wait… what’s the Information Paradox!?

    Kurzgesagt: breathes heavily

  • SkyMark 791 says:

    Vibration

  • Jeff Xors says:

    “Say my name”

    Only Breaking Bad fans will understand

  • andreas carsten says:

    red mal deutsch

  • Simplicitas says:

    This is a poor and very dated video

  • dolphintattoogirl says:

    In other words, string theory is more of a hypothesis than an actual theory.

  • WackoMcGoose says:

    "Depending on the readings we get, we might just disprove string theory. That would make my day…"
    two minutes later
    "THIS IS A BAD EXPERIMENT! WE ARE BAD PEOPLE! WHY DID WE USHER FORTH THE GREEN APOCALYPSE?!"

  • Jasper Klee says:

    this is beautiful

  • Oneandonly Escaton says:

    If wave length increses the waves should be further apart. I think my scentence is self evident. More wave length = lower pitch. Btw i dont know shit about anything else in the vid, just thought the graphic looked weird getting shorter. Maybe its wave amplitude thats increasing, again idk just an observation.

  • Param P says:

    You lost me at abouttttt: 0:01

  • krishna birla says:

    At 2:09 you say "more wavelengths means more energy" where I think you mean "more frequency" or "less wavelength". Amazing video. ❤

  • DUBBED BY AI says:

    In the background on the board The infinity sum of Srinivas Ramanujan

  • Piyush V says:

    2:05 how can "more wavelength mean more energy? "Isn't energy inversely proportional to wavelength and directly proportional to frequency?

  • Adwait Upadhyay says:

    They made a mistake at 2:07
    They said "More wavelengths means more Energy" but in reality smaller wavelengths means more Energy since Energy is inversely proportional to wavelength and directly proportional to frequency.

  • Samuel Poulston says:

    If quantum physics is showing that math as we know it doesn't work there, then maybe math as we know it doesn't work there. There's nothing scientific about making reality fit around a pre-existing model.

  • Jeevanandham Ayyavu says:

    At the end we still don't know the true nature of reality.
    Nothing is the true nature of reality.

  • mae Fuentes says:

    Lacerta Files led me to this..

  • C.L Mckenzie says:

    It's just a little annoying when the video uses words like "stories" and "inventing" particle. No one invented the particles. They really do exist. If the graviton is real – then its real. The language just delegitimizes the science.

  • Grant Ostol says:

    Why ami imaginig sheldon?

  • Sweta srivastava says:

    I got the most new theory… Please read this……time is the intersection of the 3 dimensions…so if we have a motion of the Galaxy … traveling in space would be traveling in time…or in simple words we can say that the space is only in 3 dimensions the point of intersection is the time we live in…..so if just stop the motion of Galaxy we will be able to live for infinite amount of time….and if we retraces the path we will just go back in time..

  • K Rel says:

    I think this video is all sorts of stupid because it tries to postulate that strong theory doesnt work because 10 dimensions dont exist. I postulate they do indeed exist its just we cant directly interact with them using our senses because we are only 3 dimensional beings. However we can interact with the other dimensions possibly through deep meditation as the human mind can go through something called the gateway process and gain access to higher dimensions through our consciousness. This may also bring about horrific and jarring conclusions ie there are higher dimensional lifeforms that are more intelligent and powerful than us beyond comprehension and description and they may even be limiting our power and understanding of the universe by attacking and manipulating our consciousness.

  • Hlraeth says:

    I laughed so hard at that pun in 5:28 LMAO

  • Grant Sehrt says:

    But another thing more complex than a point is a 3 dimensional shape or a 2d line

  • Ace McShred says:

    It seems to me that if you have to create 10 spacial dimensions to make the math work, its probably a waste of time. But then again I'm a garbage man so what the hell do I know

  • Steven Xiao says:

    3:35 I am gonna guess that number is 20 quadrillionth, someone correct me if I am wrong.

  • Josh The mango says:

    1:42 so if I look at a girls ass, I’m touching it? That’s a win in my book

  • Preethi Param says:

    It's true reality of nature

  • ppprX says:

    'Until one day, hopefully, we do know.'
    Lol, no. Nature is not a mathematical question with one right answer. Who searches the meaning, has found it. Because the meaning is the search for the meaning.

  • ComHelper says:

    "Theory of Everything"

    i'm starting to get bad memories from geometry dash

  • IamagutTrue says:

    Just smash elementary partical together to divide them

  • H S says:

    bullshit from the beginning.

  • vishnu kant says:

    Wow i am watching 10d photo on 3d screen. At 5:47

  • Rishabh Malhotra says:

    You are wrong at a point..you said higher the wavelength, higher the energy but that should be frequency

  • Monarch Varma says:

    Seeing is touching ? It's not like the eye is intentionally sucking in the rays that hit the duck. More precisely, making the rays hit the duck and direct those rays towards the eye whenver we look at the duck, basically just controlling a set of rays TO HIT THE DUCK AND HIT THE EYE EVERTIME LOOKING AT THE DUCK. That's seems highly misinterpreted. SO I STATE THAT Seeing is not touching. Seeing is BEING TOUCHED (WITH SAME PASSIVE PROPERTY). Just like being touched when in someone's way, if eyes are aligned in the way of rays that scatter after hitting the duck, then the eye flips the input then gets compiled and output is ironically goes further inside, into the brain. So, it's not the duck that get hits onlly when we look at it. It already being constantly hit even when we don't look at it. To See it, we align our eyes in the way of scattering rays such that the eye can get enough input to process the image . NOW THE SEEING WONT GIVE THE Particle momentum. It's already in a continuous hits and in fullll momentum. If anything, seeing only reduces the high momentum that the particle already is in, with the constant hits from the rays.

  • Tom Fischer says:

    Why actually does no model of the universe include consciousness even though it is obviously there ?? Maybe our consciousness can be described with these dimensions that everybody wants to get rid of. Not very verifiable though … Or does somebody have an idea how to experimentally test that theory ??

  • A Cat is fine too says:

    What if they cut the strings of string theory. Does the theory fall flat? 😂

  • Sangiboy Khongsai says:

    no Sheldon Cooper?

    btw video about string theory begibs at 5:00

  • Melia N says:

    Ever heard of the electric universe?

  • Maharshi Bilgi says:

    2:08 more wavelength means more energy. Wtf E=hf!!!!!!! Any physics students???????

  • Gakills' s says:

    Wow… you deserve so much more subscribers. if I had a teacher like this I think I would have been einstein already.

  • sinnerslight says:

    I don't claim to be smart. As a matter of fact. I know I'm not. But sometimes we as humans are so prideful that when we can't figure something out we either condemn it or change it to fit whatever we beleieve. With that in mind. I always wondered. What if OUR math is wrong. You can say 2+2=4 as a fact. Because that's how we developed math. But what if it doesn't. And that's why gravity destroys our math. But we're too set that we are right with our physics and math calculations. Or maybe, just like with string theory, 2+2=4 is false AND fact. Idk…I'm sure to all u smart asses I sound pretty dumb. But maybe we're looking at the problem the wrong way. That's all. Food for thought.

  • Srikar P B says:

    If you feel you are stupid, think about Flat Earthers.

  • Brodie Tikitiki says:

    Our universe is a particle to superior life and the particles we see are life. Aliens are bigger or smaller, maybe we need a size gun lol

  • Jake Kelley says:

    Gravity isn’t a product of large quantities of mass it coincides with electromagnetic frequency and they work together

  • JZ DABZ says:

    No one:
    Philosophers in Greece: 1:22

  • Shrinidhi M S says:

    5:31 String Theory comes with a lot of strings.
    Wait…What!

  • Yan Shyla says:

    What is the atom in the start of the video on English?
    (sorry my periodic table is on Latvian)

  • Vheen Audrey Soriano says:

    Came here coz of sheldon

  • blues says:

    string theory is fun and interesting but it would never make for a good research subject. the number of prerequisites you need to have to even study the maths behind this is ridiculous

  • walid sadi says:

    6:20 there are also only 2 genders no matter how you feel about it!

  • Stag Dragon says:

    I love everything about 1:25 – 1:47 Sound effect of a particle entering your eyeball, a bird getting pissed off because you hit it with an electromagnetic wave. It's just great.

  • Sávio Gabriel says:

    O que mais me surpreende em tudo isso é a quantidade de legendas disponíveis para o vídeo kkkkkkkkkkkkkkk

  • Chris Cross says:

    Not the Heisenberg uncertainty principle. Im sure im just repeating at this point tho. Im sure you guys know tho after all everything is meticulously researched and fact checked😜👌

  • PolitischTourette says:

    I edited this comment because most people don't seem to find the first comment interesting

  • PolitischTourette says:

    This is a Video where I have to go back to some earlier point because my brain wanders off "Homer Simpson- Style"

  • MSH24 says:

    Why do u want to make your life complicated??

  • ThaSmashor says:

    Nobody:
    The universe when humanity get it wrong: I don't know how, but you used the wrong formula and got the right answer.

  • Something You Said says:

    I have never taken reality as seriously as I do right now. More than ever I'm recognizing it for the nightmare-equivalent that it is.

  • Something You Said says:

    If you don't take reality seriously, reality will take you.



    Seriously.

  • Thomas Sahatra says:

    2+2 is 4 minus 1 that's 3

  • Wul Vershon says:

    I didnt understand shit

  • AndrewUnruh says:

    My understanding of the Heisenberg Uncertainty Principal is different. It is not that you cannot measure both the position and momentum of a particle with absolute precision because photons perturb the measurement, instead, I believe it comes from the Schrodinger equation itself. In support of my point, I would say that if it had to do with photons perturbing the measurement, then the energy of the photons used to make the measurement would have to be incorporated into the equation, right? I am not saying that photons do not perturb a measurement, I am saying I don't think that is what the uncertainty principal is about.

  • Roger ZHOU says:

    I have studied cosmic string for a year I started in year 3

  • Judgement Ravi says:

    Tats it interesting to hear👌👈

  • Helmi Halim says:

    2:19 spider man into the spider verse

  • I Apologize for this Comment says:

    Thanks, I still don't get it

  • Moin Khan says:

    I was never explained the Heisenberg uncertainty principle in this manner!

  • tadmiti com says:

    5:27 😂😂😂😂😂

  • Pixelers says:

    I wish i could explain things like this to my friends

  • Shady 18 says:

    It all came out of nothing and it goes into nothing. You cannot understand or grasp it. You can just experience it. You cannot make knowledge out of it. You can just disslove in it. If you're happy , neither time nor space exists. If you're angry everything suffocates. A day for us is and year for an insect. We don't even know a single atom in its entirety. The best solution is dissolution.

  • Mauricio Ruiz says:

    You literally slaughtered knowledge with this one. My brain is thanking from its own heart. THANK YOU!

  • Sum Guy says:

    What a fucking dummy I've become, watching a show about this instead of reading an article.

  • Кирило Хацько says:

    Mathematically, 2+2 can be also 0 and 1
    But only this 3 answers (0, 1, 4) are correct, if from "2+2" we assume, that "+" is adding and "2" is "second" == "next after 1"

  • Кирило Хацько says:

    What about other theories about combining relativity and gravity?

  • DSXmachine says:

    Our view of gravity is ridiculous.

  • Akio says:

    Baited from the german title lmao

  • Dai Remmei says:

    Ba dum tiss

  • Bee Waifu says:

    Wait, so the atomic string theory is related to that retarded dimensional one? Grand…

  • dread true says:

    Very good video explaining what the heck are the String Theories.
    For those who want to know lolol

  • Tahir Raj Bhasin says:

    Opened more questions than it answered

  • Aspern Park says:

    I want to know everything. I want to know why & how. But I will never be able to.

  • Axel Shark's Theoretical Discovery says:

    Get ready for a real theory! I plan with september this year.

  • Sid Wangkhem says:

    3:06 well the mass of an electron can be taken as zero (1 by 1867th of that of hydrogen atom or 9.11 x 10^-31kg) but I don't understand why you took it's charge as zero. Isn't it suppose to be one unit charge 1.6 x 10^19 C ???

  • DarkVortex42 says:

    So The Lion King predicted all this in its music the circle of life? ~^

  • Como Assim, meu jovem?! says:

    I am in love with ur videos. Thx!

  • engin yildirim says:

    Speaking for those lazy asshole scientists: get yor ass off and learn that reality than teach me. I cant waste my whole life waiting for ya. You cant do a fuck, can u? U guys just wanna explore space to have sex with aliens

  • Tran Bao says:

    7:30 Doctor who anyone?

  • Lumos & Nox says:

    I thought this was ted Ed until it said that it was Kurzgesagt

  • Angelo San says:

    Black holes are not holes!!!! stop spreading misinformation !

  • Poggers M8 says:

    Surely, if the wavelength, the visible light, is bigger than the particles displayed in the video, the light wouldn’t have a problem touching the particles due to its vast size, the particles just wouldn’t be as clear due to half the light missing the particles, and half of the light beaming upon and bouncing off the particles??

  • steven pearce says:

    the universes
    hi user steven

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