String theory: Can It reveal the actual nature of the universe?

 

Imagine you went to the library of your school or college and started reading a book written on substance and molecules. Eventually you came o know that every thing we looked up close like wonderous landscapes in the dust, zoos of bizarre creature, complex protein robots etc, all are made from certain structure of molecules made up of countless even smaller things: Atoms. From atoms we get elementary particles. The more you are going in the book, your curiosity is pampering and a question arise in your mind,” Are elementary particles are the smallest things in the universe?” and there comes the string theory to save your day.

 

What is String Theory?

So, what is string theory? Before that we need to know what, an elementary particle is. Elementary particles are substances that are not made of other elements or stuff. 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. But the particles are very very small that the electromagnetic waves are way to big to touch them. Visible Light just passes over them. So how can we solve this problem? One way is that we can create electromagnetic waves with much smaller wavelengths so that the wavelength touches the particles and our eyes will capture the reflection wave of the particles and we’ll be able to see it. 

But there comes another problem, smaller the wavelengths, the more energy it means. So, when we touch a particle with a wave that has a lot of energy, it alters 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? 

Physicists came up with a new story: A mathematical fiction. The story of the point particle. Scientist that they 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 0.0000000000002 %. 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 every day. 

 

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 or a string. Thus, String theory was born.

 The Theory of Everything?

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 math 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.

 

References:

1. https://www.britannica.com/science/string-theory

2.  https://www.livescience.com/65033-what-is-string-theory.html

3. https://www.britannica.com/science/uncertainty-principle

Maidul Islam is a struggling student as well as a failed coder. He is currently studying Computer Science and Engineering at Brac University. Send him your sympathies at maidul.islam1@g.bracu.ac.bd  T__T