What is String Theory? by Joaquin Lopez

 Please enjoy this article by a student in DMHS's "Introduction to Journalism" class!

This may seem like some sort of odd question to ask but what is string theory? I apologize if I am asking you (or any other teachers) this question again, but I am being serious this time. I have heard of it but most of the time it is glossed over as some sort of complex topic. But every time I have heard about it, I never really get an exact answer on what it is. Most of the time when I ask about what it is I see people struggling to even really give an answer despite it being an interesting topic. Due to the lack of information about what it really is, I will attempt to give a (simplified) answer to this question and cover the basics of what forms this theory.

Why was string theory made? (Introduction to important ideas)

Before we discuss what string theory is, a few things need to be made clear. String theory is a candidate for the theory of everything that tries to fully understand what gravity is, as there are four fundamental forces which are gravity, electromagnetism, the weak force which is responsible for beta decays, and the strong force that is responsible for binding quarks intro neutrons and protons. Physicists understand all of these forces except gravity. In this context “understand” should be taken loosely as physicists know what the Lagrangian is and how it describes how these forces interact with matter, and at the very least in principle physicists understand how to use Lagrangians to make defined predictions. Gravity is a force that physicists only understand partially, as it is easy to understand gravity without asking any questions on how it works on a smaller scale. Despite popular belief (although it is fine for much simpler terms) it is possible to conceptualize a way to fuse quantum mechanics into gravity without asking questions about what happens at distances lesser than Planck length. Although this may not be true for some forces, the forces that this is not true for can be included in quantum mechanics at any scale of distance. While quantum mechanical understanding of gravity does exist, a complete understanding of quantum gravity does not which leaves many questions unanswered such as what was the “big bang” or what happens at the singularity of a blackhole and what exactly goes wrong gravity at scales of distance lower than Planck length and so on. String Theory attempts to answer this question as it is a Lagrangian with only one parameter that is fixed by experiment thus making it a candidate for a possible theory of everything that could potentially explain all possible physical phenomena. While explanation may be much lower than even a dramatic simplification, in principle it is correct. 

What is string theory?

String theory in essence replaces point particles with what is called “strings,” and these strings can be either open or closed although this is dependent on what type of particle becomes replaced by the string. In string theory you replace things such as worldlines with worldsheets and also replace the Feynman Diagram with surfaces as well. There are also multiple versions of string theory although I will not detail them all. An extremely simplified explanation of string theory is that instead of point particles there are strings, and these strings vibrate at different modes, and depending on how they are vibrating, they form different particles such as electrons, quarks, photons and most importantly gravity. The problem with string theory is that it requires at the minimum of 10 dimensions to work while our universe has 4 dimensions, and getting rid of all these extra dimensions in string theory is not something that has been accomplished. This is why it was so far unable to become the theory of everything, although it is still a possible candidate for the theory of everything.