String Theory - A Novice Take
Kurzesagt’s thumbnail for their video on string theory because they are better at making thumbnails than me.
So I watched a video on string theory, and obviously that makes me an expert on this complicated scientific field. Here goes!
To understand string theory, you first need to understand what the Quantum Standard Model is. Basically, current quantum physics is trying to unravel the smallest parts of the universe. Though protons and neutrons and electrons are widely known as the building blocks of atoms and all matter, physicists have to wonder what builds these as well.
Standard Model
The standard model outlines 18 particles, which is supposed to make up all matter on earth. We have the standard quarks, which are quite popular, you might have heard them before. Up and down quarks make up neutrons and protons in their respective combinations. As well, two other versions of each quark also exist, though slightly heavier and less stable.
Leptons are based around the ever-popular electrons, and their non-charged counterpart, the neutrino. There are also six of these like the quarks. Finally, there are the bosons, which are interactions between particles, embodied in particles. This is the most interesting section, because it is usually unintuitive that forces can be particles. Among these are particles for the weak force, strong force, and the electromagnetic force.
The chart showing all the particles in the standard model
Practically, this model has treated physicists well until the big boy Einstein came along.
Einstein’s Theory of General Relativity
Einstein’s revolutionary idea about gravity was unexpectedly very impactful to the field of quantum particle theory. He stated that gravity was not a Newtonian force, but rather all mass curved space time in a way that a constant velocity would seem like acceleration to an inertial observer. Basically, the earth does not pull you towards it, but the standard trajectory is to go towards the earth! (if this made no sense, watch this cool Veritasium video about it).
The consequence of this theory, is that gravity now became an interaction of particles! Particles interact based on their mass to curve space time, and so gravity should also be a particle in the standard model. Tragically, the standard model does not work with this extra particle because of some unfortunate maths.
How Does String Theory Work?
Finally we get to string theory. After the realization that the standard model was wrong, many people tried to fix it with a new theory. Among these was the most popular one (in respect to media), String Theory! String theory states that the particles, such as up quarks, down quarks and electrons, are all fundamentally strings!
That’s right, I said a string. Obviously, strings are just an analogy, but it is a good one for this theory. Quantum strings, like normal strings, have the ability to vibrate. Vibrations can have different, whole number frequencies. Think about a rope, like one at a gym, where one end is tied to a wall and the other is in your hand. You can create waves on this rope by moving the free end up and down. There are many different waves you can create. One is by going slow, where there is only ever one hump. Then, you could oscillate faster, and create two humps, one above and one below, that switch back and forth. Then so on and so forth. These are the frequencies of the rope (string).
Now, imagine these but small. As well, there is a possibility for the string to tie back to itself, creating a circle. This way, the string can have many different orientations (linear or circular, different frequencies). This makes up the different particles!
An example of what strings may look like
It turns out, the strings can mimic the standard model, but it also includes the graviton! That’s a success, but it is too good to be true. Unfortunately, string theory hosts some major issues. Most of the issues are resolved in superstring theory (no, I do not know what it adds). However, there is still one major issue that prevails, that superstring theory does not exist in our universe of 3 spacial and 1 temporal dimension. In fact it requires 10 dimensions! (better than string theory that requires 26)
Ew dimensions
Now what I was thinking when I heard this was: haha dumb physicists don’t know that we live in a 4 dimensional space-time world! But who am I to doubt physicists?
Introducing the idea of (drumrolll….) Compactification!! This method is how 10 spacial dimensions could fit in our 3 spacial dimensions. The common analogy is a straw. Imagine a vertical straw. Now the surface of a straw is two dimensional, and if extended to infinity, it would almost be like a normal 2D cartesian plane. However, the x axis connects to itself like a circle. An object on the surface of our straw would have the ability to move up and down and to the left and the right. Let now craft an observer who is far enough away that the width of the straw is insignificant, miraculously making the straw basically transparent. An object moving on this plane would now seem to only be moving up and down, as the movement on the y-axis is compacted so that it is not observable! The object moving on two dimensions now seems to be moving in one dimension, we have lost a dimension!
The idea is that the strings in string theory may be moving around in compacted dimensions which are completely unobservable by us. This reconciles the initially ridiculous idea that the mathematic basis of particles are in 10 dimensions.
So Everything’s a String?
Unfortunately, string theory still has a lot to go before it can replace the standard model. In the end, all theories in physics are just theories, and there is currently no way to definitely know what exactly everything is made of. Maybe they are strings, or maybe something else entirely.
If some topics I presented did not make sense, I encourage you to check out the wikipedia pages (where it will totally make more sense) or do some digging yourself. As well, if anyone knows more than me and I made a fatal mistake, please let me know!
