Unification of the 4 Forces, GUT, and String Theory

Author: Will Pepi

Topic: Unification of the 4 Forces, GUT, and String Theory

Everything.

Intro

In order to understand the ideas behind a grand unified theory, or a theory of everything, we first need to understand what the universe was like a fraction of a second after the Big Bang. Astrophysicists have categorized the history of the universe under the Big Bang theory into a number of different eras. The only eras covered by the scope of this blog are those that occurred less than one second after the Big Bang. There are four fundamental forces in the universe: the strong force, the electromagnetic force, the weak force, and gravity (in order from strongest to weakest). Immediately after the Big Bang, it is theorized that all these forces were essentially unified into one force. If we found a cohesive theory of the universe that reconciles all the fundamental forces (which describe both large scale phenomena and quantum physics) being unified a split second after the Big Bang, then we will have found a theory of everything (TOE). Much in the same way that electricity and magnetism were thought to be separate forces and were discovered to be unified, modern science is seeking to unify the four fundamental forces. A theory of everything would fundamentally describe the universe in a way our current theories cannot.

THE ELECTROWEAK EPOCH. N.d. Http://crestroyertheory.com, n.p.

Planck Era
The Planck era is the first time period of the universe. It is theorized to have lasted from the first moment of the universe, until 10^-43 seconds after the Big Bang. Little is known for sure about this time period but it is the only time in the universe where all four fundamental forces may have been combined. Our current model of physics breaks down when we try to apply it to the Planck era. One of the biggest gaps in our knowledge of physics is how gravity behaves at quantum scales. Perhaps by studying the Planck era and/or similar conditions, we will be able to come up with a model of physics that works at all times during the universe's history and for all size scales. Hopefully, experiments with particle super colliders will be able to simulate these early universe conditions so that we can gain more insight into the physics of the Planck era.

Lohith, Kvr. File:FOUR FUNDAMENTAL FORCES.png. N.d. Wikipedia, n.p.

GUT Era
Like the Planck era, theories about the GUT or grand unified theory era are theoretical; however, the GUT era is slightly less speculative than the Planck era. The GUT era is theorized to have began when gravity became separate from the other three fundamental forces 10^-43 seconds after the Big Bang, creating the GUT force, made up of the strong force, the electromagnetic force, and the weak force, and gravity as its own force. The GUT era ended when the strong force became separate from the electromagnetic force and the weak force, 10^-38 seconds after the Big Bang. It is thought that the strong force freezing out is what triggered inflation.

Electroweak Era
The Electroweak era is much less theoretical than the time periods closer to the Big Bang. It is thought that after inflation, about 10^-38 seconds after the Big Bang, the strong froze out to become its own distinct force, leaving gravity, strong and electroweak (made up of the electromagnetic and weak forces) forces. Inflation also occurred during the Electroweak ear, during which the universe expanded faster than the speed light. It is thought that much of the observed large scale structure of the universe is the result of quantum mechanical variations being blown up to macroscopic scale during the extremely rapid expansion experienced during inflation (pictured below). After the electroweak era, the current four fundamental forces had all separated. 

The Greatest Story Ever Told. N.d. Scienceblogs.com, n.p.

String Theory 
Much of the field of modern physics is now dedicated to finding a theoretical framework that can coherently describe all the known phenomena of the universe--in essence describe the universe with a

deeper, all-inclusive, fundamental theory or "Theory of Everything." A theory of everything should not only predict all events in the universe, it should reveal in mathematical terms, why things are the way they are. For example, through experimentation and observation, we know how much a proton weighs, but we don't really know why. A TOE would mathematically show exactly why a proton has to weigh as much as it does, and should explain and predict the nature of everything in the universe. String theory is a broad term that basically describes a theory in physics that postulates matter is made up of tiny, one dimensional strings. The theory predicts that all the elementary particles, and subsequently everything, is comprised of the same vibrating strings. Different vibrations yield different particles. This simple idea has spawned an incredibly complex theory of the universe that rules out very little in terms of possibility. For example, string theory indicates that there does not necessarily need to be four dimensions and there could very well be multiple dimensions. String theory also suggests that there are likely multiple (maybe even an infinite number) of universes. Strings theory is applicable to a wide variety of topics in physics given that it could be a theory of everything. It is still an active field in physics and it has neither been disproved nor proved that it is indeed a theory of everything; rather, physicists are continuing to, in laymen's terms, work out the details. However, it seems like a promising candidate to describe the unification of all four forces.

String Theory Could Be The Foundation Of Quantum Mechanics. N.d. Futurism.com, n.p.

Why?
Why do we care about unifying the four fundamental forces? What sort of gain are we getting from pouring billions of dollars into supercolliders in attempt to better understand what was happening during a tiny fraction of a second, 14 billion years ago? Well, there are any number of good answers to this question, but my favorite is the following story. When Nima Arkani-Hamed (leading theoretical physicist) was giving a talk about discovering the Higgs Boson particle using the Large Hadron Collider, he was asked by an economist in the crowd what the economic return is by running this massively expensive experiment; how does he justify the experiment? Nima responded, "It's a very very simple answer: I have no idea. We have no idea. When radio waves were discovered they weren't called radio waves because there were no radios. They were discovered as some sort of radiation. Basic science for BIG breakthroughs needs to occur at a level were you are not asking 'what is the economic gain?' you're asking "what do we not know?" So what is the Large Hadron Collider good for? Could be nothing other than understanding everything."

Bibliography

The Official String Theory Web Site

http://superstringtheory.com/

"Http://ljournal.ru/wp-content/uploads/2016/08/d-2016-154.pdf." (2016): n. pag. Web.

[Lecture Notes!]