String Theory Primer

I am not completely sure how to write this blog as I am not really an authority on the subject. I have immensely enjoyed Brian Greene’s book “The Elegant Universe” and I highly recommend it to anyone (not just those savvy in the area of advanced physics). I do feel that I can talk about it some as I do have a degree in physics and astronomy and have dealt with it some both in and out of classes. I suppose I will try and give a “primer” on what String Theory is and tries to accomplish. If this entry ends up being too long, I am sorry, I really enjoy physics and it is fairly complicated and even more complicated to explain it on a somewhat non-technical level. I will apologized now for switching tenses throughout my writing, I tend to do that a lot and I don’t really plan on editing this very much for perfect grammar – sorry!

A large majority of physicists believe that there should be an “Ultimate Theory” or “Theory of Everything (ToE).” This means that there would be a somewhat “simple” set of equations that would account for all the forces that we see in the universe. Progress in this area has been going on for many years with periods of great advancement and periods of sweeping it under the carpet. There are 5 forces that essentially hold the entire universe together: magnetic, electric, gravitational, weak and strong nuclear. As many of you are aware, the magnetic and electric forces have been successfully combined into the electromagnetic force. The four remaining forces are still waiting to be united into this ToE. The problem that arises is essentially scale. Gravity is EXTREMELY weak. For example, the gravitational attraction of two like charged particles is 10^42 times weaker than the electromagnetic repulsion. That is a HUGE difference in strength. Scale also comes into play in the physics used to describe different events. It had appeared that special relativity was incompatible with Newtonian gravity. Einstein was able to resolve the inconsistencies by showing that, as opposed to what Newton thought, gravity actually manifests itself at the speed of light and not instantaneously as previously believed. This was a great advancement because it brought Newtonian physics up to speed with the more modern experimental physics. It didn’t completely replace Newtonian physics, just modified it so it would not only describe classical physics but also relativistic physics. The next problem that arose was different in that it couldn’t be simply resolved with modification of an existing theory (like Einstein did with Newton’s gravity). General relativity is understood very well and predictions have held up in experiments but it seems to break down at the quantum level (quantum mechanics has also be very consistent with its predictions matching experiments). One thing string theory hopes to do is to resolve the incompatibilities between general relativity and quantum mechanics.

String theory essentially was born in order to describe how everything worked together, at both large and small scales and more importantly, incorporate gravity. Gravity has always been somewhat of a “black sheep” in the world of forces. It seemed like it was never really able to mesh well with any theory and any existing theory that it was added to seemed to break down.

Here is the basic idea of what a string is: every elementary particle is actually made up of a vibrating string, similar to that of a guitar or piano string. Each particle is a different note or different vibration. This helps support the merging of quantum mechanics and general relativity because string theory does not require events to occur at a single point as in particle physics.

Ok, there is MUCH more to this, I haven’t even really scratched the surface. This is already probably too long and I am kinda all over the place so I should stop now. I will hopefully get back to the subject and delve a little deeper into the elegance of string theory. I would recommend checking out PBS’ Elegant Universe page . It has a lot of Brian Greene’s stuff there from his NOVA series. Sorry if I was all over the place!

EDITOR’S NOTE: This post is from a previous blog so the original comments no longer exist.

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