Physics Project Online - Kendriya Vidyalaya Pattom

String theory - an introduction
“String theory” is one of those theories, which, if proved, would mark a milestone in the world of Physics. Here I will try to make a brief explanation about what is “string theory”, look at some of the scientific terms related to it, look at the brief history of development of “string theory” and finally, we will have a very simple and brief explanation about “string theory” which would be very helpful even to the beginners who don’t know much about the “string theory”.

The 4 fundamental forces united into one?!!!

We all know that there are 4 fundamental forces existing in nature, namely the most widely known gravitational force, electromagnetic force, strong nuclear force and weak nuclear force. We also know that one of the main thrusts of physics is unification of forces. Similarly, “string theory” is the theory, which tries to tie all these 4 fundamental forces into one.

Brief details of string theory

According to the “string theory”, all the particles are tiny vibrating strings and each type of vibrations also correspond to a different particle, that is the electrons and quarks within an atom are not 0(zero)-dimensional objects but rather 1-dimensional (length) oscillating lines or strings which vibrate, giving the particles their flavor, charge, mass and spin. Although the strings of “string theory” do not look like the strings of a violin, however the different particles are like the different notes that can be played by bowing a violin string. The following diagram represents matter magnified upto the string level:-

Levels of magnification:

1. Macroscopic level - Matter

2. Molecular level

3. Atomic level - Protons, neutrons, and electrons

4. Subatomic level - Electron

5. Subatomic level - Quarks

6. String level

Existence of extra dimensions
Also, another fascinating fact about “string theory” is that it requires us to accept the existence of 7 extra dimensions in the universe, excluding the 4 dimensions that we are familiar with, namely up-down (height), forwards-backwards (length), left-right (width) and time. Of course, a universe of 11 dimensions may seem very very strange, but even now, many physicists are thinking that these extra dimensions are possible and are going on looking for newer and newer ways to detect them.

History of string theory

5 major string theories were developed, each having different mathematical structures and each one could best describe different physical circumstances. All the 5 theories seemed to be correct but the main difference between these 5 theories was the number of dimensions in which the strings developed and their characteristics were also different. Finally, it was Edward Witten from the Institute for Advanced Study, who, in the early 1980s, considered that all the 5 previous major versions of the “string theory” might be representing the same phenomena from different perspectives. Then, resulted his M theory, which was a proposed unification of all previous superstring theories, asserting that strings are really 1-dimensional slices of a 2-dimensional membrane vibrating in an 11-dimensional space. But according to Tim Betwell, a research engineer working in Hong Kong, there is the possibility that not a single theory exists which can describe all the 4 fundamental forces in a neat and tidy manner, in the way that we like. I hope that you would be at least benefited a little from my simple presentation on the vast topic of “string theory”.

Simplest explanation of string theory
Here is a simple procedure of an experiment, which was posted by Mark about the amount of energy present in the strings. This experiment may not be of much use to the masters of string theory and although I am not totally satisfied with it, but I am sure that it will be definitely a boon to the beginners.

AIM
To determine the amount of energy present in strings of String Theory.

MATERIALS REQUIRED

A string of Christmas tree lights
A tree
A bag

PROCEDURE
Step one : We should decorate a tree with the Christmas tree lights.

Step two : Now we should undecorate the tree.

Step three : Then we should put the lights in the bag.

Step four : We, then, have to put the bag in our loft.

Step five : Then we should wait for one year.

Step six : We should then retrieve the bag.

Step seven : Finally, we should untangle the string of lights.

OBSERVATIONS
We will observe that a simple inoffensive thing such as a string with bulbs on it, contains staggering amounts of energy.

If we had put 2 strings instead of 1, then they would have had double the amount of the energy than that of the previous case.

INFERENCE
Similarly, the universe is like that bag in the loft containing more Christmas tree lights than we can imagine, i.e. infinite number of bulbs. So, we can understand what a tremendous amount of energy the strings have!!!!

String Theory-why are we going behind that ?!!!
1.For instance, String theory proclaims that the observed particle properties—that is, the different masses and all other properties of both the fundamental particles and the force particles associated with the four forces of nature (the strong and weak nuclear forces, electromagnetic force, and gravitational force)—are a reflection of the various ways in which a string can vibrate. Just as the strings on a violin/piano have resonant frequencies at which they prefer to vibrate—the same holds true for the loops of string theory. But rather than producing musical notes, each of the preferred mass and force charges are determined by the patterns of string's oscillation. The electron is a string vibrating one way; the up-quark is a string vibrating another way, and so on.

2.First of all, String Theory will explain why our universe is the way it is? If some of the fundamental laws of universe were even slightly different, our world would be a strange, lethal and a completely different place. Instead, it seems as if the whole universe is designed to make life possible. It is only the String Theory which can explain the reason.

3.Physicists believe that there was only one force just after the big bang (the cause behind the formation of universe) and as the universe cooled, it split into the four fundamental forces that we now observe. String theory is the most popular idea for explaining why these four forces exist in nature.

4.Another publicized aspect of string theory is its need for extra "tiny" dimensions of space. But these extra dimensions may not be necessary at all – at least, not if a 40-year-old idea called "twistor theory" has something to do with it.
5.String theory can explain that billions of billions of billions of universes exist.

6.String theory, definitely provides a single explanatory framework capable of encompassing all forces and all matter.

I am not an expert in String Theory and not even a person who can even define it. So, let us understand it from Brian Greene, who is an expert in this matter and presents his views in a clear, logical, systematic and humourous way.