Watching TV in Japan has its own advantages too. Two weeks back I happened to watch a program on String Theory, which is relatively a new theory in physics. It is the first time that I have heard of such a theory. It was an informative program and the presentation was too simple that any school kid without even having a basic understanding of gravity and relativity would be able to comprehend it fully. So I thought of presenting what I understood from that program. Please note that I am not a physicist by qualification. I performed only average (or even below average) in my physics classes in the school and college levels. So whatever I am presenting here is based on what I understood in my own capacity from the TV program which I have watched. There is every possibility that anybody who is having a basic knowledge of physics may find lot of errors in my writing. Please bear with me. The only thing which I can say confidently at this moment is that there is a theory called “String Theory” in physics. If you are interested, you will get plenty of information in the internet as well as from books regarding “String Theory”. You will not get any specific information on String Theory in this write-up. Even a proper explanation of String Theory is not given here. With this disclaimer, let me start my journey into the Universe.
What I understood from that program is that there exists theory of relativity as well as quantum mechanics, both explain the Universe, rotation of earth around sun etc. In the theory of relativity, it is assumed that earth is rotating around the sun in the form of a ball rolling over an elastic mat. When it rotates, it will form small depressions on the mat. Also, theory of relativity is based on the concept of gravity. Everything is based on gravity here. Theory of relativity is one way we can explain the Universe and the planets where gravity is the important aspect. Here things are assumed to be very smooth and without much disturbance. Theory of relativity is very calm in that respect!
Another way of explaining universe is quantum mechanics. If you want to understand quantum mechanics, we need to imagine everything in a very very small space. That means we need to imagine that the whole universe is in nano or even less than that in dimension. Then we can see lots of elementary particles and large vibration in the Universe. Here the rotation of earth around sun is not in the form of smooth wavy form as in the case of theory of relativity, but in the form of disturbances or the movement is chaotic. However, gravity has little role here. Here everything is chaotic and quantum mechanics having lots of disturbances associated with it. It is like looking at human skin using a high resolution microscope where you can see lots of bumps, hills and valleys!
In quantum mechanics, there are mainly three forces:
1. Strong nuclear forces. This is the kind of force exists in atoms which holds neutrons and protons in the nucleus.
2. Weak nuclear forces which are responsible for radioactive frequencies etc.
3. Electromagnetic forces.
Now the problem is that so far, there is no theory which connects these three forces in the quantum mechanics with the gravity force in the theory of relativity. Both theories can explain Universe in their own way, but there is no connection between the two theories. If we can connect these three forces with the force of gravity, which will be the absolute theory which will explain the whole Universe in a single theory.
Now let me copy’n’paste from the website on String Theory (plenty of websites on String Theory are available in the internet). I have copied the following write-up from this site:
http://superstringtheory.com/basics/basic3.htmlGeneral relativity has yielded a wealth of insight into the Universe, the orbits of planets, the evolution of stars and galaxies, the Big Bang and recently observed black holes and gravitational lenses. However, the theory itself only works when we pretend that the Universe is purely classical and that quantum mechanics is not needed in our description of Nature.
Relativistic quantum field theory has worked very well to describe the observed behaviors and properties of elementary particles. But the theory itself only works well when gravity is so weak that it can be neglected. Particle theory only works when we pretend gravity doesn't exist.
So we can say that, as of now, there is no good quantum theory on gravity!
Here comes the String Theory!
String theory is believed to connect the two theories-that is theory of relativity and quantum mechanics. In fact is believed to connect the forces associated with quantum mechanics (that is, strong and weak nuclear forces and electromagnetic force) with forces associated with theory of relativity (that is, force of gravity).
I don’t know how to explain String Theory. But what I understood is that if we apply this theory to the Universe, what it is doing is that it will reduce the chaotic nature in the quantum mechanics to such an extent that it can be fit into the theory of relativity. This means that the rotation of earth around the Universe may not be as smooth as explained in theory of relativity, at the same time, it may not be as chaotic or disturbed as explained by quantum mechanics. A sort of compromise, we can say.
Let us consider the three forces in the quantum mechanics in one side and the force of gravity in the other side. Now we want to connect these two. For this we can use a string in the guitar. Tie the three forces in one side with the force in the opposite side using the string. This is string theory!
In order to explain String Theory, I shall again copy’n’paste from websites.
Think of a guitar string that has been tuned by stretching the string under tension across the guitar. Depending on how the string is plucked and how much tension is in the string, different musical notes will be created by the string. These musical notes could be said to be excitation modes of that guitar string under tension. In a similar manner, in string theory, the elementary particles we observe in particle accelerators could be thought of as the "musical notes" or excitation modes of elementary strings. In string theory, as in guitar playing, the string must be stretched under tension in order to become excited. However, the strings in string theory are floating in space-time; they aren't tied down to a guitar. Nonetheless, they have tension. The string tension in string theory is denoted by the quantity 1/(2 p a'), where a' is pronounced "alpha prime” and is equal to the square of the string length scale. If string theory is to be a theory of quantum gravity, then the average size of a string should be somewhere near the length scale of quantum gravity, called the Planck length, which is about 10-33 centimeters, or about a millionth of a billionth of a billionth of a billionth of a centimeter. Unfortunately, this means that strings are way too small to see by current or expected particle physics technology (or financing!!) and so string theorists must devise more clever methods to test the theory than just looking for little strings in particle experiments.What I understood from the TV program is that as of now there are at least five different String Theories! This cannot be true because there should be only one theory to explain the Universe. Also, so far, there is no experimental technique to explain the String Theory. So many theoretical physicists are not ready to accept the String Theory.
I got some very interesting and simple websites on String Theory.
1.
http://superstringtheory.com/index.html Claimed to be the official website on String Theory.
2.
http://theory.tifr.res.in/~mukhi/Physics/string.html This site explains string theory in a simple and non-technical way. It is written by an Indian working in Tata Institute of Fundamental Research (TIFR), Mumbai.
3.
http://theory.tifr.res.in/~mukhi/Physics/string2.html This is again by the same scientist in TIFR, a long non-technical description.
4.
http://tena4.vub.ac.be/beyondstringtheory/ This also seems to be a good site on String Theory.
So friends, there is something called String Theory and it is interesting. At least, after watching that TV program, I got some information on quantum physics and theory of relativity (please don’t ask me to explain!). In India, we need such programs in popular TV channels so that both students and adults would be equally benefited.
