So, you are walking down the street, enjoying your ice cream and suddenly your friend tells you that everything in this world is made up of strings!! You will probably brush aside his argument at that point of time, but it still makes you think. Can we actually be made up of strings? On a broader perspective, we live in a complex universe and we have wondered time and again – what is the universe made up of? When would it end? Where did we come from?
The Standard Model of Particle Physics
Standard Model describes the fundamental building blocks out of which the world is made, and the forces of interaction between these blocks. There are 12 basic particles, six of which are quarks - up, down, charm, strange, bottom and top. So, a proton, for instance, is made of two up quarks and one down quark. The other six are leptons which include the electron, its two heavier siblings, the muon and the tauon, and three neutrinos.
The four fundamental forces in the universe are gravity, electromagnetism, and the weak and strong nuclear forces. Each of these is produced by fundamental particles that act as carriers of the force. The most familiar of these is the photon, a particle of light, which is the mediator of electromagnetic forces. What does that mean? Well it means that, for instance, a magnet attracts a nail because both objects exchange photons. The graviton is the particle associated with gravity. The strong force is carried by eight particles known as gluons. Finally, the weak force is transmitted by three particles, the W+, the W- , and the Z.
Standard Model describes the behavior of all of these particles and forces in an impeccable manner. Though there exists a notable exception: gravity. The gravitational force has proven to be very difficult to describe due to technical constraints. Here is when string theory comes into the picture which attempts to provide a unified and complete theory of structure of the universe – ‘The Theory of Everything’.
The String Theory
So, what exactly is string theory you must be wondering. The string theory suggests that all the fundamental particles are nothing but different manifestations of a single object – a string. Sounds very unconvincing right? Imagine a guitar. Depending upon the tension in the guitar strings and the way they are plucked, different musical notes can be created by the same set of strings. Similarly, consider an electron. It is just a point with no internal structure. According to string theory, when observed under a very powerful microscope, we would notice that it is not really a point – it is a loop of string and the length of the string is to the order of 10-33cms.!! And this string could oscillate in different ways and it does that so fast, that it would be seen as a point from a distance. It may oscillate in a particular direction to produce electron and in some other direction to produce photon or a quark. It is postulated that these strings can vibrate in 10 or 11 dimensions, the dimensions that we cannot see at present.
The theory smoothens out the inconsistencies between quantum theory for tiny mysterious universe of fundamental particles and theory of relativity for big things. It has the potential to explain the theory of multiverses or parallel universes, the Big Bang Theory and supernatural experiences too!! There has not been an experimental proof of the string theory, the whole picture is still missing but with time and technical advances, we might as well be able to justify many unexplained phenomenon and build time machines based on string theory!!