# STRING THEORY ( 1 st ULTIMATE THEORY OF EVERYTHING )

As with everything, physics also have an ultimate goal. Each discovery is a step ahead towards the ultimate desire, the theory of everything. String theory is one of the earliest candidates for the theory of everything. It claims to explain the entire universe, from stars to photons, black holes to bosons, spacetime to cells and every single entity by use of one single elementary basis, the strings.

### BACKGROUND

During the twentieth century, two new fields of physics emerged. The general relativity by Albert Einstein and the Quantum Mechanics by Bohr, Schrodinger, and others. Both these theories were massive success and explained the universe quite well. General relativity explained gravity by the structure of spacetime, it said that unlike other forces gravity is caused by bending of spacetime fabric around massive objects.

On the other hand, Quantum mechanics explained each fundamental force with an associated particle. So, it linked gravity to particles known as “gravitons “.  But when they try to calculate what happens when two “gravitons” smash together, they get an infinite amount of energy packed into a small space — a sure sign that math is missing something.

These two theories explained objects at different scales. Combining them would ultimately give us the theory of everything, the eternal bliss of science. This is where String theory cames in.

### THE SCIENCE OF THE STRING THEORY

One possible solution of contradiction of Quantum mechanics and relativity, which theorists borrowed from nuclear physicists in the 1970s, is to get rid of the problematic, point-like graviton particles. Strings, and only strings, can collide and rebound cleanly without implying physically impossible infinities.

String theory changed the description of the universe by stating

All the matter and force particles are different forms of one fundamental element, a one-dimensional tiny vibrating string. They twist, turn and vibrate in a complicated way in super higher dimensional space, that from our perspective look like different particles “

So, String theory tells us that a string of a particular length, vibrating on a particular note gains the properties of photon. While same string vibrating with different frequency will become boson, quarks, and other particles.

One of the vibrational state of the string corresponds to graviton , causing the force of gravity .Thus it accounts for gravity as a vibrating string (particle ) instead of curvature of spacetime , so string theory is also called “  Theory of  Quantum Gravity “ .

String theory has addressed many questions. It has been used to solve black hole science, early universe cosmology, condensed matter physics and many more. The greatest outcome of string theory is the progress in Pure mathematics . Several mathematical phenomena, including infinity, power series and infinites diverging series has seen unprecedented progress due to the development of the string theory.

### VERSIONS OF STRING THEORY

In a given version of string theory, there is only one kind of string, which may look like a small loop or segment of ordinary string, and it can vibrate in different ways. Following are some versions:

• Bosonic String Theory: Strings vibrate in 26-dimensional hyper space. It was developed in late 1960s and incorporated only the class of particles known as bosons.
• Superstring Theory: Strings vibrate in 10-dimensional space. It accounts for all particles and fundamental forces. It uses supersymmetry to links bosons and fermions and also to model gravity.
• M String Theory: It unifies all the consistent versions of superstring theory. The strings vibrate in 11-dimensional space. It is still under the process of development. It is based on dualities and leads to 11-dimensional supergravity.

Today, String theory is a controversial and hot topic in physics world. Many still see it as a candidate for the theory of everything, others regard it only as speculations that will never be proved. Regardless of how it evolves in the future, it remains a fact that this theory has a legacy of its own. Even if it fails, it will remain as one of the biggest research programs that led to lots of advancement in mathematics, geometry and several other fields.

##### MS ASHIR
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A Physics Geek with lavishing , mind torturing research and papers on Quantum Mechanics and Space exploration .