General relativity and quatum mechanics are the 2 main current theories (that you can discover throughout this website). They provide accurate explaination of our universe on different scale. While particles, atoms and molecules are governed by the rules of quantum mechanics ; general relativity explains the way the universe behaves large scales (like the solar sytem but may not be accurate in the extremly large (group of galaxies)).
Why this grand unification?
As said before general relativity and quantum mechanics are very good at explaining repectively atoms or large group of bodies but does not performwell together.-------scale on which everything breaks down
What are the main theories?
Where concretly
String theory in 5 concepts:
String theory predict that particles are made of tiny vibrating strings (and of branes: membranes of energy)
The main objective of string theory is to provide a simple explanation of the universe while reconciliating general relativity with quantum mechanics
String theory unifies all the forces of the universe (the strong and weak nuclear forces, electromagnetism, and gravity)
String theory predicts a new symmetry: supersymmetry that pair up each particles with a superpartner (bosons and fermions would actually be linked)
In order for string theory to mathematically make sense, new dimensions wrapped up in a tiny portion of the universe around strings that we can not see nor experience in any way have to exist.
