The Theory of General Relativity creates the Space-time fabric. Which if you look at the above picture it shows us a sheet that acts like the surface of a trampoline. When you stand in the middle of the trampoline then the fabric will bow and will create a circular path around you. Therefore, if we take the sun and place it on this space-time fabric, the surrounding planets then will then follow this circular path long the fabric.
Quantum Mechanics explain some of the smallest thing in the universe. This tells us that there may be parallel universes in which every possibility is played out. This area of modern physics is related as a game of chance. Therefore, if we rolled dice on a table every combination that we get is played out in a parallel reality.
Four Fundamental Forces:
One of the 4 fundamental forces we all experience at every point of everyday is gravity. Gravity is the weakest force because it is stretched over a long distance. Gravity is the force that holds us to the floor and what keeps the moon spinning around the Earth. Electromagnetism is another force that we experience quite often, its most commonly known as light. Electromagnetism deals mainly with electric fields and magnetic fields. Strong nuclear force is mainly known for the creation of the Atom bomb. This force holds the protons and the neutrons extremely close together. Weak nuclear force is primarily known as radiation. Constant exposure to radiation can lead to health problems.
The movement to unify General Relativity with Quantum Mechanics was brought up when the math for both theory's wouldn't work for each other. Albert Einstein worked on trying to find a way to unify these theories all the way to his death bed. Some believe that String theory may be the answer to unifying these two theories.
String theory is suggested to be the theory of everything. The theory tells us that everything is made up of extremely small strings. These Strings are so small that they are thought to be 10^-35. You are unable to see these strings but the math for this theory suggests that these do exist and are the makeup of everything around us. This theory tells us that there are many different universes that have different realities.