One of the goals of Physics is to find a single theory that unites all of the four forces of nature. These are; electromagnetism, gravity, and the strong and weak nuclear forces. The first two are familiar. Electromagnetism is the force that holds a fridge magnet to a refrigerator while gravity is trying to pull it off towards the earth.
The strong nuclear force is responsible for holding the central part of atoms (their nuclei) together, while the weak nuclear force is involved in the decay of these nuclei.
In the attempt to tie all the four forces together a lot of interesting ideas and new theories have been proposed. One of the most promising of these new theories is string theory. In attempting to unite gravity with the three other forces, string theory requires us to change the way we view the universe.
According to the theory all particles are actually tiny vibrating strings and each type of vibration corresponds to a different particle. The different particles are like the different notes that can be played by bowing a violin string. However, the strings of string theory almost certainly would not look like violin strings.
String theory also requires us to accept the existence of extra dimensions in the universe. We are familiar with the four usual dimensions: up-down, forwards-backwards, left-right and time, but string theory requires seven more dimensions!
A universe of eleven dimensions seems strange to us but many physicists think these extra dimensions are possible and are looking for ways to detect them.
The attempt to unify the 4 forces of nature is one of the most exciting areas of physics and I hope to be around if this is successful, whether it is string theory or some other candidate that is successful. On the other hand there is the possibility that no single, theory exists that can describe all the forces of nature in a neat and tidy way as we would like.
Whatever the outcome, scientists from all over the world will continue working together to discover what could be the ultimate theory of everything.