String theory is a theory that tries to explain everything about the physical nature of our universe. I am not a string theorist, nor do I know anyone who is, but I found a website that is written simply and clearly explains string theory, and I've pulled several paragraphs from it:

"Strings are all around you. Your clothes are made of strings woven into cloth. Spider webs are string. To physicists, who study energy and matter, a string is anything much longer than it is wide. The cables that hold up suspension bridges are strings even though they are six inches thick. Some people collect string and wind it in a ball. No one knows why. A scientist would even call your DNA a string, though it curls up and those curls curl up and so on. Your DNA stretched out like a string would be a few meters long. To a mathematician a string has no width, only length. Scientists are beginning to believe that absolutely everything, from stars to cotton candy, may be made of string, very tiny mathematician´s string. This is string theory.

String theory is very weird, more than you can imagine. It involves higher dimensions and other universes. Vibrating strings make up everything. Everything is chunky and fuzzy when you look at it close enough. You can still hear and see the Big Bang that started the universe. Black holes are hairy. Is dark energy making you lose weight? Is dark chocolate matter making you gain weight? Instead of using the dog-ate-my-homework excuse, try this one. "I left it in the eighth dimension."

String theory is the first theory of physics that tries to explain everything. What does it mean to explain everything? We would know how the universe began and where it is going. A theory of everything would explain everything we feel, see, or measure. We would understand all the forces and all types of matter. We would know what is most basic and how everything else is composed of these basic parts. Could the universe have been different? Are there other universes? A theory of everything should answer these questions. Every big scientific discovery changes how we think about our purpose and ourselves. String theory is the biggest, most exciting change that ever happened in science.

[According to string theory], everything and every force is the result of vibrations of strings. Strings vibrate in more than the four dimensions of spacetime [up-down, forward-backward, left-right, time]. There are also seven tightly curled up dimensions. We may never be able to see these dimensions, unlike the four dimensions of spacetime. The shape of these dimensions sets the properties of the forces and particles. It also determines the laws of physics of the universe. String theory allows multiple universes.

Particles and forces are bound to branes, higher dimensional objects. The only exception is gravity´s graviton that moves between branes. Multiple universes can be very close but in different branes and not be detectable except by extremely weak gravitational effects.

Back to our very first question, do strings hold the world together? Most physicists would say yes. String theory does have problems, but it is still under construction. A theory of everything is a gigantic challenge. String theory makes many predictions. We just cannot accelerate particles to high enough energy to check them. Most important is that string theory pulls together all of physics into a beautiful consistent whole. String explains many things we know, like black holes, quantum gravity, elementary particles, quantum mechanics, relativity, the unification of forces, and the structure of the universe. It also requires things we may never be able to prove, like the seven extra dimensions and unlimited choices of universes. It is a theory of everything but it is just being discovered. That leaves lots of room for heated debate.

Is there a multiverse? Most physicists would say probably not. The big hope is that we will find an arrow saying this is our universe and the shape of our curly dimensions.

If string holds the universe together, then everything, energy, forces, and matter, is made from string. Strings vibrating in different spaces, at different frequencies, and interacting cause all the amazing things in our universe. Strings are always vibrating. The whole universe is always singing. You are part of the universe. You also are singing, in every little bit of you. Take time to listen to the music, the music of the spheres. It is the music between your ears.

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