What is string theory? There are two worlds we live in, the world of the large, the world we can see, which is familiar, calm, and predictable. And there is the world of the small, the world we can’t see, the quantum world, which bizarre, chaotic, and unpredictable.
The large is described by Einstein’s equations of relativity, and the small is described by the equations of quantum mechanics. These two parts of nature are seemingly utterly incompatible in when it comes to the equations of physics.
The small is ruled by 3 forces – the strong nuclear force, the weak force, and electromagnetism. The large is ruled by gravity. Gravity is not like the other forces, and nobody has been able to figure out how it is related to the other forces. String theory attempts to do just that. And if it can, it would unite the small and large worlds of our universe into one set of equations, and would explain all particles and forces in the universe. This could be the theory of everything.
String theory dispenses with the idea that the tiniest particles in nature are points, rather, string theory hypothesizes that at the smallest scales, nature is made of tiny vibrating bits of energy in the shape of filaments or strings. According to string theory all the elementary particles in the standard model are not points, but rather vibrating strings. Different vibrations of a string create the different particles, like different vibrations of piano strings create different notes.
So according to ST, for example, one vibration may result in an electron, another may result in an Up quark. In fact the unique vibrations of these strings determine the mass, electric charge, and spin of all elementary particles. And it so happens that in one of its vibrations, a particle that has the properties of a graviton emerges from its mathematics. The graviton is a theoretical quantum particle that would carry the force of gravity. And this is the key to uniting the two worlds of the small quantum world and the large celestial world.Thus String theory can model quantum gravity, similar to the way loop quantum gravity also models quantum gravity.
Ok, so if we can model gravity at the quantum scale, then our work should be done. We should have a theory of everything, right?
You might say, well, all we have to do is look inside these elementary particles, and if we find a string, we’re done. String theory would be confirmed. The problem is that the math predicts these strings to be extremely small. If an atom was the size of the earth, one string would be the size of a 2 inch piece of yarn. To detect something this small, we would need a particle accelerator the size of the milky way galaxy. So detecting them physically is out of the question.
There is another imaginary leap you have to make, that I didn’t tell you about earlier, and that is that these strings are not 3 dimensional, but rather 1 dimensional – so they have a size in only in 1 dimension. They are really little more than bits of energy. And in order to make the various particles emerge from its mathematics, these strings need to vibrate in 9 spacial dimensions. So where are the other 6 dimensions? String theorists will tell you that these dimensions, are so small that we cannot perceive them.
The mathematics of String theory makes some strange cosmological predictions, which may explain the nature of existence. Just like vibrations through a French horn vs a trumpet are different because of the difference in the twists and turns of the instrument, the vibrational patterns of strings are also different depending on the shape of the extra dimensions.
We happen to be living in a universe where the shapes of the extra dimensions are such that the universe that we observe happens to exist. And here is a 2d representation of what our 6D universe would look like. It is called a calabi-yau manifold. It so happens, that if the shape of the extra dimensions are slightly different, a different universe can emerge. These would be universes with completely different properties than our.
More on Calabi-Yau manifold here:
So this is how String theory implicates that we may be living in a multiverse, where we just happen to be on a kind of membrane of a multitude of membranes which may contain other universes. This implies that we exist because if you have a near infinite number of universes with lots of different properties, then a universe like ours where gravity can form planets and complex molecules can form life, is bound to exist. And if we are living in a membrane, then the mathematics shows that a collision with another membrane would have caused energy on a huge scale – which would look a lot like the big bang, which is of course what we observe.
Watch video for concluding remarks..
