Today, the scientific picture of the world is formed in such a way that our universe is governed by two sets of laws - general relativity, which explains the wonderful work of gravity, and quantum mechanics, which describes the other three interactions of the universe (strong nuclear, weak nuclear and electromagnetism). You can take these laws and apply them to things on a large scale - planets, galaxies, and then to the smallest scales - protons and neutrons. But why did nature make two separate sets of laws for the universe?
Superstring theory is an attempt to answer two questions: Is there a way to combine general relativity and quantum mechanics to create a "theory of everything"? What does it all consist of?
Superstring theory
We used to think that the building blocks of life were atoms, the smallest components of matter. But then we hit the atoms and found elementary particles, so small that we can't even see them without changing in a certain way. To see something, we need the light first to bounce off the object and hit our eyes, making up the picture. Light consists of electromagnetic waves that freely pass through elementary particles. We can make these waves denser, add energy to them so that they hit the particles and we can see them, but as soon as something hits the particle, it changes, so we cannot see it in its original state. We have no idea what elementary particles look like. Like dark energy, dark matter, we cannot observe these phenomena directly, but we have reason to believethat they exist.
We regard these particles as points in space, although in reality they are not. For all its flaws, this method - the quantum mechanics idea that forces are carried by particles - gives us a pretty good idea of the universe and leads to breakthroughs like quantum solvents and magnetic levitation trains. General relativity itself has also stood a good test of time, explaining neutron stars and Mercury's orbital anomalies, predicting black holes and curving light. But the equations of general relativity, unfortunately, stop working in the center of the black hole and on the eve of the Big Bang. The problem is that it is impossible to bring them together, because gravity is associated with the geometry of space and time, when distances are measured accurately, and in the quantum world there is no way to measure anything.
When scientists tried to invent a new particle that would marry gravity with quantum mechanics, their mathematics simply failed.
In a sense, I had to go back to the blackboard. Therefore, scientists have suggested that the smallest components of the universe are not dots, but strings. Different vibrations of strings create different elementary particles like quarks. The vibrating strings could make up all matter and all four forces in the universe - including gravity.
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Higher dimensions
Superstring theory has a problem. It won't work if we assume that there are only three spatial dimensions and one temporal dimension in which we live. String theory requires that you play at least ten dimensions.
When GR was first conceived, gravity distorted space and time to describe this force. Therefore, if someone wanted to describe another force, such as electromagnetism, he would need to add a new dimension. Scientists wrote equations describing the curves and defects of the universe with an extra dimension, and obtained the original equation of electromagnetism. An amazing discovery.
The extra dimensions of string theory can help us explain why the numbers in our universe are so calibrated that they allow everything to exist. For example, why is the speed of light 299,792,458 meters per second? They also try to answer the question about gravity - why is this force so weak? It is the weakest of the four fundamental interactions: 1040 times weaker than the electromagnetic force. It will be enough to simply bend over and lift the book off the floor to resist it. In theory, this is because gravity seeps into higher dimensions. Gravity is made up of closed loop strands that allow it to leave our dimension, as opposed to open strands, which are better grounded.
Why can't we see all these dimensions?
Because they exist on such a small level that they are invisible to us and defy detection. They are compact, equipped in such a way that they reproduce the physics of our world, folding into interesting Calabi-Yau shapes. Different forms of Calabi Yau allow for different string vibrations and very different universes.
We can even test alleged multiple universes. Since we assume that gravity seeps into higher dimensions, there should be less time after the collision of two particles than before the collision. But even under the most favorable conditions, testing something like this would be incredibly difficult, elusive.
String theory calculations are done in simulated universes with 10 or 11 dimensions where mathematics works. Scientists then try to erase the extra dimensions, but so far no one has succeeded in describing our universe or devising an experiment to prove a theory. However, this does not mean that we have no applications for string theory.
A mathematical tool being developed as part of string theory research helps us understand parts of our universe. We can use it to better explain the information paradox, quantum gravity, and some problems in pure mathematics. Some scientists use the theory for their calculations in particle physics or when observing exotic states of matter.
String theory may not be a theory of everything, but at least it is a theory of something.
Ilya Khel