What is the smallest unit that makes up our vast world? This is the question that human beings have always wanted to figure out. As early as a few hundred years BC, the ancient Greek philosopher Democritus put forward the atomism from the perspective of philosophical speculation, everything is composed of atoms and the void, and the atom is the smallest particle that makes up matter. In the 18th century, the British physicist Dalton formally proposed atomism in the scientific sense.
After the unremitting efforts of several generations of scientists, we know that atoms are far from the most basic and small particles that make up everything. Atoms are made up of nuclei and electrons. The nucleus is made up of protons and neutrons. Protons and neutrons are made up of more basic quarks. If so pounded, what is the composition of the quark? Sorry, at the current level of technology, quarks have "come to an end". For example, quarks, electrons, gluons, etc. these are collectively referred to as elementary particles. They can be roughly divided into three categories, namely hadrons, leptons, and propagators.
As research continues, scientists have found dozens of elementary particles, and it seems that this set of theories that describe the smallest units that make up all things is not so "basic". Is there a more concise, fundamental theory of the composition of matter? There is indeed such a beautiful theory - "string theory".
In fact, as early as 1968, scientists created the prototype of string theory when they were looking for a mathematical formula that described strong force. The basic idea of this theory is that the basic unit of nature is not a point-like particle such as electrons, photons, and quarks, but a very small linear "string" in one dimension, which has two structures: open and closed strings. The different vibrations and movements of the strings produce a variety of different elementary particles, and energy and matter can be transformed into each other. In the 1990s, Edward Wiighton proposed the M-theory, in which he argued that our universe has 11 dimensions in addition to length, width, and height, and that it is only the other dimensions that are severely curled, and the vibration of strings in these dimensions produces everything in our world.
To explain the cause of all things with such an outrageous theory is to imagine how the world would view string theory—ignore it. When quantum mechanics, which described the microscopic world, first emerged, bohr led the Copenhagen School to fight with Einstein for it. However, the academic community is simply too lazy to take care of string theory. Until one day, the fans of string theory used closed strings to derive gravitons. At this time, the academic community can be fried, and everyone has changed their attitude and begun to look up to string theory. Why did gravitons make string theory suddenly become hot, and it is also known as the "ultimate unified theory"?
As the name suggests, this elementary particle is the particle that propagates gravity. We know that there are four powerful fundamental forces in the universe, namely gravity, electromagnetism, strong force, and weak force. The realization of "force" requires the exchange of particles. For example, two experimenters, they are standing on the ice in skates, A throws a small iron ball to B, B catches the iron ball, feels the force, and slides back a short distance. This little iron ball is the propagator we mentioned above.
Electromagnetic forces exchange photons to achieve transmission. The power of the microscopic world is achieved by exchanging gluons between quarks. The weak force is transmitted by the w and z bosons. What about gravity? "Gravitons", of course. These three words blurted out are difficult to prove, and after decades of searching, it is difficult for the academic community to find the traces of gravitons in the large hadron collider or in the cosmic rays.
Today, scientists can use existing quantum theories to unify strong, weak and electromagnetic forces very well, but gravity cannot be included. But in string theory, gravitons are successfully derived, and the four fundamental forces are unified. It also has an important significance, that is, it can perfectly chimerize the microscopic field and the macroscopic world. Although, Einstein's general theory of relativity describes the universe well, interpreting gravity. But if you go deep into the microscopic quantum world, it is powerless. Quantum mechanics has successfully explained the strange behavior of microscopic particles, but it is not suitable for the macroscopic world.
String theory starts from a more basic and fundamental point of view, interpreting everything in the universe with the vibration of one-dimensional strings, and integrating macroscopic and microscopic. Physicists' centuries-long dream of unification is finally on track to come true, and a single "formula" is enough to describe the laws of the universe. Our universe turned out to be a magnificent symphony played by "strings" in space!
Written at the end, although string theory is the hottest unified theory at the moment. But at present, it is only a gorgeous mathematical technique, stacked up in the air. It is estimated that in order to knock out the "string" in the collider, at least the diameter of the collider must be expanded to the entire solar system...
(Well, string theory we will talk about here today, the editor is shallow, the ability is limited, the article must have many deficiencies, let's take a look, the right to be a pastime. ）
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