One of the most prominent features in the history of the development of physics is the unification of the laws of nature into a single idea that can explain two or more things that were previously considered unrelated. Isaac Newton can be noted as a successful originator in this unification effort, where his gravitational theory can explain that the force that causes apples to fall to earth is the same as that which causes the moon to circle the earth. The incorporation of the celestial and terrestial forces into one which he calls the force of gravity proves a fantastic thing about the forces acting in nature. Three hundred years later, James Maxwell, a Scottish physicist, was also successful in combining two previously perceived phenomena: electricity and magnetism. Maxwell's electromagnetic equation shows that two distinct natural phenomena turn out to be actually derived from the same principle.
The next unification becomes one of the main agenda of physicists to be able to explain the various styles that work in nature into one single idea or one parent equation that can certainly explain everything. Albert Einstein originated a general theory of relativity that improved Newton's theory of gravity, also attempted to unify it. He tried to combine the force of gravity with the electromagnet force because both work in the same universe and move at the speed of light, so it is suspected both have the same basic thing. Until the end of his lifetime, the effort of merging these two styles failed to be done by Einstein. Einstein's efforts are unsuccessful, since the general theory of general relativity that has succeeded in explaining how the universe works and predicted in space-time based on the force of gravity cannot be combined with the electromagnet force which is also the working force in the very small universe, the atom and the sub- atom, which is based on the principle of uncertainty where the level of events can only be predicted with probability only.
The development of physics shows that there are four basic styles that work in this universe. The four basic forces are so far explained by two theories: quantum mechanics which describes the existence of three fundamental forces acting on an atomic scale; while there is one more force to work in the great universe (ie gravity). The three basic forces in this atomic scale are the electromagnetic force (which binds the electrons to the atomic nucleus and the underlying interactions between atoms), the strong core force (which causes the protons and neutrons in the nucleus are not mutually rejected) and the weak nucleus force the case of beta ray decay) has been successfully tried combined with so-called standard models. But the attempt to combine these two great theories has not worked; likewise when trying to combine one or the three basic forces of quantum mechanics with the force of gravity has never worked (as Einstein did).
This becomes an interesting challenge for physicists because to explain some natural phenomena, these four basic styles must be able to explain them appropriately. For example, in the event of the creation of the universe called the Big Bang where there is a very large energy emergence when atoms have not been formed at all; or the black hole when the mass of a very large star shrinks its volume drastically becomes very small. So far attempts to explain both events by combining the four basic forces have never been successful, one of the reasons is that there is no single theory to use.
Some physicists believe that the universe is based on a single theory rather than what is tried separately by the theory of general relativity and quantum mechanics. For this reason, physicists try to combine the four basic forces in a single theory. This is certainly a search effort in extraordinarily heavy science, considering the efforts made by Einstein was trying to combine the electromagnetic force with the force of gravity just did not bring results.
The String Theory (String Theory) is an attempt to formulate the four basic forces that are being worked on by today's various physicists. The essence of this theory is very simple, all particles in nature are composed of wavelengths of energy smaller than electrons. This string theory states that all the particles in this universe and all the forces that cause the interacting matter are made from the vibrations of that energy. The difference in the vibration energy of this strand is so unique that it causes the appearance of particles with different mass and charge eg. This theory began to be initiated in the late 1960s decade and has the development up and down. In the 1980s the challenge in string theory was the existence of an anomaly of calculations, where the equation calculations found different results (a mathematical inconsistency). Fortunately, in 1984 this was solved. The next challenge is the development of this string theory into five variations, which of course confuses the activists, how can a basic theory of the universe that attempts to combine the four basic styles can have different versions? Which version is the right one? Fortunately, in the mid-1990s these five theories could be combined into a single theory which was then called M-theory. If this theory is true then it will be helpful in explaining the events of the origin of the universe or the formation of Black Holes. Unfortunately, so far the String Theory has no confirmation that can be obtained through laboratory experimentation. Though science including physics in it is the proof of a theory through experiments that must be replicated by other parties or in the case of astronomy and geology through observation. So the status of String Theory cannot be accepted as a scientific truth. In fact, some physicists consider it a new class of philosophy, some even mention this theory potential wrong and level with science fiction only.
Some reasons why there has been no experimental evidence supporting this theory suggests that string theory physicists cannot yet fully understand this theory. The other thing is that the so-called strings of energy are very, very small (about one trillionth of an atom's size), where technologies such as accelerators and detectors are not yet able to sense them.
Different at the time of science in the last three centuries that has not been developed for example, where only by observation alone, scientists can conceptualize a theory (eg the story of the fall of apples observed by Newton and the formulation of the theory of gravity). While at the present time shows that the more advanced and sophisticated one discipline of science (in this case modern physics), then the proof of a theory through experiment should be done and that too usually hinted from the theory. Unfortunately, in the case of string theory, until now we can not do that yet.
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Reference :
https://en.wikipedia.org/wiki/Superstring_theory
https://www.britannica.com/science/physics-science
https://futurism.com/brane-science-complex-notions-of-superstring-theory/
https://whatis.techtarget.com/definition/superstring-theory-string-theory-Theory-of-Everything