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String theory is a mathematical model that attempts to find a common explanation for the four main forces observed in nature: gravity, electromagnetic force, strong nuclear force and weak nuclear force. String theory proposes that the electrons and quarks in an atom are one-dimensional oscillating lines or strings not 0-dimensional objects. Unlike Classical, physics that defines the universe as being made of small particles that are static and unchanging, String theory posits that the particle is a string or line vibrating in diverse ways to form the four different forces. String theory dismisses the common scientific thinking that matter is made up of very small particles that we cannot observe and determine their shape and upholds the idea that the small particles are shaped as tiny loops of string (Holt). These tiny loops move fast back and forth in different and diverse ways to form different types of matter.
The theory owes a lot of its origin to the work of Albert Einstein. It originally came up in the 1960s and 1970s as a theory of hadrons- referring to subatomic particles (for instance the proton and neutron), that feel the strong interaction. In the 1960s, two scientists (Geoffrey Chew and Steven Frauschi) established that mesons were responsible for families that were called Regge trajectories. These families had masses that were later understood by the scientists Leonard Susskind Yoichiro Nambu and H. Bech Nielsen as the relationships arising from rotating strings. Geoffrey Chew proposed coming up with a theory that took into account the interactions of the trajectories. The proposed theory had no presumption that the trajectories had any fundamental particles, but held that they used self-consistency conditions to construct their interactions. Self-consistency conditions were based on the S-matrix approach, which was developed in 1940s by Werner Heisenberg. This was a means of coming up with a theory that had a bias on the local ideas of space and time. Heinsenberg viewed such a theory as breaking away at the nuclear scale (Susskind 403). Other names of important mention in the development of the string theory include Ferdinando Gliozzi, David Olive, John Schwarz, Daniel Friedan, Tom Banks, Cumrun Vafa and most recently (1997) Juan Maldecenona.
String theory can be elaborated using an action principle. This involves using the Nambu-Goto action and the Polyakov action, which are descriptions of the movement of strings through space and time. When there are no external interactions, string dynamics use a combination of tension and kinetic energy to produce oscillations. The theory’s spectrum is that quantum mechanics of strings make the oscillations to adopt discrete vibration modes. On distance scales that are larger than the radius of the string, every oscillation made conducts itself as a different particle species, having mass, spin and charge established by the dynamics of the string. Split or recombined strings correspond to the emission and absorption of particles, activities that result to particle interactions. A point-like particle's motion can be shown by sketching a graph of the particle’s position against time. The picture that is depicted is the worldline (history) of the particle expressed in space-time.
An important characteristic of the theory is its ability to predict extra dimensions. The classic string theory has no fixed criterion for the number of dimensions. However so as to come up with a consistent quantum theory, the string theory has to live in the space-time of the “critical dimension”. Thus, the bosonic string should have 26 space-time dimensions, and the superstring should have 10. This is important to enable the disappearance of the conformal anomaly (as described in the conformal field theory).
String theory is a good way of describing how some things work. This is especially true given that scientists cannot use one theory to prove everything, or give answers to every question that can be imagined. The theory differs from other theories as it can aid scientists to give explanations to all sorts of questions possible. This has led to many scientists to exhibit enthusiasm towards the ideas forwarded by the theory. Just as Albert Einstein dreamt of, the string theory could in future be the theory of “everything”.
The theory asserts that there are two ideas that can predict the identical physical observations of the whole world. One of this is "as large as we think the universe is”, that is approximately “the 74 billion light years circumference predicted in Weeks' model. The other is much smaller than the Planck Length” (Polchinski). These two mathematical expressions effectively explain what human beings see in the world.
Different versions of string theory exist. There is the superstring theory that proposes 10 or 11 dimensions. The Bosonic string theory proposes 26 dimensions. The latter theory holds gravity as the central force. It maintains that four of the 10 dimensions are visible to human eyes. These other dimensions hint at visible forces. The string theory is noted for not judging the other theories in physics as right or wrong. It is also credited with coming up with lots of new ideas like the ones used in the mathematics of Calabi-Yau spaces, folding and knots.
On the other hand, string theory has many issues of controversy. Many versions of the theory exist, and surprisingly, none of the versions is accurate. The versions solely depend on good guesses. The proponents of this theory justify this shortfall by arguing that development of the theory is o There is also the problem of the mathematical laws used in string theory. These laws can result to many different possible solutions. The proponents of string theory normally solve the problem through settling for the results that match their observations and holding that with time it will be established why the other results were not good. Critics point out that the truthfulness of the theory cannot be established by only using the bits that work, without any reason for leaving those which do not (Polchinski). This discrepancy has rendered the theory of little use, given mathematical laws should be used to foretell what will take place in a situation. String theory lacks this essential feature of mathematical laws because it needs trying first before scientists single out the answers that work.
Another major shortfall of the theory is the proposition that the world encompasses at least 10 dimensions. In reality, human beings see only four dimensions that are time, depth, width and height. The proponents of the theory hold that some human beings cannot see some dimensions, an argument seen by the majority as weak (Susskind 403). There is widespread doubt that there can be six dimensions (or more) that are hidden, or that cannot be accessed even if they are in existent.
Some scientists hold that this theory should not be taken as part of science because it lacks new experimental predictions at accessible scales of energy. In addition, String theory lacks guesses that scientists can test in the present time or in the future (Klebanov and Juan ). This adds to the claim that the theory is unscientific.
In conclusion, the string theory should be treated with caution in the study of physics. This is despite the fact that Albert Einstein would be happy with it, having himself envisaged such a theory to explain every situation in the world.