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# What is string theory?

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String theory is a theory that attempts to explain and group the four known fundamental interactions of the universe, which are electromagnetism, strong nuclear force, weak nuclear force and gravitation, into one theory. String theory is a model that attempts to elucidate the phenomena of the universe that are incomprehensible under standard models of quantum physics.

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At its foundation, string theory utilizes one-dimensional strings with specific frequencies in place of the standard particles of quantum physics. The formulas stemming from string theory predict a multitude of dimensions, which number 10 or 11 in common string theory models but up to 26 in other versions.

These added dimensions, however, “curl up” within the strings. The average size of these strings is roughly a millionth of a billionth of a billionth of a billionth of centimeter, which is much too small to be seen by current or applied particle physics technology. String theory also refers to another fundamental object known as a “brane.” Branes contain multiple dimensions, and, in some theories, the universe exists within a 3-dimensional brane.

String theory is an evolving science; however, all variations of string theory posit the existence of multiple dimensions and attempt to explain the relationship between gravity and quantum physics. String theory was developed in the 1970s to explain the ambiguities associated with physics and the energy behavior of hadrons.

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## Related Questions

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Some examples of MCAT physics equations include the equation for law of gravitation, which is F = Gm1m2/r^2; the equation for centripetal force, which is F=mv^2/r; and the equations for potential energy, such as PE = mgh, PE = 1/2kx^2 and PE = -GmM/r. Other equations include momentum = mv, impulse = Ft and KE = (1/2)mv^2.

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Universal gravitation is the name given to the law that Isaac Newton devised to explain the gravitational attraction between two massive bodies. Essentially, it states that the force of gravity is proportional to the sum of the combined mass of the two bodies, divided by the distance between them squared. While Newtonian physics are no longer what modern physicists use, its predictions and accuracy were accurate for objects on Earth.

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Non-contact forces arise from long-range interactions, such as gravity and electromagnetism. Weight is an example of non-contact force, as objects are attracted to massive bodies without touching them.