Uniform Field Theory, in particle physics, is the effort to describe all the basic forces and relations among the elementary particles within the scope of a single theoretical framework. Modern unified field theories have attempted to explain how fundamental forces such as gravity and electromagnetism will appear as distinct aspects of a single fundamental field. Later, Albert Einstein and others attempted to build a theory of unified fields where electromagnetism and gravity would emerge as different aspects of a single fundamental field. In the 1920s, when Einstein began work on the theory of the unified field, electromagnetism and gravity were the only known forces, while electrons and protons were the only known subatomic particles. [Sources: 4, 8, 9]

By 1905, Albert Einstein had used the constancy of the speed of light from the theories of James Clerk Maxwell to unite our concepts of space and time into a single entity that we now call spacetime, and in 1915, he extended that special relativity theory into a description of gravity, General Relativity, using the field to describe the curving geometry of 4-dimensional spacetime. Scottish physicist James Clerk Maxwell created the first field theory in the mid-19th century, which concerned electromagnetism. Then came electromagnetism, generally written in the form of a set of four equations known as the Maxwell equations. One such theory was his general relativity, which had its phenomenon, gravitational attraction. [Sources: 1, 10, 11]

At that time, there were two foundational theories central to the way that physicists understood their universe. As far as anyone could tell, general relativity and electromagnetism seemed essentially disconnected from each other. In Albert Einstein’s final years, Einstein became more and more isolated from the physics community, refusing to accept the weird yet powerful theory of quantum mechanics – with its particles being waves too, and existing nowhere in particular before being observed. Quantum mechanics – with its particles being waves too, and existing nowhere in particular before being observed. One of Albert Einstein’s reasons for not discovering a unifying theory might be that his rejection of quantum mechanics led him to overlook new developments in physics and distanced himself from the rest of the physics community. [Sources: 1, 2, 4]

After becoming known for several brilliant discoveries in physics, including Brownian motion, the photoelectric effect, and special and general theories of relativity, Albert Einstein spent the last thirty years of his life on an unsuccessful search for a way to integrate gravitational and electromagnetic forces in one elegant theory. Albert Einstein was an effort to combine the force of gravity–which he had described successfully in his theory of general relativity–with that of electromagnetism, two forces that are in many ways analogous. Erwin Schrodinger was trying to unify gravity, electromagnetism, and a field of scalar mesons…all within a framework of classical field theory, not anything quantum. Albert Einstein coined the term unified field theory, describing any attempt to unite the basic forces of physics among the elementary particles into a single theoretical framework. [Sources: 2, 3, 4, 7]

One of the main theoretical obstacles to the achievable synthesis of the present theories of particles and forces interactions in the grand unification theory, also known as grand unified field theory, Grand Unified Theories, or GUT, is the necessity of reconciling the evolving principles of quantum theory with those of general relativity, advanced nearly a century earlier by German-American physicist Albert Einstein (1879-1955). The “Theory of Everything” and Grand Unified Theories are closely related to unification field theories but differ in that they do not require that the fundamentals of nature are fields, and they generally try to account for physical constants in nature. For centuries, researchers have attempted to describe all of nature’s fundamental forces and the way that they interact within a single theory. [Sources: 5, 10, 11]

One success in the past 40 years has been to unite the electromagnetic force and weak force into an electroweak theory. After Gerardus t Hooft showed that American Steven Weinbergs electroweak interactions were mathematically coherent, a partly unified electroweak theory became the model for further attempts at uniting forces. Both electromagnetism and general relativity had involved such symmetries, but an important step was to discover that the quantum field theory for the second nuclear force, which is invariant concerning the gauge, must incorporate a complementary interaction, that is, an electroweak interaction. [Sources: 6, 9, 10]

Although electromagnetism and the strong and weak nuclear forces had long been explained with a single theory known as the Standard Model, gravitation did not fit in that equation. Quantum theory describes a quantum field with a gravitational force-carrying particle–which, though still undiscovered, is called the graviton. Although undiscovered, a theoretical gravitational force particle would be the graviton. [Sources: 0, 5, 11]

This theory treats particles (quanta) as excited states of their underlying quantum field, which is more fundamental than a particle. Quantum electrodynamics (QED) works very well and has been a prototype for theories about other forces. Grand unification theories have made predictions about the relative strengths of the strong, weak, and electromagnetic forces, and LEP determined in 1991 that the supersymmetric theories had the right ratios for the conjunctions, based on a grand unification theory by American physicist Sheldon Glashow. [Sources: 8, 9, 10]

With Isaac Newtons Theory of Universal Gravity, Newton combined or combined, these vastly disparate phenomena into one unified overarching principle. Unconvinced that nature would prescribe completely different modes of behavior for phenomena that were merely sized differently, Albert Einstein’s search for a theory that would reconcile these two irreconcilable theories formed the foundation for modern physics. Like so many of the greatest physicists who preceded Einstein, Einstein wanted to create a more powerful, broadly applicable theory that would be able to predict and explain far more than his predecessors had been able to. The theory that Einstein wanted to uncover would be much stronger, and more widely applicable than any one of those separate theories ever was on their own. [Sources: 0, 1]

Sources:

[0]: https://www.techtarget.com/whatis/definition/unified-field-theory-or-Theory-of-Everything-TOE

[1]: https://www.wondriumdaily.com/what-is-einsteins-unified-field-theory/

[2]: https://www.discovermagazine.com/the-sciences/einsteins-grand-quest-for-a-unified-theory

[3]: https://golem.ph.utexas.edu/category/2019/12/schrdingers_unified_field_theo.html

[4]: https://www.aps.org/publications/apsnews/200512/history.cfm

[5]: https://science.jrank.org/pages/3095/Grand-Unified-Theory.html

[6]: https://physics.stackexchange.com/questions/53467/unified-field-theory-in-laymans-terms

[7]: https://www.thoughtco.com/what-is-unified-field-theory-2699364

[8]: https://byjus.com/physics/unified-field-theory/

[9]: https://www.britannica.com/science/unified-field-theory

[10]: https://en.wikipedia.org/wiki/Unified_field_theory

[11]: https://www.livescience.com/58861-unified-field-theory.html