Unified Field Theory

Scientific tragedy of late Einstein. He tried hard to unify all fundamental forces in a framework like his General Relativity. While GR ranks among the greatest achievements of physics, UFT never worked out. According to CF von Weizsäcker, Einstein's UFT was far from explaining sharply separated types of elementary particles, while Heisenberg's attempts on UFT came a little closer.

It's an unsolved problem to fit gravitation and quantum physics into one mathematical framework.

Unified Field Theory, also referred to as the Grand Unified Theory in its more complex state, is a physical theory that attempts to unite the four known forces in nature - the Electrostatic, the Strong Nuclear, the Weak Nuclear, and the Gravitational. Unifying these four forces under one single set of mathematical expressions was long considered the 'Holy Grail' of modern physics, and absorbed the efforts of thousands of physicists for the better part of a century.

Unified Field Theory started out as Albert Einstein's attempts to reconcile his own view of the universe with the emerging field of Quantum Mechanics. Einstein despised quantum theory in its infancy, perceiving it as a threat to the foundations upon which his theories of Special and General Relativity were built. His famous statement, "God does not play dice with the universe", is a reflection of his disposition towards a probabilistic universe. By contrast, all of Relativity is based on Newtonian determinism. Einstein was partially successful in unifying these wildly different forces, but ultimately failed. Heisenberg later took up the gauntlet for the more noble reason of preserving the elegance of physics - he believed that the ultimate goal of physics would be to great an 'equation for everything'. Currently however, there is no theory of gravitation at the quantum mechanical level.

Interest in the Unified Field Theory waned as some of the greatest minds of the twentieth century fell in pursuit of the ultimate equation. Research was recently rekindled however with the theorization of the Higgs Boson, the currently theoretical particle thought to give particles mass. The reason for this is difficult to explain in words, but I will try. Under the Standard Model of particle physics and our current understanding of field theory, we can plot graphs describing each of the four forces. If we plot them on the same axes, at increasing energies, the four lines begin to converge to a point, but without including the Higgs Boson, they miss convergence by a tiny but significant margin. By including the Higgs into the Standard Model, it is possible to unify all four fields, at a very high energy state known as the Unification Energy. This energy level also gives rise to several other 'fringe theories' such an over-unity (free energy) and Magnetic Monopoles.

Currently, the conclusion of the UFT, for good or ill, is still a dream for physicists. However, the construction of ever more powerful particle accelerators may eventually change this situation, perhaps leading to the final discovery of the Higgs and beyond.

There are reasons for suspecting that some sort of Unified Field Theory exists. It can be seen in the equations.

In days of yore, Sir Isaac Newton "discovered" gravity. The force of gravitational attraction between two objects of masses m1 and m2, at a distance of r, is given by the equation

F_g = (g*m₁*m₂)/(r²)
where g is simply a constant. The constant, of course, changes depending on the units of measurement that are chosen. Simply put, g is completely arbitrary and could be eliminated if we chose the right units.

As a side note, the force of gravity felt by each object due to the presence of the other object is identical. The reason that an astronaut falls toward the earth, while the earth does not appear to fall toward the astronaut is an issue of mass. F=m*a where F is force, m is mass, and a is acceleration. The Earth is far more massive than the astronaut, and hence does not accelerate nearly as quickly as the astronaut. In fact, you wouldn't even notice it.

Similarly, there is an equation which describes the amount of force felt (either attraction or repulsion in this case) by a charge due to the presence of another charge at some distance r. Much like gravity, the force felt by each particle due to the presence of the other will be identical.

F_E = (k*q₁*q₂)/(r²)
Where k is another one of those arbitrary constants, and q1 and q2 are the charges on each of the two particles. k is also sometimes expressed as the inverse of 4*pi*E, where E is the permeability of free space and is really the Greek letter which looks like a capital E. Once again, though, it's arbitrary. Change the units, and the constant disappears. Suppose we changed the units for mass, charge, and distance in a way that would eliminate the constant for both equations. We would be left with the following:

F_g = (m₁*m₂)/(r²)
F_E = (q₁*q₂)/(r²)

Gasp! Those equations... look the same. Perhaps mass is related to charge, meaning electricity, in some manner. This is the stuff of Physicists' wet dreams.

The unified field theory was originally a dream held by Albert Einstein believing that all the fundamental forces of nature may be sufficiently unified into a single theory framework. When Einstein attempted to do this, he had an incomplete knowledge of the universe - he was not aware of all the fundamental forces at the time. Even if he had, it is hard to say he would have been able to fare better - such a task is daunting for a number of reasons.

One reason is that such a theory needs to be a mathematically-sound theory which can successfully account for the beginning of our universe and the birth of the forces as we could understand it. Not only is this knowing the mind of God, but the theory also needs to be universally-acceptable so that everyone may come to agree on it - which is a task in itself.

The reason for believing there is such a unification is compelling. Einstein showed that using relativity one can successfully describe magnetism as another side of the electric force. Then of course, Einstein attempted to unify his General theory of Relativity with electromagnetism itself. He largely failed to do this, however Theodor Kaluza a bright German physicist did find a way to unify General Relativity and electromagnetism but at the expense of having to introduce a new dimension of space - the 5th dimension of spacetime to be exact. There is no concrete evidence any more than 3 spatial dimensions exist in nature.

let's be clear what physicists are trying to achieve, they are attempting to describe all the forces in nature under one name; gravito-electro-magneto-strong-weak force. They are wanting to do this by increasing the temperature of the system. The electromagnetic force was successfully unified with the weak force which is responsible for the decay of particles. It was predicted by Sheldon Glashow. In 1967 physicists Abdus Salam and Steven Weinberg had independently revised Glashow's theory by having the masses for the W particle and the Z particle arise through spontaneous symmetry breaking using the Higgs mechanism. Recently we think we have found a Higgs particle however it has around 50% more likelihood to decay into photons than it is predicted by the Standard Model, raising questions whether

a) it is even a Higgs Boson?

b) it is even a Standard Higgs Boson?

Nevertheless, electroweak currents where observed. If one studies the Langrangian (the equations which describe the kinetic energy), electroweak currents have a Langrangian which is split up for a weak part and an electromagnetic part, which indicates that both forces are present at this temperature further indicating they have been unified into different sides of the same the force, just how like electric and magnetic forces are present at low temperatures but are completely relative for moving and stationary systems.

There is a growing number of physicists now who are making the argument that gravity may not not actually be fundamental which of course, presents a large problem in the basic idea of unifying the forces - after all, you can only unify the fundamental forces assuming the force you are dealing with is fundamental! It may not actually be in the same league as the other forces to add to the mystery as it could also be a psuedoforce... in fact Richard Feymann made this point himself at one time. So not only might gravity not be a force in the same sense as electromagnetic or strong or weak nuclear forces... it may not even be fundamental (or better said) it may be emergent.

What does it emerge from?

The answer is that gravity emerges from the geometry of spacetime, alongside matter as well. In fact, John Archibald Wheeler's Geometrogenesis actually explains that geometry is a late phenomenon in the universe, it appears when the universe has sufficiently cooled down. If this is the case, and the source of gravity is in fact the geometry of the universe, then gravity also appeared around the same time and did not originate at the Big Bang under some grand unification like many are led to think. In a sense, it is not hard to understand that maybe we had the idea of this unification wrong to begin with, because so many start theorizing without all the facts.

String theory is a theory which has attempted to unify physics, by introducing an astonishing 11 to 26 new dimensions, depending on which string theory is considered. For many reasons (not all we shall cover in this) physicists don't like this theory very much as it seems to be purely mathematical with little to no experimental data to be predicted from it. Because of that, some have criticized it is ''not even wrong.'' It does on the other hand give a remarkably beautiful picture of gravity, seeping from universe-to-universe connecting all universes like one giant string. In string theory, instead of parallel universes which there can be an infinite amount, string theory deals with a landscape which allows up to 10^(500) vacua.

An unlikely surfer dude by the name of Anthony Garret Lisi was to propose a theory of everything also involving multiple new dimensions. It also predicted new exotic particles outside of the standard model (which, if this newly discovered particle is a Higgs Boson, it is becoming increasingly unlikely there will be any new physics outside of the standard model). His theory is based on the complicated E_(8) Lie Group and it attempts to describe a complicated geometrical web of forces connected to their particles under a unification.

To this day, there is no common agreement on a unified theory and many unified theories often lack a certain appeal. Some of the most daring unified field theories have unfortunately been some of the most complicated and often introducing superfluous amounts of dimensions and new particles. Perhaps within the next 100 years a new Einstein will come along and radically reshape our thinking of the forces at large... on the very small.