Unification: The Metaphysics of Physics

ResearchBlogging.orgOne of the great metaphysical ideas of theoretical physics is the conviction that the forces that act between the things must be described somehow uniform. But just the force that we experience in everyday life and feel completely without the use of measurement devices or even small tools, the gravitational force, will simply not be forced into a single model. Nevertheless, the theorist can not stop to seek a unified description of all forces.

Before we get an actual step on this “road to unification” (as nature writes on the front page of its edition dated 04/11/2010), I will briefly outline once again what the so-called “fundamental forces”, which one day are to be placed on an even more fundamental mechanism, actually have to do with the experience:

As I said, the gravitational force is the force of everyday life. It ensures that it is painful when in the prone position from the three-meter springboard diving into the water, an experience I had as a boy ever made again, it is responsible for ensuring that dishes shattered on the ground, that the air we need to breathe, remain near the Earth, and that the Moon is not independent but regularly is visible again in the same size on the sky.

Magnetism and electricity, we mostly know only by technical inventions from personal experience, even if their inventions, such as the compass or the electric current, we have become familiar from childhood and we have learned that other everyday phenomena, such as lightning, have to do with electricity.

With the unification of magnetism and electricity in the theory of the electromagnetic field, the dream of the unified field theory was in the world, a theory that contains all forces, which ensure that objects are on the move or prevented from free movement, and reduce all these forces to a single description.

But first, however, other forces were found, forces involved with our everyday experience not the least. They display their power within the nucleus (the “weak force” that holds protons and neutrons together) or at even smaller scale (the “strong force” that binds the quarks inside the protons and neutrons together).

On the edge, I would say that these forces are part of a model, which is copied more or less from the original force field models of everyday experience, even when looking at their illustration (small particles that are held by attraction or repulsion forces, the strength of these forces depends on the distance between the particles) and also when looking at their mathematical descriptions in certain types of field equations. While we can observe the effect of the field and the power of gravitation – as I said – in the behaviour of everyday objects and (even if we don’t see, hear, feel, smell or taste forces and fields themselves), the weak and the strong force are accessible only by theories, and the objects to which they contribute, constructions of the theory, whose existence we are able to show only by experiments very mediated by theories.

The unification of electromagnetic and weak force has succeeded in the electroweak force and for the strong force, there are good prospects that it can be the “third in the league”. Only gravity is acting like a Gaul, who bravely resisted the interrogation.

This is where the new attempt by the British physicist David J. Toms [1]. Giovanni Amelino-Camelia [2] says, Toms’ approach may be essential for finding the desired uniformity, which in turn is important for theoretical physics, because, Amelino-Camelia says, “all of the most studied approaches to theoretical physics, at least partly inspired by the possibility of unification.”

Toms’ work shows what sort of steps the theorists make on this “road of unification”, it shows that there is a button rather, that the road is obviously poorly lit, full of potholes, maybe it’s more of a path that again and again leads into the dark, lose a bad move.

Toms is based on the widely accepted and partially experimentally confirmed assumption that the coupling constants are no constants, but that they decrease with increasing energy, so they were at infinite energy infinitely small (a concept that is namend “asymptotic freedom”). The coupling constant of the electromagnetic force is the charge, that of the gravity is the gravitational constant.

But for the electromagnetic field, this asymptotic freedom can not be easily derived. On the contrary, in quantum electrodynamics the coupling constant increases with increasing energy. Toms has now shown that such a derivation is possible if the gravitational brings into play, in a manner as described by Einstein’s general relativity theory, although this is possible only for energies below the Planck scale.

If now the famous cosmological constant is 0 or very small, then one can show Toms say, that the gravity has a negative contribution to the coupling constant of the electromagnetic force, in quadratic dependence on energy, so that at high energies the coupling constant would actually be smaller, just as the idea of “asymptotic freedom” demands.

The question remains, on what grounds such structures are actually conceived. The idea of the unified field theory comes from the first half of the 20th Century and we must not be a prophet to predict that it celebrates its 100th Birthday as an idea and not celebrate it as proven fact description. What the physicists so fascinating about it?

One thing is certain: the unification of the fields is a great metaphysical story, it drives further thought. Where the mind is driving, is uncertain.

[1] Toms DJ (2010). Quantum gravitational contributions to quantum electrodynamics. Nature, 468 (7320), 56-9 PMID: 21048760
David J. Toms (2010). Quantum gravitational contributions to quantum electrodynamics Nature 468:56-59,2010 arXiv: 1010.0793v1

[2] Amelino-Camelia G (2010). Fundamental physics: Gravity’s weight on unification. Nature, 468 (7320), 40-1 PMID: 21048752

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