Unified Quantum Field Theory
Pondering the Planck Era
We are here dealing with a vast no mans land, where all known laws of physics have broken down and where the four ordinary forces have merged into one force - supergravity. Neither standard Quantum Field Theory nor General Relativity, can help us now. Gravity has leveled with the other three forces and standard Quantum Field Theory deals only with the microscopic scale, where ordinary gravitational effects are too feeble to even be detected. General Relativity, on the other hand, deals only with gravity on the macroscopic scale. To ponder this era, what is needed is a unified theory which can handle gravitation at the microscopic level. Currently, several theoretical research schemes are taking place throughout physicist communities, each advancing along their own lines. The only consensus, if such exists, seems to be that the sought for unified theory should combine the conceptual elements of General Relativity and Quantum Field Theory. However, so far no sufficient and consistent theory has been put forth. A few of the more popular schemes, such as Super-symmetry Theory and Superstring Theory, solve some problems in certain areas, but even their strongest supporters admit that the suggested solutions give rise to seemingly unsolvable problems in other areas. - This author shall not attempt to give an account of the various schemes. Let us concentrate on the essentials of the one that is the most natural extension of standard Quantum Field Theory.
Unified Quantum Field Theory
The starting point for this unification scheme is to quantize the gravitational field along the lines described in the quantum physics section of this site. Accordingly, the gravitational force is assumed to be mediated by an exchange of massless gauge-bosons - or gravitons, as they are dubbed. Gravitation is a long-range force which, as an example, is responsible for holding together the whole Milkyway as well as the whole universe. Consequently, the seemingly empty space, i.e. the interstellar vacuum, must be flooded with gravitons rushing in each and every direction with the speed of light. Vacuum is all-pervasive. Actually, all compound bodies - including human ones, planets, stars and furnitures - are mainly vacuum. If all vacuum were squeezed out of your body, so that all its elementary matter constituents where gathered in one tight clump, you would be tinier than the tip of a needle. So, according to Unified Quantum Field Theory, every physical phenomenon is, as far as its particle aspects are concerned, substantially a sea of rapidly moving gravitons interacting with themselves and with the ordinary elementary particles such as electrons, quarks, etc. - Nevertheless, owed to their tinyness, no graviton has ever been detected. If they exist, gravitons are expected to be about 10^+15 (1 million billion) times smaller than the tiniest entity that can possibly be detected by the currently available means. As a matter of fact, the assumed gravitons are as tiny compared to ordinary particles, as you are tiny compared to the whole solarsystem. Consequently, electrons and quarks are influenced as much by gravitons as an entity the size of the solarsystem would be influenced by humans moving around in its vicinity.
Above, we have only considered the particle aspect of gravity. However, as explained in greater detail in the quantum physics section, gravitons are field-quanta - i.e. discrete manifestations of underlying gravitational fields. It is here that General Relativity enters. Applying the concept of space-time curvatures to elementary particles, the massive ones must be regarded as minute packets of warped space-time. Gravitons and photons are massless, so it is not quite clear how these are supposed to be fitted into the space-time packet scheme. One line of thought considers the sea or web of rapidly moving gravitons to constitute the very fabric of space-time. A related line of thought suggests that the points of the space-time continuum come into existence only by means of interactions between gravitons and other quanta. However, these - and a variety of similar ideas - are essentially just attempts to give physical substance to space and time.
No complete and consistent theory has yet been put forth, so it is very much an open question what a successful Unified Quantum Field Theory will be like. Maybe, the answers should be sought for along the lines implicated by this saying of Einstein:
- "Space and time are not conditions in which we live, but modes in which we think."
After all - since thoughts, emotions, etc. actually do appear in this universe - no unification theory of the universe would be ultimate unless it accounts also for the mental activities of human minds - as well as the entities called minds themselves.
