When asked to describe art, J M W Turner, probably Britain's finest pictorial artist, described it as 'a rummy business'; much the same could be said about 20th century physics. 'Rummy', which has little to do with the drink or the card game, in this context is an archaism for 'odd', 'peculiar'.
Despite the Victorians' belief that after Newton, Faraday and Maxwell et al, there was little to be discovered about the physical universe that was not already known, Planck and Einstein (together with their legions of followers) turned that particular myth upside down and inside out. The twin pillars of Quantum Mechanics and General Relativity have driven the tale of the universe from the smallest to the largest. As each new aspect of the two theories expanded into purely theoretical, that is to say mathematical, territory, experiment continued to 'prove' the basic tenets of the two theories despite the fact that each theory was, to a large extent, mutually exclusive. Relativity only applied at a macro level to planetary systems, galaxies, galactic clusters, pulsars and black holes, the kingdom where gravity rules while quantum mechanics could only be applied to the infinitessimily small; the realm of atoms and sub-atomic particles where the strong and the electro-weak forces held sway and gravity was almost a complete no-show at the party..
All theories in the physical realm have a tendency to start life as extremely tentative hypothoses, an idea born out of an examination of the world that surrounds us and a leap of imagination about how that might be explained. The fundamental cornerstone of any physical theory is that it possible to explain the world, the universe, in a way that seems reasonable to other human beings. Even the unscientific explanations still must have a widespread belief that a God or some pantheon of Gods can explain the world in we have lived and continue to live. As bizarre and ridiculous as Mount Olympus or Valhalla may seem to modern minds, peopled as they are with Gods endowed with supernatual powers and all too human emotions and motivations, they are no more ridiculous than a simple supreme creator or even modern relativity or quantum physics.
However, what grew out of simple curiosity about how the world was and how it might be explained in terms that human beings might comprehend, there was a growing realisation that simple, blind faith in some form of deity, or deities, was no longer enough to explain the universe and all that it contained. As humanity learned by a slow and often painful process that certain aspects of the world could be explained using empirical facts learnt from their forebears; that the seeds of wheat could be made to grow into adult plants where you wanted them to grow; how animals could be bred ever larger for meat merely by choosing the strongest and largest to breed from; how a certain 'sand' from a certain part of Italy could be used to 'weld' stone together to create buildings resistant to the elements (concrete) so humanity began to expand into the realms of theories about how the world was which did not necessarily derive from observations.
As the dark ages wound their way into the middle ages and thence into the 'age of reason', the effects of the imports from the Indian and Arab worlds started to exert their stranglehold on Western civilisation; mathematics. In the main, all physical theories about the cosmos we inhabit have been expressed in terms of mathematics since at least the fifteenth century and humanity has not been content to rely on the algebraic mathematics of the Greeks and the Moors; with each passing century, new kinds of mathematics have been invented, or perhaps discovered. Newton's and Leibnitz's calculus; the multi-dimensionality of Hilbert space; Cantor's set theory; Russell's axioms of a complete mathematics and Godel's subsequent refutation; the mysteries of imaginary numbers and their complex number derivitives, so essential to the quantum world. The universe is no longer described in tangible, concrete, objective terms but only in the language of mathematics. It is this power of mathematics which allows theories to be so finely wrought but also enables the hypotheses derived from theory to be so accurately measured and confirmed.
The way in which our observed reality conforms to theory in some ways beggars belief. Richard Feynman, the great, perhaps the greatest, physicist of the twentienth century*, remarked that the power of Quantum Electrodynamics, that strange interaction between light and matter, could accurately predict events equivalent to measuring the distance between New York and Los Angeles to the thickness of a human hair. The theory, at that time, was only accurate to three decimal places; now its accuracy may be measured to seven or eight decimal places. Feynman's insight was to dispel the infinities which had so plagued quantum mechanics since its inception sixty years earlier by incorpaorating them into the fundmantal equations, path integrals, the so-called 'sum over histories' approach. And yet, this was. by Feynman's own admission, a 'trick', a 'cheat'; you got rid of the infinities of the equations by assuming that 99.99% of them cancelled each other out! More importantly they seem actually to do so. Light travels in a straight line (a geodesic in relativistic, curved space time) not because it does but simply because all of its other available paths mathematically cancel each other out.
We humans have a natural, instinctive attraction towards symmetry that probably stems from our perception of ourselves and which is reflected in all other animate life. This symmetry is usually only in one plane, lateral, left to right, and yet it dominates our perceptiion of reality; the 'Golden Mean'; our perceptions of what it is beautiful, idiosyncatic cultural influences notwithstanding; our beliefs about what we feel to be intrinisically, intuitively 'right'. So we search for such symmetry in our theories about how the world, the cosmos, might behave. Odd is good, even is better. It took twenty years after Gell-Mann's initial postulate of quarks to find a candidate for the 'top' quark to filll the gap in the 'up', down', 'strange' and 'charm', 'bottom' and 'top' symetrical table; it took forty years to find a candidate for the 'Higgs boson' to fulfil the expectations of another force to balance the potential trio of 'W', 'Z' and 'X' (the Higgs) in the table of triads that constitute the 'standard model' of quantum physics. Is there a reason why God should do everything in 'threes'.
Moreover, is nature really symmetrical in this way? And if so, why should it be so? Do we not simply map our desire for order on to the chaos of the universe. It is difficult, at times, to escape the inevitable conclusion that the only order in the universe is the one which we impose, hard to escape the the 'anthromorphic principle'. We do not understand the supposed inflation of the early universe and are consequently at a complete loss to explain what appears to be be an ever accelerating expansion of this universe; we do not begin to understand how the 'Higgs' field contributes mass to particles; we do not understand how matter appears to be merely 'crystalised energy', why else should the mass of a 'particle' be expressed in GeV, giga electron volts, a measure not of weight, mass but of energy; we do not understand how 'space' is filled with a 'virtual' quantum foam, the constant creation and subsequent annihilation of pairs of particles whose existence is too brief to be measured; how does the universe 'borrow' energy, is the cosmos so 'uncertain'; what is dark matter, what is dark energy, those bizarre candidates for what constitutes much of the matter of the universe? The mathematics leads us to believe that this is so, that reality works in this way; that our being, our very existence is merely a product of some probabilty and yet, we are not beholden to mere probability but probability amplitudes; imaginary numbers multiplied by real numbers. How can we believe in such things; that this is reality?
In the end, how are we constrained by the patterns of our brains, our history. If there is an objective reality, a reality that exists outside of ourselves; how is that reality to be defined? Perhaps the events of the last century should be dismissed as merely a blip along the way. We seek enlightenment; it is the 'human condition'. What if the scientific path were just one more 'cul-de-sac'. Perhaps it is time for another Planck, another Einstein or perhaps it is the time for another Christ, another Buddha?
* In labelling Feynman 'the greatest', I wish to bear no disrespect to Planck, Einstein, Shrödinger, Heisenberg, Dirac, Bohr et al. However, Feynman, almost single handedly, loosed quantum mechanics from the Gordian knot of infinities which envelopped it; stopped it from being a real theory about the world. Physicists still draw 'Feynman diagrams' and all the subsequent theories about the quantum world draw upon Feynman's initial equations about quantum electrodynamics. I tend on the whole not to give much thought to string or 'M' theory not because it is not a valid theory but because it seems to make no testable predictions which are not already covered in quantum theory.
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