The Quantum Universe
In human terms, we might assume that the universe has to begin at time=0 seconds. However, on the Planck scale, there may be no meaning to time below 10-43 seconds. If so, there may be no real measure of time against which to judge how long the bubble universe existed in this state or how to dimension any wider quantum universe, from which it presumably emerged, in terms of either time or space.
The logic of the original cosmological models suggested that the expansion of our universe, when played back in time, leads to an initial state that was described in terms of a ‘cosmic singularity’, which was then assumed to have essentially zero dimensions and infinite density. Again, within the context of the Planck scale, there may be no meaning of spatial size below 10-35m. Even so, if all the energy-mass of the universe was contained within something called a singularity approaching the Planck scale, we have to assume a density that would have exceeded 10+100kg/m3 and have a temperature in excess of 1032 degrees Kelvin. At this energy-density temperature, science has speculated that the four fundamental forces would collapse into one fundamental force.
Note: There may be a significant dichotomy in the argument being presented at this point, as we have also raised the possibility that the universe may have net zero energy based on the negative potential energy verse positive kinetic energy 'model'. Of course, this argument would be questionable in terms of the previous outline because it might also suggest a zero energy density.
As the universe expanded and cooled from the Planck epoch, gravity is thought to have been the first to separate from the unfied fundamental force, followed shortly after by the strong nuclear force. At this point, there are two attractive forces, the short-range strong nuclear force that binds quarks into atomic nuclei and the long-range force of gravity. However, it is highlighted that the initial energy-temperature is far too high to allow normal matter to exist. However, given the existence of these attractive forces, so early in the life of the universe, it is also assumed that inflation must have occurred at a very early stage, otherwise the Planck universe would have simply been crushed back into a singularity. Of course, at this point, we might raise the issue of the gravitational centre within the singularity.
Inflation is now a collective term for a class of models attempting to describe the very early universe, which involves a short period of extremely rapid, i.e. exponential, expansion in which the universe may have grown by ~2100, i.e. from about 10-35 metres to 10 centimetres in something in the order 10-32 of a second. Due to the implications of gravity unravelling from the unified forces, it is assumed that the inflationary era took place very early in the history of the universe. This early phase of expansion attempts to explain many of the properties that we see in our universe today, i.e. why the universe is both homogeneous and isotropic.
Baryogenesis is a rather impressive name given to a process in which the balance between matter and anti-matter may have been resolved in the very early universe. Quantum theory predicts that every particle should have a corresponding antiparticle with the same mass and lifetime, but opposite charge. By virtue of these properties, particles and anti-particles would annihilate on contact.
Note: Given the timeframe of baryogenesis, can we assume
that the only particles that could have existed, at this time, were
the most elementary, i.e. quarks and electrons plus their anti-particles?
Of course, it might be realised that no mention has been made of the role of neutrinos in the early universe - see neutrino.pdf for more details as this topic is beyond the scope of this discussion.
What is strange in this process is that we start with the singularity apparently containing all the mass-energy of the universe, where the temperature and density of the singularity does not initially allow matter to exist, at least, not in the normal sense. In fact, from E=mc2, we might visualise matter `condensing` out of some form of quantum energy-density, as it cools. However, baryogenesis goes onto suggest that for every billion antiparticles created, 1 billion photons plus 1 normal particle are created, which are then all effectively converted back into energy, presumably in the form of photons, through the process of particle-antiparticle annihilation leaving a net-gain of only 1 matter particle per billion pair particles. Today, there are several hypotheses that try to explain the asymmetry of baryogenesis, but no solid theories.
At about 10-12 seconds, the symmetry of the electro-weak force breaks and some of the most fundamental particles may therefore have started to acquire mass. Also, at this point, neutrinos decouple and begin travelling freely through space. This process is analogous to the cosmic microwave background decoupling, although this specific event will be described in more detail later in the evolutionary timeline. Following this process, the super-hot quark-gluon plasma, which defines the composition of the quantum universe, begins to cool allowing particles, such as protons and neutrons, to form.