Physics of the early Universe is at the boundary of astronomy and
philosophy since we do not currently have a complete theory that
unifies all the fundamental forces of Nature at the moment of
Creation. In addition, there is no possibility of linking
observation or experimentation of early Universe physics to our
theories (i.e. its not possible to `build' another Universe). Our
theories are rejected or accepted based on simplicity and aesthetic
grounds, plus there power of prediction to later times, rather than
an appeal to empirical results. This is a very difference way of
doing science from previous centuries of research.|
Our physics can explain most of the evolution of the Universe after the Planck time (approximately 10-43 seconds after the Big Bang).
However, events before this time are undefined in our current science
and, in particular, we have no solid understanding of the origin of
the Universe (i.e. what started or `caused' the Big Bang). At best,
we can describe our efforts to date as probing around the `edges' of
our understanding in order to define what we don't understand, much
like a blind person would explore the edge of a deep hole, learning
its diameter without knowing its depth.|
One of the reasons our physics is incomplete during the Planck era is a lack
of understanding of the unification of the forces of Nature during this time.
At high energies and temperatures, the forces of Nature become symmetric.
This means the forces resemble each other and become similar in strength,
i.e. they unify. When the forces break from unification (as the Universe
expands and cools) interesting things happen.|
An example of unification is to consider the interaction of the weak
and electromagnetic forces. At low energy, photons and W,Z particles
are the force carriers for the electromagnetic and weak forces. The
W and Z particles are very massive and, thus, require alot of energy
(E=mc2). At high energies, photons
take on similar energies to W and Z particles, and the forces become
unified into the electroweak force.|
There is the expectation that all the nuclear forces of matter (strong, weak and electromagnetic) unify at extremely high temperatures under a principle known as Grand Unified Theory, an extension of quantum physics using as yet undiscovered relationships between the strong and electroweak forces.
The final unification resolves the relationship between quantum forces and gravity (supergravity).
In the early Universe, the physics to predict the behavior of matter is determined by which forces are unified and the form that they take. The interactions just at the edge of the Planck era are ruled by supergravity, the quantum effects of mini-black holes. After the separation of gravity and nuclear forces, the spacetime of the Universe is distinct from matter and radiation.
Cosmic Singularity :
One thing is clear in our framing of questions such as `How did the
Universe get started?' is that the Universe was self-creating. This
is not a statement on a `cause' behind the origin of the Universe,
nor is it a statement on a lack of purpose or destiny. It is simply
a statement that the Universe was emergent, that the actual of the
Universe probably derived from a indeterminate sea of potentiality
that we call the quantum vacuum, whose properties may always remain
beyond our understanding.|
Extrapolation from the present to the moment of Creation implies an origin of infinite density and infinite temperature (all the Universe's mass and energy pushed to a point of zero volume). Such a point is called the cosmic singularity.
The cosmic singularity, that was the Universe at the beginning of time, is shielded by the lack of any physical observers. But the next level of inquiry is what is the origin of the emergent properties of the Universe, the properties that become the mass of the Universe, its age, its physical constants, etc. The answer appears to be that these properties have their origin as the fluctuations of the quantum vacuum.
The properties of the Universe come from `nothing', where nothing is the quantum vacuum, which is a very different kind of nothing. If we examine a piece of `empty' space we see it is not truly empty, it is filled with spacetime, for example. Spacetime has curvature and structure, and obeys the laws of quantum physics. Thus, it is filled with potential particles, pairs of virtual matter and anti-matter units, and potential properties at the quantum level.
The creation of virtual pairs of particles does not violate the law of
conservation of mass/energy because the only exist for times much less
than the Planck time. There is a temporary violation of the law of
conservation of mass/energy, but this violation occurs within the
timescale of the uncertainty principle and, thus, has no impact on
macroscopic laws. |
The quantum vacuum is the ground state of energy for the Universe, the lowest possible level. Attempts to perceive the vacuum directly only lead to a confrontation with a void, a background that appears to be empty. But, in fact, the quantum vacuum is the source of all potentiality. For example, quantum entities have both wave and particle characteristics. It is the quantum vacuum that such characteristics emerge from, particles `stand-out' from the vacuum, waves `undulate' on the underlying vacuum, and leave their signature on objects in the real Universe. In this sense, the Universe is not filled by the quantum vacuum, rather it is `written on' it, the substratum of all existence.
With respect to the origin of the Universe, the quantum vacuum must have been the source of the laws of Nature and the properties that we observe today. How those laws and properties emerge is unknown at this time. The fact that the Universe exists should not be a surprise in the context of what we know about quantum physics. The uncertainty and unpredictability of the quantum world is manifested in the fact that whatever can happen, does happen (this is often called the principle of totalitarianism, that if a quantum mechanical process is not strictly forbidden, then it must occur).
The same principles were probably in effect at the time of the Big Bang (although we can not test this hypothesis within our current framework of physics). But as such, the fluctuations in the quantum vacuum effectively guarantee that the Universe would come into existence.
Planck Era :
The earliest moments of Creation are where our modern physics
breakdown, where `breakdown' means that our theories and laws have no
ability to describe or predict the behavior of the early Universe.
Our everyday notions of space and time cease to be valid.|
Although we have little knowledge of the Universe before the Planck time, only speculation, we can calculate when this era ends and when our physics begins. The hot Big Bang model, together with the ideas of modern particle physics, provides a sound framework for sensible speculation back to the Planck era. This occurs when the Universe is at the Planck scale in its expansion.
Remember, there is no `outside' to the Universe. So one can only
measure the size of the Universe much like you measure the radius of
the Earth. You don't dig a hole in the Earth and lower a tape
measure, you measure the circumference (take an airplane ride) of the
Earth and divide by 2
(i.e. C = 2
The Universe expands from the moment of the Big Bang, but until the Universe reaches the size of the Planck scale, there is no time or space. Time remains undefined, space is compactified. String theory maintains that the Universe had 10 dimensions during the Planck era, which collapses into 4 at the end of the Planck era (think of those extra 6 dimensions as being very, very small hyperspheres inbetween the space between elementary particles, 4 big dimensions and 6 little tiny ones).
During the Planck era, the Universe can be best described as a quantum foam of 10 dimensions containing Planck length sized black holes continuously being created and annihilated with no cause or effect. In other words, try not to think about this era in normal terms.
Spacetime Foam :
The first moments after the Planck era are dominated by conditions
were spacetime itself is twisted and distorted by the pressures of
the extremely small and dense Universe into a mass of black holes and wormholes. |
Most of these black holes and wormholes are leftover from the Planck era, remnants of the event horizon that protected the cosmic singularity. These conditions are hostile to any organization or structure not protected by an event horizon. Thus, at this early time, black holes are the only units that can survive intact under these conditions, and serve as the first building blocks of structure in the Universe, the first `things' that have individuality.
Based on computer simulations of these early moments of the Universe,
there is the prediction that many small, primordial black holes were
created at this time with no large black holes (the Universe was too
small for them to exist). However, due to Hawking radiation, the
primordial black holes from this epoch have all decayed and
disappeared by the present-day.|
Matter arises at the end of the spacetime foam epoch as the result of strings, or loops in spacetime. The transformation is from ripping spacetime foam into black holes, which then transmute into elementary particles. Thus, there is a difference between something of matter and nothing of spacetime, but it is purely geometrical and there is nothing behind the geometry. Matter during this era is often called GUT matter to symbolize its difference from quarks and leptons and its existence under GUT forces.