The
previous blog posts have already explained the origin and evolution of the
universe which include the creation of the primordial patch of spacetime,
changes (events) that occurred in the primordial patch which led to the big
bang and the universe after the big bang. But in those blog posts, the beginning
of time is not clearly pinpointed even though it has generally been described
about. The purpose of this blog post is to describe clearly about the beginning
of time. When was the actual beginning of time?
As
mentioned in the first blog post, the possible answers are – with the creation
of the primordial patch of spacetime, with the nucleation of the bubble of false vacuum,
with the decay of the bubble releasing the enormous amount of energy contained in it and with the very instant of the bang.
Time is
relative. There must be an observable reference for the measurement of time. We
cannot determine the age of an object or an event if it is unobservable. So the
beginning of time must be the first observable change that took place in the
universe – which of course was the creation of the primordial patch of spacetime.
Before big
bang there was space and there was energy but these were in the absence of
time. The normal space that we observe has a vacuum energy density associated
with it i.e. the ground state energy of that space is not zero or to say the
vacuum expectation value of normal space is not zero. This simply means that
for normal space, the lowest energy state is not zero. In VFT, there are two
types of space – 1) space with vacuum energy density (non-zero ground state
energy) called the normal space with energy and 2) space without vacuum energy
density called no-energy space or space without energy. In the pre-big
bang phase, space with energy got condensed by the action of gravity to form
the initial singularity. The region outside the singularity was no-energy space or space without
energy. In the post-big bang phase, space with energy expands into the regions
of no-energy space.
SOME
IMPORTANT QUERIES AND ANSWERS
1) The universe cannot be oscillatory which
existed for an infinite time. Why?
An
oscillatory universe which expands and contracts in continuous cycles, existing
for almost an infinite time is not possible as it contradicts the second law of
thermodynamics which states that entropy (measure of disorder) increases with
time. In an oscillatory universe, entropy increases with each oscillation and
reaches the maximum so that it cannot oscillate further. Thus it is not
possible for the universe to be oscillatory i.e. oscillating for an infinite
period of time.
2)
Events before the big bang have no observational consequences. Why?
The
beginning of the universe was a singularity of infinite density where all the
laws of physics (except the law of conservation of energy) would break down. So what was present before the big bang
cannot actually influence the post-big bang universe because at the singularity
all the laws of the pre-big bang universe and generally speaking, all the laws
of physics broke down. So to explain what happened before big bang one must
explain the singularity, the physics governing it and also the creation of the
singularity from the pre-big bang vacuum fields.
3)
The laws of the pre-big bang universe or what was present in the pre-big bang
universe could not influence the post-big bang universe. Why?
This
is because there was a break (discontinuity) in between in the form of a
singularity at which all the known laws of physics (except the law of conservation of energy) broke down so that there
were no laws or to say unknown laws that could govern the singularity. Laws of
physics could be applied only after the big bang to create all the matter and
radiations now seen in this world. Thus the laws of physics which applied to
the pre-big bang universe (special set of laws as time was absent during those
events) broke down at the singularity and so could not affect the post-big bang
universe. For this reason what was there before big bang had no observational
consequences in the post-big bang universe. But the laws of the pre-big bang
universe could have affected the singularity. To understand more about that we
need to develop the formalism of Quantum Gravity for which active research is
going on. We can hope that this mystery will be solved soon…
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