The
universe is essentially a zero energy universe meaning that the total energy of
the universe (positive energy) is balanced by an equal amount of negative
gravitational potential energy. So the law of conservation is satisfied in the
case of energy and we have law of conservation of energy. But this is not the
case with space. If we assume that the initial patch of space with almost
infinite density of space appeared from regions of no space at all or to say an
enormous positive density of space appeared from zero density of space, we
cannot formulate a conservation law for space. In other words, we cannot
formulate a law of conservation of space...
There
are two possible solutions to this problem. The first is to assume that to
balance the positive density of space, there are regions of space with negative
density of space. That of course does not seem a practical solution as the
concept of negative space seems ridiculous. Then comes the second viable
solution. In this second case, we assume that space does not have any density.
That is to say, we assume that the space before big bang and the space after
big bang are the same except in the case of their energy content...
The space before big bang had no energy while
the space after big bang had energy. Thus the case of a positive density of
space or in other words the case of quantifying space is ruled out. This
concept rules out a conservation law for space and also gives us a great
advantage in the case of trying to solve the problem of the origin of the
universe. We just need to account for the appearance of positive energy (the
total energy of the universe) and an equal amount of negative gravitational
energy out of initial zero energy of the universe which seems explicable. It is
no more required to explain the creation of space from "nothing",
instead we just need to explain the appearance of positive and negative
energies from zero energy or "nothing". That simplifies the problem
of origin of the universe a great deal as we don't need to explain the
appearance of space anymore and just need to account for the appearance of the
energy which can be explained by the law of conservation of energy. What we
call space in our universe is actually space with energy. It is the amount of
energy contained within that space, which distinguishes that space from the
space before big bang. If we don't consider that energy (like the zero-point
energy), the space of post-big bang universe and the space of pre-big bang
universe are the same.
