264 The Poetry of Physics and The Physics of Poetry
shortly examine. The adoption of the theory still leaves open the question
of the finiteness of the universe. Does the universe close in upon itself or
is the region beyond the 13.7 billion light year radius empty space, which
extends to infinity? Other questions also present themselves. Will the
universe continue to expand forever eventually becoming infinite in size
after an infinite time has passed? If this is true, what happened before the
creation of the universe? Was there such a thing as time before the Big
Bang?
Another possibility that the theory allows is that the expansion would
eventually slow down as a result of the gravitational attraction of all the
clusters for each other. It is even possible that the expansion could be
reversed and that the universe would eventually shrink back into a point
and explode again starting another cycle of the universe. If this is true
which cycle are we currently living through? Does history in the cosmic
sense repeat itself? This possibility seems remote as the expansion of the
universe seems to be increasing rather than decreasing.
Still another possibility is that the universe began an infinite time ago
as an infinitesimally dilute gas of infinite extent, which began collapsing.
Then 13.7 billion years ago the universe had collapsed down to a point
and exploded. The universe is now expanding and will continue to
expand forever eventually returning to the state from which it began. In
this model there is only one cycle of the universe.
This model and the model just discussed in which the universe is
continually oscillating between expanding and shrinking phases, have
one feature in common. In both models the universe always was and
always will be. I personally find this an appealing principle because of
the conservation of energy. If the universe were suddenly to start at time
zero from nothing, I would want to understand how such a colossal
violation of energy conservation could take place. If the total energy of
the universe were decreasing, one could go forward in time to when there
would be no energy and hence the end of the universe. If the total energy
of the universe were increasing, then one could go backward in time to
when there was no energy or the point when the universe just began. But
since total energy is conserved I believe that the universe has neither a
beginning nor an end. It always was and always will be “an ever-kindling
fire” as Heraclitus described it.
There is one aspect of the observable universe that the Big Bang
theory cannot take into account and that is the fact that the rate at which
the universe is expanding is accelerating. The acceleration is believed to