Frequently
when debating with an atheist I will bring up the beginning of the universe as
evidence for a creator and the typical response is, “We don’t know that the
universe had a beginning.” Their claim
is that models exist that are eternal, so the universe may not have had a
beginning. So far, this claim has not been
supported by the math. Alex Vilenkin and
Audrey Mithani wrote a paper called, “Did the universe have a beginning?” where they examine,
“three
candidate scenarios which seem to allow the possibility that the universe could
have existed forever with no initial singularity: eternal inflation, cyclic
evolution, and the emergent universe.”
Here is what they wrote about each type of model:
Eternal Inflation Models
These
models theorize that there was a period of exponential inflation during the
very early phases of the Big Bang. These
type of models solve several questions surrounding the standard Big Bang model,
which makes it a likely candidate for being plausible. One of the consequences of these models is
that they predict a multi-verse. Once
started inflation will continue into the infinite future. The science magazines love to talk about this
prediction as possible evidence for a multi-verse, but there’s a catch; the BGV
Theorem has shown that if on average the universe is expanding, the universe/multiverse
had a beginning.
“Therefore, although inflation may be eternal in the future, it
cannot be extended indefinitely to the past.”
Cyclic Models
Another
type of model examined is the cyclic model.
These are the models that have an infinite series of big bangs followed
by big crunches. Entropy gives these
models a couple of problems:
1). With each bang/crunch cycle, the entropy
continues to increase. If the universe
were eternal, we should have run out of usable energy and entered a state of “thermal
death”.
2). One way to avoid the thermal death scenario is
to have each subsequent expansion get bigger and bigger for an infinite amount
of time. If this were to happen, the
universe would on average be expanding more than it is contracting, which
brings you back to the BGV theorem and a beginning.
Emergent Universe Models
In
the emergent universe scenario, the universe is in a static quantum state until
the “cosmic egg” decides to crack open.
This would bypass the requirement of the BGV theorem such that the
average state of the universe would not be one of expansion. In order for this type of model to succeed, a
couple of conditions must be met.
“First, the universe should be stable, so that quantum fluctuations
will not push it to expansion or contraction. In addition, it should contain
some mechanism to exit the stationary regime and begin inflation.”
Vilenkin
and Mithani demonstrate that quantum instability exists because there is a
non-zero probability of quantum collapse, so the universe could not have
existed in a quantum state for an infinite amount of time.
“Since the tunneling probability is nonzero, the
simple harmonic universe cannot last forever…..there do not seem to be any
matter sources that admit solutions that are immune to collapse”
Summary
While
in scientific terms we are not 100% certain that the universe had a beginning, since
nothing in science is considered to be 100% certain, all of the evidence we
have suggests that it does. This paper
demonstrates that “eternal” models can only be eternal in one direction; the future.
“At this point, it seems that the answer to this question is probably
yes. Here we have addressed three
scenarios which seemed to offer a way to avoid a beginning, and have found that
none of them can actually be eternal in the past.”
